1 00:00:05,880 --> 00:00:07,480 Speaker 1: Hey, are you welcome to Stuff to Blow Your Mind? 2 00:00:07,520 --> 00:00:10,360 Speaker 1: My name is Robert Lamb and I'm Joe McCormick, and 3 00:00:10,560 --> 00:00:13,399 Speaker 1: we're running some vault episodes because we're out this week. 4 00:00:13,840 --> 00:00:17,639 Speaker 1: This episode originally aired February third, twenty twenty two, and 5 00:00:17,640 --> 00:00:20,800 Speaker 1: it's part two of our series on thirst. Get right 6 00:00:20,840 --> 00:00:26,279 Speaker 1: in Welcome to Stuff to Blow Your Mind, a production 7 00:00:26,320 --> 00:00:35,760 Speaker 1: of iHeartRadio. Hey, welcome to Stuff to Blow your Mind. 8 00:00:35,880 --> 00:00:38,479 Speaker 1: My name is Robert Lamb and I'm Joe McCormick, and 9 00:00:38,520 --> 00:00:41,479 Speaker 1: we're back with part two of our series on thirst. 10 00:00:41,920 --> 00:00:44,960 Speaker 1: What are you drinking right now? Absolutely nothing? Oh no, wait, 11 00:00:45,000 --> 00:00:47,200 Speaker 1: I do have I have water here at my desk. Water. 12 00:00:47,320 --> 00:00:50,360 Speaker 1: I'm always drinking water. I'm a water guy. You know, 13 00:00:50,400 --> 00:00:53,440 Speaker 1: some people are really into tea. I almost never drink tea. 14 00:00:53,600 --> 00:00:57,400 Speaker 1: I go coffee water. That That's pretty much it during 15 00:00:57,400 --> 00:01:01,080 Speaker 1: the daytime hours at least. Oh yeah, well, I'm currently 16 00:01:01,160 --> 00:01:07,960 Speaker 1: drinking tea. I generally go coffee tea, tea, water tea, 17 00:01:08,319 --> 00:01:11,480 Speaker 1: and then water, and then when the evening comes, you know, 18 00:01:11,600 --> 00:01:14,440 Speaker 1: maybe I'll have something something else to drink. But yeah, 19 00:01:14,520 --> 00:01:18,720 Speaker 1: right now it is tea, which is essentially water but 20 00:01:18,880 --> 00:01:21,200 Speaker 1: with extra things added to it. You know, I sometimes 21 00:01:21,280 --> 00:01:25,080 Speaker 1: get confused about what tea means because I think of 22 00:01:25,120 --> 00:01:28,680 Speaker 1: tea as being a specific kind of plant, Like, isn't 23 00:01:28,720 --> 00:01:31,800 Speaker 1: there a tea tree? Again, I don't know much about tea, 24 00:01:31,840 --> 00:01:35,160 Speaker 1: so I think about it in that way. But then 25 00:01:35,319 --> 00:01:38,640 Speaker 1: you can make a tea out of like anything basically 26 00:01:38,680 --> 00:01:41,360 Speaker 1: that you steep in water, right, people make mushroom teas, 27 00:01:41,480 --> 00:01:43,160 Speaker 1: people with all kinds of just like oh yeahs and 28 00:01:43,200 --> 00:01:46,840 Speaker 1: plant stuff in water, and that's tea. Also, yeah, like 29 00:01:46,880 --> 00:01:48,760 Speaker 1: I mean, there's there's proper tea, and that's generally what 30 00:01:48,840 --> 00:01:51,720 Speaker 1: I'm what I'm drinking. I'm drinking, you know, a dark 31 00:01:51,720 --> 00:01:54,360 Speaker 1: tea or maybe a green tea. But also sometimes I'll 32 00:01:54,400 --> 00:01:58,280 Speaker 1: have a tumeric tea, which is like like tumeric and 33 00:01:58,360 --> 00:02:01,080 Speaker 1: ginger and a little coconut oil and a little honey 34 00:02:01,320 --> 00:02:04,120 Speaker 1: hot water. But it doesn't actually contain tea, So it's 35 00:02:04,520 --> 00:02:07,480 Speaker 1: not completely accurate to call it such, because it's sort 36 00:02:07,480 --> 00:02:10,960 Speaker 1: of how not all band aids are technically band aids 37 00:02:11,440 --> 00:02:14,640 Speaker 1: or xeroxis or whatever. Has this been a terrible intro, 38 00:02:14,760 --> 00:02:17,000 Speaker 1: Maybe we can cut my tea thing. No, No, this 39 00:02:17,040 --> 00:02:19,919 Speaker 1: is a This is an intro that the people can 40 00:02:19,960 --> 00:02:22,040 Speaker 1: relate to people are can have thoughts on this. It's 41 00:02:22,040 --> 00:02:24,639 Speaker 1: always good to start off asking what a word means. 42 00:02:25,040 --> 00:02:27,520 Speaker 1: So I turns out I know nothing about tea. I 43 00:02:27,520 --> 00:02:29,600 Speaker 1: have no no, there you go. We need to come 44 00:02:29,600 --> 00:02:32,160 Speaker 1: back and do an episode or a series of episodes 45 00:02:32,200 --> 00:02:36,160 Speaker 1: on t It's a fascinating subject, fascinating history. Okay, well, 46 00:02:36,240 --> 00:02:39,080 Speaker 1: we're going to jump back into some of the science 47 00:02:39,120 --> 00:02:41,200 Speaker 1: that we were talking about in the last episode, where 48 00:02:41,240 --> 00:02:44,919 Speaker 1: I was reviewing an interesting paper that I had read 49 00:02:44,960 --> 00:02:50,400 Speaker 1: summarizing the recent state of research on the biology of thirst. 50 00:02:50,560 --> 00:02:53,400 Speaker 1: That was it was a paper published in Current Biology. 51 00:02:53,960 --> 00:02:55,639 Speaker 1: We had to break off in the middle of talking 52 00:02:55,639 --> 00:02:59,160 Speaker 1: about it. But but before we get back into that, Rob, 53 00:02:59,200 --> 00:03:02,320 Speaker 1: I think you want to talk about the taste of water, 54 00:03:02,400 --> 00:03:06,160 Speaker 1: which I think is in itself a very interesting subject. Yeah, 55 00:03:06,160 --> 00:03:08,480 Speaker 1: it's it's a strange one because we probably don't think 56 00:03:08,480 --> 00:03:11,720 Speaker 1: about it enough, but but we often talk about it, 57 00:03:11,800 --> 00:03:14,280 Speaker 1: especially when we when we travel from one place to another. 58 00:03:14,760 --> 00:03:18,120 Speaker 1: UM we if you look back on I think back 59 00:03:18,400 --> 00:03:21,200 Speaker 1: on water that you've consumed in the past, you may 60 00:03:21,240 --> 00:03:25,600 Speaker 1: have specific memories of different waters. Um Like I remember 61 00:03:25,600 --> 00:03:28,520 Speaker 1: when my family lived in the country and we had 62 00:03:28,560 --> 00:03:32,240 Speaker 1: well water and it had it had a distinctive taste, 63 00:03:32,800 --> 00:03:35,240 Speaker 1: and I don't I can't say that I loved it, 64 00:03:35,720 --> 00:03:38,360 Speaker 1: But if I were to encounter the exact same flavor 65 00:03:38,400 --> 00:03:40,800 Speaker 1: profile again, it would probably make me nostalgic, you know, 66 00:03:40,920 --> 00:03:44,320 Speaker 1: like it it's it's a definite flavor that is tied 67 00:03:44,360 --> 00:03:46,720 Speaker 1: to a definite place and time. Warning that this is 68 00:03:46,720 --> 00:03:48,640 Speaker 1: a little crude, but I don't know of how else 69 00:03:48,680 --> 00:03:53,600 Speaker 1: to explain it. You've ever been somewhere that had farty water, Um, well, 70 00:03:53,640 --> 00:03:56,200 Speaker 1: it's kind of sulfury water. Yeah, it kind of kind 71 00:03:56,200 --> 00:03:58,840 Speaker 1: of like water from the Yes, that's kind of what 72 00:03:58,880 --> 00:04:00,920 Speaker 1: this was like. Yeah, it was that had kind of 73 00:04:00,960 --> 00:04:05,240 Speaker 1: a fire and brimstone kind of flavor to it. Oh okay, 74 00:04:05,320 --> 00:04:06,960 Speaker 1: that's a more elegant way to put it. Well, the 75 00:04:07,040 --> 00:04:09,360 Speaker 1: denizens of Hell are not insalted. They're flatter that you 76 00:04:09,360 --> 00:04:12,720 Speaker 1: would you would compare this foul drinking water two flats, 77 00:04:13,240 --> 00:04:17,080 Speaker 1: uh huh. But um, you know, but then sometimes I 78 00:04:17,120 --> 00:04:19,160 Speaker 1: don't know, there's there's also beech water, you know, like 79 00:04:19,200 --> 00:04:23,320 Speaker 1: I anytime I'm in Florida and I'm having Florida water, 80 00:04:23,720 --> 00:04:25,480 Speaker 1: like it has its own it tends to have its 81 00:04:25,480 --> 00:04:29,880 Speaker 1: own bouquet, its own flavor. Profile that at the time 82 00:04:29,920 --> 00:04:32,640 Speaker 1: I'm not enjoying, but then after I'm back and drinking 83 00:04:32,760 --> 00:04:35,880 Speaker 1: taste your water, I'm kind of kind of long for it, 84 00:04:35,920 --> 00:04:39,080 Speaker 1: you know, because like this is the water of the 85 00:04:39,200 --> 00:04:42,200 Speaker 1: vacation that I am no longer on that sort of thing. 86 00:04:42,520 --> 00:04:44,719 Speaker 1: I remember when I was in like a middle school, 87 00:04:44,760 --> 00:04:47,240 Speaker 1: I went to New Mexico and we went somewhere there 88 00:04:47,240 --> 00:04:50,800 Speaker 1: where the water was very I don't know, the tap 89 00:04:50,839 --> 00:04:54,200 Speaker 1: water was almost kind of frothy somehow. It was like 90 00:04:54,240 --> 00:04:57,320 Speaker 1: a kind of kind of white and cloudy, and I 91 00:04:57,320 --> 00:05:00,360 Speaker 1: remember thinking it had a strange taste. I don't know 92 00:05:00,400 --> 00:05:02,200 Speaker 1: what to connect that too, if it was supposed to 93 00:05:02,200 --> 00:05:05,720 Speaker 1: be like that or not. Yeah, So I guess one 94 00:05:05,760 --> 00:05:10,080 Speaker 1: thing we can definitely establish here is that there certainly 95 00:05:10,080 --> 00:05:12,960 Speaker 1: seems to there is an objective difference in drinking waters 96 00:05:13,480 --> 00:05:17,520 Speaker 1: from one place to another, Atlanta water versus Florida water, 97 00:05:17,560 --> 00:05:20,719 Speaker 1: that sort of thing. But there's also this wide variety 98 00:05:20,839 --> 00:05:25,159 Speaker 1: in how people just interpret the taste of water, you know. 99 00:05:25,200 --> 00:05:28,520 Speaker 1: I think we often think of water as being neutral 100 00:05:28,720 --> 00:05:32,120 Speaker 1: or tasteless. If you're mixing a cocktail, for example, you 101 00:05:32,120 --> 00:05:34,640 Speaker 1: don't want to shake it too long with the crushed 102 00:05:34,640 --> 00:05:36,919 Speaker 1: ice because you will what will happen, You will water 103 00:05:37,040 --> 00:05:40,160 Speaker 1: it down. Water in this case is the antithesis of 104 00:05:40,160 --> 00:05:43,520 Speaker 1: an interesting flavor profile. Well, but the other half of 105 00:05:43,560 --> 00:05:46,679 Speaker 1: that is sometimes people screw up making a drink because 106 00:05:46,720 --> 00:05:48,400 Speaker 1: they don't shake it with ice at all when they're 107 00:05:48,440 --> 00:05:51,880 Speaker 1: supposed to, and they don't understand that shaking with ice 108 00:05:52,000 --> 00:05:54,400 Speaker 1: not only cools the drink, but it also adds a 109 00:05:54,440 --> 00:05:56,560 Speaker 1: certain amount of water to the drink, which is an 110 00:05:56,600 --> 00:06:00,480 Speaker 1: important ingredient. Yes, absolutely so. You suppose to shake a 111 00:06:00,520 --> 00:06:02,400 Speaker 1: cocktail and you don't, you end up with a drink 112 00:06:02,440 --> 00:06:05,599 Speaker 1: that's usually too strong or too sweet. Yeah, there's a 113 00:06:05,600 --> 00:06:08,160 Speaker 1: balance to be maintained there, much like the balance of 114 00:06:09,000 --> 00:06:11,120 Speaker 1: water in the human body that we discussed in the 115 00:06:11,200 --> 00:06:13,480 Speaker 1: last episode. Many of you out there have probably met 116 00:06:13,520 --> 00:06:15,880 Speaker 1: someone who claims to not like the taste of water. 