1 00:00:09,440 --> 00:00:14,160 Speaker 1: Hey, everybody, Welcome to another edition of Wisdom Wednesdays. Today, 2 00:00:14,480 --> 00:00:16,720 Speaker 1: I want to do a bit of a deep dive 3 00:00:17,040 --> 00:00:23,120 Speaker 1: into a topic that is so controversial in nutrition, it's 4 00:00:23,239 --> 00:00:27,840 Speaker 1: almost not how controversial is and that is about our 5 00:00:27,920 --> 00:00:32,400 Speaker 1: intake of saturated fats, should we have any and how much? 6 00:00:32,880 --> 00:00:35,640 Speaker 2: And I'm actually going to be a sist on a really. 7 00:00:35,280 --> 00:00:39,640 Speaker 1: Really good peer reviewed articles that was published in the 8 00:00:39,680 --> 00:00:44,760 Speaker 1: journal Nutrients in twenty twenty one, and the title of 9 00:00:44,800 --> 00:00:49,800 Speaker 1: it is Dietary Saturated Fats and Health. Are the US 10 00:00:49,880 --> 00:00:53,479 Speaker 1: guidelines And in brackets what they don't say is and 11 00:00:53,560 --> 00:00:57,920 Speaker 1: Australian and British and New Zealand and et cetera, et cetera. 12 00:00:58,560 --> 00:01:02,880 Speaker 1: Are they evidence best a good place to start obviously, 13 00:01:03,440 --> 00:01:04,240 Speaker 1: or what are. 14 00:01:04,319 --> 00:01:05,640 Speaker 2: The recommended guidelines? 15 00:01:06,000 --> 00:01:09,600 Speaker 1: So in the United States, the doger guidelines are for 16 00:01:09,680 --> 00:01:13,640 Speaker 1: Americans are recommended that saturated fat intake should be less 17 00:01:13,680 --> 00:01:17,839 Speaker 1: than ten percent of daily calories. And in the UK, 18 00:01:18,160 --> 00:01:22,360 Speaker 1: the UK's NTS follows suit and the guidelines there are 19 00:01:22,400 --> 00:01:25,880 Speaker 1: to keep saturated fat to a minimum, ideally below ten percent. 20 00:01:26,400 --> 00:01:30,119 Speaker 1: And in Australia it is the same thing, limiting saturated 21 00:01:30,160 --> 00:01:34,200 Speaker 1: fat as part of heart healthy eating and keeping it 22 00:01:34,240 --> 00:01:40,200 Speaker 1: below ten percent. So where did we get this idea from. Well, 23 00:01:40,240 --> 00:01:44,760 Speaker 1: this is about something called the diet heart hypothesis. So 24 00:01:44,880 --> 00:01:48,520 Speaker 1: back in the nineteen fifties, there's a physiologist named Ansel 25 00:01:48,680 --> 00:01:51,680 Speaker 1: Keys and he was the first to propose the heart 26 00:01:52,000 --> 00:01:55,640 Speaker 1: that are the diet heart hypothesis, and he suggested that 27 00:01:55,720 --> 00:02:00,840 Speaker 1: saturated fat raises total serum cholesterol, which increases the risk 28 00:02:00,960 --> 00:02:05,240 Speaker 1: for heart disease. And the idea took off, especially after 29 00:02:05,320 --> 00:02:10,640 Speaker 1: he presented his very famous seven country study and to 30 00:02:10,919 --> 00:02:16,240 Speaker 1: the American Cardiology Society meeting. And this study that he 31 00:02:16,320 --> 00:02:21,840 Speaker 1: had published link saturated fat to heart disease across populations 32 00:02:21,880 --> 00:02:25,160 Speaker 1: in seven different countries, and he showed in these seven 33 00:02:25,200 --> 00:02:30,320 Speaker 1: countries that greater intakes of saturated fat were associated with 34 00:02:30,480 --> 00:02:34,120 Speaker 1: greater intakes of or sorry, greater incidents of heart disease. 35 00:02:34,600 --> 00:02:37,400 Speaker 1: But here's something that's really important. A couple of things 36 00:02:37,440 --> 00:02:40,840 Speaker 1: that are really important. It wasn't a clinical trial. It 37 00:02:40,880 --> 00:02:46,760 Speaker 1: was observational, but it only collected detailed dietary data on 38 00:02:46,880 --> 00:02:51,120 Speaker 1: less than five percent of the participants, right, and it 39 00:02:51,160 --> 00:02:54,760 Speaker 1: was fewer than one hundred people per country, And that's 40 00:02:54,880 --> 00:03:00,840 Speaker 1: not exactly a strong foundation for decades of global nutrition policy. 