WEBVTT - Thirst, Part 2 0:00:00.160 --> 0:00:05.240 My Welcome to Stuff to Blow Your Mind, the production 0:00:05.240 --> 0:00:14.320 of My Heart Radio. Hey, welcome to Stuff to Blow 0:00:14.360 --> 0:00:17.280 Your Mind. My name is Robert Lamb and I'm Joe McCormick, 0:00:17.360 --> 0:00:20.440 and we're back with part two of our series on thirst. 0:00:20.880 --> 0:00:23.880 What are you drinking right now? Absolutely nothing? Oh no, wait, 0:00:23.920 --> 0:00:26.080 I do have I have water here at my desk. 0:00:26.239 --> 0:00:29.280 I'm always drinking water. I'm a water guy. You know, 0:00:29.360 --> 0:00:32.400 some people are really into tea. I almost never drink tea. 0:00:32.520 --> 0:00:35.800 I go coffee water. That that's pretty much it. Uh, 0:00:36.120 --> 0:00:39.640 during the daytime hours at least. Oh yeah, well, I'm 0:00:39.720 --> 0:00:46.720 currently drinking tea. I generally go coffee, uh, te tea, water, tea, 0:00:47.320 --> 0:00:50.080 and then water and then then when the evening comes, 0:00:50.200 --> 0:00:52.360 you know, maybe I'll have something something else to drink. 0:00:52.440 --> 0:00:55.760 But uh yeah, right now it is tea, which is 0:00:56.120 --> 0:00:59.600 essentially water, but with extra things added to it. You know, 0:00:59.640 --> 0:01:02.720 I some times get confused about what tea means because 0:01:03.600 --> 0:01:07.319 I think of tea as being a specific kind of plant, like, 0:01:07.440 --> 0:01:10.320 isn't there a t tree? Again, I don't know much 0:01:10.319 --> 0:01:12.640 about tea, so I think about it in that way. 0:01:13.640 --> 0:01:16.640 But then you can make a tea out of like 0:01:16.720 --> 0:01:19.280 anything basically that you steep in water. Right, people make 0:01:19.400 --> 0:01:21.720 mushroom teas, people with all kinds of just oh, we 0:01:21.800 --> 0:01:25.560 have and plant stuff in water, and that's tea. Also yeah, 0:01:25.680 --> 0:01:27.760 like I mean, there's there's property and that's generally what 0:01:27.800 --> 0:01:30.679 I'm when I'm drinking. I'm drinking, you know, a dark 0:01:30.680 --> 0:01:33.320 tea or maybe a green tea. But also sometimes I'll 0:01:33.319 --> 0:01:37.080 have a tumeric tea, which is uh like like tumeric 0:01:37.160 --> 0:01:39.720 and ginger and a little coconut oil and a little 0:01:39.720 --> 0:01:42.800 honey hot water. But it doesn't actually contain tea, so 0:01:42.880 --> 0:01:46.200 it's not completely accurate to call it such because it's 0:01:46.240 --> 0:01:49.559 sort of how not all band aids are technically band 0:01:49.600 --> 0:01:52.920 aids or xerox it's or whatever. Has this been a 0:01:53.000 --> 0:01:55.680 terrible intro? Maybe we can cut my tea thing? No, No, 0:01:55.800 --> 0:01:58.680 this is a This is an intro that the people 0:01:58.720 --> 0:02:01.280 can relate to. People can thoughts on this. It's always 0:02:01.320 --> 0:02:04.120 good to start off asking what a word means. So 0:02:04.160 --> 0:02:06.560 I turns out I know nothing about T. I have 0:02:06.640 --> 0:02:08.720 no little There you go. We need to come back 0:02:08.760 --> 0:02:11.320 and do an episode or a series of episodes on T. 0:02:11.520 --> 0:02:15.440 It's a fascinating subject, fascinating history. Okay, well, we're going 0:02:15.480 --> 0:02:18.280 to jump back into some of the science that we 0:02:18.280 --> 0:02:20.480 were talking about in the last episode, where I was 0:02:20.560 --> 0:02:25.480 reviewing an interesting paper that I had read summarizing the 0:02:25.480 --> 0:02:29.360 the recent state of research on the biology of thirst. 0:02:29.520 --> 0:02:32.360 That was it was a paper published in Current Biology. 