The study about dietary fat in women which we covered for Nightly News Tuesday night (video link; full story) and followed up again Wednesday night (link) has a fascinating political history. The Women's Health Imitative, conceived during the 1980s, was designed to reverse the biases that had led many medical studies to concentrate mostly on men – and often on white men. The $2 billion effort recruited more than 48,000 women aged 55 to 79. The biggest achievement of the study was that it cast doubt on the safety of hormone replacement, a finding that brought a sea change to women's health.
But it was the dietary component of the study that caused the controversy. Up until the mid 1980s some small preliminary studies had suggested that excess dietary fat might increase the risk for breast and colon cancer. But as the study was being designed several researchers, most notably Dr. Walter Willett of the Harvard School of Public Health, said the evidence for the connection was receding. Willett predicted today's negative results about cancer. He also said that the study, by looking only at total fat in the diet, would not show any effect on heart disease risk because by then it was well known that saturated fats, such as the type in meats, increased heart risk, but vegetable oils were actually beneficial. As a result of those objections, the National Institutes of Health originally turned down the study. But the scientists who wanted the research done turned to friendly members of Congress., An effort led by then Senator Brock Adams of Washington forced the NIH to undertake the study., The result, all these years later, is a finding about fat in the diet that sheds little light and could actually lead some to the mistaken conclusion that diet does not affect health. There is lots of evidence that diet is a key aspect of a healthy lifestyle. But it took a lot of time and money to prove that getting rid of all fat in the diet is not the answer.
And that is why we turned to Dr. Willett for Wednesday's story to help answer some of the questions that people might have in light of these latest revelations about the connection between nutrition and health.