41 00:03:01,320 --> 00:03:05,240 Speaker 1: And what we now know is that ansel Keys didn't 42 00:03:05,360 --> 00:03:10,080 Speaker 1: just study seven countries. He studied twenty two countries, but 43 00:03:10,400 --> 00:03:15,000 Speaker 1: fifteen of them didn't fit his hypothesis, so he left 44 00:03:15,000 --> 00:03:18,079 Speaker 1: it out. Now, that is not poor research. 45 00:03:18,600 --> 00:03:21,960 Speaker 2: That is fraudulent research. There's nothing. 46 00:03:21,960 --> 00:03:25,280 Speaker 1: I just finished my PhD and we I had to 47 00:03:25,400 --> 00:03:31,079 Speaker 1: redo something on ethics and ethical research. And it's very 48 00:03:31,240 --> 00:03:36,200 Speaker 1: clear that ansel Keys conducted unethical research. And if I 49 00:03:36,280 --> 00:03:39,080 Speaker 1: had a present of that in my PhD, I wouldn't 50 00:03:39,120 --> 00:03:41,520 Speaker 1: have just feel I would have just been kicked off 51 00:03:41,560 --> 00:03:46,040 Speaker 1: the course for doing something like that. Now, despite all 52 00:03:46,120 --> 00:03:49,560 Speaker 1: of this, right, and despite the fact that even his 53 00:03:49,760 --> 00:03:53,880 Speaker 1: study that he produced and had fewer than one hundred 54 00:03:53,880 --> 00:03:54,880 Speaker 1: people per country, so. 55 00:03:54,840 --> 00:03:55,960 Speaker 2: It's a very. 56 00:03:57,880 --> 00:04:04,600 Speaker 1: Low participant of observational study. Despite all of this, saturated 57 00:04:04,600 --> 00:04:09,080 Speaker 1: fat became public enemy number one, especially after President Eisenhower 58 00:04:09,440 --> 00:04:12,160 Speaker 1: had a heart attack. So there was this big drive 59 00:04:12,600 --> 00:04:17,239 Speaker 1: to reduce heart disease. And then in nineteen early nineteen eighties, 60 00:04:17,279 --> 00:04:21,960 Speaker 1: the first Diarty Guidelines for Americans recommended limiting It was 61 00:04:22,000 --> 00:04:26,520 Speaker 1: about cholesterol in then and and the early nineteen nineties, 62 00:04:26,920 --> 00:04:30,760 Speaker 1: it was to limit your intake of saturated fats and 63 00:04:30,880 --> 00:04:33,440 Speaker 1: ten percent was the hardcap, and that. 64 00:04:33,560 --> 00:04:35,919 Speaker 2: Has actually stayed to this day. 65 00:04:36,400 --> 00:04:39,360 Speaker 1: Now, if you go and you look back the sixties 66 00:04:39,400 --> 00:04:46,240 Speaker 1: and seventies, there were several large randomized control trials testing this, 67 00:04:46,240 --> 00:04:50,480 Speaker 1: this diet heart hypothesis. And these randomized control trials, which, 68 00:04:50,680 --> 00:04:52,159 Speaker 1: as you'll know if you listen to this, are the 69 00:04:52,240 --> 00:04:53,360 Speaker 1: best form of evidence. 70 00:04:53,800 --> 00:04:55,000 Speaker 2: They included around. 71 00:04:54,720 --> 00:04:59,200 Speaker 1: Sixty seven thousand participants and ran for up to seven years, 72 00:04:59,279 --> 00:05:03,040 Speaker 1: so long enough to track hard outcomes like heart attacks 73 00:05:03,040 --> 00:05:03,520 Speaker 1: and death. 