0:02:32.919 --> 0:02:34.600 We had to break off in the middle of talking 0:02:34.600 --> 0:02:38.119 about it. But but before we get back into that, Rob, 0:02:38.160 --> 0:02:41.240 I think you wanted to talk about the taste of water, 0:02:41.360 --> 0:02:45.000 which I think is in itself a very interesting subject. Yeah, 0:02:45.120 --> 0:02:47.400 it's it's a strange one because we probably don't think 0:02:47.440 --> 0:02:50.640 about it enough, but but we often talk about it, 0:02:50.760 --> 0:02:54.280 especially when we when we travel from one place to another. Um. 0:02:54.440 --> 0:02:57.520 We if you look back on I think back on 0:02:58.080 --> 0:03:01.360 water that you've consumed in the past, may have specific 0:03:01.400 --> 0:03:04.840 memories of different waters. Um Like, I remember when my 0:03:04.880 --> 0:03:08.120 family lived in the country and we had well water, 0:03:08.760 --> 0:03:12.040 and it had a it had a distinctive taste, and 0:03:12.200 --> 0:03:14.800 I don't I can't say that I loved it, But 0:03:15.040 --> 0:03:17.959 if I were to encounter the exact same flavor profile again, 0:03:18.000 --> 0:03:20.280 it would probably make me nostalgic, you know, like it's 0:03:20.440 --> 0:03:23.480 it's it's a definite flavor that is tied to a 0:03:23.480 --> 0:03:26.320 definite place. And time warning that this is a little crude, 0:03:26.400 --> 0:03:28.280 but I don't know of how else to explain it. 0:03:28.320 --> 0:03:32.480 You've ever been somewhere that had farty water, Um, well, 0:03:32.600 --> 0:03:35.320 it's kind of sulfury water, kind of kind of like 0:03:35.400 --> 0:03:38.600 water from the That's kind of what this was like. Yeah, 0:03:38.640 --> 0:03:41.320 it was that had kind of a a fire and 0:03:41.360 --> 0:03:44.680 brimstone kind of flavor to it. Okay, that's a more 0:03:44.680 --> 0:03:46.760 elegant way to put it. Well, the denizens of Hell 0:03:46.800 --> 0:03:48.839 are not insulted. They're flattered that you would you would 0:03:48.880 --> 0:03:54.320 compare this foul drinking water to flattens. But um, you know, 0:03:54.480 --> 0:03:57.560 but then sometimes I don't know, there's there's also beech water, 0:03:57.720 --> 0:04:00.880 you know, Like I I anytime I'm I'm in Florida 0:04:01.040 --> 0:04:03.600 and I'm having Florida water, like it has its own 0:04:03.680 --> 0:04:06.720 it tends to have its own bouquet, its own flavor 0:04:06.760 --> 0:04:10.120 profile that at the time I'm not enjoying. But then 0:04:10.160 --> 0:04:13.360 after I'm back and drinking tastier water, I'm kind of 0:04:13.880 --> 0:04:15.720 kind of long for it, you know, because like this 0:04:15.840 --> 0:04:19.440 is the water of of of the vacation that I 0:04:19.480 --> 0:04:21.880 am no longer on that sort of thing. I remember 0:04:21.920 --> 0:04:24.000 when I was in like a middle school. I went 0:04:24.040 --> 0:04:26.479 to New Mexico and we went somewhere there where the 0:04:26.520 --> 0:04:30.160 water was very I don't know, the tap water was 0:04:30.160 --> 0:04:33.880 almost kind of frothy somehow. It was like a kind 0:04:33.920 --> 0:04:36.960 of kind of white and cloudy, and I remember thinking 0:04:36.960 --> 0:04:39.520 it had a strange taste. I don't know what to 0:04:39.520 --> 0:04:41.480 connect that too, if it was supposed to be like 0:04:41.520 --> 0:04:44.960 that or not. Yeah, So I guess one thing we 0:04:44.960 --> 0:04:49.320 can definitely establish here is that there there certainly seems 0:04:49.360 --> 0:04:51.919 to there is an objective difference in in drinking waters 0:04:52.440 --> 0:04:55.280 from one place to another. Uh, you know, Atlanta water 0:04:55.480 --> 0:04:58.680 versus Florida water, that sort of thing. But there's also 0:04:58.720 --> 0:05:03.880 this wide variety in people just interpret the taste of water. Um. 0:05:03.920 --> 0:05:06.440 You know, I think we we often think of water 0:05:06.520 --> 0:05:10.440 as being neutral or tasteless. Um. If you're mixing a cocktail, 0:05:10.480 --> 0:05:12.520 for example, you don't want to shake it too long 0:05:12.600 --> 0:05:15.240 with the crushed ice because you will what will happen, 0:05:15.320 --> 0:05:18.039 You will water it down. Water in this case is 0:05:18.040 --> 0:05:21.839 the antithesis of an interesting flavor profile. Well. But the 0:05:21.880 --> 0:05:24.920 other half of that is sometimes people screw up making 0:05:24.920 --> 0:05:26.880 a drink because they don't shake it with ice at 0:05:26.880 --> 0:05:29.880 all when they're supposed to, and they don't