Lighting the Fire
In the spring of 2005, I wrote a review of Dr. T. Colin Campbell’s The China Study for the Weston A. Price Foundation’s journal Wise Traditions. The mostly unchanged version of this review on Cholesterol-And-Health.Com, “What Dr. Campbell Won’t Tell You About the China Study.” currently ranks on the top page of Google results for a “china study” search. We offered Dr. Campbell the opportunity to respond within the pages of Wise Traditions, but after intially accepting the offer and continuing a lengthy private dialogue with me over email, he later rejected the offer and published a mostly ad hominem attack on me the following year on the VegSource.Com website. My original review and my much broader and more in-depth response to Campbell have served as essential reading among those looking for critical reviews of The China Study for several years now.
Burning it Down
Well, there’s a new contender in town and while I may have hit the beast with a few strong punches and made a run for it, Denise Minger went for the jugular and then put a nail through the coffin.
Not the gentlest metaphor, but this “beast” is not The China Study itself and certainly is not its well respected author, Dr. Campbell, but is rather the misuse and abuse of statistics and logical inference that has falsely elevated The China Study into proof that, as Dr. Campbell wrote, “Eating foods that contain any cholesterol above 0 mg is unhealthy.” Ms. Minger’s lengthy but powerfully scathing review of The China Study can be found here:
The China Study: Fact or Fallacy?
Minger makes a number of great points. She provides an excellent preliminary analysis showing that schistosomiasis, a parasitic infection, confounds many of Dr. Campbell’s conclusions. Minger, herself a lover of green vegetables, makes an excellent argument showing that frequency of green vegetable consumption is often inversely correlated with a disease when total green vegetable consumption is not — a phenomenon she calls “The Green Veggie Paradox” — because the “frequency” variable is just a marker for a warmer climate. She also devoted an entire section to the Tuoli people, the “outliers” among the rural Chinese who consumed almost two pounds of dairy every day. These “mysterious milk drinkers” defy the central theme of The China Study by possessing excellent health.
None of these points, however, great as they may be, constitute nails in the coffin. None of them cast the fatal blow, slaying the beast of statistical misuse and logical abuse that has inflated the findings of what would otherwise be an interesting observational study into supposed proof of the superiority of a “plant-based” (vegan) diet. None of these blades, sharp as they may be, bring their incision even close to the jugular vein.
Of what substance, then, is this fatal blow made?
Back to the Experimental Evidence
Denise Minger went not just beyond the bestselling book and into the abyss of thousands upon thousands of data points known loosely as the original monograph but traveled even further through the lands of the roughly one thousand references Campbell provides among his supporting evidence to find a critical study that Campbell himself had published showing, in fact, that the central thesis of his book — that animal foods, and specifically animal protein, are uniquely harmful to consume — is false.
That’s right. Minger’s detailed analysis of the China Study’s raw data is superb, but it’s a handful of sentences she devotes to Campbell’s animal experiments using protein to promote alflatoxin-induced pre-cancerous lesions in rats that lay the issue clearly to rest.
Why are these so important? Because these experiments are, while conducted in rats, the most solid experimental evidence Campbell presents in his entire book that animal products might have a unique ability to promote disease.
Let’s consider for a moment the evidence he presents. The China Study itself is an observational study. It can be used to generate ideas, but not to test them. Moreover, the data from the China Study do not support Dr. Campbell’s position anyway. Even if they did, there were over 8,000 statistically significant correlations. With p values <0.05, this means five percent or one in twenty of them are false correlations that arose by chance. Thus, chances are that there are about 400 correlations in the China Study that are statistically significant but nevertheless false and arose completely by chance. Campbell uses far fewer than 400 correlations to make his argument, so all but the most rigorous correlations significant at the p<0.001 value could well be false. Campbell did indeed cite some experimental evidence in humans, such as the experiments of Esselstyn and Ornish, but these experiments were either poorly conducted or failed to isolate animal foods as a variable.
Of Lab Rats and Men — Men Who Feed Them Protein Isolates
The only rigorously controlled experimental science that Campbell cites in favor of his hypothesis that animal foods, and specifically animal protein, are uniquely harmful to our health, is his own experiments in rats showing that casein, but not wheat or soy proteins, promoted cancer in lab animals.
After finding that feeding rats increasing amounts of casein (one of the several proteins in cow’s milk) promoted tumor growth in rats induced by aflatoxin (the carcinogen found in peanut butter), Campbell went on to investigate whether plant protein also promotes cancer. He wrote on page 59 of The China Study:
So the next logical question was whether plant protein, tested in the same way, has the same effect on cancer promotion as casein. The answer is an astonishing “NO.” In these experiments, plant protein did not promote cancer growth, even at the higher levels of intake. An undergraduate pre-medical student doing an honors degree with me, David Schulsinger, did the study. Gluten, the protein of wheat, did not produce the same result as casein, even when fed at the same 20% level. We also examined whether soy protein had the same effect as casein on foci development. Rats fed 20% soy protein diets did not form any early foci, just like the 20% wheat protein diets.
After discussing similar effects in other animal models of cancer and a few studies showing the ability of antioxidants to prevent cancer growth, Campbell concluded that “a pattern was beginning to emerge: nutrients from animal foods increased tumor development while nutrients from plant-based foods decreased tumor development.”
Really? Was such a pattern truly emerging?
The Fatal Blow
When I wrote my review in spring of 2005 I pointed out that Campbell was jumping the gun by making conclusions about other animal proteins and even all “nutrients from animal foods” when he only studied powdered casein, but I went no further than that. Denise Minger, however, dug up the original study and used it to blow a death knell to Dr. Campbell’s argument. You can find the study here. When the amino acid lysine was provided in the diet, wheat protein had the same effect as casein! The research showed definitively that the only reason wheat protein didn’t promote the cancer was because it is not a complete protein!
Grains like wheat tend to be deficient in lysine while legumes like soy tend to be deficient in methionine. When we say “deficient,” we mean deficient to provide optimal growth. For example, a study from 1979 found that infants fed soy formula in the first six weeks of life grew less and failed to thrive as well as infants who were breast-fed or fed animal milk unless the soy protein was supplemented with methionine.
For a time it was thought that vegetarians must meticulously combined grains and legumes at every meal in order to make a complete protein. But, as Dr. Campbell informs us on pages 30 and 31 of The China Study,
While the “lower quality” plant proteins may be lacking in one or more of the essential amino acids, as a group they do contain all of them. . . . We now know that through enormously complex metabolic systems, the human body can derive all the essential amino acids from the natural variety of plant proteins that we encounter every day. It doesn’t require eating higher quantities of plant protein or meticulously planning every meal.
Yet, amazingly, Dr. Campbell never informs us that while soy protein or wheat protein alone does not promote cancer, as a group plant proteins do contain all the amino acids to promote cancer, and that we now know that “the natural variety of plant proteins that we encounter every day” can, in fact, promote cancer just as powerfully as animal protein.
It appears, then, that what Dr. Campbell found was that under certain experimental conditions where high doses of a carcinogen have been used to initiate pre-cancerous lesions, complete proteins divorced from all the natural protective factors they are associated with in whole foods will, through their growth-promoting properties, promote the growth of those cancers.
Dr. Campbell and his colleagues, including one of his graduate students, conducted the study, and should have informed us of the result.
But it took the skepticism and skillful detective work of Denise Minger for us to find out.
Read more about the author, Chris Masterjohn, PhD, here.