Endocrinologists release vitamin D guidelines

For optimal health, Americans should maintain a serum vitamin D level of 30–60 ng/mL, a feat that probably requires the use of supplements, according to new clinical practice guidelines from the Endocrine Society. The guidelines appear in the July issue of the Journal of Clinical Endocrinology and Metabolism. Vitamin D insufficiency is defined in the guidelines as a serum 25-hydroxyvitamin D level of 21–29 ng/mL, and vitamin D deficiency occurs when levels are below 20 ng/mL. Studies of vitamin D deficiency and insufficiency cited in the guidelines give variable estimates of the conditions, with rates in different populations ranging from 20% to 100%. The guidelines state that the major cause of vitamin D deficiency is inadequate exposure to natural sunlight. Decreased sun exposure and the use of sunscreens reduce the risk of skin cancer but also sharply limit the production of vitamin D in the skin, the guidelines explain. With sun exposure minimized, people can turn to dietary sources of vitamin D to meet their daily requirements. But that isn’t enough, said Michael Holick, professor of medicine, physiology, and biophysics at Boston University School of Medicine and the lead author of the guidelines.