understand that 0:05:30.040 --> 0:05:32.400 shaking with ice not only cools the drink, but it 0:05:32.480 --> 0:05:35.000 also adds a certain amount of water to the drink, 0:05:35.040 --> 0:05:39.040 which is an important ingredient. Yes, absolutely so, you're supposed 0:05:39.080 --> 0:05:40.840 to shake a cocktail and you don't. You end up 0:05:40.839 --> 0:05:44.000 with a drink that's usually too strong or too sweet. Yeah, 0:05:44.040 --> 0:05:46.280 there's a balance to be maintained there, much like the 0:05:46.640 --> 0:05:49.479 balance of of water in the human body that we 0:05:49.520 --> 0:05:51.840 discussed in the last episode. Many of you out there 0:05:51.880 --> 0:05:54.039 have probably met someone who claims to not like the 0:05:54.080 --> 0:05:59.320 taste of water. Sometimes they'll these individuals will will use 0:05:59.360 --> 0:06:02.080 flavored water or other beverages instead, and we'll tend to 0:06:02.120 --> 0:06:05.920 shy away from just drinking straight water. Um. But I 0:06:05.960 --> 0:06:08.479 don't know if you're like me, you know, perhaps you've 0:06:08.520 --> 0:06:10.960 noticed times when a glass of ice water is just 0:06:11.040 --> 0:06:14.240 super satisfying. Um, you know, particularly on a hot day, 0:06:14.440 --> 0:06:17.200 like a just a super cold water, lots of ice 0:06:17.240 --> 0:06:20.040 in it. Um, I would I would tend to. I 0:06:20.600 --> 0:06:24.800 found myself wanting to categorize that as delicious, though at 0:06:24.839 --> 0:06:27.680 the same time feeling weird for thinking that because it's 0:06:27.720 --> 0:06:30.040 like it's water, it I can't say it's delicious. It 0:06:30.480 --> 0:06:33.880 has no flavor, right, that's what we're we believe. Another 0:06:33.960 --> 0:06:37.200 another one I really like is the first sip of 0:06:37.360 --> 0:06:41.440 cold water that I have after I have brushed my teeth. Now, 0:06:41.520 --> 0:06:43.720 after I've brushed my teeth and rinsed and spit, I'm 0:06:43.760 --> 0:06:47.479 not drinking um water that way, but yeah, like, after 0:06:47.480 --> 0:06:49.839 I've brushed my teeth, I've walked into another room, I 0:06:49.880 --> 0:06:52.600 have a sip of water, super cool and refreshing, agreed, 0:06:52.680 --> 0:06:54.720 much better than the sip of orange juice after you 0:06:54.800 --> 0:06:57.160 brush your teeth, which is I don't know if you've 0:06:57.160 --> 0:07:02.039 ever tried that. It's it's fame disgusting. Oh this is 0:07:02.120 --> 0:07:05.000 this is always the worst. Really getting into the weeds here. 0:07:05.120 --> 0:07:09.080 But um, that that feeling when you you were you're 0:07:09.120 --> 0:07:11.640 busy in the morning, you go brush your teeth, You 0:07:11.680 --> 0:07:13.640 come back and you find your coffee cup and it 0:07:13.720 --> 0:07:16.840 still has half a cup of coffee in it. Heartbreaking 0:07:17.240 --> 0:07:19.000 because you know you can't drink it. Now, if you drink, 0:07:19.040 --> 0:07:20.960 you can drink it, you can you can throw it back, 0:07:21.200 --> 0:07:23.640 but it's gonna taste awful. I wonder if anybody's ever 0:07:23.680 --> 0:07:26.080 done a controlled study of how long you have to 0:07:26.120 --> 0:07:29.440 wait after brushing your teeth before those those horrible flavor 0:07:29.480 --> 0:07:33.160 interactions fade away. I don't think it's too long, it's 0:07:33.480 --> 0:07:35.280 I mean, if I had to venture to guess, I'd 0:07:35.320 --> 0:07:38.920 say it couldn't be more than like twenty minutes. Right. Yeah. Now, 0:07:38.960 --> 0:07:39.960 of course, a lot of this, some of this is 0:07:40.000 --> 0:07:42.600 gonna very culture to culture. In some cultures, it's not 0:07:43.560 --> 0:07:46.600 it's not considered advisable to drink cold water. You want 0:07:46.640 --> 0:07:50.120 to drink hot water. Uh, So you know, there's it's gonna, 0:07:50.160 --> 0:07:51.920 it's gonna, it's gonna vary. There's a lot of cultural 0:07:51.960 --> 0:07:54.240 stuff going on here as well. Oh, I've never heard 0:07:54.240 --> 0:07:56.320 of that. What's what's an example of of a culture 0:07:56.360 --> 0:08:00.560 