In a recent blog, I said that many researchers and nutritionists were alarmed last November by the Institute of Medicine's proposal to keep the recommended daily intake of vitamin D quite low. The IOM's decision looks even more problematic since researchers are now finding some links between vitamin D deficiency and unhealthy weight gain.
Less vitamin D = more fat?
A recent Michigan study found, for example, that children deficient in vitamin D had larger fat deposits around their waists and gained weight faster than did the children in the study with adequate vitamin D levels.
Another, larger study in Bogota, Colombia, followed 479 school children ages 5 years to12 years for approximately 30 months (2006-2009), and tracked the vitamin D levels in their blood. The researchers, from the National University of Colombia, also closely kept track of 3 markers in the body that over time can point toward increases in body fat: body mass index (BMI), waist circumference, and skinfold thickness ratios (which offer a way to measure fat content in areas such as the triceps and abdomen).
The Colombian researchers found that, compared to children who had started the study with adequate levels of vitamin D, children with the lowest blood levels of the vitamin tended to gain weight faster and to experience significant increases in central (belly) fat. Girls who had inadequate vitamin D levels at the start also grew more slowly than did the girls whose levels were normal (a trait not seen in the boys).
The Colombia study has just been published in the American Journal of Clinical Nutrition, and its first author, Dr. Diane Gilbert-Diamond, thinks the findings could turn out to be exciting because--since both vitamin D insufficiency and childhood obesity are common worldwide--further study might reveal a convincing association between the 2 conditions. In any case, more research must be done to see if obesity and vitamin D deficiency are associated with each other in any way.
Sunlight is often not enough
One other point to mull over: Bogota, Colombia, happens to be located in a subtropical region, and yet even the sunlight there was often not intense enough to induce the skin of these children to produce adequate amounts of vitamin D. Similarly, other studies have indicated that the sunlight in Sao Paolo, Brazil, and Costa Rica, is not strong enough to prevent vitamin D insufficiency.
• Even if you consume wild salmon, sardines, and plenty of vitamin D-fortified milk during meals, your blood levels of this vitamin might still be low.
• Keep in mind that vitamin D likes to hide out inside fat cells, and that it is not absorbed as easily in darker skin, making you at higher risk for vitamin D deficiency if you have any weight challenges or have a lot of melanin in your skin.
• And even though you live near the equator, if you and your family have never had your vitamin D levels checked, consider getting a 25-OH vitamin D analysis, which is the most sensitive test.