Vitamin D, a nutrient found in fatty fish, meat, dairy and fortified soy beverages, helps build and maintain strong bones by helping in the absorption of calcium, according to the NIH. It also helps muscle, nerve and immunity functions. While the use of dietary supplements containing vitamin D has increased for both men and women since 1988, it hasn't been enough, according to some healthcare professionals.
"Vitamin D is either low or deficient in 50% to 60% of people in the United States. They should take at least 800 to 1,000 IU of vitamin D a day," they say. "And optimally, whenever an individual gets a physical examination, they should get their vitamin D level measured and then supplement accordingly."
Most agree by saying that people really need to make sure their vitamin D levels are high enough. "Vitamin D is the only vitamin that I measure first and, depending on the level, determine how much they should be taking. Then I re-test until they get to the optimum level."