that favors hot water drinking. There's a connection if Maray services, 0:08:00.600 --> 0:08:04.360 a connection to traditional Chinese medicine here where um uh, 0:08:04.400 --> 0:08:06.920 the idea is that it's better for your health to 0:08:07.040 --> 0:08:09.920 drink hot water as opposed to cold water. But I 0:08:09.920 --> 0:08:13.240 don't remember any of the deeper details of regarding it all. Right, Well, 0:08:13.280 --> 0:08:16.080 to get us back on track, you had mentioned that 0:08:17.480 --> 0:08:19.960 maybe maybe it was wrong to say that tap water, 0:08:20.200 --> 0:08:22.160 you know, cold water coming in on a hot day 0:08:22.240 --> 0:08:26.840 was delicious because water itself doesn't really have a taste. 0:08:26.960 --> 0:08:30.800 And I think this is a common understanding, but is 0:08:30.840 --> 0:08:33.839 that true? Like it does it have a taste? Does 0:08:33.840 --> 0:08:35.520 it not have a taste? Does it have a taste. 0:08:35.520 --> 0:08:39.680 We're just so used to that we can't taste it anymore. Yeah, 0:08:40.760 --> 0:08:43.959 we'll like to We'll go back to Aristotle. Aristotle was 0:08:44.000 --> 0:08:47.080 certainly kind of in the no taste camp, stating that 0:08:47.160 --> 0:08:50.040 it was for the most part tasteless. Uh. The idea 0:08:50.120 --> 0:08:53.760 that water is it made liver flavors, but it it's 0:08:54.080 --> 0:08:56.600 in and of itself, does not have flavor. But a 0:08:56.640 --> 0:08:58.760 lot of a lot of work has gone into this 0:08:58.760 --> 0:09:03.080 this question of Uh, some some interesting studies. UM. I 0:09:03.120 --> 0:09:06.880 was reading an article by Berlin Game at All titled 0:09:06.960 --> 0:09:10.640 Understanding the Basics of Tap Water Taste, publishing the American 0:09:10.679 --> 0:09:15.560 Water Works Association Journal in two thousand seven. UM, and Uh. 0:09:15.600 --> 0:09:20.480 They point out that the basically you get the water 0:09:20.559 --> 0:09:24.920 is going to contain negatively and positively charged ions as minerals. 0:09:25.440 --> 0:09:27.160 You're gonna find that in your tap water, and that 0:09:27.240 --> 0:09:31.480 can positively and negatively affect taste. This is especially key, 0:09:31.559 --> 0:09:34.240 they point out as far as water regulations and reverse 0:09:34.280 --> 0:09:37.200 os moses go, which is to say, without without getting 0:09:37.240 --> 0:09:40.080 into all the chemistry, there are certainly differences in water 0:09:40.200 --> 0:09:43.840 flavor due to different minerals and other elements in the water. Now, 0:09:43.880 --> 0:09:48.760 another interesting thing about about tap water, especially uh, generally 0:09:48.800 --> 0:09:52.440 when you're drinking tap water, UH, the drinking water probably 0:09:52.440 --> 0:09:59.400 contains calcium, magnesium, sodium um. And according to Azila at 0:09:59.440 --> 0:10:03.160 all In in an article in the Journal of General 0:10:03.200 --> 0:10:06.800 Internal Medicine from two thousand one titled Comparison of Mineral 0:10:06.840 --> 0:10:09.960 content of tap water and bottled waters, the mineral content 0:10:09.960 --> 0:10:14.559 of drinking water UH like this ultimately maybe an important 0:10:14.640 --> 0:10:18.760 source of daily recommended mineral dosages. UH, certainly in the 0:10:18.840 --> 0:10:21.120 United States, which was the the area they were looking 0:10:21.160 --> 0:10:25.080 at here um and UH. And so basically, why we 0:10:25.160 --> 0:10:27.319 might think of water as being this thing that we 0:10:27.360 --> 0:10:30.000 would will, let's just purify the heck out of it. Uh, 0:10:30.040 --> 0:10:32.800 just give me the purest water possible. The purest water 0:10:32.880 --> 0:10:36.120 possible isn't necessarily going to be the healthiest or the 0:10:36.160 --> 0:10:40.000 tastiest UM, which I thought that was an interesting distinction. 