[Osteoporosis and sunlight]

Abstract

Vitamin D deficiency causes osteomalacia, osteoporosis and may contribute to bone fractures. Vitamin D is synthesized in the skin by the sunlight exposure and is also obtained from dietary sources. In the U.S., it was recommended that the adequate intake of vitamin D for adults aged from 51-70 years and 70 and more required 400 and 600 IU/day, respectively. Since dietary intake of vitamin D for middle-aged and elderly Japanese is estimated to be 300-400 IU/day, approximately 100-200 IU/day should be provided through the skin. Considering the risks of skin cancer caused by sunlight exposure, short trips outside amid life's daily routine on sunny days, and 30-60 minutes on rainy days and during times when sun exposure is inadequate to produce enough vitamin D in the skin would be appropriate.