117 00:06:16,960 --> 00:06:21,560 Speaker 1: Sometimes these individuals will will use flavored water or other 118 00:06:21,600 --> 00:06:23,840 Speaker 1: beverages instead, and we'll tend to shy away from just 119 00:06:23,920 --> 00:06:27,920 Speaker 1: drinking straight water. But I don't know if you're like me, 120 00:06:28,400 --> 00:06:31,080 Speaker 1: you know, perhaps you've noticed times when a glass of 121 00:06:31,120 --> 00:06:34,560 Speaker 1: ice water is just super satisfying. Um, you know, particularly 122 00:06:34,640 --> 00:06:37,279 Speaker 1: on a hot day, like a just a super cold 123 00:06:37,320 --> 00:06:39,919 Speaker 1: water lots of ice in it. Um I would, I 124 00:06:39,960 --> 00:06:43,720 Speaker 1: would tend to. I found myself wanting to categorize that 125 00:06:43,800 --> 00:06:47,200 Speaker 1: as delicious, though at the same time feeling weird for 126 00:06:47,279 --> 00:06:50,200 Speaker 1: thinking that because it's like it's water. I can't say 127 00:06:50,200 --> 00:06:53,960 Speaker 1: it's delicious. It has no flavor, right, that's what we believe. 128 00:06:54,560 --> 00:06:57,919 Speaker 1: Another another one I really like is the first sip 129 00:06:57,960 --> 00:07:00,760 Speaker 1: of cold water that I have after I have brushed 130 00:07:00,800 --> 00:07:04,159 Speaker 1: my teeth. Now, after I've brushed my teeth and rinsed 131 00:07:04,160 --> 00:07:08,320 Speaker 1: and spit I'm not drinking water that way, but yeah, like, 132 00:07:08,320 --> 00:07:10,640 Speaker 1: after I've brushed my teeth, I've walked into another room, 133 00:07:10,800 --> 00:07:13,640 Speaker 1: I have a sip of water, super cool and refreshing. Agreed, 134 00:07:13,760 --> 00:07:15,880 Speaker 1: much better than the sip of orange juice after you've 135 00:07:15,880 --> 00:07:18,040 Speaker 1: brushed your teeth, which is, Yeah, I don't know if 136 00:07:18,040 --> 00:07:23,120 Speaker 1: you've ever tried that, it's famously disgusting. Oh this is 137 00:07:23,160 --> 00:07:26,040 Speaker 1: this is always the worst. Really getting into the weeds here, 138 00:07:26,160 --> 00:07:30,440 Speaker 1: but that that feeling when you you were you're busy 139 00:07:30,440 --> 00:07:32,880 Speaker 1: in the morning, you go brush your teeth, you come 140 00:07:32,880 --> 00:07:34,960 Speaker 1: back and you find your coffee cup and it still 141 00:07:35,000 --> 00:07:37,880 Speaker 1: has half a cup of coffee in it. Oh, heartbreaking, 142 00:07:38,280 --> 00:07:40,080 Speaker 1: because you know you can't drink it. Now. If you drink, 143 00:07:40,120 --> 00:07:42,040 Speaker 1: you can drink it, you can you can throw it back, 144 00:07:42,240 --> 00:07:44,560 Speaker 1: but it's going to taste awful. I wonder if anybody's 145 00:07:44,560 --> 00:07:46,880 Speaker 1: ever done a controlled study of how long you have 146 00:07:47,040 --> 00:07:50,080 Speaker 1: to wait after brushing your teeth before those those horrible 147 00:07:50,120 --> 00:07:53,840 Speaker 1: flavor interactions fade away. I don't think it's too long, 148 00:07:54,000 --> 00:07:56,160 Speaker 1: it's yeah. I mean, if I had to venture to guess, 149 00:07:56,160 --> 00:08:00,000 Speaker 1: I'd say it couldn't be more than like twenty minutes, right, Yeah, 150 00:08:00,080 --> 00:08:01,040 Speaker 1: of course, a lot of this, some of this is 151 00:08:01,040 --> 00:08:03,440 Speaker 1: going to vary culture to culture. In some cultures, it's 152 00:08:03,480 --> 00:08:07,480 Speaker 1: not it's not considered advisable to drink cold water. You 153 00:08:07,480 --> 00:08:10,920 Speaker 1: want to drink hot water. So you know, there's it's 154 00:08:11,000 --> 00:08:12,520 Speaker 1: gonna it's gonna it's gonna vary. There's a lot of 155 00:08:12,560 --> 00:08:15,040 Speaker 1: cultural stuff going on here as well. Oh I've never 156 00:08:15,080 --> 00:08:17,360 Speaker 1: heard of that. What's what's an example of a culture 157 00:08:17,400 --> 00:08:21,240 Speaker 1: that favors hot water drinking. There's a connection if memory 158 00:08:21,240 --> 00:08:24,080 Speaker 1: serves as a connection to traditional Chinese medicine here, where 159 00:08:25,400 --> 00:08:27,960 Speaker 1: the idea is that it's better for your health to 160 00:08:28,120 --> 00:08:30,960 Speaker 1: drink hot water as opposed to cold water. But I 161 00:08:30,960 --> 00:08:34,320 Speaker 1: don't remember any of the deeper details of regarding it all. Right, Well, 162 00:08:34,320 --> 00:08:37,120 Speaker 1: to get us back on track, you had mentioned that 163 00:08:38,520 --> 00:08:41,040 Speaker 1: maybe maybe it was wrong to say that tap water, 164 00:08:41,280 --> 00:08:43,199 Speaker 1: you know, cold water coming in on a hot day 165 00:08:43,320 --> 00:08:47,960 Speaker 1: was delicious because water itself doesn't really have a taste. 166 00:08:48,000 --> 00:08:51,840 Speaker 1: And I think this is a common understanding. But is 167 00:08:51,880 --> 00:08:54,880 Speaker 1: that true? Like it does it have a taste? Does 168 00:08:54,920 --> 00:08:56,560 Speaker 1: it not have a taste? Does it have a taste? 169 00:08:56,559 --> 00:09:00,720 Speaker 1: We're just so used to that we can't taste it anymore. Yeah, 170 00:09:01,800 --> 00:09:04,880 Speaker 1: we'll like to. Well, to go back to Aristotle, Aristotle 171 00:09:04,960 --> 00:09:08,000 Speaker 1: was certainly kind of in the no taste camp, stating 172 00:09:08,040 --> 00:09:11,120 Speaker 1: that it was for the most part tasteless. The idea 173 00:09:11,160 --> 00:09:14,440 Speaker 1: that water is that it made liver flavors, but it's 174 00:09:15,160 --> 00:09:17,640 Speaker 1: in and of itself does not have flavor. But a 175 00:09:17,679 --> 00:09:19,800 Speaker 1: lot of a lot of work has gone into this 176 00:09:19,800 --> 00:09:24,240 Speaker 1: this question. Uh, some some interesting studies. UM. I was 177 00:09:24,280 --> 00:09:28,520 Speaker 1: reading an article by Berlin Game at All titled Understanding 178 00:09:28,520 --> 00:09:32,240 Speaker 1: the Basics of Tapwater Taste, publishing the American Water Works 179 00:09:32,280 --> 00:09:36,800 Speaker 1: Association Journal in two thousand and seven. UM, and they 180 00:09:36,840 --> 00:09:41,640 Speaker 1: point out that the basically you get the water is 181 00:09:41,679 --> 00:09:45,960 Speaker 1: going to contain negatively and positively charged ions as minerals, 182 00:09:46,480 --> 00:09:48,080 Speaker 1: you're going to find that in your tap water, and 183 00:09:48,120 --> 00:09:52,560 Speaker 1: that can positively and negatively affect taste. This is especially key, 184 00:09:52,600 --> 00:09:55,280 Speaker 1: they point out as far as water regulations and reverse 185 00:09:55,320 --> 00:09:58,439 Speaker 1: osmoses go, which is to say, without without getting into 186 00:09:58,480 --> 00:10:01,720 Speaker 1: all the chemistry, there are certain differences in water flavor 187 00:10:01,800 --> 00:10:04,880 Speaker 1: due to different minerals and other elements in the water. Now, 188 00:10:04,920 --> 00:10:09,960 Speaker 1: another interesting thing about about tap water, especially generally when 189 00:10:10,000 --> 00:10:17,959 Speaker 1: you're drinking tap water, the drinking water probably contains calcium, magnesium, sodium, 190 00:10:18,040 --> 00:10:22,600 Speaker 1: and according to Azolae at All in an article in 191 00:10:22,640 --> 00:10:26,319 Speaker 1: the Journal of General Internal Medicine from two thousand and 192 00:10:26,360 --> 00:10:28,880 Speaker 1: one titled Comparison of Mineral Content of tap water and 193 00:10:28,920 --> 00:10:33,440 Speaker 1: bottled waters, the mineral content of drinking water like this 194 00:10:33,679 --> 00:10:38,800 Speaker 1: ultimately may be an important source of daily recommended mineral dosages, 195 00:10:39,400 --> 00:10:41,760 Speaker 1: certainly in the United States, which was the area they 196 00:10:41,760 --> 00:10:46,400 Speaker 1: were looking at here. And so basically, while we might 197 00:10:46,480 --> 00:10:48,840 Speaker 1: think of water as being this thing that we would 198 00:10:48,640 --> 00:10:51,360 Speaker 1: will just purify the heck out of it, just give 199 00:10:51,400 --> 00:10:55,280 Speaker 1: me the purest water possible, the purest water possible isn't 200 00:10:55,320 --> 00:10:58,800 Speaker 1: necessarily going to be the healthiest or the tastiest, which 201 00:10:58,880 --> 00:11:01,839 Speaker 1: I thought was an interest distinction, like when when we 202 00:11:02,000 --> 00:11:05,400 Speaker 1: when we purchase bottled water, we're not going and buying 203 00:11:05,440 --> 00:11:08,199 Speaker 1: the distilled water usually. I mean, maybe, you know, maybe 204 00:11:08,240 --> 00:11:09,960 Speaker 1: that's what you are doing, but for the most part, 205 00:11:10,240 --> 00:11:14,720 Speaker 1: people are are not buying distilled water for drinking purposes. Right. 