World Osteoporosis Day is celebrated every year on October 20, and this year’s theme is “Concern about the silent killer – osteoporosis”. The increasing number of unhealthy habits of urbanites has led to the trend of osteoporosis, a traditional disease of the elderly, becoming younger. Experts suggest that exercise in the sun is a basic measure to prevent osteoporosis. At present, urban people have less outdoor activities, heavy brain work, less movement and more static, coupled with too fine diet and low intake of vitamin D, etc., more and more people suffer from osteoporosis. The ultraviolet radiation from the sun can make the human skin produce active vitamin D. Active vitamin D is essential for bone metabolism and can promote the absorption of calcium in the intestine, so that the intake of calcium can be absorbed more effectively, which is conducive to the deposition of bone calcium. Conversely, vitamin D deficiency can lead to osteoporosis. Therefore, sunbathing and outdoor activities have the effect of both treating osteoporosis and preventing it from occurring. It is especially necessary for the elderly, children and women during pregnancy, lactation and postmenopause. In general, when 15% of the body’s skin is exposed to sunlight, young people can get a total of 40 minutes of sunlight per week, and elderly people can get 60 minutes of sunlight per week to get sufficient vitamin D. Regardless of spring, summer and autumn, it is very beneficial to go outdoors to get more sunlight. But the appropriate time to sunbathe as much as possible to arrange in the morning 6:00 to 9:00, 4:00 to 7:00 p.m. two time, because at this time the sun’s ultraviolet A beam increased, is a good time to reserve vitamin D in the body, if the elderly calcium deficiency or osteoporosis, should be in these two periods of time to sunbathe well. Of course, the occurrence of osteoporosis is affected by a variety of factors, in addition to ensuring regular sun exposure, supplementing the right amount of calcium, intake of recombinant protein, maintaining good lifestyle habits and proper physical exercise is also very necessary!