Cancer was more common in those with low cholesterol.
Low Cholesterol and Cancer
One of the things that Stamler told me at the beginning of my visit with him was that he remembered certain things very well, “and other things I don’t remember at all.” What that meant, I discovered, is that Stamler recalled the smallest detail of the evidence in favor of the diet-heart hypothesis and little of the evidence against it. Regarding cancer, for instance, he probably should have remembered that his MRFIT findings were far from unusual. By 1981, nearly a dozen sizable studies on humans had found a link between lowering cholesterol and cancer, principally for colon cancer.
In the Framingham study, men with cholesterol levels below 190 mg/dL were three times more likely to get colon cancer than men with cholesterol greater than 220 mg/dL. In fact, ever since corn oil had been shown to double the rate of tumor growth in rats in 1968, there had been a baseline level of concern about vegetable oils and cancer. (Other studies from this time led to the supposition that corn oil might cause cirrhosis of the liver.) And there were other problems. People who had successfully lowered their cholesterol in trials of diet or drugs turned out to have higher rates of gallstones.XIV Strokes were also a concern. In Japan, for instance, a country of interest to heart disease researchers due to the relatively low rates of heart disease found in rural areas, NIH investigators found that Japanese people with cholesterol levels below 180 mg/dL suffered strokes at rates two to three times higher than those with higher cholesterol.
The NHLBI became so concerned about the cancer findings that it hosted three workshops in 1981, 1982, and 1983. The evidence on the topic was reviewed and rereviewed by an extremely prominent group of scientists, including Keys and Stamler. One suggestion was that low cholesterol might be an early symptom of cancer, rather than a cause. It was a plausible bit of logic. In the end, however, although the assembled researchers could find no convincing explanation for the cancer findings, they concluded that they did “not present a public health challenge” and did not “contradict” the more urgent, “commonsense” public health message for everyone to lower their cholesterol.
On the whole, said Manning Feinleib, an associate director at the NHLBI who attended the meetings as a rapporteur, the committee seemed to consider the downside of cancer to be less important than the upside of reducing heart disease. I spoke to him in 2009, and he was clearly dismayed that the issue of low cholesterol and cancer had still not been settled. “Oh boy, it’s been more than twenty-five years, and they have still not shed more light on what’s going on, and why not? That’s even more puzzling.”