The Evidence for a Plant-Based Diet: Examining the China Study

The Evidence for a Plant-Based Diet: Examining the China Study

More than ten years have passed since the publication of The China Study, a book by T. Colin Campbell and his son Thomas trumpeting the benefits of plant-based nutrition that was immediately espoused by vegans and vegetarians worldwide. The evidence amassed in support of the Campbells’ conclusions is impressive, if somewhat more equivocal than originally thought. However, a great deal can be learned in the quest for optimum nutrition by examining the Study’s findings carefully.

So what is the China Study?

It was a massive observational study under the joint auspices of Cornell University, Oxford University, and the Chinese Academy of Medical Sciences. The idea for the China study germinated in the late 70s and early 80s from observations that diet and the incidence of cancer were strongly correlated. Specifically, individuals eating a diet high in fat and meat, but low in fiber, were more likely to have colon cancer. Furthermore, if someone moved to another region of China and adopted the natives’ dietary practices, the individual soon had a risk profile in keeping with those practices, irrespective of ethnicity or genetics.

The Study, begun in 1983-1984, examined dietary, lifestyle, and disease statistics for 100 individuals in each of 65 different rural counties in China. The China Study included data from 1973-1975 epidemiological studies alongside new data, looking at mortality rates for several cancers and other diseases. An expanded survey, China Study II, conducted in 1989-1990, added 20 new counties in mainland China and Taiwan to the earlier participants.

What were the Study’s conclusions?

In their book based on the Study, the Campbells concluded, among other findings,  that:

  • Plasma cholesterol is positively correlated with most cancer mortality rates.
  • Colorectal and stomach cancers are inversely correlated with fiber intake.
  • Animal protein, especially casein (a milk protein) is positively correlated with several types of cancer.
  • Cardiovascular disease is inversely correlated with green vegetable consumption.
  • People eating more animal protein are prone to more chronic disease and higher mortality rates than those eating less; those eating plant-based protein avoid chronic disease.

The Campbells’ Study suggests the optimum amount of animal-source food may be none! But what do the data really say?

Why is the China Study controversial?

The China Study takes a strong, and polarizing, position. As so often happens, the truth may be somewhere between the extremes.

  • Mortality rates, including death from all cancers and myocardial infarction, were very similar in the five counties consuming the most animal protein (some 135 grams per day) and those that were exclusively vegan. Wheat flour, intriguingly, was correlated (extremely) positively with mortality rates.
  • The Campbells’ Study too often overlooked what seem in retrospect obvious confounding factors. If cholesterol is to be linked to disease, then non-nutritive factors have to be filtered out. If more animal foods are consumed in regions with high rates of infectious disease and more industrial pollution (as often happened in the China-Cornell-Oxford Project), then can we conclude that it’s the nutritive factors alone that make the difference.  
  • If casein, and more generally milk protein, is so damaging, then should we be discouraging mothers from nursing their newborns with casein-rich milk, or researchers from using whey protein to enhance immune function?

What is needed is a critical re-examination of the data, from top to bottom. There can be little doubt about the benefits of a diet rich in greens, beans, onions, mushrooms, berries and seeds (GBOMBS diet) but the data do not support giving up all animal protein. What we need is balance, reason, and consistency. We need both science and wisdom.

 


CATEGORIES: Vegan, Vegetarian, Nutrition, Plant-based Diet, Omnivore, China Study