Vitamin D has become one of the hottest nutrients in pharmacies and health food stores. That’s because epidemiological studies have suggested that low levels of this hormone are linked to weakened bones, hypertension, autoimmune diseases, arthritis, diabetes, muscle spasms, depression and cancer. Most of this research is observational, which is to say that it has not been conducted in rigorous randomized, double-blind, placebo-controlled trials. Such a study is underway, but it will be years before the data are analyzed.
In the meantime, physicians and patients have been trying to determine the optimal levels of vitamin D for good health. Some experts have recommended that people have at least 30 ng/ml of 25-hydroxyvitamin D circulating in their blood. With that cutoff, more than two-thirds of American adults don’t have enough vitamin D. But a new recommendation from the Institute of Medicine would drop that level to less than one-third by re-defining adequate vitamin D as 20 ng/ml or more. That means nearly 80 million Americans will no longer be considered insufficient in vitamin D. This guideline is likely to create controversy within the nutrition community.
[PLOS ONE, Oct. 24, 2012]