0:10:40.080 --> 0:10:42.960 Like when when we when we purchased bottled water, we're 0:10:42.960 --> 0:10:45.720 not going and by and buying the distilled water usually, 0:10:45.760 --> 0:10:48.320 I mean, maybe maybe that's what you're doing. But for 0:10:48.360 --> 0:10:51.600 the most part, people are are are not buying distilled 0:10:51.600 --> 0:10:55.240 water for drinking purposes, right. But distilled water, even though 0:10:55.280 --> 0:10:58.120 it is probably the purest form of water you can get, 0:10:58.240 --> 0:11:02.160 is not necessarily better for any reason, not for not 0:11:02.240 --> 0:11:06.560 for health or for experience of drinking. Now, in terms 0:11:06.640 --> 0:11:08.360 of just trying to get down to the question, though, well, 0:11:08.360 --> 0:11:10.840 what what does it taste like? Okay, you know we're 0:11:10.840 --> 0:11:12.840 saying it can can go a little in this direction, 0:11:12.840 --> 0:11:15.920 a little in that direction. We have these mineral components, uh, 0:11:15.960 --> 0:11:18.640 you know, adding to the the flavor. But but what 0:11:18.880 --> 0:11:20.800 is the taste itself? And I think one of the 0:11:20.840 --> 0:11:23.040 interesting things about that question is that it forces you 0:11:23.120 --> 0:11:26.760 to take a step back and think about taste itself. Um. 0:11:26.800 --> 0:11:30.800 You know, taste involves both sensations on the tongue and 0:11:31.120 --> 0:11:34.240 olfactory information as well. So it's not only it's not 0:11:34.320 --> 0:11:38.160 only tasting with the mouth, it's smelling, uh whatever you 0:11:38.200 --> 0:11:42.319 know it is that you're consuming as well. Um and uh. 0:11:42.360 --> 0:11:46.400 And certainly we do taste contents in the water, though 0:11:46.640 --> 0:11:49.360 under ideal circumstances that not that's not going to push 0:11:49.360 --> 0:11:52.240 you hard in any direction. But but obviously if you 0:11:52.320 --> 0:11:55.360 dilute some sugar and a glass of the universal solvent 0:11:55.400 --> 0:11:59.199 and drink it, you'll find it sweet saltwater taste salty. 0:11:59.400 --> 0:12:02.000 Your sense of taste is still weighing in on the water. 0:12:02.760 --> 0:12:05.560 But in terms of the this kind of brings us 0:12:05.559 --> 0:12:07.320 back to the same question. Does the water itself have 0:12:07.440 --> 0:12:09.559 a taste or is it just the vehicle for these 0:12:09.640 --> 0:12:13.400 various flavors, be it salt or sugar, or you know, 0:12:13.760 --> 0:12:16.959 a slight hint of of magnesium, that sort of thing. 0:12:18.440 --> 0:12:21.280 So one idea proposed in the sixties and seventies by 0:12:21.360 --> 0:12:25.400 psychologist Linda barda Shut was that the taste of water 0:12:25.640 --> 0:12:29.000 is more of an after taste of prior eating and drinking. 0:12:29.440 --> 0:12:31.400 And this too, I guess it is more in line 0:12:31.400 --> 0:12:33.679 with the idea of water as the vehicle flavor, but 0:12:33.800 --> 0:12:37.480 something that is in and of itself flavorless. So the 0:12:37.520 --> 0:12:40.920 idea would be that, like when you take a drink 0:12:40.960 --> 0:12:46.200 of water, you are somehow re experiencing flavors of foods 0:12:46.280 --> 0:12:49.760 you may have eaten most recently. Yeah, and this this 0:12:49.800 --> 0:12:52.200 will become important. And again we have to realize that 0:12:52.360 --> 0:12:55.080 when you take a sip of water, you were not 0:12:55.160 --> 0:13:00.280 introducing water no matter how sterile your water is, your 0:13:00.320 --> 0:13:03.680 mouth is is not sterile. You know your your mouth 0:13:03.880 --> 0:13:05.600 is going to even if you if you've just brush 0:13:05.640 --> 0:13:08.400 your teeth, great, but that you're going to have some 0:13:09.080 --> 0:13:13.000 semblance of of the of that experience in your mouth. 