206 00:11:14,880 --> 00:11:17,760 Speaker 1: But distilled water, even though it is probably the purest 207 00:11:17,840 --> 00:11:21,120 Speaker 1: form of water you can get, is not necessarily better 208 00:11:21,320 --> 00:11:24,520 Speaker 1: for any reason, not for not for health or for 209 00:11:24,640 --> 00:11:28,160 Speaker 1: experience of drinking. Right now, in terms of just trying 210 00:11:28,160 --> 00:11:29,880 Speaker 1: to get down to the question though, well, what what 211 00:11:29,960 --> 00:11:32,240 Speaker 1: does it taste like? Okay, you know, we're saying it 212 00:11:32,280 --> 00:11:34,200 Speaker 1: can can go a little in this direction, a little 213 00:11:34,240 --> 00:11:37,200 Speaker 1: in that direction. We have these mineral components, uh, you know, 214 00:11:37,240 --> 00:11:40,040 Speaker 1: adding to the to the flavor. But but what is 215 00:11:40,040 --> 00:11:42,280 Speaker 1: the taste itself? And I think one of the interesting 216 00:11:42,280 --> 00:11:44,240 Speaker 1: things about that question is that it forces you to 217 00:11:44,240 --> 00:11:47,800 Speaker 1: take a step back and think about taste itself. Um, 218 00:11:47,840 --> 00:11:51,880 Speaker 1: you know, taste involves both sensations on the tongue and 219 00:11:52,160 --> 00:11:55,320 Speaker 1: olfactory information as well. So it's not only it's not 220 00:11:55,360 --> 00:11:59,199 Speaker 1: only tasting with the mouth, it's smelling, uh whatever you 221 00:11:59,240 --> 00:12:03,520 Speaker 1: know it is that you or consuming as well. And 222 00:12:04,000 --> 00:12:07,959 Speaker 1: certainly we do taste contents in the water, though under 223 00:12:08,120 --> 00:12:11,080 Speaker 1: ideal circumstances that that's not going to push you hard 224 00:12:11,120 --> 00:12:14,280 Speaker 1: in any direction. But obviously, if you dilute some sugar 225 00:12:14,400 --> 00:12:17,000 Speaker 1: in a glass of the universal solvent and drink it, 226 00:12:17,240 --> 00:12:20,960 Speaker 1: you'll find it sweet. Saltwater taste salty. Your sense of 227 00:12:21,000 --> 00:12:24,160 Speaker 1: taste is still weighing in on the water. But in 228 00:12:24,240 --> 00:12:26,880 Speaker 1: terms of this kind of brings us back to the 229 00:12:26,880 --> 00:12:29,320 Speaker 1: same question, does the water itself have a taste or 230 00:12:29,360 --> 00:12:31,640 Speaker 1: is it just the vehicle for these various flavors, be 231 00:12:31,720 --> 00:12:37,240 Speaker 1: it salt or sugar, or a slight hint of magnesium, 232 00:12:37,280 --> 00:12:41,160 Speaker 1: that sort of thing. So one idea proposed in the 233 00:12:41,200 --> 00:12:45,600 Speaker 1: sixties and seventies by psychologist Linda Bartschuk was that the 234 00:12:45,640 --> 00:12:48,760 Speaker 1: taste of water is more of an after taste of 235 00:12:48,840 --> 00:12:51,959 Speaker 1: prior eating and drinking. And this, too, I guess, is 236 00:12:52,000 --> 00:12:53,720 Speaker 1: more in line with the idea of water as the 237 00:12:53,800 --> 00:12:55,840 Speaker 1: vehicle of flavor, but something that is in and of 238 00:12:55,840 --> 00:13:00,760 Speaker 1: itself flavorless. So the idea would be that, like when 239 00:13:00,840 --> 00:13:04,640 Speaker 1: you take a drink of water, you are somehow re 240 00:13:04,880 --> 00:13:10,280 Speaker 1: experiencing flavors of foods you may have eaten most recently. Yeah, 241 00:13:10,280 --> 00:13:12,480 Speaker 1: and this this will become important. And again we have 242 00:13:12,559 --> 00:13:15,040 Speaker 1: to realize that when you take a sip of water, 243 00:13:15,679 --> 00:13:20,160 Speaker 1: you are not introducing water. No matter how sterile your 244 00:13:20,160 --> 00:13:24,199 Speaker 1: water is, your mouth is not sterile. You know your 245 00:13:24,280 --> 00:13:26,240 Speaker 1: your mouth is going to even if you if you've 246 00:13:26,280 --> 00:13:28,920 Speaker 1: just brushed your teeth, great, but that you're going to 247 00:13:29,000 --> 00:13:34,040 Speaker 1: have some semblance of the of that experience in your mouth. 248 00:13:34,080 --> 00:13:35,880 Speaker 1: If you're eating dinner, you know there's going to be 249 00:13:35,920 --> 00:13:39,360 Speaker 1: the hint of food or drink as well. So, yeah, 250 00:13:39,360 --> 00:13:41,920 Speaker 1: you're not introducing the water into a neutral place. If 251 00:13:41,920 --> 00:13:45,640 Speaker 1: nothing else you your saliva is present. Emily Underwood wrote 252 00:13:45,640 --> 00:13:48,600 Speaker 1: in an excellent short twenty seventeen piece for the American 253 00:13:48,640 --> 00:13:51,480 Speaker 1: Association for the Advancement of Science on this topic, the 254 00:13:51,600 --> 00:13:55,960 Speaker 1: Flavor of Water, And at one point she's a sighting 255 00:13:56,040 --> 00:13:59,040 Speaker 1: Zachary Knight, Oh, who is one of the three authors 256 00:13:59,080 --> 00:14:03,200 Speaker 1: of the research summary thirst in Current Biology that I 257 00:14:03,240 --> 00:14:05,040 Speaker 1: was referring to in the last episode and I'll be 258 00:14:05,280 --> 00:14:08,680 Speaker 1: talking about again in a few minutes. Yeah, So Underwood 259 00:14:08,679 --> 00:14:12,560 Speaker 1: points to something that that we discussed in the last 260 00:14:12,559 --> 00:14:14,840 Speaker 1: episode that you know, ultimately, when we're getting into taste, 261 00:14:15,160 --> 00:14:19,160 Speaker 1: when we're getting into water detection in the mouth, the 262 00:14:19,200 --> 00:14:23,080 Speaker 1: molecular and cellular mechanisms here are not that well understood. 263 00:14:23,520 --> 00:14:28,080 Speaker 1: And then she also touches on some of nights research 264 00:14:28,160 --> 00:14:32,560 Speaker 1: regarding the thirst trigger. Uh, you know where where that 265 00:14:32,720 --> 00:14:35,920 Speaker 1: is seems to locate in the brain and then ultimately 266 00:14:35,960 --> 00:14:38,080 Speaker 1: what's where is the trigger in the in the rest 267 00:14:38,080 --> 00:14:40,080 Speaker 1: of the body. But we'll come back to that in 268 00:14:40,080 --> 00:14:43,240 Speaker 1: a bit. Yeah, but I guess there are somewhat separate 269 00:14:43,320 --> 00:14:48,400 Speaker 1: questions for can you detect water in your mouth versus 270 00:14:48,480 --> 00:14:54,080 Speaker 1: can you taste water? I mean those are slightly slightly different, right, yeah, well, 271 00:14:54,200 --> 00:14:56,880 Speaker 1: but but then again when you start thinking about like 272 00:14:56,920 --> 00:15:00,520 Speaker 1: what taste is, maybe they're not that different, like it's 273 00:15:00,960 --> 00:15:02,840 Speaker 1: but but it basically comes down to, yeah, it's not 274 00:15:02,880 --> 00:15:05,800 Speaker 1: about interpreting these minerals or sweetness or saltiness, but like 275 00:15:06,520 --> 00:15:10,040 Speaker 1: the just the basic signal of it is water. It 276 00:15:10,160 --> 00:15:13,680 Speaker 1: is in my mouth, you know, and then ultimately being 277 00:15:13,720 --> 00:15:17,520 Speaker 1: able to tell if something is not water, like or 278 00:15:17,560 --> 00:15:19,200 Speaker 1: if it or if the water is you know, too 279 00:15:19,200 --> 00:15:21,560 Speaker 1: far in a particular direction, like oh it is it 280 00:15:21,680 --> 00:15:25,600 Speaker 1: is actually oil and water and not just water. I 281 00:15:25,640 --> 00:15:29,160 Speaker 1: wanted water. That's sort of question. So research has been 282 00:15:29,160 --> 00:15:32,760 Speaker 1: trying to isolate water sensing taste receptor. It sells on 283 00:15:32,880 --> 00:15:36,240 Speaker 1: the tongue of a particular note. Here is the paper 284 00:15:36,280 --> 00:15:39,400 Speaker 1: The Cellular Mechanism for Water Detection in the Mammalian Taste 285 00:15:39,440 --> 00:15:43,600 Speaker 1: system by Zocchi at All, published in Nature Neuroscience in 286 00:15:43,640 --> 00:15:48,280 Speaker 1: twenty seventeen. This was a team i believe from the 287 00:15:48,320 --> 00:15:51,760 Speaker 1: California Institute of Technology in Pasadena, and they were working 288 00:15:51,760 --> 00:15:54,280 Speaker 1: with mice and this is this is one of those 289 00:15:54,400 --> 00:15:57,120 Speaker 1: the studies that I mean, it's already an interesting area, 290 00:15:57,240 --> 00:15:59,840 Speaker 1: like using mice to figure out how we're tasting, but 291 00:16:00,000 --> 00:16:04,840 Speaker 1: and it goes in ultimately strange directions that are pretty fascinating. 292 00:16:05,200 --> 00:16:08,280 Speaker 1: So they were they were using different varieties of mice 293 00:16:08,400 --> 00:16:12,760 Speaker 1: with specific types of taste receptor cells genetically knocked out 294 00:16:13,160 --> 00:16:16,680 Speaker 1: in order to try and isolate which ones were seemingly 295 00:16:16,800 --> 00:16:20,240 Speaker 1: useful in tasting water. And they found that the acid 296 00:16:20,360 --> 00:16:24,680 Speaker 1: sensing sour taste receptor cells seem to be the most involved. 297 00:16:25,480 --> 00:16:29,960 Speaker 1: Mice with those knocked out took far longer distinguishing oily 298 00:16:30,000 --> 00:16:34,560 Speaker 1: water from clean water. In the words of the study, 299 00:16:34,920 --> 00:16:39,760 Speaker 1: this quote compromise discrimination between water and non aqueous fluids. 