Sun exposure is best for obtaining vitamin D, because the skin manufactures the nutrient upon exposure to sunlight. However, during the winter, UVB rays in the Northeast are insufficient for vitamin D production, experts say, and sunscreen use in summer can also reduce the skin's ability to produce vitamin D. Only a few foods contain vitamin D naturally, namely fatty fish such as salmon, egg yolks, some cheese and some meats, including liver. Milk and some cereals are fortified with vitamin D.
Mansbach recommends vitamin D supplements, especially for those living in areas where the sun is scarce in the winter. Here again, the authors say more research is needed to determine the appropriate dosage.
"Summer sunlight exposure is the major source of vitamin D for most people," he said. "But [too much] sun exposure can cause sunburns and eventually skin cancer. Until more research is performed, we think the safest bet is to take vitamin D supplements," he said.
Some experts argue that more foods, such as pasta and bread, should be fortified with vitamin D.
"Food fortification would raise the levels of vitamin D for the U.S. population as a whole, but not everyone in the U.S. is vitamin D-deficient," Mansbach said. "Therefore, on a population basis, it's probably easier to have people take vitamin D supplements."
Samantha Heller, a registered dietitian, clinical nutritionist and exercise physiologist in Fairfield, Conn., also agreed that children should take vitamin D supplements. "Vitamin D deficiency has been linked to osteoporosis, fractures, muscle strength and falls, and low levels of vitamin D have been associated with several kinds of cancers, and there may be a link with cardiovascular disease," she said.
Adults would benefit from vitamin D supplements too, Heller said. Adults and children need somewhere between 800 and 1,000 International Units (IUs) of vitami
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