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April 25, 2000 Health Advice: A Matter of Cause, Effect and Confusion It is a popular sport to joke that scientists change their minds from year to year about what people should do to stay healthy. One year, we should all be taking beta carotene supplements. The next year, the supplements themselves seem to cause cancer. One year, it is high iron levels in the blood that are causing heart disease. The next year it is low levels of folic acid. It becomes all too tempting to recall the scene from Woody Allen's movie "Sleeper" in which the hero wakes up in the future and discovers that science has decreed that all those health foods he had been forcing down are actually injurious to health. The healthy foods are things like sumptuous desserts and hamburgers. The bad foods are things like bran and vegetables. Predictably, references to "Sleeper" are starting again. It is not hard to see why when, within weeks, data from large and rigorous studies have thrown into question two long-held assumptions about preventive medicine. First it was estrogen and heart disease. People knew -- or thought they did -- that taking estrogen pills at menopause, when estrogen levels wane, protected women with heart disease. People knew -- or thought they did -- that high-fiber diets protected against colon cancer. Now, however, preliminary data from a large federal study indicate that at least initially hormone replacement therapy is not protecting postmenopausal women from heart disease and may even be leading to a tiny increase in heart attacks, strokes and blood clots in the legs and lungs. The data are far from conclusive, and few would conclude at this point that estrogen was dangerous. But the point is that no one really knows whether it protects against heart disease. Last week, two large and rigorous federal studies of high-fiber diets failed to show that they protected against colon cancer. Once again, the results emphasize that this truth about diet and cancer is far from established. Scientists will say they knew it all along. If these truths were so evident, there would be no need to do large studies in which people were randomly assigned to take estrogen or, for comparison, to take a dummy pill. There would be no need to do similar studies with high-fiber diets. In fact, such studies would be unethical because they would deprive the control groups of a valuable preventative measure. The same goes for other questions now being investigated: does examining the colon with sigmoidoscopy screening prevent colon cancer deaths? Does the P.S.A. test and a digital rectal exam for prostate cancer save lives? Does a high-fiber diet prevent heart disease? Maybe the problem is one of language. Scientists and the public alike use words like "prevents" and "protects against" and "lowers the risk of" when they are discussing evidence that is suggestive, and hypothesis-generating, as well as when they are discussing evidence that is as firm as science can make it. As reactions to the estrogen and high-fiber diet studies show, years of such careless use of language can make preliminary evidence appear to be ironclad. "It's one of the biggest problems in this business," said Dr. Gilbert S. Omenn, a public health expert who is executive vice president for medical affairs at the University of Michigan. Yet even in the aftermath of the high-fiber diet studies, researchers were speaking confidently about other measures people could take to "prevent" colon cancer, like exercising and staying thin. And they were saying that there were reasons to keep eating fiber because it could "reduce the risk" of heart disease. When asked about the evidence for these statements, the researchers confessed that it was, of course, the lower level hypothesis-generating kind. Dr. Omenn came across this problem after a study he directed, and he has some advice. Dr. Omenn's large and rigorous study asked whether beta carotene, the ingredient in fruits and vegetables that many thought protected against cancer and heart disease, could, in fact, protect people. He found that not only were beta carotene supplements ineffective but they actually increased the risk of lung cancer in smokers. His findings, and those of others who found the same thing, were met with shock, denial and dismay. In an article published in 1995 in Annals of Epidemiology, Dr. Omenn urged scientists to be more careful about the words they used. "We should be fastidious in referring strictly to 'associations' when the studies have generated associations; we should reserve the terms 'effects,' 'reductions,' 'decreases' and 'protects' to studies that actually alter incidences of end points, preferably in randomized, double-masked designs," he wrote. "That's exactly right," said Dr. Barnett Kramer, deputy director of the division of cancer prevention at the National Cancer Institute. As editor of The Journal of the National Cancer Institute, Dr. Kramer deals directly with authors whose words convey more certainty than their data. "We often have to work with them to change the wording," Dr. Kramer said. The ambiguous language is understandable, Dr. Kramer added, because scientists studying preventive measures fervently want their findings to be meaningful. "It's easy to look at your data and say, 'Gee, I believe it has strong implications for human health,' " Dr. Kramer said. "It takes a lot of discipline to slow down and say, 'There are a lot of steps between what I observed and what I hope is true.'" By GINA KOLATA Copyright 2000 The New York Times Company "http://www.nytimes.com/library/national/science/health/042500hth-health-adv ice.html" janet paterson 53 now / 41 dx / 37 onset a new voice: http://www.geocities.com/janet313/ 613 256 8340 PO Box 171 Almonte Ontario Canada K0A 1A0