0:13:13.040 --> 0:13:14.840 If you're eating dinner, you know there's going to be 0:13:14.880 --> 0:13:18.280 the hint of food or drink as well. So, yeah, 0:13:18.320 --> 0:13:20.880 you're not introducing the water into a neutral place. If 0:13:20.880 --> 0:13:24.560 nothing else you your saliva is present. Emily Underwood wrote 0:13:24.600 --> 0:13:28.199 in an excellent short seventeen piece for the American Association 0:13:28.240 --> 0:13:30.920 for the Advancement of Science on this topic, the Flavor 0:13:30.960 --> 0:13:34.480 of Water, um and uh. At one point she's a 0:13:34.600 --> 0:13:37.520 citing Zachary Knight, oh, who is one of the three 0:13:37.520 --> 0:13:42.040 authors of the research summary thirst in Current Biology that 0:13:42.080 --> 0:13:43.839 I was referring to in the last episode, and I'll 0:13:43.880 --> 0:13:47.040 be talking about again in a few minutes. Yeah, So 0:13:47.160 --> 0:13:51.160 Underwood points to um, something that that we discussed in 0:13:51.200 --> 0:13:53.200 the last episode that you know, ultimately, when we're getting 0:13:53.240 --> 0:13:57.240 into taste, when we're getting into water detection in the mouth, 0:13:58.040 --> 0:14:01.120 the molecular and cellular mechanisms here are are not that 0:14:01.200 --> 0:14:04.400 well understood. And then she also touches on some of 0:14:04.640 --> 0:14:10.560 nights UM research regarding the thirst trigger, Uh, you know 0:14:10.600 --> 0:14:13.760 where where that is seems to locate in the brain 0:14:13.960 --> 0:14:16.320 and then ultimately what's where is the trigger in the 0:14:16.440 --> 0:14:18.600 in the rest of the body. But we'll come back 0:14:18.640 --> 0:14:21.120 to that in a bit. Yeah, but I guess there 0:14:21.120 --> 0:14:26.120 are somewhat separate questions for can you detect water in 0:14:26.200 --> 0:14:29.760 your mouth versus can you taste water? I mean those 0:14:29.800 --> 0:14:34.160 are slightly slightly different, right, yeah, well, but but then again, 0:14:34.440 --> 0:14:37.360 when you start thinking about like what what taste is, 0:14:37.800 --> 0:14:40.240 maybe they're not that different, like it's but but it 0:14:40.280 --> 0:14:42.880 basically comes down to, yeah, it's not about interpreting these 0:14:42.920 --> 0:14:46.080 minerals or sweetness or saltiness, but like the just the 0:14:46.560 --> 0:14:49.840 basic signal of it is water. It is in my mouth, 0:14:50.120 --> 0:14:53.320 you know, um, And then ultimately being able to tell 0:14:53.520 --> 0:14:56.680 if something is not water, um, like or if it 0:14:56.920 --> 0:14:58.520 or if the water is you know, too far in 0:14:58.520 --> 0:15:01.120 a particular direction, like oh it is it is actually 0:15:01.160 --> 0:15:05.200 oil and water and not just water, Um, I wanted water. 0:15:05.360 --> 0:15:08.400 That's sort of question. So researchers have been trying to 0:15:08.440 --> 0:15:12.400 isolate water sensing taste receptor. It sells on the tongue 0:15:12.920 --> 0:15:15.320 um of a particular note here is the paper the 0:15:15.360 --> 0:15:19.160 segular Mechanism for Water Detection in the Mammalian Taste system 0:15:19.200 --> 0:15:24.800 by Zocchi at All published in Nature Neuroscience in UM. 0:15:24.840 --> 0:15:28.240 This was a team I believe from the California Institute 0:15:28.240 --> 0:15:31.280 of Technology in Pasadena, and they were working with mice 0:15:31.920 --> 0:15:33.400 UH and this is this is one of those the 0:15:33.520 --> 0:15:36.320 studies that I mean, it's already an interesting area, like 0:15:36.520 --> 0:15:39.080 using mice to figure out how we're tasting, but then 0:15:39.160 --> 0:15:43.760 it goes in ultimately strange directions that are pretty fascinating. 0:15:44.160 --> 0:15:47.160 So they were they were using different varieties of mice 0:15:47.360 --> 0:15:51.640 with specific types of taste receptor cells genetically knocked out 0:15:52.120 --> 0:15:55.560 in order to try and isolate which ones were seemingly 0:15:55.720 --> 0:15:59.200 useful in tasting water. And they found that the acid 0:15:59.280 --> 0:16:03.640 sensing sour taste receptor cells seemed to be the most involved. 0:16:04.440 --> 0:16:08.920 Mice with those knocked out took far longer distinguishing oily 0:16:08.960 --> 0:16:13.520 water from clean water. UM. In the words of the study, 0:16:13.880 --> 0:16:18.720 this quote compromise discrimination between water and non aqueous fluids. 