What If Americans Ate Less Saturated Fat?
Eat less saturated fat, live longer. For 30 years, this has stood as one cornerstone of nutritional advice given to Americans (see main text). But how much longer? Between 1987 and 1992, three independent research groups used computer models to work out the answer. All three analyses agreed, but their conclusions have been buried in the literature, rarely if ever cited.
All three models estimated how much longer people might expect to live, on average, if only 10% of their calories came from saturated fat as recommended. In the process their total fat intake would drop to the recommended 30% of calories. All three models assumed that LDL cholesterol--the "bad cholesterol"--levels would drop accordingly and that this diet would have no adverse effects, although that was optimistic at the time and has become considerably more so since then. All three combined national vital statistics data with cholesterol risk factor data from the Framingham Heart Study.
The first study came out of Harvard Medical School and was published in the Annals of Internal Medicine in April 1987. Led by William Taylor, it concluded that individuals with a high risk of heart disease--smokers, for instance, with high blood pressure--could expect to gain, on average, one extra year by shunning saturated fat. Healthy nonsmokers, however, might add 3 days to 3 months. "Although there are undoubtedly persons who would choose to participate in a lifelong regimen of dietary change to achieve results of this magnitude, we suspect that some might not," wrote Taylor and his colleagues.
The following year, the U.S. Surgeon General's Office funded a study at the University of California, San Francisco, with the expectation that its results would counterbalance those of the Harvard analysis. Led by epidemiologist Warren Browner, this study concluded that cutting fat consumption in America would delay 42,000 deaths each year, but the net increase in life expectancy would average out to only 3 to 4 months. The key word was "delay," for death, like diet, is a trade-off: Everyone has to die of something. "Deaths are not prevented, they are merely delayed," Browner later wrote. "The 'saved' people mainly die of the same things everyone else dies of; they do so a little later in life." To be precise, a woman who might otherwise die at 65 could expect to live two extra weeks after a lifetime of avoiding saturated fat. If she lived to be 90, she could expect 10 additional weeks. The third study, from researchers at McGill University in Montreal, came to virtually identical conclusions.
Browner reported his results to the Surgeon General's Office, then submitted a paper to The Journal of the American Medical Association (JAMA). Meanwhile, the Surgeon General's Office--his source of funding--contacted JAMA and tried to prevent publication, claiming that the analysis was deeply flawed. JAMA reviewers disagreed and published his article, entitled "What If Americans Ate Less Fat?" in June 1991. As for Browner, he was left protecting his work from his own funding agents. "Shooting the messenger," he wrote to the Surgeon General's Office, "or creating a smoke screen--does not change those estimates."
Related articles in Science:
The Soft Science of Dietary Fat.
Science 2001 291: 2536-2545.
(in News Focus)
- The Epidemic That Wasn't?.
Science 2001 291: 2540.
(in News Focus)
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Copyright © 2001 by The American Association for the Advancement of Science.