The July issue of Mayo Clinic Women's HealthSource reports the body produces vitamin D when exposed to the sun's ultraviolet rays but many people need a supplement to reach recommended levels. Many multivitamins contain vitamin D but the nutrient, also found in milk, can be purchased alone or combined with calcium.

Vitamin D deficiency is increasingly recognized as an important cause of muscle pain and weakness, the newsletter says.

Several studies have found vitamin D supplements may benefit muscle strength and balance, helping older adults stay steadier on their feet and observational research indicates low levels of vitamin D increase the risk of some cancers.

In addition, some research indicates lower vitamin D levels are associated with factors that affect cardiovascular health, including coronary artery calcification and, possibly, congestive heart failure.

In one study, researchers found a 40 percent lower risk of multiple sclerosis in women who supplemented their diet each day with at least 400 international units of vitamin D, the newsletter says.