Diet Change: Vegan to Grain-Free
February 25, 2011 5 Comments
I am an extremist. The simplicity of extremes is appealing as one avoids the complexities of grays. For the past two years or so, I have followed a rather strict vegan diet motivated by the health benefits claimed by The China Study, and not particularly by the idea that it is immoral to eat animals. Recently I have had a number of questions in my mind as to the evidence for and against such diets, and ultimately decided to add preferably lean, organic and non-feedlot meats back into my diet. At the same time, I am experimenting with removing grains from my diet. Here’s why:
Is the evidence for a vegan diet very strong?
The China Study presents a few lines of evidence to support that protein, probably by IGF-1, can increase cancer risks. However, upon reading The Protein Debate, it seems to me that Dr. Campbell believes all protein does this and a primary reason to go Vegan is that such a diet very likely limits total protein to less than 10%. If you are vegan and you eat enough legumes or vegan protein supplements to get that number to 20-30%, are you not violating the fundamental argument for the anti-cancer benefit?
Virtually none of the people studied in The China Study were vegan. An extrapolation is made that goes from low animal protein to zero should be helpful. Is that reasonable? As recently as 1998, new nutrients were recognized as essential. What essential nutrients have yet to be discovered? Perhaps even low levels of meat supplies something essential that is as of yet unknown, without which health is impaired. No population of humans that I am aware of have lived on vegan diets for their entire lives. I’d prefer to be conservative and adopt a diet with some consensus behind it, namely, what did groups of healthy and long-lived people eat? The Blue Zones project seeks to address this. They identified many groups of long-lived people. Only one of them had significant populations of vegetarians (Seventh-day Adventists), and even most of them consumed some fish and eggs. Granted, Adventists who ate more meat had higher cancer rates, but how controlled were the studies? Were those processed meats? A recent meta-analysis found processed meats increased heart disease and diabetes, but not red meat. Many studies lump all meats together, which may be throwing the baby out with the bathwater.
What will I eat?
If you are not on a tight budget, you have many options for food. My current experiment is to add meats back to my diet, but remove grains. Why am I removing grains? I was influenced by two arguments. The first being The Paleo Diet, the second being general low-carb diets that avoid grains such as rice, bread, pasta, and so on to reduce insulin production. The core idea is that there are some foods to which were are more adapted to eating than others, and grains are particularly bad. This is a reasonable hypothesis, but it needs to be substantiated by evidence before it should be treated as true. My ancestors have likely been farming for 10,000 years or more, and that may have been enough time to completely adapt to a grain-based diet. However, for this experiment, I’m removing grains. From a standpoint of nutrient density, grains are not so great. Take a look at the The World’s Healthiest Foods. Very few grains compare favorably against fruits, vegetables, and meats for nutrients per calorie. I am going to focus on very low glycemic index foods. The exception will be during or after longer running events or workouts. I will use bananas, watermelon, pineapple and sweet potatoes after workouts to get non-grain high-GI foods. I will also eat lentils and beans, which are low-GI, but not Paleo-approved. Some might say, this sounds like an Atkins diet, and that is not healthy. It appears to me concerns about lower carbohydrate diets seem to lack evidence. A recent 2-year study, sometimes called the ATOZ study, found Atkins dieters lost more weight and improved metabolic risk factors more than traditional, Ornish or Zone dieters. I can’t find any evidence that these diets are a risk. Can you?
Should you change your diet?
I believe humans are very metabolically flexible. If you have no problems with your health, athletic performance, or happiness that could plausibly be connected to diet, and you are pleased with your diet, I’m not sure there is strong evidence to change. If you are overweight, struggle to maintain your weight, are frequently injured, or feel that your workouts don’t go well, perhaps changing your diet is worth a try. I don’t think anyone can convincingly say much about diet other than if you are obese, it is harming your health. If your diet is not preventing obesity, you probably need a change.
Update 2/27/2011: I found this criticism of the China Study to make good points (and a few of the same ones I made). It would be interesting to see more a response to these questions and criticisms from Dr. Campbell.