April 23, 2014


Dr. Walter C. Willett, a Harvard epidemiologist who has spent many years studying cancer and nutrition, sounded almost rueful as he gave a status report. Whatever is true for other diseases, when it comes to cancer there was little evidence that fruits and vegetables are protective or that fatty foods are bad.

About all that can be said with any assurance is that controlling obesity is important, as it also is for heart disease, Type 2 diabetes, hypertension, stroke and other threats to life. Avoiding an excess of alcohol has clear benefits. But unless a person is seriously malnourished, the influence of specific foods is so weak that the signal is easily swamped by noise. . . .

The hypothesis that fatty foods are a direct cause of cancer has also been crumbling, along with the case for eating more fiber. The idea that red meat causes colon cancer is shrouded in ambiguity. Two meta-analyses published in 2011 reached conflicting conclusions — one finding a small effect and the other no clear link at all. If hamburgers are carcinogenic, the effect appears to be mild. One study suggests that a 50-year-old man eating a hefty amount of red meat — about a third of a pound a day — raises his chance of getting colorectal cancer to 1.71 percent during the next decade, from 1.28 percent. Spread over a population of millions, that would have an impact. From the point of view of an individual, it barely seems to matter.

Yet all the nutritional commands — like the command to avoid sunlight — have been issued in the Voice Of Authority, with doubters and skeptics condemned as disrespecters of science. There’s even the suggestion that the war on tobacco caused people who quit smoking to gain weight, with more cancers resulting from obesity than from cigarettes. If that proves out, will the anti-smoking folks be targeted like the tobacco companies were?

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