74 00:05:04,040 --> 00:05:05,360 Speaker 2: What did these trials show. 75 00:05:05,600 --> 00:05:08,960 Speaker 1: Well, certainly not what you expect if you support the 76 00:05:09,040 --> 00:05:12,680 Speaker 1: ditary guidelines or believe in them. The totality of evidence 77 00:05:13,000 --> 00:05:17,599 Speaker 1: did not support the idea that lowering saturated fat reduces 78 00:05:17,640 --> 00:05:22,839 Speaker 1: cardiovascular risk. Yet, and this is crucial, these trials were 79 00:05:23,040 --> 00:05:28,320 Speaker 1: largely ignored in the shaping of official dietary guidelines, and 80 00:05:28,360 --> 00:05:33,719 Speaker 1: in fact, at twenty eighteen, Citation network analysis showed very 81 00:05:33,839 --> 00:05:39,040 Speaker 1: clear bias in the literature, with eighty two percent of 82 00:05:39,200 --> 00:05:43,000 Speaker 1: supportive reviews. These are reviews that support reducing saturated fat 83 00:05:43,560 --> 00:05:49,719 Speaker 1: only cite one positive trial while ignoring others with contradictory findings. 84 00:05:49,720 --> 00:05:54,839 Speaker 1: So there was very clear bias right now going on 85 00:05:55,240 --> 00:06:00,000 Speaker 1: about saturated fat. So let's revisit the evidence. That's fast 86 00:06:00,080 --> 00:06:02,920 Speaker 1: forward and now to twenty ten. And by the way, 87 00:06:02,960 --> 00:06:05,880 Speaker 1: what tends to happen with these things When they get 88 00:06:06,120 --> 00:06:12,360 Speaker 1: enshrined in the recommendations, it becomes very hard to shift 89 00:06:12,400 --> 00:06:14,839 Speaker 1: them out of it. And then you have people who've 90 00:06:14,839 --> 00:06:17,839 Speaker 1: based their whole career on this who tend to sit 91 00:06:17,920 --> 00:06:22,640 Speaker 1: and influence the diactary guidelines, and that's how it becomes 92 00:06:22,720 --> 00:06:23,520 Speaker 1: very hard to shape. 93 00:06:23,560 --> 00:06:25,360 Speaker 2: But let's talk about the evidence. Now. 94 00:06:25,839 --> 00:06:30,159 Speaker 1: Since twenty ten, we've seen a wave of systematic reviews 95 00:06:30,160 --> 00:06:35,520 Speaker 1: and meta analysis on this topic, including from heavyweights like 96 00:06:35,560 --> 00:06:38,800 Speaker 1: the Cochrane Collaboration. So if you know anything about researcher, 97 00:06:38,839 --> 00:06:42,600 Speaker 1: you can just google it. Anything that the Cochrane Collaboration 98 00:06:42,880 --> 00:06:44,960 Speaker 1: puts out tends to be the. 99 00:06:45,000 --> 00:06:46,800 Speaker 2: Strongest form of evidence. 100 00:06:46,839 --> 00:06:51,719 Speaker 1: These our meticulously done reviews, and these reviews find that 101 00:06:51,880 --> 00:06:58,919 Speaker 1: reducing saturated fats does not significantly impact mortality, heart attacks. 102 00:06:58,760 --> 00:06:59,479 Speaker 2: Or strokes. 103 00:07:00,040 --> 00:07:04,240 Speaker 1: And the twenty twenty Cochrane review, which was considered very 104 00:07:04,360 --> 00:07:10,679 Speaker 1: very rigorous, found no significant benefit when trials that less 105 00:07:10,880 --> 00:07:16,160 Speaker 1: successfully reduced saturated fat were analyzed separately and on the 106 00:07:16,240 --> 00:07:21,080 Speaker 1: observational front. Out of at least eight large meta analysis 107 00:07:21,480 --> 00:07:25,800 Speaker 1: most found no association between saturated fat and cornary heart disease, 108 00:07:26,360 --> 00:07:30,080 Speaker 1: and one twenty twenty Umbrella review, which is a review 109 00:07:30,160 --> 00:07:36,520 Speaker 1: of reviews, concluded that the diet heart hypothesis is of 110 00:07:36,920 --> 00:07:44,160 Speaker 1: uncertain validity. So let's talk about this word is this idea? 111 00:07:44,280 --> 00:07:48,840 Speaker 1: Why is it still so pervasive? Well, the whole basis 112 00:07:48,840 --> 00:07:53,480 Speaker 1: of this is about LDL cholesterol. So there is a 113 00:07:53,480 --> 00:07:58,360 Speaker 1: big are's a well documentary mack documented fact that saturated 114 00:07:58,400 --> 00:08:03,720 Speaker 1: fat can increase ld L cholesterol, often dubbed the bad cholesterol. 