300 00:16:40,360 --> 00:16:43,200 Speaker 1: So these cells seem like they may they may well 301 00:16:43,240 --> 00:16:47,920 Speaker 1: be very much involved in the process. Interesting, Okay, so 302 00:16:48,040 --> 00:16:52,280 Speaker 1: if we are actually tasting water, it may rely more 303 00:16:52,400 --> 00:16:56,520 Speaker 1: on the cells that normally taste sourness or acidity than 304 00:16:56,600 --> 00:16:59,280 Speaker 1: other taste receptor cells, or at least in mice, And 305 00:16:59,360 --> 00:17:01,560 Speaker 1: if the same held true in humans, that would be 306 00:17:01,640 --> 00:17:04,399 Speaker 1: the case for us. Right. But this is where the 307 00:17:04,440 --> 00:17:09,400 Speaker 1: mouse experiment from this team gets weird. So to further 308 00:17:09,480 --> 00:17:12,600 Speaker 1: test this out, they bred mice that could taste light 309 00:17:13,000 --> 00:17:18,120 Speaker 1: with these acid sensing TRCs taste receptor cells. They train 310 00:17:18,240 --> 00:17:20,960 Speaker 1: them to drink water from a spigot, and they replace 311 00:17:21,080 --> 00:17:26,760 Speaker 1: that spigot with an optic fiber cable. So they apparently 312 00:17:26,800 --> 00:17:29,840 Speaker 1: treated the mice in this case, they apparently treated the 313 00:17:29,920 --> 00:17:33,240 Speaker 1: light as if they were tasting water, but they didn't stop. 314 00:17:33,280 --> 00:17:37,840 Speaker 1: They kept drinking the light long after they would have 315 00:17:38,320 --> 00:17:42,680 Speaker 1: normally stopped drinking water. So the acid sensing TRCs might 316 00:17:42,720 --> 00:17:45,919 Speaker 1: be involved in triggering drinking, but they might not be 317 00:17:45,960 --> 00:17:48,640 Speaker 1: involved in stopping you from drinking, like saying, Okay, well, 318 00:17:48,640 --> 00:17:50,800 Speaker 1: that's that's all the water I need to drink right now, 319 00:17:52,440 --> 00:17:55,480 Speaker 1: and I'm not sure there may be other complications there. 320 00:17:55,520 --> 00:17:58,159 Speaker 1: I mean, once you have an animal drinking light and 321 00:17:58,280 --> 00:18:01,159 Speaker 1: not actual water. It just seems to me like there 322 00:18:01,240 --> 00:18:02,879 Speaker 1: might there might be other things going on there. I'll 323 00:18:02,920 --> 00:18:05,639 Speaker 1: on a very physical basis, so this would be taste 324 00:18:05,680 --> 00:18:09,880 Speaker 1: receptor cells in the mouth, but they're like optically sensitive cells. 325 00:18:10,200 --> 00:18:13,480 Speaker 1: Am I right about this? It's literally like drinking light 326 00:18:13,600 --> 00:18:17,720 Speaker 1: with their mouth, like letting light shine into the oral cavity. Yes, 327 00:18:17,960 --> 00:18:21,400 Speaker 1: it h I mean, it sounds insane when you say 328 00:18:21,440 --> 00:18:23,600 Speaker 1: it out loud, but but yeah, there's there's actually a 329 00:18:24,359 --> 00:18:27,840 Speaker 1: YouTube video about it from Science Magazine titled these mice 330 00:18:27,880 --> 00:18:31,840 Speaker 1: are drinking light. So if anyone needs to actually see 331 00:18:31,880 --> 00:18:34,600 Speaker 1: what we're talking about here, pull that up. And yeah, 332 00:18:34,680 --> 00:18:38,239 Speaker 1: just it's it's a this, this black mouse going up 333 00:18:38,280 --> 00:18:41,919 Speaker 1: to this um this little receptacle, and it appears to 334 00:18:41,920 --> 00:18:45,520 Speaker 1: be drinking, but there's blue light flooding out of the hole, okay, 335 00:18:45,520 --> 00:18:48,240 Speaker 1: and it's got light sensitive cells in its mouth, So 336 00:18:48,280 --> 00:18:51,400 Speaker 1: the mouse's brain is reacting as if by shining light 337 00:18:51,480 --> 00:18:56,080 Speaker 1: into its mouth it was swallowing water. Yes, that's crazy, man, 338 00:18:56,720 --> 00:19:00,760 Speaker 1: Yeah it is. This is this is it's it's mind 339 00:19:00,760 --> 00:19:04,640 Speaker 1: blowing on several levels here. So ultimately this this all 340 00:19:04,720 --> 00:19:08,000 Speaker 1: might be related to changes in pH level when in 341 00:19:08,040 --> 00:19:10,560 Speaker 1: a normal situation, when you know, a mouse or any 342 00:19:10,680 --> 00:19:14,400 Speaker 1: mammal supposedly is drinking something that is not light. When 343 00:19:14,440 --> 00:19:18,080 Speaker 1: it tries out the water, saliva is washing around in 344 00:19:18,119 --> 00:19:21,720 Speaker 1: the mouth, and the removal of saliva might be key 345 00:19:21,880 --> 00:19:24,280 Speaker 1: to sensing water. Again, coming back to what we said 346 00:19:24,280 --> 00:19:27,600 Speaker 1: earlier about you know, water is not entering into a 347 00:19:27,640 --> 00:19:30,280 Speaker 1: neutral environment when it goes in your mouth. It's going 348 00:19:30,280 --> 00:19:33,040 Speaker 1: to interact with at least saliva, and in doing so 349 00:19:33,359 --> 00:19:36,280 Speaker 1: that might change the pH level which triggers these these 350 00:19:36,359 --> 00:19:39,840 Speaker 1: TRCs on the tongue. That seems to be the basic 351 00:19:39,880 --> 00:19:43,240 Speaker 1: framework we're potentially looking at here. Oh, that's interesting. So 352 00:19:43,320 --> 00:19:46,600 Speaker 1: at least according to the idea here, part of the 353 00:19:46,720 --> 00:19:51,440 Speaker 1: sensation of drinking water might be the water stability to 354 00:19:51,480 --> 00:19:55,600 Speaker 1: wash natural saliva out of the mouth. Right though, of 355 00:19:55,600 --> 00:20:00,679 Speaker 1: course standard caveat that. More researches quired and then we 356 00:20:00,680 --> 00:20:02,720 Speaker 1: still don't We still don't have this one knocked one, 357 00:20:03,400 --> 00:20:06,520 Speaker 1: but it's yeah, it's it. Ultimately, it makes you rethink 358 00:20:06,560 --> 00:20:10,239 Speaker 1: again what taste actually is and consider that there may 359 00:20:10,240 --> 00:20:12,920 Speaker 1: be precise triggers in place for detecting water and distinguish 360 00:20:12,960 --> 00:20:16,080 Speaker 1: it from other liquids. And then also letting you know 361 00:20:16,119 --> 00:20:18,080 Speaker 1: that you have had enough water. Like all these things 362 00:20:18,119 --> 00:20:19,800 Speaker 1: that we just take for granted, we think of them 363 00:20:19,840 --> 00:20:22,440 Speaker 1: as we think of them as choices that we make, 364 00:20:22,880 --> 00:20:25,680 Speaker 1: like I have I am, I've decided now I must 365 00:20:25,760 --> 00:20:29,159 Speaker 1: have water. I have decided now that I don't need 366 00:20:29,240 --> 00:20:31,640 Speaker 1: any more water. But but these are all tied into 367 00:20:31,840 --> 00:20:42,360 Speaker 1: the you know, this intricate biological system. Than all right, well, rob, 368 00:20:42,440 --> 00:20:45,600 Speaker 1: if you're ready, I wanted to discuss some more of 369 00:20:45,760 --> 00:20:48,920 Speaker 1: the things I was reading in that twenty sixteen article 370 00:20:48,960 --> 00:20:53,320 Speaker 1: in Current Biology that was about the biology of thirst. Again. 371 00:20:53,400 --> 00:20:58,000 Speaker 1: This was by David Leeb, Christopher Zimmerman, and Zachary Knight. 372 00:20:58,560 --> 00:21:00,840 Speaker 1: Let's do it all right now. We already talked about 373 00:21:00,880 --> 00:21:05,000 Speaker 1: some of the conditions that will trigger thirst and water 374 00:21:05,080 --> 00:21:10,040 Speaker 1: seeking behavior in animals such as rodents. In humans, commonly, 375 00:21:10,600 --> 00:21:14,440 Speaker 1: one thing would be a decrease in water volume in 376 00:21:14,520 --> 00:21:16,800 Speaker 1: the body. But another thing would be an increase in 377 00:21:16,920 --> 00:21:22,440 Speaker 1: what's called blood osmolality osmol A L I T Y 378 00:21:23,200 --> 00:21:25,199 Speaker 1: I spell it because that word will keep coming up 379 00:21:25,280 --> 00:21:30,879 Speaker 1: in this discussion. Osmolality is the concentration of substances dissolved 380 00:21:31,160 --> 00:21:34,160 Speaker 1: in the water content of the body. So the blood 381 00:21:34,200 --> 00:21:37,720 Speaker 1: osmolality will go up, say if you consume salt or 382 00:21:37,920 --> 00:21:41,440 Speaker 1: consume other kinds of salts of various minerals, whether that's 383 00:21:41,480 --> 00:21:45,200 Speaker 1: sodium or magnesium or whatever, there are lots of things 384 00:21:45,320 --> 00:21:48,080 Speaker 1: dissolved in the blood, and as the concentration of those 385 00:21:48,200 --> 00:21:51,359 Speaker 1: things dissolved in the blood goes up, that's known as 386 00:21:51,480 --> 00:21:55,600 Speaker 1: increasing osmolality. And as we discussed in the last episode, 387 00:21:55,680 --> 00:21:59,840 Speaker 1: you your osmolality really needs to be pretty tightly constrained 388 00:22:00,080 --> 00:22:03,000 Speaker 1: within an ideal range, or it can start leading to 389 00:22:03,880 --> 00:22:08,240 Speaker 1: system wide problems with cellular function because cells need a 390 00:22:08,400 --> 00:22:12,440 Speaker 1: pretty tightly controlled electrochemical gradient on each side of their 391 00:22:13,040 --> 00:22:17,040 Speaker 1: membranes in order to control the passage of ions in 392 00:22:17,160 --> 00:22:19,200 Speaker 1: and out of the cell to you know, take in things, 393 00:22:19,280 --> 00:22:22,040 Speaker 1: the cell needs to release waste products and so forth. 