Vitamin D is a key to good health, but 3 in 7 of us are short of it

Some sources of vitamin D are fish, milk, eggs, peas, mushrooms and supplements. (Health.com) 

Vitamin D plays many important roles in the body, but about three out of seven Americans don't get enough. 

Beyond helping bones absorb calcium, the vitamin helps immune health, muscle function, and brain cell activity. Research by the National Institutes of Health shows that approximately 42% of the U.S. population is deficient in vitamin D, and some groups are more prone to deficiency than others.

For example, breast-fed infants are a high-risk group because breastmilk, despite its many health benefits, is low in vitamin D, according to Kenya Parks of the University of Texas at Houston. Parks also said that children and teens who are obese and who take anti-convulsant and anti-fungal medications are more likely to be deficient in vitamin D.

Other high-risk groups include African Americans, because higher melanin levels inhibit vitamin D production, and the elderly, institutionalized, and hospitalized. One study published in Pharmacotherapy reported that 60% of nursing home residents were low in vitamin D, and another study published in The New England Journal of Medicine reported that 57% of hospitalized patients were low in the vitamin.

Vitamin D can be obtained through sunlight, food, or supplements; but considering how sun exposure can increase a person's risk for skin cancer and how many areas do not receive enough sunlight for people to reach necessary daily limits, food and supplements may be better options.

NIH says the daily recommended amount of vitamin D is 400 international units for infants up to 12 months old, 600 IU for children and adults up to 70 years old as well as breastfeeding women, and 800 IU for adults who are at least 71 years old.