Many vacationers venture to the beach wearing only sun hats, T-shirts and thick oils. Children are not allowed to leave the shade of sunshades when playing: Fearing the risks, many people now only go out in the sun with bad feelings. But it all depends on the dose. And those who avoid the sun also miss out on its numerous positive effects.
Sun for natural well-being
Thomas Luger, director of the University Dermatology Clinic in Münster, Germany, examined the skin before and after sunbathing. He found that the areas of skin exposed to the sun contained small amounts of a hormone that induces the release of endogenous beta-endorphins. These are substances chemically related to opiates. So the sun provides a natural sense of well-being.
Production of vitamin D
UV rays convert cholesterol directly into vitamin D in the skin. More than 90 percent of the vitamin D needed by the body is made in the skin. Only a small remainder comes from food, such as fatty fish. How much vitamin D is formed depends on the type of skin. The darker the skin, the more sunlight is needed to produce the same amount of vitamin.
Michael F. Holick and his team of researchers at Boston University showed that vitamin D also has a strong influence on preventing certain types of cancer. Some vitamin D is converted into hormones that stop abnormal cell growth and strengthen the body’s defenses. Sunlight also has an effect on blood pressure. Hypertensive patients were exposed to artificial sunlight for eight weeks. A comparison group received vitamin D in tablet form. But although they achieved a similarly high vitamin D level, the blood pressure-lowering effect was absent here. Only sunlight had the positive effect.
So how much sun is good and at what dose does it cause harm?
Professor Michael F. Holick recommends a simple rule: “Most people know from experience how long it takes for their skin type to develop sunburn. Expose their skin to the sun for a quarter of that time each day the sun is out. If they want to stay in the sun longer, they use the usual sunscreens.” Using this method, the U.S. expert says, people store enough vitamin D to get well through the next winter.
