In the first official book review at Summer Tomato I examine Dr. Colin Campbell’s The China Study. Several readers have asked about this book since I wrote last week about who you can trust for diet advice, so I think it is a perfect subject for my first review.

The China Study was published in 2006 and branded itself as “The most comprehensive study of nutrition ever conducted.” It is written by Colin Campbell, PhD, a highly accomplished scientist that has worked for decades in the fields of nutrition and disease research. It was co-authored by his own son, Thomas Campbell.

Clearly both these men care deeply about health and nutrition and believe the information they provide can relieve a huge proportion of the world’s suffering. Their sincerity is apparent and, given the current dietary trends in Western culture, I am sure their recommendations would help the vast majority of people become healthier. Yet there are several logical flaws in The China Study that prevent me from giving it an A grade. Overall, however, The China Study offers a compelling view of nutrition and health from one of the leaders in the field and is worth reading.

My biggest disappointment with The China Study is how little of the book is devoted to the study itself–a large ecological-style research project, conducted by Dr. Campbell and his colleagues, examining the relationship between diet and health in rural China. As a scientist, I am a bit of a data junkie and always most impressed by strong statistics and rigorous logic.

UPDATE: [Denis Minger has taken it upon herself to re-analyzed the data from The China Study, and makes it pretty clear that Campbell vastly overstates his case. I agree with everything Denise writes, and every educated person who cares about these findings should read her analysis.]

Only a single chapter in the book is specifically dedicated to the work done in China (Chapter 4), and it conveys little new information. Most of Chapter 4 is spent reiterating the links between diet and chronic diseases such as cancer, heart disease and diabetes, discoveries that did not surprise me in the least. The two most important novel findings reported in the China study are discussed below.

The China Study is divided into four major sections. The first section describes Dr. Campbell’s original research and is the part I enjoyed most. It begins by discussing his work in the Philippines where he discovered a tight link between animal protein consumption and a specific kind of liver cancer induced by aflatoxin, a dangerous poison that is sometimes found in contaminated peanuts. He follows up this work with extensive studies in his U.S. laboratory elucidating the mechanisms of cancer promotion by the main protein found in cow’s milk, casein. Dr. Campbell makes a compelling case that this protein can influence cancer development in the presence of an extremely potent carcinogen, and his work should be taken very seriously in this regard. However,  he goes on to argue that this finding can be generalized to support the view that all animal proteins promote cancer and he recommends they be completely eliminated from your diet.

This was a logical leap I was not able to make after reading through his evidence. What about the benefits of fish for the heart and brain?

As mentioned above, the final chapter of the first section describes the China study. According to the book, the Chinese consume much less fat and protein than Americans, but more fiber and iron. Nothing too surprising there. It also reports that rural Chinese have substantially less heart disease, cancer and diabetes than Americans, but in more urban areas where diets follow more Western patterns the incidences of these diseases are higher. Again, not surprising.

Two pieces of information out of the China study did pique my interest. The first is that participants in the China study reportedly consume more, not fewer calories than Westerners. This was true even for Chinese office workers who consume 30% more calories but weigh 20% less than average Americans.

Part of this difference was accounted for by differences in physical activity (even office workers in China get more exercise than we do), but not all of it. Data in the China study suggests that Chinese have a more active metabolism and burn more calories than typical Americans. Dr. Campbell argues that this is because they eat less animal protein and fat, but the China study is observational (non-intervention) and cannot prove cause and effect.

Isn’t it possible that the Chinese metabolize their food differently because it is less processed than Western food (no matter the source)? From the literature I have read, this seems like a more plausible explanation. But regardless of the reason, the data from China suggests that all calories are not created equal in terms of both health and metabolism. This argues against the dogma offered by most nutrition experts that a calorie is a calorie.

The other surprising finding from the China study is the degree to which blood cholesterol levels predict heart disease. Although most Americans assume there is some connection between blood cholesterol and heart disease, there is still debate regarding how strong this connection is. Data from the China study suggests lower total cholesterol levels decrease risk of heart disease and death. Moreover, the data suggests that optimal cholesterol levels are far below what are recommended by Western medicine (150 mg/dL to 180 mg/dL). The healthiest Chinese had total cholesterol levels from 170 mg/dL to as low as 90 mg/dL. In the China study, lower cholesterol levels were also linked to decreased rates of several cancers. However, some scientists question the validity of this data.

The second section of the book is titled “Diseases of Affluence” and discusses the role of nutrition in the various chronic diseases that plague Western culture. In the third section Dr. Campbell offers his ideal (i.e. vegan) diet. If you are not familiar with the literature on diet and nutrition Dr. Campbell does a decent job going over it, particularly with respect to the role of dairy in prostate cancer, type 1 diabetes and multiple sclerosis. However, most of this information is available in other books that are easier to follow and less dogmatic about the need to eliminate all animal protein from the diet, which even Dr. Campbell admits “has not been absolutely proven” (p. 242).

In my opinion the most incongruous part of The China Study is the fourth section titled, “Why Haven’t You Heard This Before?” Here Dr. Campbell goes into great detail explaining the ties between food industries, drug companies, our government and, sadly, our education system from K1 through post graduate medical residency. While this section of The China Study is fascinating, it dilutes the primary nutrition message of the book with a disconcerting illustration of the roles money and politics play in our education system. But despite the jumbled message, the facts provided in this final section of The China Study are eye-opening and may be the best reason to read the book. It is shocking to learn how deeply opposed to and uneducated most of the medical community is about the life-saving benefits of dietary intervention for chronic diseases. Personally I would have liked this section to be an entirely separate book, as I would recommend it more often.

To summarize, The China Study provides an interesting but not entirely compelling argument for adopting a vegan diet. It also offers a hefty dose of skepticism about who you can trust for nutrition advice, particularly when it comes to the medical community. Overall I enjoyed reading the book and, despite my criticisms, agree with most of it. I have no doubt that for the vast majority of Americans Dr. Campbell’s advice and recommendations would be immensely beneficial.

Final Grade: B

Please add your thoughts on The China Study in the comments below.