by Chantal Charo Ph.D.   Vitamin D or the “sunshine vitamin” has seen a lot of popularity lately thanks to discoveries about deficiencies in the general population. Shocking data from the National Health and Nutrition Examination Survey (NHANES) demonstrate that more than 90% of the non Caucasian population and 75% of the Caucasian population of the United States suffer from vitamin D insufficiency. What exactly does Vitamin D do?

Vitamin D plays a role in bone metabolism and calcium homeostasis and many researchers have shown the benefits of vitamin D supplementation in preventing bone loss and muscle injury in older women. However, in recent years it has become clear that the health risks associated with low levels of Vitamin D go beyond age related diseases. Hypovitaminosis D is linked to an increased risk of osteoporosis, diabetes, cardiovascular diseases, and cancer.  Much of the growing interest in vitamin D was caused by its association with obesity, a known risk factor for the chronic conditions described. A study published in the journal Nutritional Research showed that excessive administration of vitamin D lead to a significant decrease in body fat of rats. In this study, researchers separated rats into two groups: one overfed mostly with calories from fat, and the other group overfed with a sugar rich diet. Each of these groups was split in half, with one half receiving a “sub-optimal” dose of Vitamin D and the other receiving 10,000 IE of Vitamin D, and a slightly higher amount of calcium than what the other group received. The results of this study were surprising; researchers found that even though the rats were overfed, administering large dose of Vitamin D and calcium resulted in weight loss and hypertrophy compared to the group that received the sub optimal doses of Vitamin D.  Data from this study demonstrated a correlation of high doses of Vitamin D and protein synthesis. They claim that the rats receiving the high Vitamin D and calcium doses manufactured more of a protein that helps muscles burn fat for energy which lead to the decrease in body fat and increase in musculature. However, this study was clearly done in rats, not in humans. Nevertheless, similar results were obtained from studies done in humans. it is now well established that low vitamin D status, may increase body fat and that increasing Vitamin D levels may inhibit adipogenesis . And, reciprocally, a modest weight loss of 10% could increase the levels Vitamin D according to Holecki M.’s group. It has even been suggested that Vitamin D supplementation contributes to both upper and lower body muscle strength and could be used to preserve age related muscle loss. Muscle cells contain vitamin D receptor and several studies have demonstrated that serum levels of Vitamin D correlate with improved physical performance. On the other hand, people with insufficient or deficient levels of Vitamin D are likely to have fatty muscles because of an increase in fat infiltration. Obviously, this information is valuable for everyone not only for both dieters and fitness enthusiasts- who wouldn’t want to lose fat and gain some definition? All it takes, according to these studies, is a adding a couple of Vitamin D/Calcium pills to your diet. However, should you supplement your diet with Vitamin D? Vitamin D is synthesized when the skin is exposed to UV from the sun, or it is obtained from food, especially fatty fish. Moderately increasing Vitamin D by diet or sun exposure is harmless. Although rare, excess Vitamin D can cause toxicity by causing hypercalcemia, or an increase of calcium build up in the blood, kidney problems and death. Toxic doses for Vitamin D are not yet established, however, reports show that a dose of 50 000 IU or greater for several months can cause Hypervitaminosis D related toxicity. The RDA of Vitamin D is 600 IU/day. As always, talk to your doctor before taking vitamin and mineral supplements.

BIO

Dr. Chantal Charo  is an assistant professor of virology and immunology and a licensed sports nutritionist from Miami, FL.  She is an interdisciplinary biomedical researcher with a particular focus on women’s health. Her research studies and teaching interests include insulin resistance, the biological pathways by which IGF-1 affects gynecological cancers, Vitamin D, the metabolic syndrome, PCOS, female athlete triad syndrome, microRNAs, breast and ovarian cancer. Dr. Charo is also involved in many clinical trial, including a Phase I trial for metastatic ovarian cancer. Chantal earned her Ph.Ds. in Biomedical Sciences and Cancer Biology from the University of Texas Houston and the UT MD Anderson Cancer Center; and she holds an M.Sc in Biomedical Sciences and a B.S. in biology with a minor in chemistry. As sports nutritionist trained with a leading supplement company, Dr. Charo investigated the effects of carbohydrate intake and hormonal balance in women, as well as the Euthyroid Sick syndrome and the female athlete. Chantal hosts a medical segment on a local daily talk show which aims at promoting awareness to women and combating health illiteracy. In support of her research, Chantal has received fellowships from National Cancer Institute, the National Institute of Health and more. She is a Fellow of the American Association of Cancer Researchers, the American Pancreatic Association and the American Breast Cancer Association, and was the recipient for many outstanding scientist awards.

REFERENCES

Holick MF  2004 Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. American Journal of Clinical Nutrition;79(3):362-371. Siddiqui SM  2008 Dietary intervention with vitamin D, calcium, and whey protein reduced fat mass and increased lean mass in rats. Nutritional Research ;28(11):783-790.

Holick MF 2003 Vitamin D: a millennium perspective. J Cell Biochem 88:296–307

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Kuchuk NO, van Schoor NM, Pluijm SM, Chines A, Lips P 2009 Vitamin D status, parathyroid function, bone turnover, and BMD in postmenopausal women with osteoporosis: global perspective. J Bone Miner Res 24:693–701

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Holick MF 2008 Vitamin D: a D-lightful health perspective. Nutr Rev 66:S182–194

Koutkia, P. 2001 Vitamin D intoxication associated with an over-the-counter supplement. N Engl J Med.; 345 (1): 66-7.

Vieth, R. 2006 Critique of the considerations for establishing the tolerable upper intake level for vitamin D: critical need for revision upwards. J Nutr. 136 (4): 1117-22.