Sun Exposure

A: Because calcium absorption depends on adequate amounts of vitamin D (which comes from the sun, among other sources), bone strength can be adversely affected by underexposure to the sun. Moderation works, though: 10 to 15 minutes of sun a few times each week (preferably when the suns rays are not at their strongest) probably creates enough vitamin D to head off problems. Avoid sunscreen and sun-protective clothing during sun time, as they can nearly eliminate vitamin D production; after a few minutes, apply sun protection with SPF 15 or higher. I prefer sunblocks, which typically contain titanium dioxide or zinc, rather than sunscreens that contain chemicals such as octyl methoxycinnamate. Also, if you live in New England, the upper Midwest, the Pacific Northwest or another cold-weather area, ask your doctor about giving your child vitamin D supplements during the winter months.