394 00:22:22,600 --> 00:22:26,080 Speaker 1: So in order for your body to work right, it 395 00:22:26,240 --> 00:22:29,320 Speaker 1: needs to have the right level of the right concentration 396 00:22:29,720 --> 00:22:33,200 Speaker 1: of things like salts dissolved in its water. But you 397 00:22:33,359 --> 00:22:38,360 Speaker 1: also have to keep your body, your body's water volume 398 00:22:38,440 --> 00:22:42,200 Speaker 1: at the right level in order to maintain ideal blood 399 00:22:42,240 --> 00:22:44,960 Speaker 1: pressure because that blood's got to flow, and if you 400 00:22:45,040 --> 00:22:48,320 Speaker 1: suddenly are to remove a lot of liquid from the body, 401 00:22:48,720 --> 00:22:51,399 Speaker 1: suddenly the heart has to pump harder and harder to 402 00:22:51,480 --> 00:22:53,960 Speaker 1: get the red blood cells to all the different parts 403 00:22:54,000 --> 00:22:57,040 Speaker 1: of your body. So keeping up keeping up the right 404 00:22:57,119 --> 00:22:59,920 Speaker 1: amount of water in the body and the correct concentration 405 00:23:00,280 --> 00:23:04,600 Speaker 1: of substances dissolved in that water is crucial. And that 406 00:23:04,760 --> 00:23:07,760 Speaker 1: dichotomy we talked about last time actually breaks down into 407 00:23:08,040 --> 00:23:13,040 Speaker 1: two distinct types of dehydration that the authors talk about, 408 00:23:13,560 --> 00:23:16,719 Speaker 1: and these two types of dehydration actually lead to different 409 00:23:16,880 --> 00:23:21,720 Speaker 1: behavioral reactions in animals. So you can have dehydration within 410 00:23:21,920 --> 00:23:26,800 Speaker 1: cells or dehydration between cells. A loss of water from 411 00:23:26,920 --> 00:23:32,119 Speaker 1: within cells, known as intracellular dehydration, is usually caused by 412 00:23:32,280 --> 00:23:36,200 Speaker 1: high blood osmolality, so the introduction of salts or other 413 00:23:36,720 --> 00:23:40,320 Speaker 1: things like that into the body. This draws water out 414 00:23:40,359 --> 00:23:43,960 Speaker 1: of cells by osmosis and causes the cells to shrink, 415 00:23:44,119 --> 00:23:49,680 Speaker 1: which certainly doesn't sound good. Standard behavioral response to that 416 00:23:50,000 --> 00:23:54,960 Speaker 1: kind of thing that intracellular dehydration is thirst. You want water, 417 00:23:55,160 --> 00:23:57,760 Speaker 1: so you go get it. Loss of water from between 418 00:23:58,040 --> 00:24:02,240 Speaker 1: cells is known as extra cellular dehydration, and this usually 419 00:24:02,560 --> 00:24:05,639 Speaker 1: is caused by a loss of total blood volume, for 420 00:24:05,800 --> 00:24:08,320 Speaker 1: example by bleeding. You know, if you cut yourself and 421 00:24:08,480 --> 00:24:10,800 Speaker 1: lose a bunch of liquid out of your arm or something. 422 00:24:11,560 --> 00:24:16,359 Speaker 1: You will lose total blood content without changing the body's osmolality. 423 00:24:16,480 --> 00:24:17,960 Speaker 1: You know, you think about it that way, like you're 424 00:24:18,600 --> 00:24:21,040 Speaker 1: the liquid is going down, but you're not changing how 425 00:24:21,200 --> 00:24:24,840 Speaker 1: salty the liquid that's left is. So in order to 426 00:24:25,440 --> 00:24:28,320 Speaker 1: recover from that condition, you will actually need both water 427 00:24:28,640 --> 00:24:32,600 Speaker 1: and salt to replenish the lost volume. Just drinking water 428 00:24:32,720 --> 00:24:36,800 Speaker 1: alone would leave your osmolality too low. So the behavioral 429 00:24:36,880 --> 00:24:40,920 Speaker 1: response to loss of total water content or content from 430 00:24:40,960 --> 00:24:45,000 Speaker 1: between cells is usually thirst plus what the author is 431 00:24:45,040 --> 00:24:47,800 Speaker 1: called salt appetite. You want water and salt at the 432 00:24:47,840 --> 00:24:52,080 Speaker 1: same time, But interestingly, many things that happen to the 433 00:24:52,160 --> 00:24:55,920 Speaker 1: body cause both types of dehydration at the same time. 434 00:24:56,800 --> 00:24:59,719 Speaker 1: Then the example they give is sweating. This is very common, right, 435 00:25:00,000 --> 00:25:02,960 Speaker 1: you go out in the sun and you sweat. Well, 436 00:25:03,160 --> 00:25:07,199 Speaker 1: sweat is not only a loss of blood volume. Sweat 437 00:25:07,359 --> 00:25:11,480 Speaker 1: is salty, but sweat is actually less salty than your blood. 438 00:25:12,000 --> 00:25:14,960 Speaker 1: So if your body is losing liquid that is less 439 00:25:15,119 --> 00:25:18,879 Speaker 1: salty than its water content overall, like sweat is, the 440 00:25:19,040 --> 00:25:22,920 Speaker 1: salt content of what's left behind is therefore increasing. Does 441 00:25:22,960 --> 00:25:26,680 Speaker 1: that make sense, So the extra salt left over inside 442 00:25:26,720 --> 00:25:30,160 Speaker 1: you when you sweat causes an increase in blood osmolality, 443 00:25:30,320 --> 00:25:33,879 Speaker 1: again triggering a thirst for water. It's kind of counterintuitive 444 00:25:33,880 --> 00:25:36,280 Speaker 1: because if you ever do taste sweat it, you know, 445 00:25:36,359 --> 00:25:38,520 Speaker 1: it tastes salty, so you would think it would feel 446 00:25:38,560 --> 00:25:41,040 Speaker 1: like you're losing salt, but you're actually gaining salt is 447 00:25:41,200 --> 00:25:44,240 Speaker 1: in relationship to the amount of water left in you. Yeah, 448 00:25:44,280 --> 00:25:46,480 Speaker 1: I think we've touched on this on the show before 449 00:25:46,600 --> 00:25:50,200 Speaker 1: that sometimes we give too much credit to sweat in 450 00:25:50,320 --> 00:25:53,480 Speaker 1: its ability to remove things from our body. Certainly when 451 00:25:55,160 --> 00:25:58,760 Speaker 1: some arguments for the removal of impurities through sweat, for example, 452 00:25:59,160 --> 00:26:01,240 Speaker 1: Oh yeah, yeah, right with people who think that you 453 00:26:01,320 --> 00:26:04,200 Speaker 1: can like cleanse all the toxins by sweating or something. 454 00:26:04,280 --> 00:26:06,560 Speaker 1: I mean, sweating is great, no, no knocking on sweat 455 00:26:06,600 --> 00:26:09,720 Speaker 1: and it memory serves like there is some toxin removal, 456 00:26:09,760 --> 00:26:12,560 Speaker 1: but not not anywhere near as good as say, good 457 00:26:12,600 --> 00:26:15,040 Speaker 1: old fashioned urination. I mean, that's that's right, That's why 458 00:26:15,119 --> 00:26:18,440 Speaker 1: we have urination exactly. So I guess from here we 459 00:26:18,520 --> 00:26:22,159 Speaker 1: go on to talk about how the brain senses and 460 00:26:22,320 --> 00:26:26,720 Speaker 1: monitors osmolality. This is what the authors say is quote, 461 00:26:26,760 --> 00:26:30,960 Speaker 1: probably the most important homeostatic signal for drinking in everyday 462 00:26:31,040 --> 00:26:34,640 Speaker 1: life is the brain's ability to monitor osmolality. That's what's 463 00:26:34,680 --> 00:26:38,280 Speaker 1: going to be causing you to go drink water. And 464 00:26:38,480 --> 00:26:41,240 Speaker 1: the authors point out some interesting things, one of which 465 00:26:41,440 --> 00:26:45,600 Speaker 1: is that when blood osmolality and blood volume are both 466 00:26:45,760 --> 00:26:48,920 Speaker 1: threatened at the same time, for example, if they both 467 00:26:49,240 --> 00:26:52,520 Speaker 1: increase above the ideal range at the same time, the 468 00:26:52,640 --> 00:26:58,200 Speaker 1: body places a higher priority on defending the ideal osmolality 469 00:26:58,320 --> 00:27:01,879 Speaker 1: than it does on defending volume. So examples of this 470 00:27:02,000 --> 00:27:05,040 Speaker 1: would be, you know, hypernetremia having too much sodium, or 471 00:27:05,200 --> 00:27:09,680 Speaker 1: hyperglycemia having too much glucose in the blood, whatever it is. 472 00:27:10,000 --> 00:27:13,440 Speaker 1: The state of having too high of an osmolality, which 473 00:27:13,480 --> 00:27:17,760 Speaker 1: they call hyper tonicity, is probably more threatening, more of 474 00:27:17,800 --> 00:27:21,800 Speaker 1: a danger overall than having not quite the right amount 475 00:27:21,800 --> 00:27:25,520 Speaker 1: of water volume in your body. But anyway, well, you know, 476 00:27:25,600 --> 00:27:27,800 Speaker 1: so what takes care of this whole job. Well, you've 477 00:27:27,800 --> 00:27:30,840 Speaker 1: got some physical structures in your brain that sort of 478 00:27:31,520 --> 00:27:34,760 Speaker 1: dip their finger into the soup to taste it for 479 00:27:34,880 --> 00:27:38,639 Speaker 1: salt and let you know what's going on. Both of 480 00:27:38,720 --> 00:27:42,119 Speaker 1: them are small, They reside in the forebrain, and they 481 00:27:42,160 --> 00:27:46,080 Speaker 1: are known as first of all, the subfornical organ or SFO, 482 00:27:46,880 --> 00:27:51,800 Speaker 1: and then the organum vasculosum of the lamina terminalis or OVLT. 483 00:27:53,280 --> 00:27:56,199 Speaker 1: Now you've probably heard before of something called the blood 484 00:27:56,400 --> 00:28:01,200 Speaker 1: brain barrier. This is a system of borders that prevent 485 00:28:01,480 --> 00:28:04,159 Speaker 1: things that happen to be floating around in the blood 486 00:28:04,680 --> 00:28:08,760 Speaker 1: from passing non selectively into the brain. So you know, 487 00:28:08,880 --> 00:28:11,600 Speaker 1: the brain does need blood. It has to receive oxygen 488 00:28:11,680 --> 00:28:15,120 Speaker 1: and other nutrients from blood flow, but the brain has 489 00:28:15,160 --> 00:28:20,040 Speaker 1: to also protect itself against totally unregulated exchange with the blood. 490 00:28:20,400 --> 00:28:22,919 Speaker 1: And there may be multiple reasons for this, but one 491 00:28:22,960 --> 00:28:26,400 Speaker 1: of the main ones I've seen is that this prevents 492 00:28:26,560 --> 00:28:31,119 Speaker 1: blood borne pathogens from infecting brain tissue, so that seems important. 