As we progress in this series, I want to make something undeniably clear - I DO NOT THINK THAT VEGETARIANISM IS THE DEVIL!
My primary critique of vegetarianism has nothing to do with its healthfulness as a dietary lifestyle per se. Rather, my main concern is that many people 1) have a an irrational fear of all animal products; a fear that is not at all founded upon solid empirical evidence, and 2) many people, because they fail to truly understand the nutritional shortcomings of a purely plant based diet, fail to properly supplement their diets so as to prevent disastrous nutrient deficiencies; deficiencies which one could otherwise avoid by keeping animal sources of food in one's diet.
Now......back to my (or rather Denise Minger's) critique:
Point #3 of Minger's Critique
Another of Campbell's claims, which he makes in his book The China Study, is that animal-based foods induce liver cancer to develop in people who already have an increased risk of the disease (such as those with hepatitis B). Once again, Campbell, here, attempts to show that animal foods may indirectly cause cancer by spurring cancer's development when other risk factors already have a presence. This argument seems strikingly similar to another of Campbell's arguments (which I've talked about already in this series) that animal protein indirectly leads to cancer via its effect upon serum cholesterol. Needless to say, but I'll say it anyway, I think I satisfactorily made apparent why such a chain of causation has no real viable empirical support. But, does today's topic follow suit? Frankly - YES.
The above list represents data taken from Minger's site. The odd, unpronounceable names in the far left column are the names of various Chinese counties. In the middle left column, we have the % of people living in these counties who have hepatitis B. The middle right column indicates the amount of animal products the people from these counties consume on a regular basis (represented in grams per day). Finally, the far right column indicates the rate of mortality from liver cancer.
Of this data table, Minger states -
When we map out liver cancer mortality and animal product consumption only in areas with high rates of hepatitis B infection (18% and higher), we should see cancer rates rise as animal product consumption increases—at least, according to Campbell. That would indicate animal-based foods do encourage cancer growth.To the contrary, however, we get the following data -
As you can see, hardly any connection at all exists to incriminate animal foods as causative of liver cancer. In fact, according to Minger, we can only inductively infer a +1 correlation between animal-based foods and liver cancer based on this data. In case you were wondering, a +1 correlation hardly counts as significant.
Minger, however, goes a step further to actually hash out how particular sources of animal products correlate with liver cancer risk -
Very interesting to say the least. As a side note, I find it truly ironic that fish, a source of animal protein many people, vegetarian or otherwise, find acceptable, has a positive correlation with liver cancer, while meat, eggs, and dairy all seem inversely correlated with liver cancer. Don't mistake this note as a suggestion that we ought to avoid fish, however.Meat correlates at -7 with liver cancer in high-risk countiesFish correlates at +11Eggs correlate at -29Dairy correlates at -19
But what of plasma cholesterol?
It is true that plasma cholesterol correlates with increased risk of liver cancer (+37); however, when we factor in hepatitis B, this correlation drops (to +8). A +8 correlation, though higher than +1, still falls short of strong statistical significance.
Minger posits the following -
If I were Campbell, I’d look at not only animal protein and cholesterol in relation to liver cancer, but also at the many other variables that correlate positively with the disease. For instance, daily liquor intake correlates at +33*, total alcohol intake correlates at +28*, cigarette use correlates at +27*, intake of the heavy metal cadmium correlates at +38**, rapeseed oil intake correlates at +25*—so on and so forth. All are statistically significant. Why doesn’t Campbell mention these factors as possible causes of increased liver cancer in high-risk areas? And, more importantly, why doesn't Campbell account for the fact that many of these variables occur alongside increased cholesterol and animal product consumption, making it unclear what’s causing what?
Closing Remarks
In response to Minger's question, I'd suggest this - Campbell doesn't account for other variables which occur alongside increased cholesterol and animal product consumption because he wants to indict cholesterol and animal protein consumption. Am I accusing Campbell of bias? You bet!
If Campbell took the more humble route, indicating the epistemological limits of his conclusions, I'd say he would sell far fewer books. People, consumers really, want to hear a reductionist message. Put another way, reductionism sells. People easily fall for the trap (and I have numerous times) that health and well-being can be reduced to just a handful, or even less, of dietary changes. In reality, a host of factors play a role in our health; in ways which complicate and frustrate our attempts to nail down prime causes. But, complexity and frustration, and epistemological honesty, don't sell.
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