Hi everybody. Sorry to have dropped off the blogosphere, been busy with the day job. I'm going to steal a few minutes from writing software to share a few thoughts.
I've been increasingly frustrated with the narrow thinking and shoddy logic which goes into "dietary recommendations", because it seems to me that the situation is really pretty simple. Everybody and their sister is getting into this game, with the drive towards very specific "eat 12% of this" sort of thinking, usually accompanied by some sort of pseudo-logical justification. Example: Jimmy Moore had a great interview (Part 1, Part 2) with Dr. Stephen Gundry, author of yet another diet book. In the interview, Gundry claims we should eat 95% plants. Why? Because that's what gorillas eat. Gorillas are genetically similar to humans, and maintain massive size and very low body-fat. That argument ignores the important differences between gorillas and humans, not the least of those being gorillas' vastly larger digestive tract and jaws with associated musculature, both required for effective digestion of large quantities of plant matter (gorillas eat upwards of 30 lbs. of vegetation daily). Indeed, by Dr. Gundry's logic of genetic similarity, we should eat like chimpanzees, genetically closer to us than gorillas, and whose diet is mostly fruit. Maybe Dr. Gundry doesn't like fruit, or chimps aren't muscley enough for him.
Another example, also courtesy of Jimmy Moore: Dr. Richard Johnson, author of another of the plethora of diet and nutrition books, claims that it's really fructose that is the root cause of our current rash of metabolic diseases. I think the metabolic science certainly indicates that overconsumption of fructose has significant potential for negatively impacting health. But in his explanation to Jimmy, Dr. Johnson focuses on animal studies rather than the underlying metabolic processes. Animal studies as such can never be more than suggestive about the corresponding effects in humans. Worse, Johnson seems to think that his fructose hypothesis excludes all other hypotheses as to the origin of obesity and other metabolically-related diseases, specifically targeting Taubes' hypothesis from Good Calories, Bad Calories. That's shaky ground, as Taubes builds on broadly accepted fundamentals of biochemistry and cellular biology, while Johnson largely seems to be making inferences from mouse studies. But the thing that annoys me the most is that the two hypotheses are clearly not mutually exclusive; indeed, one might expect the two effects to be synergistic in driving the development of metabolic syndrome, an effect certainly reflected in the decreasing average age of the onset of Type II diabetes.
At the top of the whole mess is the government's food pyramid. I don't have the time to get into it here, but if you want a real laugher some time, you should read the scientific justification for the food pyramid. And for the life of me I can't understand why our society takes that as the standard for nutrition. Anybody who's even semi-conscious can look around right now and see how skilled our government is in screwing things up just as badly as possible. Why would their nutritional recommendations be any different? Jimmy Moore recently pointed to a bit in the New York Times showing how diet has changed since 1970. You'll note that the major changes involve food pyramid-ish recommendations, like eating more veggies, grains, and vegetable oils. Yet public health is swirling down the toilet, but maybe that's to be expected given the usual governmental competency.
I would assert that there is no single "expert opinion" that constitutes the final word on human nutrition. Most of these experts are trying to sell books, videos, food, etc. and to do so must necessarily distinguish themselves from all of the other "experts". By the way, this extends to the government as well, as you'll find that appointees to head departments like the USDA generally come from the food industry. As a society, we've fallen into the trap of uncritical reliance on "experts" to tell us how to live our lives, rather than using our own brains to figure some fairly obvious things for ourselves. I can tell you from first-hand experience that, on average, most scientists are no smarter than you, regardless of your education or profession. More than anything, scientists know a lot of big words and few actual concepts, and spend most of their careers blindly misapplying them.
In the excellent book The Omnivore's Dilemma, Michal Pollan points out that omnivores devote a significant amount of brain-power to figuring out what is edible. That's an obvious necessity when you can eat just about anything. Humans and their big brains represent the extreme endpoint of this pattern. Two million years of human evolution have pushed brain development with the primary goal of becoming more effective at hunting and gathering food, allowing us to populate an extraordinary variety of ecological niches around the planet. Only over the last several thousand years, and mostly the last 100 or so, have we sacrificed evolution's gift in favor of "experts": doctors, scientists, media, government, etc. If you want to eat healthy, you need to use that big brain and figure out what works for you.
I don't want to offer yet another "expert" opinion on this topic, but to get the thinking started, let me throw out a few broad ideas. None of these are particularly original, but I think we need to "think bigger and eat simpler". A lot of the confusion around dietary recommendations stems, I believe, from the "experts" taking a narrow view, often a single idea (e.g. "animal products are bad", "all carbs are bad"). They also need to make the money you spend on their book seem worthwhile. Combine this with the narrow viewpoint, and you can wind up with "diet plans" that are complicated and difficult to follow. More often than not it also seems like the food sucks. Healthy eating should be easy - after all, we did it for hundreds of thousands of years with no experts or books. Major lifestyle changes are hard enough without having to do a bunch of math and suffering through unsatisfying meals.
