The "China Study"

The "China Study" refers to a book by T. Colin Campbell and his son Thomas M. Campbell II: The China Study: Startling Implications for Diet, Weight Loss and Long-Term Health. In the book, the Campbells claim that most diseases can be prevented or cured by diet alone. The evidence comes mainly from the study of some villages in China, although references to other studies are made throughout the book to support their grandiose thesis. The life-saving diet they promote is a plant-based, low protein diet with little meat and no dairy products. It may be stated up front that diet is important in cancer prevention and a diet rich in fruits, vegetables, whole grains, and legumes and low in red meat is probably a healthy diet for most people. But it is a pipe dream to think that such a diet by itself will prevent cancer or any other disease, much less cure cancer, heart disease, liver disease, or any of the other diseases that the Campbells claim are fixed by their recommended diet.

Dr. Harriet Hall of Science-Based Medicine has reviewed the book and I recommend that anyone interested in an unbiased evaluation of the Campbells' work read her review. Dr. Hall writes:

It would be wonderful if we could prevent cancer and all those other diseases by avoiding animal protein.

Unfortunately, the evidence doesn't support the Campbells' radical thesis about animal protein and plants. Denise Minger writes:

...the China Study data speaks for itself: Animal protein doesn’t correspond with more disease, even in the highest animal food-eating counties—such as Tuoli, whose citizens chow down on 134 grams of animal protein per day.

Nor is the link between animal food consumption and cholesterol levels always as strong as Campbell implies. For instance, despite eating such massive amounts of animal foods, Tuoli county had the same average cholesterol level as the near-vegan Shanyang county, and had a slightly lower cholesterol than another near-vegan county called Taixing. (Both Shanyang and Taixing consumed less than 1 gram of animal protein per day, on average.) Clearly, the relationship between animal food consumption and blood cholesterol isn’t always linear, and other factors play a role in raising or lowering levels.

For an extremely detailed critique of the Campbells' work I recommend Minger's "The China Study: Fact or Fallacy?" Minger writes:

In sum, “The China Study” is a compelling collection of carefully chosen data. Unfortunately for both health seekers and the scientific community, Campbell appears to exclude relevant information when it indicts plant foods as causative of disease, or when it shows potential benefits for animal products. This presents readers with a strongly misleading interpretation of the original China Study data, as well as a slanted perspective of nutritional research from other arenas (including some that Campbell himself conducted).

Dr. Hall revisited Campbell's book and found a troublesome recurring methodological error: Campbell finds correlations of animal products with cancers and implies causality; he also ignores correlations of vegetable products with cancers. Dr. Hall writes (emphasis added):

The data do show that cholesterol is positively associated with various cancers, that cholesterol is positively associated with animal protein, and that cholesterol is negatively associated with plant protein. So by indirect deduction they assume that animal protein is associated with cancers and that reducing intake is protective. But if you compare animal protein intake directly with cancer, there are as many negative correlations as positive, and not one of those correlations reaches a level of statistical significance. Comparing dietary plant protein to various types of cancer, there are many more positive correlations and one of them does show strong statistical significance. The variable “death from all cancers” is four times as strongly associated with plant protein as with animal protein. And Campbell fails to mention an important confounder: cholesterol is higher in geographic areas with a higher incidence of schistosomiasis and hepatitis B infection, both risk factors for cancer. Campbell says breast cancer is associated with dietary fat (which is associated with animal protein intake). The data show a non-significant association with dietary fat, but stronger (still non-significant) associations with several other factors and a significant association with wine, alcohol, and blood glucose level. The (non-significant) association of breast cancer with legume intake is virtually identical to the (non-significant) association with dietary fat. Animal protein itself shows a weaker correlation with breast cancer than light-colored vegetables, legume intake, fruit, and a number of other purportedly healthy plant foods.) He indicts animal protein as being correlated with cardiovascular disease, but fails to mention that plant protein is more strongly correlated and wheat protein is far, far more strongly correlated. The China Study data show the opposite of what Campbell claims: animal protein doesn’t correspond with more disease, even in the highest animal food-eating counties.

Personally, I think that the likelihood that one diet is the right diet for every human being is nonsense. There are lots of healthy diets, some vegan, some vegetarian, some omnivorous. I don't have a quarrel with those who avoid meat or dairy products. I do have a quarrel with those who claim they have the evidence to prove that meat and dairy products cause cancer and should be avoided altogether. The evidence isn't compelling and cherry-picking studies to support your lifestyle isn't healthy, either.

The ardent Campbell defenders give nature (genetics) short shrift in favor of nurture (diet), especially when it comes to claims about preventing and curing cancer. Yes, inadequate diet alone can cause some diseases (e.g., scurvy from lack of vitamin C), but genetics plays a major role in such diseases as cancer. I recommend that those who think nurture alone (whether diet or supplements) can prevent cancer should read The Emperor of All Maladies: A Biography of Cancer by Siddhartha Mukherjee. In my review of Mukherjee's book, I write, quoting the author:

"Cancer, we now know, is a clonal disease. Nearly every known cancer originates from one ancestral cell that, having acquired the capacity of limitless cell division and survival, gives rise to limitless numbers of descendants....Cancer is an age-related disease—sometimes exponentially so. The risk of breast cancer, for instance, is about 1 in 400 for a thirty-year-old woman and increases to 1 in 9 for a seventy-year-old." Every gene in every cell in your body has the potential to mutate. Some of those mutations affect the genes that regulate cell division in ways that cause cancer. Finding just those mutations and developing ways to mitigate or eliminate their uncontrolled effects is the center of today's cancer research.

Those who claim that either diet or vitamin and mineral supplements alone can prevent cancer don't have the evidence on their side. I have yet to run across anyone who gives the genetic data its proper weight and who claims that diet, exercise, not smoking, and environmental factors don't matter in the development of diseases.

note: Minger's page has links to Campbell's responses to her critique and links to her responses to Campbell. Minger's critics have their say here.

further reading

The China Study Revisited: New Analysis of Raw Data Doesn’t Support Vegetarian Ideology by Harriet Hall, M.D.

Stomach Cancer in China by T. Colin Campbell, Ph.D. Campbell attributes the high rate of stomach cancer in China to preserved vegetables, stomach bacterial infections, and low blood levels of certain antioxidant nutrients. He makes no mention of genetic factors. For balance, I suggest reading China finds new genetic links to stomach cancer by Zhan Yuan. For more on stomach cancer, see the National Cancer Institute's (part of the NIH) page on Stomach Cancer Prevention.