115 00:08:04,000 --> 00:08:07,280 Speaker 1: Right now, there are a couple of things on this. Firstly, 116 00:08:07,640 --> 00:08:11,800 Speaker 1: saturated fat does increase your total cholesterol, increases LDL cholesterol 117 00:08:12,080 --> 00:08:15,680 Speaker 1: and increases hates the L cholesterol, which is her brackets 118 00:08:15,720 --> 00:08:19,800 Speaker 1: the good cholesterol. But it's the detail that's really important. 119 00:08:20,480 --> 00:08:27,000 Speaker 1: Saturated fats mainly rese large LDL particles. So just to 120 00:08:27,040 --> 00:08:30,640 Speaker 1: take a step back, when you look at LDL, they 121 00:08:30,680 --> 00:08:34,760 Speaker 1: are particles of different size, And what we now know 122 00:08:35,520 --> 00:08:43,920 Speaker 1: is that large LDL particles and these particles are not pathogenic, 123 00:08:44,240 --> 00:08:49,320 Speaker 1: and it's the small, dense LDL that is the issue. 124 00:08:49,760 --> 00:08:54,760 Speaker 1: And saturated fats mainly real is large LDL particles, the 125 00:08:54,920 --> 00:09:01,160 Speaker 1: non pathogenic ones and don't affect your small dense LDL particles, 126 00:09:01,200 --> 00:09:04,360 Speaker 1: And at the same time saturated fat raises. As I 127 00:09:04,360 --> 00:09:07,960 Speaker 1: said earlier, they hates DL right, and proving the total 128 00:09:08,040 --> 00:09:12,000 Speaker 1: cholesterol ratio. That's a better marker of risk, but a 129 00:09:12,360 --> 00:09:16,199 Speaker 1: much better marker of your overall risk than just LDL 130 00:09:16,200 --> 00:09:20,760 Speaker 1: particles is the amount of small dense LDL particles. So 131 00:09:21,280 --> 00:09:25,600 Speaker 1: in short, using LDL as a proxy for heart disease, 132 00:09:26,200 --> 00:09:27,920 Speaker 1: it is overly. 133 00:09:27,480 --> 00:09:30,160 Speaker 2: Simplistic, very very clearly. 134 00:09:30,080 --> 00:09:33,640 Speaker 1: And half of all people who die from heart disease 135 00:09:33,679 --> 00:09:36,600 Speaker 1: have got normal levels of LDL. So if it was 136 00:09:36,840 --> 00:09:40,840 Speaker 1: such an issue, that really wouldn't be the case now. 137 00:09:41,080 --> 00:09:47,200 Speaker 1: The twenty twenty Datary Guidelines for Americans committee excluded nearly 138 00:09:47,360 --> 00:09:53,200 Speaker 1: twenty review papers by external scientists, and they instead relied 139 00:09:53,400 --> 00:09:58,520 Speaker 1: on in house USDA reviews, and of the thirty nine 140 00:09:58,559 --> 00:10:03,600 Speaker 1: studies that they cite as support for keeping saturated fats low, 141 00:10:04,280 --> 00:10:07,640 Speaker 1: eight percent of those thirty nine studies had null or 142 00:10:07,720 --> 00:10:12,480 Speaker 1: negative finding. Yet the guidelines still recommend capping saturated fat 143 00:10:12,760 --> 00:10:16,320 Speaker 1: at ten percent of total calories. And about the food 144 00:10:16,360 --> 00:10:21,280 Speaker 1: they found that diry including butter, was either neutral or 145 00:10:21,320 --> 00:10:24,720 Speaker 1: beneficial for heart disease risk. These are these reviews and 146 00:10:24,800 --> 00:10:28,960 Speaker 1: meat had mixed findings, but again most of the studies 147 00:10:29,000 --> 00:10:33,760 Speaker 1: showed no consistent harm from saturated fat rich studs and 148 00:10:33,840 --> 00:10:37,920 Speaker 1: another noteworthy study, there's this influential what's called Pure study, 149 00:10:38,320 --> 00:10:41,200 Speaker 1: which followed over one hundred and thirty five thousand people 150 00:10:41,400 --> 00:10:45,480 Speaker 1: across five continents, and it found no link between saturated 151 00:10:45,520 --> 00:10:49,880 