I listened to the audio book. Can I get access to the references?
Indeed you can, here.
Aren’t you guilty of cherry picking the data in the same way that you criticize?
Cherry picking means selectively choosing studies that support one’s hypothesis while ignoring those that don’t. It is an accusation that can be levied at someone who is proposing a hypothesis. However, it cannot be levied at me, because I’m not proposing a hypothesis (I don’t know what causes heart disease or obesity). In my book, I suggest that excessive carbohydrates, especially of the refined kind, might be driving chronic diseases. I think the evidence is stacking up to show that a low-carb, high-fat diet is better than a low-fat diet in fighting these diseases. However, this doesn’t mean that either excessive carbohydrates or sugar themselves are the causes of these conditions. Vegetable oils high in omega 6 fatty acids may also play a role, or something else that we don’t know about. I don’t think the science is determinative on any of these questions. So again, I’m not proposing a hypothesis and therefore am not vulnerable to the cherry-picking criticism. What I do in my book is to criticize an existing hypothesis, namely, that saturated fat, total fat, and cholesterol cause disease. Because this has been the dominant hypothesis since 1961 and has been our official policy, its evidence base can legitimately be questioned. The examples I give (of the Inuit or Masai) are not meant to suggest that these are the norm or the best diet but simply to show that these observations contradict this existing hypothesis. These examples show that people can be healthy eating a high-fat diet and therefore that the diet-heart hypothesis might not be correct.
Furthermore, I think there’s no doubt that the evidence used to sustain the diet-heart hypothesis has been cherry picked. Large clinical trials have been ignored. In the case of the largest-ever trial to test the hypothesis, the investigators simply didn’t publish the results for 16 years, because apparently they were so disappointed in the way they came out. This is selection bias, or cherry picking, at work.
And one can see that this selection bias is now, finally, being corrected, as experts are re-assessing the evidence and reversing out of major pieces of the diet-heart hypothesis: the backtracking on cholesterol and total fat, for instance. And there are now major questions among experts about the advice on saturated fat. What will replace that long-standing hypothesis about the cause of chronic diseases, I don’t know. I would urge caution about jumping to conclusions. It think there are good indications that playing a role is some combination of sugar, refined carbs, and too many carbohydrates (maybe combined with sugar) overall. Perhaps vegetable oils play a role, as well as the rise of ‘snack’ culture, which means that people eat carbs all day long and are therefore chronically exposed to insulin. I don’t think we know the exact cause, but it seems likely that carbohydrates in some form and quantity are driving these epidemics.
Are you saying we can just go out and eat sticks of butter/meat 3x a day/etc?
These foods have been condemned based on their cholesterol and saturated fat content, yet now, these two pillars of the diet-heart hypothesis have been questioned: dietary cholesterol is no longer thought to lead to adverse blood lipids, and the link between saturated fat and cardiovascular mortality has been challenged, in major review papers by top scientists in the field. If saturated fat and cholesterol do not cause disease, then there is no reason to avoid these foods. That doesn’t mean gorge on them. It just means: let them out of jail. They’ve been unfairly condemned based on weak evidence.
Also, there’s quite a lot of evidence suggesting that a higher-fat diet (that is, more fat than the official “low-fat” diet, which has been anywhere from 25 to 35% of calories as fat) is healthy and safe, and largely better than a low-fat diet in fighting obesity, diabetes, and heart disease. And how do you get to a higher fat diet? Unless you’re drinking bowlfuls of vegetable oils like Italian peasants, the only way to get that fat is to eat the foods that naturally contain fat, which are animal foods. These are natural, whole fats. By comparison, vegetable oils are highly processed industrial products that were only introduced to the American diet in the early 1900s. There’s quite a lot of worrisome data on vegetable oils, especially when they’re heated (in my book, chapter 9). So for reasons of practicality and health, a higher fat diet should include animal foods.
This is not to say that some people do not thrive on a high-carb diet: certainly they do. Human responses to diet vary enormously. My point is that for the majority of Americans who are overweight, pre-diabetic or diabetic, the science shows that a diet restricted in carbohydrates to some degree is healthier and that our official recommendations should be flexible enough to recommend this option.
The positive arguments in favor of animal foods are
- They are far more nutrient dense than plant foods (and their nutrients have been shown to be more bio-available than those in plant foods). For instance, vitamin B12 is not available in plant foods. Fat-soluble vitamins A, D, E and K need fat to absorb properly—and this fat comes naturally in animal foods. (The current USDA diet is inadequate in D without fortified foods.) Choline is hard to get in plant foods. Etc.
