The primary source of vitamin D is the sun, and although it is found naturally in very few foods, commercially sold milk is usually fortified with it. Amer says as people spend more and more time indoors and slather their bodies with sunscreen when outdoors, concern is rising that many are vitamin D-deficient. But he says there is no set amount of supplementation that can bring someone up to 21 nanograms per milliliter because the way people process vitamins varies.
In research published in January 2012 in the American Journal of Cardiology, Amer and Qayyum found that increasing levels of vitamin D in the blood are linked with lower levels of a popular marker for cardiovascular inflammation c-reactive protein (also known as CRP). Beyond blood levels of 21 nanograms per milliliter, any additional increase in vitamin D was associated with an increase in CRP, a factor linked to stiffening of the blood vessels and an increased risk of cardiovascular problems. The team's unpublished research also suggests a link between excess vitamin D and elevated homocysteine levels, another danger sign for cardiovascular disease.
People should consult with their doctors, Amer says, before starting vitamin D supplements and should have their blood levels checked. Still, he says, "most healthy people are unlikely to find that supplementation prevents cardiovascular diseases or extends their lives," and there is no consensus among doctors on what is the right level of vitamin D in the blood for healthy people.
"There are a lot of myths out there and not enough data," he concludes.
|Contact: Stephanie Desmon|
Johns Hopkins Medicine