Do Obese People Need More Vitamin D?

Is the currently recommended daily dosage of vitamin D enough for obese people? The jury is still out, but initial studies suggest that the answer may be no.

Long recognized for its role in maintaining strong bones, Vitamin D has also been shown to be crucial to a surprisingly diverse range of health issues, from mood management to cardiovascular health. Decades of studies and clinical trials have shown a strong correlation between deficiency of the sunshine vitamin and risk for allergies, asthma, diabetes and other metabolic problems, neurological disorders including Parkinson’s and Alzheimer’s diseases, migraine, periodontal disease, pregnancy and neo-natal problems, and more.

Questions about vitamin D supplementation levels have been raised by many studies in recent years, and in 2008 the American Academy of Pediatrics doubled its recommendation for childhood intake of vitamin D to 400 IU per day, starting in the first few days of life. The IOM’s recommended intake for people over 70 has also been increased to 700 IU per day. However, a growing body of research indicates that high dose vitamin D has been shown to be of significant value to the treatment and management of a wide variety of conditions.

One of the newest areas of investigation is the possible association between low blood levels of vitamin D and obesity, particularly in adolescents. While experts caution that additional research is warranted, studies suggest there is indeed a powerful correlation between Vitamin D levels and obesity and that the current Recommended Daily Intake of 600 IU per day may not be enough for the clinically obese.

A retrospective study by Hasbro Children’s Hospital in Providence, RI monitored 68 obese adolescents. Blood screenings revealed that the overwhelming majority of the subjects – 100 percent of the girls and 91 percent of the boys – had either deficient or insufficient blood levels of the vitamin.  Of the 43 the subjects who had a repeat measurement after a course of supplemental vitamin D (using the RDI of 600 International Units per day), only 28 percent showed normalization of serum vitamin D. The subjects whose serum levels of the vitamin did not normalize after the first course of treatment also failed to normalize after multiple courses of treatment.

The authors of the study said the subjects’ failure to normalize serum levels of the vitamin after repeated courses of supplementation is likely attributable to the fact that vitamin D may be sequestered in body fat, preventing it from being utilized inthe blood. The researchers questioned whether a significantly higher intake of the vitamin may be required as part of treatment of obese adolescents.

A 2011 University of Missouri study indicated that a daily dose of 4,000 IU of vitamin D, the maximum intake level set by the Institute of Medicine, is both safe and effective at improving vitamin D status in obese adolescents. The researchers noted that obese adolescents utilize vitamin D only about half as efficiently as lean adolescents, requiring about twice as much of the vitamin to achieve the same increase in serum levels.