First and foremost, realize what humans must have eaten during the course of evolving that big brain. We didn't have agriculture, nor factories to tear apart and reconstitute our food into unrecognizable forms. We ate more or less whole foods of both plant and animal origin. Debates about how much of this or that type of food are probably irrelevant, and both the archaeological record and modern hunter-gatherers indicate humans can thrive over considerable dietary variety. Ultimately humans require energy (preferably from fats or carbohydrates), protein, and a variety of micronutrients (vitamins and minerals). Whatever combination gets that for you is probably workable, as witnessed by the wide dietary variety of remaining hunter-gatherers who exhibit excellent health. The Inuit eat almost all animal products and get most of their energy from fat, while the Kitavans eat a large proportion of starchy vegetables, supplemented by seafood. Both groups exhibit comparable health, and little evidence of diabetes, heart disease, cancer, etc.
The key, I think, is the emphasis on whole foods, or at least foods that have a recognizable natural source, since that is what has been on the menu for all of human existence prior to the advent of agriculture. With very little extra thought, we can narrow that group down further by considering what could be reasonably hunted (just about anything that moves) or gathered. Consider grains, for example. Try this experiment some time: find a nice field full of wild grass that has gone to seed. Now go and gather up enough seeds to provide significant calories, say about a kilogram. Then process that grain into an edible form, using only naturally available tools like rocks (and if you actually do all of this, please don't eat the grains, because if you don't prepare them right you'll wind up in the hospital). Now compare that level of effort to digging up some root vegetables, picking fruit, or taking one of your grinding rocks and bonking a deer on the head. I think everyone who spouts off about "healthy whole grains" should be forced to do this exercise.
It doesn't necessarily follow that foods outside of human evolutionary experience are bad; but it seems highly unlikely that any food types we've eaten for the last two million years or so are likely to have much negative impact on health. Processed foods don't have to be bad for you, but what's the point of eating them? We don't have to eat processed food to get our nutrients, and more often than not the processing destroys much of the nutritional content, while potentially exposing us to nutrients in forms and quantities we are not designed to handle (e.g. high-fructose corn syrup, refined starch, high concentrations of polyunsaturated fats, lectins from grains). In fact, if there's one thing I think just about all diet gurus would agree upon, it's that we should be trading in more refined foods in favor of whole foods (just remember that despite the marketing phrase "whole grain foods", whole grain foods are nearly all highly refined).
Do some research on the actual nutritional content of foods, and apply a little critical thinking. When you compare with the usual (and usually dogmatic) recommendations, you are going to find lots of surprises. For instance, NutritionData.com cites spinach as being "a very good source of calcium", yet you'd have to eat about two pounds of spinach to get 100% of the RDA of calcium (and of course the RDA levels were designed to avoid overt disease, not optimize health). I'm not saying you shouldn't eat spinach, but rather be aware of what you're actually getting for realistic intake as opposed to trusting vague characterizations like "a very good source". An interesting and surprising exercise is to use NutritionData.com (or your favorite nutrition database) to find whole foods highest in various nutrients. I did this, comparing 200 calorie servings across all of the tracked nutrients; you can view the results here.
Another use for your big omnivore brain is paying attention to your body's response to different foods. As omnivores, such feedback is important. Throughout our evolutionary history our menu choices have often been very broad (much broader even than in the supposed "plenty" of modern life, where the apparent variety is really just different manipulations of corn, soy, and wheat). Maintaining optimal health would have required the ability to make distinctions between food sources in terms of nutrient density and availability without the use of a laboratory. For example, try filling your stomach with raw leaves (like spinach). I think you'll find that while your stomach feels full temporarily, you won't feel "satisfied", and will be hungry again soon (1 kg of raw spinach has only 230 kcal). If you finish a meal and are soon after thinking about the next meal, you're probably missing something. A good meal should make you feel good, not only right after, but also for most of the time until your next meal. For example, meals high in refined carbohydrates give most people a temporary "rush", but soon after result in a "crash". Don't try to overcome the crash with another rush.
Hunger is healthy, but you should only experience intense hunger if you're actually running a serious caloric deficit. If you're starving two hours after a 1000 kcal meal, something is screwed up, since that 1000 kcal should easily last you eight hours, assuming moderate levels of activity. Cravings are not necessarily a bad thing, but you should consider them in the context of two million years of human evolution. If you're craving something sweet, consider that it may be because your body is looking for the nutrients found in fruit. If you're craving something fatty, ignore the gurus' admonitions against fat, and just eat it. Again, your craving may not be so much for fat specifically, for for the nutrients that often accompany fat in whole foods. Satisfy your fat craving with a whole nutrient-dense source (e.g. avocado, grass-fed butter, coconut milk smoothie).
Keep it simple. No other animal has the capability to count calories or exercise "willpower", and humans had no need for such until the last century. Your body will tell you what it needs. You just need to listen, and use that big brain to filter the available options down to something that is reasonably likely to fulfill those needs as opposed to refined junk that temporarily tricks your body into thinking it's requirements have been met.
Finally, find yourself a person of advanced age who's still going strong. Modern life has pretty much destroyed the social cohesiveness humans experienced over our two million years of evolution, where those who successfully made it to old age could pass along their wisdom of how they got there. You will probably learn more of value from that individual than from a room full of diet book authors. Be sure to be open to what they tell you. For instance, more than once I've heard centenarians credit their health to a daily breakfast of bacon and eggs. Don't discount this as genetics or luck just because the bozo nutritionist at your gym said those things are unhealthy. The centenarian has spent 100 years listening to their body, while the nutritionist is just blindly repeating something from a book.
And though I'm sure one exists, I have yet to hear anyone credit a daily bagel and skim milk for reaching the century mark.