0:16:19.320 --> 0:16:22.160 So these cells seem like they may they may well 0:16:22.200 --> 0:16:26.680 be very much involved in UH in the process. Interesting, Okay, 0:16:26.720 --> 0:16:30.720 So if we are actually tasting water, it may rely 0:16:31.000 --> 0:16:35.240 more on the cells that normally taste sourness or acidity 0:16:35.280 --> 0:16:38.080 than other taste receptor cells, or at least in mice, 0:16:38.120 --> 0:16:40.240 and if if the same held true in humans, that 0:16:40.280 --> 0:16:43.280 would be the case for us. But this is where 0:16:43.280 --> 0:16:47.680 the mouse experiment from this team gets weird. Um. So 0:16:47.720 --> 0:16:50.760 to further test this out, they bread mice that could 0:16:50.760 --> 0:16:55.520 taste light with these acids sensing t rcs UH taste 0:16:55.520 --> 0:16:58.920 receptor cells. They train them to drink water from a pigot, 0:16:59.120 --> 0:17:03.480 and they replace that'spigot with an optic fiber cable, so 0:17:03.640 --> 0:17:07.680 they they they apparently treated the mice in this case, 0:17:07.800 --> 0:17:10.480 they apparently treated the light as if they were tasting water, 0:17:11.040 --> 0:17:14.679 but they didn't stop. They kept drinking the light long 0:17:14.720 --> 0:17:19.560 after UH they would have normally stopped drinking water. So 0:17:19.600 --> 0:17:23.320 the acid sensing t rcs might be involved in triggering drinking, 0:17:24.080 --> 0:17:26.679 but they might not be involved in stopping you from drinking, 0:17:26.720 --> 0:17:28.679 like saying, okay, well that's that's all the water I 0:17:28.720 --> 0:17:32.840 need to drink right now, um and um. And I'm 0:17:32.840 --> 0:17:34.639 not sure there may be other complications there. I mean, 0:17:34.720 --> 0:17:37.240 once you you have an animal drinking light and not 0:17:37.400 --> 0:17:40.119 actual water. Um, it just seems to me like there 0:17:40.160 --> 0:17:41.760 might there might be other things going on there on 0:17:41.840 --> 0:17:44.560 in a very physical basis. So this would be taste 0:17:44.600 --> 0:17:48.840 receptor cells in the mouth, but they're like optically sensitive cells. 0:17:49.160 --> 0:17:52.400 Am I right about this? It's literally like drinking light 0:17:52.560 --> 0:17:55.920 with their mouth, like letting light shine into the oral cavity. 0:17:56.480 --> 0:18:00.159 Yes it uh, I mean it sounds insane and you 0:18:00.200 --> 0:18:02.439 say it out loud, but but yeah, there's there's actually 0:18:02.520 --> 0:18:06.440 a YouTube video about it from Science Magazine titled these 0:18:06.520 --> 0:18:09.800 mice are drinking light. H So if anyone needs to 0:18:10.200 --> 0:18:13.000 actually see what we're talking about here, pull that up. 0:18:13.119 --> 0:18:15.560 And yeah, it just it's it's a this, this black 0:18:15.720 --> 0:18:19.680 mouse going up to this, um, this little receptacle, and 0:18:20.160 --> 0:18:23.120 it appears to be drinking, but there's blue light flooding 0:18:23.119 --> 0:18:25.880 out of the hole, okay, and it's got light sensitive 0:18:25.920 --> 0:18:28.840 cells in its mouth. So the mouse's brain is reacting 0:18:29.000 --> 0:18:31.720 as if by shining light into its mouth it was 0:18:31.920 --> 0:18:36.680 swallowing water. Yes, that's crazy, man, Yeah it is. This 0:18:36.840 --> 0:18:40.720 is this is it's it's it's mind blowing on several 0:18:40.800 --> 0:18:43.840 levels here. Um. So ultimately this this all might be 0:18:43.960 --> 0:18:47.840 related to changes in pH level. When in a normal situation, 0:18:47.920 --> 0:18:51.159 when you know, a mouse or any mammal supposedly is 0:18:51.240 --> 0:18:54.120 drinking something that is not light. When it it tries 0:18:54.160 --> 0:18:57.440 out the water, saliva is washing around in the mouth, 0:18:58.080 --> 0:19:02.240 and the removal of saliva might be key to sensing water. Again, 0:19:02.320 --> 0:19:04.560 coming back to what we said earlier about uh, you know, 0:19:05.240 --> 0:19:08.200 water is not entering into a neutral environment when it 0:19:08.240 --> 0:19:10.040 goes in your mouth. It's going to interact with at 0:19:10.119 --> 0:19:12.960 least saliva, and in doing so that might change the 0:19:13.040 --> 0:19:15.720 pH level which triggers these um these t r c 0:19:15.960 --> 0:19:18.399 s on the tongue. Um. That seems to be the 0:19:18.480 --> 0:19:22.040 basic framework we're potentially looking at here. Oh that's interesting. 