Atkins, South Beach, Sugar Busters, and the list goes on. Fad diets will probably always surround us and continue to confuse the general public. Unfortunately, it seems that Campbell is planting the seed for another fad with The China Study (1). Don't get me wrong, as I said in the last post, Campbell is completely right that we need more fruits, vegetables, and whole grains in our diet. We also need less refined foods and meat. However, is there really truth to the claim that all animal protein is slowly killing Americans?
As I mentioned in Part I of this discussion of The China Study, Campbell bases the idea that animal protein is detrimental on a study that linked casein to cancer. On page 104, Campbell states, "casein, and very likely all animal proteins, may be the most relevant cancer-causing substance that we consume (1)." So, it is Campbell's opinion that all animal proteins cause cancer. There is no proof and in the peer-reviewed journal article, a claim about animal protein being a carcinogen is not made (2).
The second major study (3) that Campbell draws his conclusions from was an ecological study that he performed in China. In the study, nutritional intake was compared to cholesterol levels, body weight, and many other factors that may be predictive of chronic disease. The study was very interesting and gave some insight to the idea that a whole foods diet high in plants can lead to a life with less disease. Other than the fact that this type of study cannot prove cause-and-effect, it seemed that it was fairly well designed. Of course there were limitations to the study, but it still produced a lot of interesting information. The biggest concern I had with the design of the study was that blood samples were pooled by commune, age, and sex. Those pools of blood were then used to measure a number of biochemical markers. I asked several Medical Doctors and other people skilled in research about this technique. Not one person failed to raise an eyebrow at this. It seems like a lot of validity would have been lost in dumping everyone's blood sample together and just taking an average. The actual study that was published in the American Journal of Clinical Nutrition, stated that "any inferences concerning cause-and-effect relationships should be considered to be hypothetical only, with validation to be provided by intervention or prospective analytic studies on individuals." In the book that Campbell wrote, he does mention that the study cannot prove cause-and-effect. However, he goes on to basically talk about animal proteins causing disease as if they are hard and true facts. It is very important to remember that the study published in the American Journal of Clinical Nutrition is peer-reviewed; whereas the book that Campbell wrote about the study and other studies is not peer-reviewed. As far as I can remember, there is actually no mention in the actual study that it is best if humans cut out all animal products. Please correct me if I am wrong. In The China Study book, Campbell highly encourages readers to cut out all animal products.
So let's get back to my claim that Campbell's book is starting a fad diet. Why would I go that far? If you look at the data, it shows that the Chinese eat animal protein. They have not cut it out of their diets, they just eat less than Americans. I don't think it is any secret that Americans eat way too much meat and cheese. If most Americans reduced their portion sizes of meat, ate less cheese, and stuck to low fat dairy products, I imagine that there would be much less chronic disease in our country. Notice that I did not say "eliminate" these products from our diets. So if the Chinese haven't eliminated animal products from their diets and their chronic disease rates are so much lower, why must we eliminate animal products from our diet? A serving size of meat is three ounces. How many people eat more than this serving size? Probably most people do. So, maybe our chronic disease rates are so high because people are eating way more than the recommended serving size, not because they're eating any amount of animal products. I believe that any diet that promotes completely cutting out a food group belongs in the "fad diet" category. Animal products provide us with necessary nutrients and we can obtain those nutrients by eating small portions of those products.
One disclaimer I would like to add is cutting out animal products in the case of ethical concern. I support any person's ethical convictions and believe that you can live a healthy life without animal products, as long as you take a few necessary supplements.
3. Campbell, T.C. & Junshi, C. Diet and chronic degenerative diseases: perspectives from Chima. Am J Clin Nutr. 1994; 59 (suppl): 1153S-61S.