DaveMc wrote:
It does remind me of something I've been wondering for a while, though: Why isn't the science of nutrition better than it seems to be? I mean, human metabolism is a complex subject, and doing experiments is a lengthy, time-consuming, and messy process (what with all the variability from one human to another), but it doesn't seem like it ought to be beyond the reach of scientific inquiry. It seems like we ought to have pretty good information about this stuff, by now, and yet the entire discussion seems to swim in a sea of contradictory information and wild claims. My guess is that the problem is that the well-established facts of nutrition (the ones scientists in the field can all agree on) just aren't very exciting (things like "eat a variety of foods, including some protein and a good amount of fruits and vegetables") compared with the things that reporters like to report ("eat pomegranates and you'll live forever!") If my guess is correct, there's probably a sober body of research out there that we never hear about, and it's one that it would take a lot of effort to get at, because you'd have to read the actual scientific literature; you'd never hear about it in the press.
According to Michael Pollan, nutritional science is still pretty much in its infancy. I really don't think there's that much difference between one person and another -- or at least not as much difference as we might like to think. One of the things that make nutrition science so complicated is that when you add or subtract one thing from the diet, by default you decrease or increase something else. So is it the addition or subtraction of the one thing or the decrease or increase of the other that has made a change in health, weight loss or whatever it is that's being studied. OR -- is it something else altogether? The fact that we're omnivores and depending on where we live and our likes and dislikes doesn't help research either.
If you were a koala, you eat eucalyptus. Let's say something else was added to your diet -- blueberries, for instance. If there was a change in health or weight it could easily be attributed to the blueberries. It's not so simple for humans.
Add to that many researchers go into a study with a bias. Ancel Keys, for instance, began the Seven Countries Study believing that high levels of saturated fat in the diet were responsible for elevated cholesterol and heart disease. He found that men on Crete and in Japan ate diets that were low in saturated fat and had low cholesterol levels and low rates of heart disease and other chronic diseases. Americans ate diets high in saturated fats and had high levels of cholesterol and high levels of heart disease. However, he neglected to look at the fact that both the Cretan men and the Japanese men ate far more vegetables, fruits, beans and whole grains than the Americans. In addition, they ate very little in the way of processed foods.
The Mediterranean diet is very healthy, but probably not entirely for the reasons Dr. Keys thought it was healthy.
More recently T Colin Campbell and other researchers from Cornell spent nearly 20 years doing a similar study in China. Supposedly they wondered why the Chinese had much lower rates of cancer, heart disease, diabetes and obesity than Americans. There were apparently 8,000 "statistically significant correlations," but came to only one conclusion: people who ate the most animal products had the most chronic disease. By the time the book
The China Study was published, Dr. Campbell had become associated with a number of doctors who advocate a vegan diet. I'd read several articles about the study about 10 years before the book came was published. While I remember them advocating a plant-based diet, I don't remember a plants-ONLY diet at all.
But then there are populations who eat a lot more meat and are very healthy. So that's probably not the cause of ill health either.
If organically grown fruits and vegetables are compared for nutritional value, supposedly (according to those who promote organics) there is no difference. However, if factory-farmed animal products and pastured-raised products are compared, there is a huge difference in nutrition. The pasture-raised are superior. That being said, factory-farming is the best way to provide the amounts of meat (and dairy and eggs) Americans want in a cost effective manner.
The bottom line: nutrition science is complicated.