- Protein and fat are far more satiating than carbohydrates, so people eating animal foods are less likely to overeat. One of the possible explanations for the obesity epidemic is that when Americans shifted to eating more carbohydrates, these less-satiating foods left them hungry and more likely to overeat. Studies show that people have a hard time overeating on protein and fat. Think about it: if you eat bacon and eggs for breakfast, you’re not hungry until lunch, whereas that’s not true with a low-fat yogurt.
- Finally, the historical record supports a diet higher in animal foods—150 years ago, we ate far more red meat, cheese, butter and lard than we do today (butter and lard were the principal fats that Americans used for cooking before 1900). We ate this way before the epidemics of heart disease, obesity and diabetes (and plenty of people lived long enough to contract these diseases).
Why do you talk in the language of macronutrients when we should really be talking about foods?
I would also prefer to talk about foods rather than macronutrients. As I write in my book, no one asks their mom for 40% carbs and 20% fat for dinner—they ask for spaghetti and meatballs. However, the reality is that the last 50 years of nutrition science has been conducted on macronutrients. If you read 3,000 nutrition studies, you will find 90% of them are about % fat, saturated fat, carbohydrates, etc. Therefore, any analysis of that science must be on its own terms. That’s where we have the data. It’s nice to talk about “real foods,” but we have far less rigorous science on actual foods.
Even if saturated fats are OK for health, it depends on what you replace them with. Agreed that we should not replace them with carbohydrates, but let’s replace them with other things.
This argument sounds logical, but it doesn’t lead anywhere reasonable. To the question, what should we eat instead of saturated fats, here are the only options: 1. unsaturated fats (olive oil, seed oils like soybean, corn and canola, seeds, nuts, avocados), 2. carbohydrates, 3. protein. (There are only 3 macronutrients—protein, carbohydrate, and fat—and all foods are made from these). Of these options, 1. Vegetable oils are worrisome, especially when heated. And do we really want to be drinking bowls of vegetable oils? Seeds, nuts and avocados are also fine, but these don’t make up a meal. 2. Carbohydrates—too many of these are bad for health, and we are now trying to back out of a high-carb diet, 3. Protein. Yes, we could eat more of this, but too much protein without the accompanying fat is not good for health. Anyway, except for fish/shellfish, protein is most commonly found in animal foods, most of which contain saturated fats (So you’re back to saturated fats). Otherwise, there’s soy protein. In sum, saturated fats can be replaced by: avocados, seeds, nuts, non-starchy vegetables, fish olive oil, soy proteins, and vegetable oils. The last item on this list is a highly processed recent invention. And altogether, they are highly limited food choices. If you look at the human diet in history, you will find hardly any record of humans surviving on this kind of diet. If you take the limits off saturated fats, then you can introduce back into the diet a far wider variety of foods,–eggs, regular dairy, meat—all of which are dense in nutrients and highly satiating and have been part of the human diet for millennia.
You’re wrong: what changed in the late 1970s and led to our obesity/diabetes epidemics was that Americans stopped cooking at home.
This may be true. There is, indeed, an association between less home cooking and the rise of the obesity and diabetes epidemics. However, we know that an association does not mean causation. What is the evidence that the loss of home cooking caused these epidemics. The clinical trial evidence is nearly non-existent. The 2015 Dietary Guidelines report examined this question and found that the evidence to support it was Grade III, “Limited,” which is the lowest grade for available evidence. And there’s the obvious question: doesn’t it matter what you cook? A dinner of pasta has a very different metabolic effect than one of meat.
You’re wrong: the problem is that Americans aren’t eating enough fruits and vegetables.
In fact, “fruits and vegetables” is one of the fastest growing categories of food consumption over the past 40 years. Americans eat 13% more fruits and 23% more vegetables today than they did in 1970, according to government data, with the biggest increase being in leafy greens (This is availability data that has been adjusted for food loss, so the numbers are iffy, but they are the best available government data. And the percent increases in these categories are large, so one can say with some confidence that they accurately reflect overall trends). These numbers show that Americans have largely complied with government advice. It’s hard to make the case that we still aren’t eating enough fruits and vegetables when the dramatic increase in recent decades has paralleled the dramatic increases in rates of obesity and diabetes.
You’re wrong: the problem is that Americans don’t exercise enough.
