Every schoolchild knows that sunlight reaching our skin should be our primary source of vitamin D. This vitamin is essential for the development of tissues, bones, and teeth, as well as for regulating the level of calcium in the blood. Inadequate amounts of vitamin D lead to rickets, a disease resulting from the body's failure to assimilate calcium and phosphorus and characterized by softened and deformed bones. It is seen dramatically in neglected children who have been kept in dark rooms for many years. Their bodies are underdeveloped.

But too much sunlight creates other problems. Ultraviolet radiation from the sun, while beneficial in small quantities, can be hazardous or even fatal in large doses. The cultural message that a deep, dark tan makes you more attractive is a dangerous one. An important controversy, and one that receives remarkably little attention, concerns the effectiveness of sunscreens to prevent the most lethal of skin cancers, melanoma. While sunscreens clearly prevent ultraviolet rays from burning the skin and seem to protect against the more common but less fatal basal cell and squamous cell carcinomas, the manufacturers of sunscreens (formerly called tanning lotions") have never suggested that they prevent melanomas. This fact is overlooked by most consumers and health authorities alike.

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