493 00:28:32,119 --> 00:28:34,840 Speaker 1: So in regions where it's active, the blood brain barrier 494 00:28:35,000 --> 00:28:38,560 Speaker 1: only allows selective passage of certain types of material from 495 00:28:38,600 --> 00:28:41,640 Speaker 1: the blood into the neurons. But if you're part of 496 00:28:41,680 --> 00:28:44,960 Speaker 1: the brain that needs to get raw data about the 497 00:28:45,080 --> 00:28:48,440 Speaker 1: contents of the blood moment by moment, apparently it won't 498 00:28:48,520 --> 00:28:52,000 Speaker 1: do to be hiding behind this protective fence of cells. So, 499 00:28:52,440 --> 00:28:55,360 Speaker 1: according to the authors here, the SFO and the OVLT, 500 00:28:56,040 --> 00:28:59,120 Speaker 1: though they are in the brain, are located outside the 501 00:28:59,160 --> 00:29:02,200 Speaker 1: blood brain carrier, so they can sort of taste the 502 00:29:02,360 --> 00:29:05,800 Speaker 1: blood river unfiltered, undiluted to get a raw sense of 503 00:29:05,880 --> 00:29:09,520 Speaker 1: what's going on. To read directly from the paper here quote, 504 00:29:09,880 --> 00:29:13,760 Speaker 1: it is thought that these SFO and OVLT neurons monitor 505 00:29:13,840 --> 00:29:19,600 Speaker 1: the blood osmolality directly, possibly via stretch sensitive ion channels 506 00:29:19,760 --> 00:29:23,800 Speaker 1: embedded in their plasma membranes that detect changes in cell 507 00:29:24,000 --> 00:29:29,280 Speaker 1: volume following intracellular dehydration. However, the identity of the specific 508 00:29:29,360 --> 00:29:33,479 Speaker 1: ion channel or other protein responsible for OSMO sensing by 509 00:29:33,520 --> 00:29:37,880 Speaker 1: these neurons is unknown. Furthermore, the possibility cannot be excluded 510 00:29:37,920 --> 00:29:41,240 Speaker 1: that other cell types such as glia, play an important 511 00:29:41,320 --> 00:29:46,000 Speaker 1: role in OSMO sensation. So here they identify, they put 512 00:29:46,040 --> 00:29:48,160 Speaker 1: the flag up. For One more thing that hasn't fully 513 00:29:48,280 --> 00:29:51,360 Speaker 1: been figured out in the science of thirst is what 514 00:29:51,640 --> 00:29:55,400 Speaker 1: is the direct molecular mechanism that the neurons in these 515 00:29:55,480 --> 00:30:00,320 Speaker 1: brain regions use to detect changes in blood osmolality. Maybe 516 00:30:00,440 --> 00:30:04,280 Speaker 1: these stretched sensitive cells that you get dehydrated and then 517 00:30:04,320 --> 00:30:07,760 Speaker 1: send information based on that to the brain regions that 518 00:30:07,880 --> 00:30:11,480 Speaker 1: then filter out to other brain regions from there, But 519 00:30:11,640 --> 00:30:15,760 Speaker 1: we don't know for sure anyway that is sensing intracellular 520 00:30:15,880 --> 00:30:19,440 Speaker 1: dehydration or increases in blood osmolality. But what about that 521 00:30:19,520 --> 00:30:25,040 Speaker 1: other kind extracellular dehydration where the blood volume actually decreases overall, 522 00:30:25,160 --> 00:30:28,920 Speaker 1: such as after bleeding. Well. Decreases in blood volume are 523 00:30:29,000 --> 00:30:34,640 Speaker 1: known as hypovolemia, like low volume hypovolemia, and they correspond 524 00:30:34,720 --> 00:30:39,480 Speaker 1: with a decrease in blood pressure hypotension, and the body's 525 00:30:39,680 --> 00:30:44,280 Speaker 1: reactions to hypotension take places sort of a complex chain 526 00:30:44,440 --> 00:30:50,000 Speaker 1: of mechanisms involving multiple organs and several forms of a hormone, 527 00:30:50,760 --> 00:30:56,120 Speaker 1: very important hormone called angiotensin. You might see this abbreviated 528 00:30:56,240 --> 00:31:00,200 Speaker 1: sometimes with like capital letters A in GI and then 529 00:31:00,280 --> 00:31:04,440 Speaker 1: maybe A and GII for angiotensin one and angiotensin two. 530 00:31:04,960 --> 00:31:08,560 Speaker 1: Apparently the most crucial form of the hormone is angiotensin two, 531 00:31:09,120 --> 00:31:12,320 Speaker 1: which causes things like the narrowing of blood vessels. So 532 00:31:12,560 --> 00:31:15,200 Speaker 1: if you shrink blood vessels and make them smaller, that 533 00:31:15,360 --> 00:31:19,280 Speaker 1: helps keep blood pressure up when volume is low, and 534 00:31:19,520 --> 00:31:23,040 Speaker 1: it also leads to water reuptake by the kidneys. The 535 00:31:23,120 --> 00:31:26,440 Speaker 1: kidneys are like holding fast to the water content rather 536 00:31:26,520 --> 00:31:28,920 Speaker 1: than just squandering it as they might if you had 537 00:31:28,960 --> 00:31:31,640 Speaker 1: plenty of water in your body. And there's evidence that 538 00:31:31,720 --> 00:31:35,720 Speaker 1: the presence of angiotensin two this hormone also causes a 539 00:31:35,920 --> 00:31:39,320 Speaker 1: thirst drive to be generated in the brain, primarily involving 540 00:31:39,440 --> 00:31:44,960 Speaker 1: the SFO or the subforonical organ Interestingly, in rodents, if 541 00:31:45,000 --> 00:31:48,800 Speaker 1: you just give them straight angiotensin two, it causes what 542 00:31:48,960 --> 00:31:54,479 Speaker 1: the authors call profound water consumption, just like voluminous drinking 543 00:31:54,560 --> 00:31:59,600 Speaker 1: of water. But in humans, apparently, angiotensin two levels quote 544 00:31:59,640 --> 00:32:02,760 Speaker 1: do not correlate well with the perception of thirst, and 545 00:32:02,920 --> 00:32:09,800 Speaker 1: infusions of physiologic levels of angiotensin two do not stimulate drinking. Interesting, so, 546 00:32:10,120 --> 00:32:14,200 Speaker 1: perhaps while this hormone does things to increase blood pressure, 547 00:32:14,320 --> 00:32:17,720 Speaker 1: like constrict blood vessels and cause water reuptake by the kidneys, 548 00:32:18,120 --> 00:32:20,880 Speaker 1: it does not make us thirsty for water like it 549 00:32:21,000 --> 00:32:25,320 Speaker 1: does in other animals for some reason, the authors write quote. 550 00:32:25,440 --> 00:32:28,720 Speaker 1: While this suggests that angiotensin two might be less important 551 00:32:28,760 --> 00:32:32,440 Speaker 1: for regulation of drinking in humans, interpretation of these negative 552 00:32:32,440 --> 00:32:36,080 Speaker 1: results is complicated by the fact that peripheral infusion of 553 00:32:36,200 --> 00:32:40,640 Speaker 1: angiotensin two rapidly increases blood pressure, which can then feed 554 00:32:40,720 --> 00:32:44,400 Speaker 1: back to counteract any effects of angiotensin two on thirst. 555 00:32:44,840 --> 00:32:48,640 Speaker 1: So maybe they're just complicated balancing interactions here that when 556 00:32:48,760 --> 00:32:53,040 Speaker 1: you know if you directly infuse this hormone, it increases 557 00:32:53,080 --> 00:32:56,720 Speaker 1: blood pressure, which has other downstream effects which which counteract 558 00:32:56,880 --> 00:33:00,760 Speaker 1: the onset of thirst. Okay, I'm I guess just it 559 00:33:00,880 --> 00:33:03,320 Speaker 1: just goes to show, you know, one of the factors 560 00:33:03,360 --> 00:33:07,080 Speaker 1: of experiments with with with mice and other non human 561 00:33:07,160 --> 00:33:09,440 Speaker 1: mammals is that we have a whole lot in common 562 00:33:09,520 --> 00:33:12,959 Speaker 1: with them, but not everything is going to it's going 563 00:33:13,040 --> 00:33:15,360 Speaker 1: to apply to us one to one, right, A lot does, 564 00:33:15,400 --> 00:33:24,640 Speaker 1: but not everything. Okay, But anyway, I guess what we're 565 00:33:24,720 --> 00:33:27,800 Speaker 1: trying to figure out here is building a bridge from 566 00:33:27,800 --> 00:33:31,040 Speaker 1: our existing knowledge about these brain regions that play a 567 00:33:31,160 --> 00:33:35,520 Speaker 1: role in monitoring the body's osmolality and water content and 568 00:33:35,920 --> 00:33:38,720 Speaker 1: u and regulate in these hormones that help regulate the 569 00:33:38,760 --> 00:33:43,240 Speaker 1: body's physiologic response to dehydration, and how that connects to 570 00:33:43,400 --> 00:33:46,640 Speaker 1: the actual behavior and the drives that we sense when 571 00:33:46,720 --> 00:33:50,719 Speaker 1: we get thirsty and go get water. Um so there 572 00:33:50,880 --> 00:33:54,360 Speaker 1: there are sort of system wide homeostatic responses when when 573 00:33:54,480 --> 00:33:58,640 Speaker 1: we get dehydrated again. The SFO and the OVLT, together 574 00:33:58,680 --> 00:34:02,560 Speaker 1: with another region in between them, the median preoptic nucleus 575 00:34:02,720 --> 00:34:06,760 Speaker 1: or MNPO. These three regions together comprise a hub called 576 00:34:06,880 --> 00:34:09,800 Speaker 1: the lamina terminalys. This is sort of the brain's fluid 577 00:34:09,880 --> 00:34:14,680 Speaker 1: control center. What is fairly well understood is the autonomic 578 00:34:14,760 --> 00:34:18,239 Speaker 1: and neuroendocrine pathways by which the body responds to dehydration. 579 00:34:18,360 --> 00:34:20,640 Speaker 1: You know all these things we've been talking about. The 580 00:34:21,120 --> 00:34:24,880 Speaker 1: angiotensin too, the constriction of blood vessels to increase blood pressure, 581 00:34:25,000 --> 00:34:28,120 Speaker 1: water reuptake by the kidneys, the release of other hormones, 582 00:34:28,360 --> 00:34:32,320 Speaker 1: not just angiotensin, but things like vasopressin and oxytocin. But 583 00:34:32,520 --> 00:34:35,680 Speaker 1: what is less well understood are the mechanisms leading to 584 00:34:35,800 --> 00:34:39,719 Speaker 1: the generation of thirst as a motivation state. But we 585 00:34:39,880 --> 00:34:42,680 Speaker 1: know some things that are very interesting. So to come 586 00:34:42,719 --> 00:34:45,960 Speaker 1: back to something you actually mentioned earlier in the episode, Rob, 587 00:34:46,760 --> 00:34:51,200 Speaker 1: the brain's regulation of water drinking is not based only 588 00:34:51,360 --> 00:34:54,200 Speaker 1: on the current osmolality of the blood. So it's not 589 00:34:54,320 --> 00:34:56,920 Speaker 1: just these brain regions that you dip a finger in 590 00:34:57,320 --> 00:35:00,520 Speaker 1: and see how salty the soup is. The rain also 591 00:35:00,560 --> 00:35:05,520 Speaker 1: appears to change our motivation to drink water before changes 592 00:35:05,640 --> 00:35:09,680 Speaker 1: actually show up in the blood. Their behavior changes that 593 00:35:09,800 --> 00:35:15,200 Speaker 1: occur in anticipation of changes in osmolality. So what would 594 00:35:15,200 --> 00:35:17,759 Speaker 1: this mean in plain English? Okay, so you're out in 595 00:35:17,760 --> 00:35:20,319 Speaker 1: the hot sun, wrestling alligators, or you know, you're working 596 00:35:20,400 --> 00:35:22,680 Speaker 1: up a sweat, whatever it is you're doing, and you 597 00:35:22,800 --> 00:35:25,040 Speaker 1: come in, you get in the shade, and you drink 598 00:35:25,080 --> 00:35:28,960 Speaker 1: a nice glass of water. When you do that, there 599 00:35:29,080 --> 00:35:32,760 Speaker 1: is actually a delay on the order of tens of minutes. 