Is our sedentary lifestyle responsible for the obesity epidemic? Let’s remember that there were few gyms and no joggers before about 1970. Our grandparents didn’t jog and many of them held office jobs. Evidence is stacking up that aerobic exercise is largely ineffective for weight loss, according even to government reports. The reason is that your body seeks homeostasis and simply increases hunger to make you eat more to keep your weight constant. Recent research suggests that the way to break this homeostatic mechanism (and increase insulin sensitivity) is to do intense exercise, like weight lifting or interval training. While aerobic exercise is good for many aspects of health–and especially mental health– the government’s recommendation of 60-90 minutes of aerobic exercise a day for weight maintenance/loss is very likely a waste of time.
What about cholesterol? Doesn’t saturated fat clog your arteries and raise cholesterol?
Saturated fat was originally convicted for its ability to raise total cholesterol. In the 1980s, however, it was discovered that total cholesterol did not turn out to be a reliable predictor of heart attack risk. The conversation then shifted to saturated fat’s ability to raise LDL-cholesterol (the “bad” kind”). Yet again, clinical trials could not confirm the ability of LDL-C to predict heart attack risk. And it turns out that LDL-C has sub-fractions: some are small and dense, while others are light and buoyant. The small, dense ones turn out to be strongly predictive of risk. Having more light, buoyant ones is protective. And the kind of LDL that saturated fats cause to increase is the light, buouant kind. Moreover, saturated fats are the only foods that increase HDL-C, the “good” cholesterol. When your doctor tells you to raise your HDL, s/he will recommend drinking red wine or getting more exercise, but a far easier way to raise HDL is to eat more saturated fats. So, in sum, the effects of saturated fat on blood lipids can be said to be positive.
What about the environmental and ethical considerations of eating more meat (or meat at all)?
Since I avoided red meat for 25 years, I understand the arguments that anyone might have for not wanting to eat meat. People may choose not to eat meat for ethical reasons. There’s great concern now for the environmental impact of meat. And there’s the sense, going back to Frances Moore Lappe’s book, Diet for a Small Planet, that growing a pound of meat consumes too many of the earth’s resources, compared to the resources required to grow a pound of plants. Here are some points to consider: what if a pound of plants cannot provide the same nutrients and nourishment as a pound of beef? What if they are not actually equal? Meat (and eggs and dairy) contain far more essential nutrients than do plant food, and –this is a critical point—more of those nutrients are more bioavailable from animal foods than from plant foods, meaning that our bodies can absorb and use them better. Animal foods also contain the fat needed to absorb those nutrients, plus protein. If a pound of animal foods is far more nutritious and sustain human life better than a pound of plant foods, then we need to consider a debate on those terms.
Second, about the impact of red meat on global warming. I’m a bit skeptical of that science, just because I know that the anti-meat bias has become extremely strong over the past decade, and I never trust science done in the climate of prejudice. Also, there’s some data that just doesn’t fit into the picture, such as the fact that cattle herds in the US have declined by 30% over the last 3 decades, so how is it that they could be responsible for global warming? The cultivation of livestock is an ancient practice: Abel was a shepherd, and on the Parthenon friezes are ancient Greeks walking their cows to the festival of Athena. Humans domesticated animals so that they could have a convenient source of protein without having to hunt. (Cows do not exist other than as domesticated animals). It’s simply hard to believe that raising livestock could be the cause of global warming, especially when you look at what has changed in recent decades: industrialization, loss of nature to cities, the proliferation of cars and factories, etc.
But even assuming that cows do cause global warming, we still need to separate out the scientific questions. The nutritional question is: can a diet without meat sustain human life, including healthy growth (children) and reproduction (pregnant women)? Meat is the best source of iron and folate, which are crucial for growth and fetal development. The only other way to get adequate amounts of the nutrients is to eat fortified refined grains, which is presumably why our Dietary Guidelines recommend eating 3-5 servings of refined grains daily (!), the same amount as they recommend for whole grains (and this is the same amount that has been recommended since 2005, despite the recent rhetoric to reduce refined grains). Eating meat is the default diet for humans, and at this time, we have no clinical trial data to show that we can survive healthfully without meat, so I believe we should not launch into what would be an experimental diet for the human species with out evidence that this will be safe. Moreover, I believe nutrition experts should be humbled by their poor track record to date in prescribing experimental diets: obviously the low-fat diet has been a mistake, as has been restrictions on dietary cholesterol. There are excellent arguments for caution.
And if cows do cause global warming, then we ought to ask ourselves, how can we reduce their impact? Do they make a contribution to the ecosystem that will be lost if we eliminate these animals? And what, then, will be our alternative source of healthy protein given that fish are disappearing from the oceans?
More FAQs to come.
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