Diet and Doubt

The China Study, by T. Colin Campbell, PhD, and Thomas M. Campbell II, 2005.

As a reasonable person in an unreasonable country, what do you eat? What should you eat? Americans are so hungry for answers that Michael Pollan, who enlarged upon the question in The Omnivore’s Dilemma, was compelled to write a follow-up, In Defense of Food, in which he recommends a diet of plants and skepticism. But Food was evidently too circuitous a reply — “just tell us what to eat!” — and so its specific prescriptions were extracted and published as Food Rules, a no-nonsense pocket guide. (Sample guideline: if you’re not hungry enough to eat an apple, you’re not hungry.)

As sensible as these rules may be, they no more answer the original question than thousands of years of collective worship prove the existence of God. Where, then, is your empiricist to turn?

Colin Campbell, for one, went to China. After fighting malnutrition and cancer in the Philippines only to find his assumptions upended, he came across an article in Archives of Pathology that seemed to explain what he saw. So he set out to confirm — first, by conducting a series of experiments on rats and mice. He found that while carcinogens could be said to cause cancer, it was protein that activated and promoted cancer growth. Conversely, he could “turn off” cancer by decreasing protein intake; or by replacing the casein of the original experiments (as found in milk) with a plant-based protein like gluten (as in wheat) or soy.

Enter the China Project: a correlation study of 65 populations distributed throughout China, covering 24 out of 27 provinces, most of them rural. Health workers collected blood, urine, and questionnaires, surveyed household food consumption in person, and analyzed representative food samples from local markets in each region. Researchers then sifted through the data to look for associations.

For example, how does dietary fat relate to breast cancer rates? Or how does blood cholesterol relate to coronary heart disease? How does a certain kind of fatty acid in red blood cells relate to rice consumption? We could also compare blood testosterone or estrogen levels with breast cancer risk. We did thousands of different comparisons of this type.

And indeed, Dr. Campbell found enough correlations between protein intake and cancer incidence to suggest that his earlier lab results had some implications for humans. In the book he goes on to explore these implications by surveying the literature associating diet with disease. Online, however, he’s hounded by critics who take issue with the study’s design, its scope, its results, his interpretation of the results, and what they see as his agenda. Who knew that actually putting his data online would be such a mistake? Now he’s in the unenviable position of having to defend his work against a community whose idea of peer review is the trackback.

Meanwhile, Campbell reports that dairy consumption has been linked repeatedly to prostate cancer; to juvenile-onset (Type 1) diabetes in the nursing years; to multiple sclerosis (where latitude is also a factor, the wan polar climates unconducive to vitamin D production); to osteoporosis (bathing your innards in calcium may throw off the body’s natural calcium production); and to kidney stone formation. And if eliminating dairy from your diet — or meat or poultry or eggs, as Campbell likewise recommends — sounds as wrongheaded as eliminating, say, carbohydrates, I can only urge you to conduct research of your own; the demand is such that virtually any result will command an audience.