600 00:35:32,840 --> 00:35:36,640 Speaker 1: It might be ten, twenty or even more minutes before 601 00:35:36,680 --> 00:35:40,040 Speaker 1: the water that you just drank is fully absorbed by 602 00:35:40,080 --> 00:35:44,200 Speaker 1: the digestive system and added into the blood. However, it 603 00:35:44,360 --> 00:35:46,880 Speaker 1: might just take you a few seconds to drink a 604 00:35:46,960 --> 00:35:49,800 Speaker 1: glass of water and then decide whether you're going to 605 00:35:49,920 --> 00:35:53,880 Speaker 1: drink more. So, if it's taking your body tens of 606 00:35:54,000 --> 00:35:57,840 Speaker 1: minutes to fully incorporate the water you've just consumed and 607 00:35:58,000 --> 00:36:01,080 Speaker 1: for that to show up in a blood o molality test, 608 00:36:01,719 --> 00:36:05,360 Speaker 1: how come you don't just keep drinking water constantly until 609 00:36:05,520 --> 00:36:07,880 Speaker 1: that happens. You know, you don't. Even if you're thirsty, 610 00:36:08,320 --> 00:36:11,279 Speaker 1: you don't usually drink a glass of water and then 611 00:36:11,360 --> 00:36:14,000 Speaker 1: just fill up another one, and another and another and 612 00:36:14,120 --> 00:36:17,680 Speaker 1: another for you know, fifteen minutes or something. If your 613 00:36:17,760 --> 00:36:20,799 Speaker 1: level of thirst were only based on your blood osmlality, 614 00:36:21,000 --> 00:36:23,720 Speaker 1: you might do that. You might kill yourself just drinking 615 00:36:23,840 --> 00:36:27,120 Speaker 1: gallons of water while you're waiting for your fluid monitoring 616 00:36:27,200 --> 00:36:30,640 Speaker 1: system to register the changes. Right, Yeah, yeah, I mean, 617 00:36:30,760 --> 00:36:34,359 Speaker 1: I mean it needs to be Again, it comes back 618 00:36:34,400 --> 00:36:37,760 Speaker 1: to just what a fine balance it is, and therefore 619 00:36:37,840 --> 00:36:41,360 Speaker 1: you need you need different sensors in different places in 620 00:36:41,600 --> 00:36:45,520 Speaker 1: the human mechanism here, right, So the sensation of your 621 00:36:45,680 --> 00:36:50,120 Speaker 1: thirst being quenched by drinking water must be created by 622 00:36:50,200 --> 00:36:54,440 Speaker 1: a different process altogether the author's right quote. Thirst is 623 00:36:54,600 --> 00:36:59,440 Speaker 1: not quenched by the reverse of the process that generates it. Instead, 624 00:36:59,520 --> 00:37:04,200 Speaker 1: the brain appears to somehow detect the intake of liquid. 625 00:37:04,640 --> 00:37:08,040 Speaker 1: It's usually thought that this happens somewhere in the oropharyans 626 00:37:08,120 --> 00:37:11,440 Speaker 1: in the middle part of the throat, and then somehow 627 00:37:11,560 --> 00:37:15,960 Speaker 1: adjusts the feeling of thirst in anticipation of the coming 628 00:37:16,160 --> 00:37:20,000 Speaker 1: changes in blood osmolality. So it looks like what happens 629 00:37:20,239 --> 00:37:23,840 Speaker 1: is that you're dehydrated, you drink water. The swallowing of 630 00:37:23,960 --> 00:37:27,480 Speaker 1: water is somehow sensed in the throat, and then these 631 00:37:27,560 --> 00:37:32,160 Speaker 1: sensations are transmitted to the subformical organ, the sfo, and 632 00:37:32,280 --> 00:37:36,640 Speaker 1: then from there they inhibit thirst generating pathways. And so 633 00:37:36,800 --> 00:37:40,359 Speaker 1: this raises interesting questions how exactly do we sense water 634 00:37:40,520 --> 00:37:43,520 Speaker 1: intake in the throat? This was not well understood at 635 00:37:43,560 --> 00:37:45,520 Speaker 1: the time this paper was written. I actually have come 636 00:37:45,560 --> 00:37:48,440 Speaker 1: across a couple of studies in the years since that 637 00:37:48,560 --> 00:37:49,960 Speaker 1: we can talk about as we go on. We might 638 00:37:50,000 --> 00:37:52,000 Speaker 1: get more into those in the next part of the series. 639 00:37:52,800 --> 00:37:55,799 Speaker 1: But at the time, some of the ideas out there were, well, 640 00:37:55,840 --> 00:37:59,840 Speaker 1: maybe it has something to do with temperature. Apparently cooling 641 00:38:00,200 --> 00:38:05,080 Speaker 1: of the throat triggers water intake signals, and evidence for 642 00:38:05,280 --> 00:38:08,280 Speaker 1: this claim would be that research has found that cold 643 00:38:08,680 --> 00:38:13,319 Speaker 1: liquids inhibit thirst faster than warm liquids. I haven't tried 644 00:38:13,360 --> 00:38:17,560 Speaker 1: it myself, but that sounds correct to me. Interesting and 645 00:38:17,680 --> 00:38:20,040 Speaker 1: it would make sense water usually tends to cool the 646 00:38:20,120 --> 00:38:22,560 Speaker 1: mouth in the throat, and that this cooling may be 647 00:38:22,719 --> 00:38:26,000 Speaker 1: used as a rough signal that water is coming in. Also, 648 00:38:26,719 --> 00:38:29,440 Speaker 1: it seems that cooling of the mouth on its own, 649 00:38:29,520 --> 00:38:31,920 Speaker 1: even if it's not water, just making the mouth colder, 650 00:38:32,360 --> 00:38:37,920 Speaker 1: can somehow reduce thirst and reduce activity of the SFO. Interesting, 651 00:38:38,000 --> 00:38:40,279 Speaker 1: so you would potentially be able to use just like 652 00:38:40,360 --> 00:38:46,400 Speaker 1: a cooling breath of technique to inhibit thirst, possibly if 653 00:38:46,560 --> 00:38:49,719 Speaker 1: you know, if the temperature explanation has anything going for it. 654 00:38:50,520 --> 00:38:52,160 Speaker 1: But there may be other things as well. There may 655 00:38:52,200 --> 00:38:54,640 Speaker 1: be other ways of sensing water in the oral cavity. 656 00:38:54,719 --> 00:38:56,680 Speaker 1: Maybe some stuff more along the lines of what you 657 00:38:56,760 --> 00:38:58,840 Speaker 1: were talking about earlier. Things could have to do with 658 00:39:00,239 --> 00:39:04,200 Speaker 1: taste sensors that somehow to detect the presence of water 659 00:39:04,440 --> 00:39:08,520 Speaker 1: through acid sensing taste receptors or something, or there could 660 00:39:08,560 --> 00:39:11,960 Speaker 1: be there may be some limited evidence that stretch receptors 661 00:39:12,040 --> 00:39:15,520 Speaker 1: and osma sensors in the stomach might also detect water 662 00:39:15,640 --> 00:39:18,040 Speaker 1: intake before full absorption. But again, at the time of 663 00:39:18,120 --> 00:39:21,880 Speaker 1: this summary in twenty sixteen, this was just not fully understood. 664 00:39:22,160 --> 00:39:23,520 Speaker 1: I guess one way of looking at it would be 665 00:39:23,560 --> 00:39:26,040 Speaker 1: that it's it's not necessarily like one trigger or one 666 00:39:26,160 --> 00:39:30,160 Speaker 1: sensor that is that's playing a crucial role here. It's 667 00:39:30,200 --> 00:39:33,800 Speaker 1: more of a whole suite of things that is that 668 00:39:34,000 --> 00:39:38,919 Speaker 1: is generating this understanding of how much water has entered 669 00:39:38,960 --> 00:39:42,799 Speaker 1: the system. Right. But whatever the exact mechanism is, it's 670 00:39:42,920 --> 00:39:48,360 Speaker 1: definitely anticipatory in nature. It's definitely changing your behavior before 671 00:39:48,600 --> 00:39:51,279 Speaker 1: the thing that your behavior is supposed to fix has 672 00:39:51,320 --> 00:39:54,840 Speaker 1: actually changed. Yet. Wow, Like, when you're done drinking the 673 00:39:54,880 --> 00:39:57,239 Speaker 1: glass of water, you're still dehydrated. You're going to be 674 00:39:57,360 --> 00:40:00,719 Speaker 1: dehydrated for another ten to fifteen minutes at least. It's 675 00:40:00,960 --> 00:40:04,360 Speaker 1: it's the kind of excellence in supply chain management that 676 00:40:04,520 --> 00:40:07,840 Speaker 1: technology companies are chasing after, you know, the idea that 677 00:40:08,320 --> 00:40:12,680 Speaker 1: they want to anticipate the need um and then you know, 678 00:40:12,800 --> 00:40:17,600 Speaker 1: be able to h to alter the supply chain, you know, 679 00:40:18,200 --> 00:40:20,520 Speaker 1: at moment to moment to make sure that the need 680 00:40:20,680 --> 00:40:23,920 Speaker 1: is met without wasting water or product or whatever the 681 00:40:23,960 --> 00:40:27,319 Speaker 1: case may be. Yeah, I like it. Okay, there's more 682 00:40:27,400 --> 00:40:32,879 Speaker 1: anticipation to come. How about anticipatory regulation of thirst from 683 00:40:33,239 --> 00:40:37,880 Speaker 1: eating from food? Because when we eat food, thirst appears 684 00:40:38,000 --> 00:40:42,879 Speaker 1: to be generated in anticipation of coming changes to blood osmolality. 