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medical examiner: Health and medicine explained.

Your Health This MonthSaving mice from breast cancer, the magic of red wine, and the risks of long-distance running.

By Sydney Spiesel
Posted Tuesday, Dec. 5, 2006, at 1:04 PM ET

(Continued from page 1)

Implications: What does this have to do with us—can I take resveratrol, eat that triple-dip banana split, and still live to see my grandchildren graduate? Maybe, but only time will tell, since it's exceptionally difficult to think of an ethical way to conduct the definitive experiment. But here are some preliminary observations:

1) In the laboratory, resveratrol protects nerve cells against certain toxic materials and may also protect the heart. It also inhibits the growth of certain cancer cells. We don't know yet whether these effects take place in living organisms.
2) Much has been made of the presence of resveratrol in red wine (it comes from the skins of the grapes and the pits). The discovery has been invoked to explain why the French are not felled by their rich sauces. The good news is that resveratrol isn't toxic to rats in doses equivalent to 1,000 glasses of red wine a day for humans. The bad news is that the dose of resveratrol shown to extend the life of the obese mice is also equivalent to 1,000 glasses of red wine a day for humans.

The risks of long-distance running

Question: A number of dermatologists at the University of Graz in Austria are serious long-distance runners. They recently realized that over the past 10 years, they had treated eight ultra-marathon (100 to 160 kilometers) runners for malignant melanoma—the most dangerous skin cancer. The number of cases may not be high, since they were scattered among 3,000 or so over the same period of time. But this group of physicians began to muse about whether there's something about long-distance running that puts those who do it at increased risk.

New research: Writing in Archives of Dermatology, Christina Ambros-Rudolph and her colleagues decided to compare 210 marathoners who signed up at a race with a group of 210 nonrunners who signed up at a recreation center. The groups were matched for age and sex distribution. Because the risk of developing melanoma is clearly related to sun exposure, a dermatologist evaluated each participant for evidence of sun damage to the skin and for skin cancer or precancerous conditions. He or she also asked the runners about their efforts to limit sun exposure.

Findings: The findings must have been a little anxiety-provoking for the authors. In most ways the runners and nonrunners were similar. They had similar histories of sunburns earlier in life and similar hair color. The skin of the runners was even slightly less sun-sensitive than that of the others. Nonetheless, the runners showed markedly more sun damage and a higher rate of atypical moles. They were almost twice as likely to have a mole removal recommended to prevent progression to skin cancer.

Explanation: Why the difference? Sun exposure. Marathoners are outdoors for long stretches of time, training and racing, and they wear shorts and sleeveless shirts. They don't always wear sunscreen, and when they do, sweating may wash it away. In addition, sweating increases sensitivity to sun because moisture in the skin's outer layer increases absorption of damaging ultraviolet light. The authors also speculate that the intense exercise of the ultra-marathon may weaken the body's immune response and thus decrease the natural defense mechanism against cancer. But I am skeptical of this explanation since the evidence doesn't seem strong.

Conclusion: The bottom line for all of us? Marathoner or not, respect the sun and its capacity to do harm. Use clothing and sunscreen to protect your skin, and reapply sunscreen every few hours—even without intense sweating, its effectiveness wears off with time. One other thing: 40 percent of the malignant melanomas in the original eight patients began to grow in moles the patients had since birth. Pediatricians have learned to pay especially close attention to these congenital moles, often referring them early for possible removal.

Anemia in the Third World—another unwelcome cause

Problem: About 8 percent of American children are anemic. Kids here with this condition tend not to learn well (though other factors may play a role), and doctors and teachers have long recognized the great benefit in correcting the condition. However, in the developing world, the prevalence of anemia is much higher, affecting as many as three out of four people, and the consequences are far more severe.