Go ahead, get some sun; it'll do a body good

February 24, 2008 12:16 am

BOSTON--

Life on our planet requires sunlight to survive. And most organisms work hard to get it. Jungle reptiles often compete with each other to find the highest, warmest surfaces for sunbathing. Rainforest plants race to fill rare, sunny openings in the thick canopy left by fallen trees. And some flowers even bend their stems to follow the sun's movement across the sky.

Humans also need sensible sun exposure. But unlike the rest of life on Earth, we actively work to avoid the sun.

In recent years, several dubious groups have launched smear campaigns against the sun, blurring the line between overexposure--a very real threat to our health--and any exposure at all. The sunscreen industry constantly warns the public to "cover up" before venturing outside. Store shelves are flooded with products promising increasingly higher sun-protecting factors (SPF). And the latest children's swim trunks cover more skin than a nun's habit.

This frantic obscuration has hurt us in an unexpected area: nutrition. The Centers for Disease Control and Prevention estimate that more than 180 million Americans--60 percent of the population--are not getting enough vitamin D.

Though certain foods contain trace amounts, it's virtually impossible to get enough vitamin D through diet alone. The National Institutes of Health lists sunlight as "the most important source of vitamin D." Our bodies produce the aptly named "sunshine vitamin" when ultraviolet rays reach our skin. To produce the amount that most experts now agree is the minimum daily requirement (about 1,000 to 2,000 international units), one would need to expose 25 percent of one's body for around 10 minutes at least two to three times a week during spring, summer, and early fall.

We don't even come close.

Geography, weather, pollution, and sunscreen limit the amount of UV available. Even factors as simple as the season play a role. For instance, during this time of year, sunlight is a scarce commodity, especially for Americans in the northern states.

Without vitamin D, our bodies cannot build strong bones or maintain a healthy immune system. New research indicates that the sunshine vitamin plays a vital role in the prevention of many deadly illnesses, including multiple sclerosis, tuberculosis, schizophrenia, and heart disease. Health officials estimate that as many as 47,000 cancer deaths could be prevented each year in America if adequate vitamin D levels were attained. But sun-scare messengers and health "experts" irresponsibly urge us to wear lotions and cosmetics with added SPF, which can block up to 100 percent of our vitamin D production.

Vitamin D deficiency is contributing to hundreds of thousands of cases of chronic and terminal diseases. That means that the sunlight myths perpetuated by the skin-care industry aren't only misleading. They're deadly.

We need sunlight as we need water, food, and a roof over our heads.

It would be false prudence to completely avoid the sun to prevent skin cancer. Yes, too much UV light is unhealthy. However, too much of any good thing can be bad for your health. And too much UV avoidance can be downright dangerous.

When it comes to sunlight, the old adage holds true: Everything in moderation.

Michael Holick, M.D., is director of the vitamin D, skin, and bone research laboratory at Boston University Medical Center.