685 00:40:43,560 --> 00:40:46,480 Speaker 1: So why would eating food make us need water? Well, 686 00:40:46,800 --> 00:40:49,759 Speaker 1: first of all, fluids are used in digestion. You think 687 00:40:49,760 --> 00:40:52,839 Speaker 1: about when you eat food, you generate saliva you uh, 688 00:40:52,960 --> 00:40:55,080 Speaker 1: you know, not to be gross, but there's a lot 689 00:40:55,160 --> 00:41:00,759 Speaker 1: of lubrication that needs to happen, Like swallowing requires some water. Oh, 690 00:41:00,840 --> 00:41:03,560 Speaker 1: I mean you have to you have to chew up 691 00:41:03,600 --> 00:41:06,760 Speaker 1: the food and form the bolus that will then travel 692 00:41:06,880 --> 00:41:10,240 Speaker 1: down the throat. I mean, I think we've we've covered 693 00:41:10,280 --> 00:41:12,400 Speaker 1: that on the show before. Like, think about it today 694 00:41:12,760 --> 00:41:16,440 Speaker 1: your next meal. Really focus on everything that's going on 695 00:41:16,560 --> 00:41:19,160 Speaker 1: in your mouth. It's a it's a beautiful chorus of 696 00:41:19,480 --> 00:41:23,000 Speaker 1: disassembly and then reassembly into the right sort of package 697 00:41:23,040 --> 00:41:25,839 Speaker 1: to then make the journey down to the stomach. It's 698 00:41:25,920 --> 00:41:28,920 Speaker 1: really it's like, it's beautiful and it's horrible. You can't 699 00:41:29,000 --> 00:41:30,960 Speaker 1: think about it while you're eating, or at least I 700 00:41:31,040 --> 00:41:34,319 Speaker 1: find I can't just think. I mean, have you ever 701 00:41:34,640 --> 00:41:37,280 Speaker 1: thought of a more appetizing idea that you're like, mouth 702 00:41:37,360 --> 00:41:40,480 Speaker 1: and throat are lubricating the ball of food that you're 703 00:41:40,520 --> 00:41:44,560 Speaker 1: smashing up. Yeah, but anyway, so that's one thing. But 704 00:41:44,640 --> 00:41:47,560 Speaker 1: then the other half of it is that eating usually 705 00:41:47,760 --> 00:41:51,359 Speaker 1: increases blood os molality by adding salt and other things 706 00:41:51,480 --> 00:41:54,319 Speaker 1: to the body. Yes, yes, so much salt. So much 707 00:41:54,960 --> 00:41:58,360 Speaker 1: so the body appears to have an anticipatory response to 708 00:41:58,680 --> 00:42:03,160 Speaker 1: eating that is generated eating thirst before those changes even register. 709 00:42:03,800 --> 00:42:06,359 Speaker 1: And this thirst that comes from eating is known as 710 00:42:06,440 --> 00:42:10,040 Speaker 1: pran deal thirst. It seems to occur before changes in 711 00:42:10,120 --> 00:42:14,120 Speaker 1: blood osmolality come into effect, so a lot of animals 712 00:42:14,200 --> 00:42:17,200 Speaker 1: are observed to drink at the same time that they eat, 713 00:42:17,280 --> 00:42:21,640 Speaker 1: if they're able. The mechanism of this anticipatory neural pathway 714 00:42:21,680 --> 00:42:26,160 Speaker 1: is still not fully understood, but if prandial thirst is 715 00:42:26,239 --> 00:42:29,799 Speaker 1: not sated. I mentioned this earlier. Sometimes animal brains tend 716 00:42:29,840 --> 00:42:34,520 Speaker 1: to react by reducing appetite until water is consumed. This 717 00:42:34,680 --> 00:42:39,680 Speaker 1: is known as dehydration induced stanorexia. But in general, dehydration 718 00:42:39,760 --> 00:42:43,840 Speaker 1: will cause animals to restrict their food intake, with some exceptions, 719 00:42:43,880 --> 00:42:46,200 Speaker 1: of course, because some animals, you know, they get their 720 00:42:46,239 --> 00:42:49,960 Speaker 1: water entirely from food and so forth. But dehydration induce 721 00:42:49,960 --> 00:42:54,760 Speaker 1: stanorexia tends to I thought this was interesting. Reduce meal 722 00:42:55,080 --> 00:43:00,520 Speaker 1: size but not meal number, so it might not affect 723 00:43:00,719 --> 00:43:03,640 Speaker 1: how often an animal is willing to eat, but how 724 00:43:03,760 --> 00:43:07,440 Speaker 1: much they eat when they do eat, meaning that it 725 00:43:07,560 --> 00:43:11,640 Speaker 1: probably works by causing an animal to terminate feeding behaviors 726 00:43:11,760 --> 00:43:14,719 Speaker 1: earlier than they would normally each time it has a meal. 727 00:43:15,920 --> 00:43:18,080 Speaker 1: Now at the end of their rite. Up Here, the 728 00:43:18,360 --> 00:43:23,000 Speaker 1: authors acknowledge that acknowledge some exceptions to the stuff they're 729 00:43:23,040 --> 00:43:26,640 Speaker 1: talking about. These generalizations tend to be true for humans 730 00:43:26,719 --> 00:43:29,520 Speaker 1: and rodents and some other animals, but of course they're 731 00:43:30,320 --> 00:43:34,440 Speaker 1: very different ecological niches that will cause variation to these generalizations. 732 00:43:34,760 --> 00:43:38,719 Speaker 1: For example, a lot of grazing herbivores do not seem 733 00:43:38,800 --> 00:43:43,040 Speaker 1: to experience pran deal thirst or thirst related to eating. 734 00:43:43,160 --> 00:43:45,319 Speaker 1: You know, because they eat all day, but they only 735 00:43:45,440 --> 00:43:48,560 Speaker 1: drink drink water a few times a day. And then 736 00:43:48,600 --> 00:43:52,200 Speaker 1: they're very different kinds of animals like amphibians that don't 737 00:43:52,239 --> 00:43:56,279 Speaker 1: technically drink at all, like many amphibians just absorb water 738 00:43:56,400 --> 00:43:59,440 Speaker 1: through their skin. We've talked about amphibians before in the 739 00:43:59,480 --> 00:44:02,560 Speaker 1: show and about how the you know, how delicate their 740 00:44:02,600 --> 00:44:04,520 Speaker 1: place in the environment can be, and this is this 741 00:44:04,719 --> 00:44:06,160 Speaker 1: is part of it. It's like if if if I'm 742 00:44:06,200 --> 00:44:09,840 Speaker 1: in the environment, i am drinking it, I am breathing it, 743 00:44:10,680 --> 00:44:14,640 Speaker 1: and my skin is the is the barrier through which 744 00:44:14,680 --> 00:44:18,960 Speaker 1: all this takes place. Yeah, very different relationship to one's environment, 745 00:44:19,040 --> 00:44:22,000 Speaker 1: a very very different kind of chemistry of being for 746 00:44:22,200 --> 00:44:25,600 Speaker 1: the for the amphibian, I recall it's been a while, 747 00:44:25,680 --> 00:44:29,680 Speaker 1: but I recall reading a funny article about terrestrial toads 748 00:44:29,800 --> 00:44:33,640 Speaker 1: that would primarily do water absorption through their pelvic regions, 749 00:44:33,920 --> 00:44:37,040 Speaker 1: so they sort of like like thrust their lower bodies 750 00:44:37,120 --> 00:44:41,000 Speaker 1: and bellies into any surface that's wet while they're while 751 00:44:41,000 --> 00:44:44,000 Speaker 1: they're hanging out in water absorption mode. All right, We're 752 00:44:44,000 --> 00:44:45,879 Speaker 1: gonna ahead and close out this episode, but we will 753 00:44:45,920 --> 00:44:48,560 Speaker 1: be back for a third thirst episode. We have a 754 00:44:48,600 --> 00:44:51,879 Speaker 1: lot of additional information we want to get to. Don't 755 00:44:51,920 --> 00:44:54,880 Speaker 1: worry there will be parasites in it, So it should 756 00:44:54,880 --> 00:44:58,040 Speaker 1: be it should be a grotesque a good time. And 757 00:44:58,160 --> 00:45:00,560 Speaker 1: of course, in the meantime, right in, let us know 758 00:45:00,640 --> 00:45:04,240 Speaker 1: your thoughts on water. All of you are water drinkers. 759 00:45:04,440 --> 00:45:07,040 Speaker 1: You consume water one way or another or another, and 760 00:45:07,160 --> 00:45:08,800 Speaker 1: I imagine you have some thoughts on all of this. 761 00:45:09,239 --> 00:45:11,200 Speaker 1: Do you do you love drinking water? Do you hate 762 00:45:11,280 --> 00:45:15,160 Speaker 1: drinking water? Is there? What are your thoughts on the 763 00:45:15,719 --> 00:45:20,239 Speaker 1: consumption of cold water versus hot water or maybe prefer 764 00:45:20,280 --> 00:45:23,160 Speaker 1: the lukewarm water? I mean, I guess they're factors we 765 00:45:23,200 --> 00:45:25,799 Speaker 1: didn't even get into, you know, like sometimes cold water 766 00:45:25,920 --> 00:45:28,680 Speaker 1: can be sensitive on the teeth and gums. The same 767 00:45:28,760 --> 00:45:31,560 Speaker 1: can be said for hot water as well. So I 768 00:45:31,600 --> 00:45:33,640 Speaker 1: don't know. Perhaps you have thoughts on that. Have you 769 00:45:33,800 --> 00:45:37,040 Speaker 1: never drunk water? You? Are you a creature that only 770 00:45:37,120 --> 00:45:44,880 Speaker 1: absorbs water from chicken nuggets? Oh the chicken chicken nugget water? Yes? Well, anyway, 771 00:45:45,000 --> 00:45:48,160 Speaker 1: right and let us know it's all fair game. In 772 00:45:48,239 --> 00:45:51,040 Speaker 1: the meantime as usual, Core episodes of Stuff to Blow 773 00:45:51,120 --> 00:45:53,359 Speaker 1: Your Mind Tuesdays and Thursdays and the Stuff to Blow 774 00:45:53,400 --> 00:45:56,480 Speaker 1: Your Mind Podcast feed. We have a listener meant on Monday, 775 00:45:56,560 --> 00:45:58,960 Speaker 1: Artifact on Wednesday, and on Friday we do Weird House Cinema. 776 00:45:59,000 --> 00:46:01,640 Speaker 1: That's our time. Just had most serious matters aside and 777 00:46:01,760 --> 00:46:04,520 Speaker 1: just talk about a strange film. Huge thanks, as always 778 00:46:04,560 --> 00:46:08,000 Speaker 1: to our excellent audio producer Seth Nicholas Johnson. If you 779 00:46:08,000 --> 00:46:10,200 Speaker 1: would like to get in touch with us with feedback 780 00:46:10,280 --> 00:46:12,560 Speaker 1: on this episode or any other, to suggest a topic 781 00:46:12,640 --> 00:46:14,400 Speaker 1: for the future, or just to say hello, you can 782 00:46:14,480 --> 00:46:17,520 Speaker 1: email us at contact at stuff to Blow your Mind 783 00:46:17,719 --> 00:46:28,319 Speaker 1: dot com. Stuff to Blow Your Mind is production of iHeartRadio. 784 00:46:28,680 --> 00:46:31,600 Speaker 1: For more podcasts from my Heart Radio, visit the iHeartRadio app, 785 00:46:31,800 --> 00:46:34,520 Speaker 1: Apple Podcasts, or wherever you're listening to your favorite shows.