After completing The China Study by T. Colin Campbell, PhD and Thomas M. Campbell II, MD, I decided to discuss it over a few posts (1). Honestly, I feel like I could write a book about this book, but I will try to just hit the major highlights. The first topic I would like to write about concerns the question, "Are milk and other dairy products harmful to your health?"
Campbell hits this topic hard and fast in The China Study as he explains that milk products cause cancer. Throughout the book he encourages his readers to cut out all milk products and all animal products, for that matter. By the end of the book, the general idea is that if you eat any animal products, you are setting yourself up for major health failure whether it be from diabetes, cancer, heart disease, auto-immune diseases, etc.
Campbell's idea that milk products are dangerous originated from a study that examined rats which were fed different amounts of casein (a milk protein) and observed markers of early preneoplastic liver lesions (PNL)(2). Preneoplastic basically means that there is a very good chance this will eventually form into cancer. In the study, it was found that a minimum of 6-8% dietary casein was needed for proper weight gain. When rats were fed a diet 10% or less casein, there were negligible PNL; however, a diet of 12% or more casein showed a significant increase in PNL.
So what does all of this mean?
1. First of all, if you consume an 1800 calorie diet, you would have to drink about 7 cups of milk daily (or dairy equivalent) in order to ingest more than the 12% casein maximum threshold. Granted, casein does exist in very small amounts in processed foods. Most people don't come any where near 7 cups of milk daily, so chances are, you still won't exceed the 12% casein threshold even if you have a little bit of yogurt and some casein in processed foods. Of course, you should always strive to eat more whole foods and less processed foods.
2. We can certainly learn a lot by studying rats; however, it is impossible to directly extrapolate these results to humans. It even says this in the discussion section of the study.
3. What does this mean for breast milk? We know from countless human studies that breastfeeding has numerous benefits for babies and mothers. Breast milk does have less casein than cow's milk, but it still has casein and babies drink it all day long! Campbell does express the importance of breastfeeding and cautions about stopping too early. So, why is the casein in breast milk okay for babies, but Campbell believes that the casein from cow's milk is harmful? He doesn't address this question in the book.
4. It must be said that casein was given to the rats in isolation as well. When we drink milk, it is within the milk among a complex series of nutrients. We know that combining certain nutrients with other nutrients changes the way we absorb them, use them in our bodies, etc. It is a little difficult to compare casein given in isolation to rats versus humans drinking a glass of milk.
5. I am certainly no expert on cancer; however, I do know that it is a complex disease affected by a multitude of factors. I find it difficult to believe that we can easily isolate one little nutrient that causes cancer. Campbell actually has a whole chapter on "reductionism", taking specific nutrients, studying them, and making health claims about them. He disagrees with this practice and explains the complexity of nutrition and health. So, why does he make an exception for casein?
6. Campbell believes that, because casein causes cancer in his opinion, all animal protein must do the same. This is a wild extrapolation.
In summary, the data from the study done on casein and PNL suggests that you don't need to empty all of your milk cartons. It seems that moderation wins again! Drinking 7 cups of milk is a lot of calories, so I wouldn't suggest doing that anyway. Drink milk in moderation!
1. Campbell, T.C. & Campbell, T.M. The China Study. BenBella Books, Dallas, TX, 2006.
2. Dunaif, G.E. & Campbell, T.C. Dietary Protein Level and Aflatoxin B1-Induced Preneoplastic Hepatic Lesions in the Rat1. J, Nutr. 117: 1298-1302, 1987.