It is estimated that 40% of the population over the age of 50 is deficient in vitamin D. Recently, researchers have had a renewed interest in vitamin D, finding it provides various benefits to health not previously known. Vitamin D helps maintain healthy bones by stimulating the absorption of calcium in the body. Without it, the body is unable to utilize the calcium supplied via the diet or supplements.
Recent research has found correlations between low vitamin D intake and higher rates of negative health issues. Vitamin D is commonly referred to as the "sunshine vitamin," but many people do not spend enough time outdoors to obtain this benefit. The body manufactures vitamin D when the skin is exposed to sunlight; therefore, it is recommended that people living in northern latitudes, not exposed to the sunlight or who use sunscreen should supplement with the nutrient.
Even though the RDA is set at 400 IU, many experts now recommend up to 1,000 IU, especially for those at risk for deficiency such as the elderly, African-Americans, night shift workers, those living in the northern latitudes or that lack sun exposure, and those who do not consume enough vitamin D-rich foods.