Score One for Sunshine--Maybe

Medical research keeps coming up with bad news for the self-indulgent. I've felt personally attacked by discoveries showing my favorite foods, drinks, and behaviors are likely to shorten my life.

Probably the saddest news was that overindulgence in sunshine was downright unhealthy. I've always found some excuse to be outside at noon on sunny December days, and in June I've found excuses never to come inside at all. It was hard to think of giving that up in the interest of preventing skin cancer at worst, wrinkles at best. I even wrote a column back in 1988 sharing the bad news with fellow northerners, so we'd feel better about our midwinter sunlessness.

Perhaps I was whistling in the dark. A recent study by Cedric Garland, Edward Gorham, and Jeffrey Young seems to indicate that sunshine also offers benefits.

The first statement in the announcement of their work reads, "A new study of the association between sunlight energy striking the ground and age-adjusted breast cancer mortality rates in 87 locations in the United States has found that people living in the sunniest areas have lower breast cancer death rates."

Aha!

Whether likeable or loathsome, the results of a scientific study always have to be considered in light of knowing something about the scientists who did the work and the actual nature of the work itself: that is, who are these guys and how did they come to that conclusion?

The researchers seem to have suitable credentials. The team works for the Department of Community and Family Medicine at the University of California, San Diego. (The Chamber of Commerce in sunny San Diego didn't sponsor the research, but presumably they're quite happy with the findings.)

The team's work is essentially a statistical study. They obtained measurements of solar radiation from the U.S. National Oceanic and Atmospheric Administration for the 87 locations across the country; they received records of mortality rates from breast cancer for all U.S. counties from the National Cancer Institute. Working with the two kinds of data, they found a strong inverse correlation--that is, the higher the intensity of local sunlight, the lower the risk of fatal breast cancer.

Put in terms of numbers of people, the mortality rates ranged from 33 per 100,000 in the Northeast to 8 per 100,000 in the South and Southeast.

To strengthen their point, the team reported that the lowest rates of breast cancer occurrence worldwide generally are found in countries close to the equator. Soviet colleagues had provided data showing that in the USSR, for each decrease of 35 calories of sunlight energy striking a square centimeter of the earth's surface, there were two more cases of breast cancer per 100,000 each year.

This certainly seems like convincing evidence, and you may well wonder why tropical tourist agencies and similar interested parties aren't trumpeting this discovery. But consider what's missing from the study: everything except sunlight, breast cancer, and age. Yet other factors might affect the incidence and severity of this cancer, since population ethnicities, eating and drinking habits, even stress levels also change from the shadowy high latitudes to the sunny lower ones.

The researchers are aware of that limitation. They speculate that the connection of breast cancer to sunlight is through the effect of ultraviolet light in generating vitamin D. (Humans do manufacture their own vitamin D in response to sunlight.) Other researchers have shown that breast cancer patients with vitamin D receptors in breast tissue have better survival rates than those without such receptors, so the idea is certainly credible.

And doubtless will lead to more research. Garland's work will surely be followed by more detailed studies covering dietary supplements and tanning salons, work correcting for hereditary factors and alcohol intake, even--probably--for hours spent sunbathing compared to hours spent in front of a word processor. Bringing the interesting implications of these statistical investigations up to the level of valid medical advice will take effort, and time.

Meantime, I'll stay a little wary about overdoing sunshine--but moderate self indulgence in sunlight will feel better.