Vitamin D is the hormone that enhances intestinal absorption of calcium and insures healthy bone formation. The best way to obtain vitamin D is through direct exposure of the skin to sunlight, because ultraviolet B rays stimulate the skin to synthesize vitamin D3.
A decade ago, physicians ordered vitamin D levels to assess bone health. Recent epidemiological studies suggested that vitamin D deficiency may play an important role in the pathogenesis of cardiovascular disease, diabetes, cancer, multiple sclerosis, rheumatoid arthritis, asthma, periodontal disease and depression (J Am Coll Cardiol 2008;52:1949-56). Millions of people now take Vitamin D supplements every day and demand for 25(OH) vitamin D testing has skyrocketed.
In a recent JAMA Forum, Aaron Carroll, MD, MS, wrote an article entitled, “Why Take Vitamin D Supplements if they Don't Improve Health?” In this article he summarized all of the studies which have demonstrated that Vitamin D supplementation does not improve bone, muscle , cancer, or cardiovascular health.
Few would argue that people who are deficient in vitamins, including vitamin D, should not be supplemented. But screening of healthy people turns up so few truly deficient people that the US Preventive Services Task Force does not recommend screening widely for it. Physicians should stop ordering so many 25 (OH) Vitamin D tests.