Health advice abounds these days, instructions on what to eat, what to wear (or not), what pills to take or avoid, and how much sun to expose oneself to all supposedly based on scientific research. Reliance on reports of scientific evidence can sometimes be tricky, however, especially when those reports come from preliminary or otherwise unsubstantiated experiments and observations. In addition to these, though, several examples of supposedly solid, "everyone knows" advice come to mind, advice that may not be as solid as once thought.
¢Stay out of the sun excessive exposure, especially when young, can lead to the life-threatening skin cancer known as melanoma. That's what we've been told for years now. And the supposed increase in melanoma over the past couple of decades is linked to increasing amounts of leisure time spent in sunny climes, right? Maybe not. According to the July 20 New York Times, at least one expert, Dr. A. Bernard Ackerman, says that the definition of melanoma has changed over time, and that doctors now diagnose melanoma when they would not necessarily have done so in the past.1 Further, Dr. Ackerman points out that the most common sites for melanoma are not those that are most likely to be exposed to the sun, particularly in Asians and African-Americans.
¢Aspirin can help prevent heart attacks and strokes, as many news reports have told us, because of its anti-clotting effect on the blood. Apparently there exists a subset of people for whom aspirin is not particularly effective people who are "aspirin-resistant," as is described in another article in the Times.2 For these folks (around 20-25% in the practice of Dr. Mark A. Goodman), the low doses of aspirin typically used for anti-clotting activity do not seem to work.
¢And of course, there is the story of hormone replacement therapy, or HRT. Long used for amelioration of distressing menopausal symptoms, HRT was also thought to help protect women against heart disease, osteoporosis, and maybe even Alzheimer s disease. Millions of women took some form of HRT for years until recently, when large epidemiological studies found that HRT conferred no health benefit other than allaying menopausal symptoms such as hot flashes and osteoporosis and actually seemed to increase the risk of stroke and some types of cancer.
So what s a person to think of all this? Should we ignore what the latest science says? How do we decide which advice is reasonable to follow? The answer differs from case to case.
For advice on the sun, for example, reducing exposure will help prevent skin cancers other than melanoma, and will reduce sun-related drying and wrinkling. (for more information, see: ACSH's "Summer Tips"). Thus, it still makes sense to restrict sun exposure.
Aspirin therapy is more complicated. It is possible that people who seem to be aspirin-resistant may simply need a higher dose to accomplish the goal of reducing blood clotting. Or, as suggested by Dr. Goodman in the Times article, they may need a different drug. Unlike sun exposure, this is not an issue that people should decide for themselves. Although it's easy to increase the dose of aspirin, it's important that the drug's effects be monitored by a physician and that other drugs be tried if necessary.
While the advice on sun exposure is relatively easy to support, and even the issue of whether to take aspirin for reducing the risk of stroke and heart disease can be decided based on fairly straightforward testing, HRT is complex. Although HRT is not beneficial in as many ways as previously thought and may have negative health effects, it is still about the only way to treat severe menopausal symptoms. The decision to use HRT must therefore be one that is carefully considered in collaboration with a knowledgeable physician.
These situations are all examples of the dynamic status of science-based health advice. It is important to recognize this fluidity: while the basic general advice for health promotion, e.g., wear seat belts, don't smoke, etc. (see also "Resolve to Be Healthy in 2004") is time-tested, advice about specific medications and their effects may not be as reliable. In some instances, we must act on the best available evidence (in consultation with a physician), even if we know that future research may not totally support the results of today's studies.
Ruth Kava, Ph.D., R.D., is Director of Nutrition at the American Council on Science and Health.
1Kolata, G. A dermatologist who's not afraid to sit on the beach. The New York Times, July 20, 2004; p. F5.
2Pollack, A. For some, aspirin may not help hearts. The New York Times, July 20, 2004; p. F1.
