A study published in the Journal of Clinical Endocrinology and Metabolism found that an astonishing 59% of study subjects had too little vitamin D in their blood with nearly a quarter of the group exhibiting serious deficiencies (less than 20 ng/ml).
The study, by Dr. Richard Kremer, co-director of the Musculoskeletal Axis of the Research Institute of the McGill University Health Center, and co-investigator Dr. Vincente Gilsanz, head of musculoskeletal imaging at the Children’s Hospital Los Angeles of the University of Southern California, is the first to show a clear link between vitamin D levels and the accumulation of fat in muscle tissue—a factor in muscle strength and overall health.
"Vitamin D deficiency is a risk factor for other diseases," explained Kremer, the principal investigator of the study. "Because it is linked to increased body fat, it may affect many different parts of the body. Abnormal levels of vitamin D are associated with a whole spectrum of diseases, including osteoporosis and diabetes, as well as cardiovascular and autoimmune disorders."
Scientists have known for years that vitamin D is essential for muscle strength. Studies in the elderly have shown bedridden patients quickly gain strength when given vitamin D.
The study results are especially surprising, because study subjects—all healthy, young women living in California—could logically be expected to benefit from good diet, outdoor activities and ample exposure to sunshine, the trigger that causes the body to produce vitamin D.
"We are not sure what is causing vitamin D insufficiency in this group," said Kremer, who is also professor of medicine at McGill University. "High levels of vitamin D could help reduce body fat. Or, fat tissues might absorb or retain vitamin D, so that people with more fat are likely to also be vitamin D deficient."
The results extend those of an earlier study, also by Kremer and Gilsanz, which linked low levels of vitamin D to increased visceral fat in a young population. "In the present study, we found an inverse relationship between vitamin D and muscle fat," Kremer said. "The lower the levels of vitamin D, the more fat in subjects’ muscles."
Journal of Clinical Endocrinology and Metabolism 95(4):1595-1601, 2010
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