Speaker 1: fat and heart disease and a lower risk of stroke 152 00:10:50,160 --> 00:10:53,600 Speaker 1: in those who had higher levels of saturated fat. Now, 153 00:10:54,200 --> 00:10:58,079 Speaker 1: there's also something that's really important to understand, and we 154 00:10:58,160 --> 00:10:58,760 Speaker 1: eat food. 155 00:10:59,000 --> 00:11:00,520 Speaker 2: We don't eat nets. 156 00:11:00,960 --> 00:11:02,760 Speaker 1: I don't know the last time you've gone up and 157 00:11:02,800 --> 00:11:08,520 Speaker 1: you've ordered a serving of saturated fat or polyphenols are 158 00:11:08,640 --> 00:11:13,080 Speaker 1: a serving of fiber. We eat the food matrix, and 159 00:11:13,120 --> 00:11:16,760 Speaker 1: it's how these nutrients are packed together that plays a 160 00:11:16,800 --> 00:11:20,480 Speaker 1: big role in our health effects. So, for instance, the 161 00:11:20,559 --> 00:11:24,360 Speaker 1: saturated fat in cheese behaves very differently in your body 162 00:11:24,559 --> 00:11:27,239 Speaker 1: than the saturated fat in process meats. 163 00:11:27,760 --> 00:11:28,800 Speaker 2: And even more. 164 00:11:28,640 --> 00:11:32,280 Speaker 1: Than that, it's our overall diet that matters. So, for instance, 165 00:11:32,320 --> 00:11:37,679 Speaker 1: if you look at the evidence low carb diets, saturated 166 00:11:37,720 --> 00:11:40,280 Speaker 1: fat is burned for fuel when you have a low 167 00:11:40,360 --> 00:11:44,040 Speaker 1: carb diet rather than stored and can actually lead to 168 00:11:44,080 --> 00:11:48,480 Speaker 1: improved cardio metabolic health when you're having a low carb diet. 169 00:11:48,640 --> 00:11:52,240 Speaker 1: What is clear from some other studies it's saturated fat 170 00:11:52,400 --> 00:11:57,000 Speaker 1: in the presence of carbohydrate and especially sugar that actually 171 00:11:57,040 --> 00:12:01,120 Speaker 1: becomes slightly more damaging. Right, But this move away from 172 00:12:01,240 --> 00:12:05,960 Speaker 1: isolated nutrients and that's been embraced for total fat and 173 00:12:06,080 --> 00:12:10,480 Speaker 1: ditary cholesterol. Yet the whole guidelines are insaturated fat remain 174 00:12:10,559 --> 00:12:12,360 Speaker 1: pretty much stuck in the past. 175 00:12:13,120 --> 00:12:15,360 Speaker 2: So is it time for a rethink? 176 00:12:15,920 --> 00:12:21,040 Speaker 1: I think any rational scientist who has looked at the 177 00:12:21,080 --> 00:12:27,920 Speaker 1: studies and particularly the totality of evidence, including looking at 178 00:12:28,000 --> 00:12:31,559 Speaker 1: high quality randomized control trials, and then looking at meta 179 00:12:31,600 --> 00:12:36,559 Speaker 1: analysis and umbrella reviews of meta analysis and real world 180 00:12:36,600 --> 00:12:41,760 Speaker 1: observational studies would say an overwhelming yes, it is at 181 00:12:41,920 --> 00:12:45,360 Speaker 1: least time to reevaluate it. And as I'm just going 182 00:12:45,360 --> 00:12:48,200 Speaker 1: to leave you on this one with a quote from 183 00:12:48,200 --> 00:12:52,120 Speaker 1: the authors of a comprehensive twenty twenty one review put it. 184 00:12:52,800 --> 00:12:57,920 Speaker 1: They said, making a strong recommendation based on weak and 185 00:12:58,080 --> 00:13:04,840 Speaker 1: contradictory evidence does not meet scientific standards for guidelines. Yet, 186 00:13:05,320 --> 00:13:09,040 Speaker 1: and we have these guidelines in many many countries around 187 00:13:09,040 --> 00:13:13,239 Speaker 1: the world, and they are based on very flawed evidence. 188 00:13:13,920 --> 00:13:14,760 Speaker 1: That's it for this week. 189 00:13:14,800 --> 00:13:16,280 Speaker 2: Folks, catch you next time.