0:19:22.119 --> 0:19:25.399 So at least according to the idea here, part of 0:19:25.480 --> 0:19:29.480 the sensation of of drinking water might be the water's 0:19:29.560 --> 0:19:34.159 ability to wash natural saliva out of the mouth. Right, So, 0:19:34.440 --> 0:19:39.320 of course standard caveat that more researches is required, And 0:19:39.359 --> 0:19:41.360 then we still don't we still don't have this one, Kno, 0:19:42.320 --> 0:19:45.479 But it's yeah, it's it. Ultimately, it makes you rethink 0:19:45.480 --> 0:19:49.159 again what taste actually is and consider there there may 0:19:49.160 --> 0:19:51.880 be precise triggers in place for detecting water and distinguish 0:19:51.920 --> 0:19:54.960 it from other liquids, and then also letting you know 0:19:55.080 --> 0:19:57.040 that you have had enough water. Like all these things 0:19:57.080 --> 0:19:58.760 that we just take for granted, we think of them 0:19:58.800 --> 0:20:01.360 as we think of them as choices that we make, 0:20:01.840 --> 0:20:03.960 like I have to, I have, I am, I've decided 0:20:04.000 --> 0:20:06.920 now I must have water. I have decided now that 0:20:07.640 --> 0:20:09.639 I don't need any more water. But but these are 0:20:09.720 --> 0:20:13.840 all tied into the you know, this intricate biological system. 0:20:18.240 --> 0:20:22.679 Thank thank Alright, well, Rob, if you're ready, I wanted 0:20:22.760 --> 0:20:25.680 to discuss some more of the things I was reading 0:20:25.920 --> 0:20:29.840 in that article and Current Biology that was about the 0:20:29.960 --> 0:20:35.639 biology of thirst. Again. This was by David Leeb, Christopher Zimmerman, 0:20:35.840 --> 0:20:38.879 and Zachary Knight. Let's do it all right now. We 0:20:38.960 --> 0:20:43.000 already talked about some of the conditions that will trigger 0:20:43.160 --> 0:20:46.400 thirst and water seeking behavior in animals such as rodents 0:20:46.480 --> 0:20:50.720 and humans. Uh uh. Commonly, one thing would be a 0:20:51.000 --> 0:20:54.520 decrease in water volume in the body, but another thing 0:20:54.560 --> 0:20:58.520 would be an increase in what's called blood OSMO reality 0:20:58.720 --> 0:21:01.399 O S M O L A L I T Y. 0:21:02.160 --> 0:21:04.159 I spell it because that word will keep coming up 0:21:04.200 --> 0:21:09.040 in this discussion. OSM reality is the concentration of substances 0:21:09.200 --> 0:21:12.760 dissolved in the water content of the body, so the 0:21:12.840 --> 0:21:16.280 blood osmolality will go up. Say, if you consume salt 0:21:16.640 --> 0:21:20.120 or consume other kinds of salts of various minerals, whether 0:21:20.240 --> 0:21:23.920 that's sodium or magnesium or whatever, there are lots of 0:21:23.960 --> 0:21:26.760 things dissolved in the blood, and is the concentration of 0:21:26.840 --> 0:21:29.960 those things dissolved in the blood goes up. That's that's 0:21:30.000 --> 0:21:33.600 known as increasing OSMO reality. And as we discussed in 0:21:33.640 --> 0:21:36.520 the last episode, your your awsom reality really needs to 0:21:36.640 --> 0:21:40.760 be pretty tightly constrained within an ideal range, or it 0:21:40.880 --> 0:21:45.880 can start leading to system wide problems with cellular function 0:21:46.040 --> 0:21:50.359 because cells need a pretty tightly controlled electrochemical gradient on 0:21:50.600 --> 0:21:54.360 each side of their their membranes in order to control 0:21:54.480 --> 0:21:56.920 the passage of ions in and out of the cell 0:21:57.040 --> 0:21:59.040 to you know, take in things, the cell needs to 0:21:59.160 --> 0:22:02.720 release waste products and so forth. So uh So, in 0:22:02.920 --> 0:22:05.520 order for your body to work right, it needs to 0:22:05.680 --> 0:22:09.080 have the right level of the right concentration of things 0:22:09.119 --> 0:22:13.080 like salts dissolved in its water. But you also have 0:22:13.240 --> 0:22:17.320 to keep your your body, your your body's water volume 0:22:17.400 --> 0:22:20.800