Facebook Twitter

Low-fat study gobbled up a huge slice of federal pie

SHARE Low-fat study gobbled up a huge slice of federal pie

Over the last decade, the federal government spent $410 million on a study designed to determine whether a low-fat diet reduces the risk of heart disease, stroke, breast cancer and colon cancer in women. In the context of medical research this is an enormous sum, which could have funded hundreds of small-scale studies.

Yet there is a good argument for funding such an ambitious project. The problem with the typical medical study is that its limited data and less than rigorous methods can rarely if ever do more than suggest plausible hypotheses, as opposed to producing robust scientific conclusions. The idea that a low-fat diet reduces the risk of heart disease and cancer was one such hypothesis. Now, this "Rolls-Royce" of studies, as one researcher called it, has brought that claim into serious question.

The study, which has just been published in the Journal of the American Medical Association, found that a low-fat diet had no effect on any of the diseases the researchers were tracking. Given its size and comprehensiveness, the study "should put a stop to this era of thinking that we have all the information we need to change the whole national diet and make everybody healthy," said Dr. Jules Hirsch of Rockefeller University, who has dedicated his career to studying the effects of diet on health.

Given the complexity of the subject, it's no surprise that some advocates of low-fat diets found reasons to object to the researchers' conclusions. The study was designed to limit fat intake to 20 percent of total calories, yet the women who attempted to maintain that level consumed 24 percent of their calories in the form of dietary fat in the study's first year and were up to nearly 29 percent by the time of the study's conclusion (the women in the control group, who did not attempt to limit fat intake, averaged 37 percent).

Furthermore, the study made no distinction between different kinds of dietary fat. Some researchers believe that saturated fats such as butter increases health risk, while the "good" dietary fat found in, for example, olive oil, does not (this is the basis for recommending the so-called "Mediterranean diet," which is relatively low in saturated fats).

Yet these objections are themselves vulnerable to criticism. Spending hundreds of millions of tax dollars on researching a medical issue must be justified in terms of the practical benefits this investment might produce. It may turn out that, as a matter of scientific fact, an extremely low fat diet, such as that long advocated by Dr. Dean Ornish, is medically beneficial. But if almost no one is actually capable of maintaining such a diet, it's hard to justify dedicating a significant percentage of the public health research budget to an attempt to determine whether Ornish's views are correct.

As for the claim that the real health risk is posed by saturated and trans fats, this hypothesis has never been tested in the sort of large, randomized clinical trial which formed the basis of the new JAMA study — and indeed the evidence suggesting that such fats pose any serious health risk is quite slender.

(An amusing illustration of this was produced by a recent lawsuit which attempted to get California to declare Oreo cookies unfit for human consumption because they contain trans fats. Nabisco, the maker of Oreos, replied to this charge by observing that 362 billion of these supposedly poisonous items had been consumed since their invention in 1915.)

The larger lesson to be drawn from studies of this sort was pointed out by David Freedman, a University of California-Berkeley statistician. "We in the scientific community often give strong advice based on flimsy evidence," he said. "That's why we do experiments."

Bon appetit.

Paul Campos is a law professor at the University of Colorado and can be reached at Paul.Campos@Colorado.edu.