When It Comes To Heart Health, How Much Is Too Much Vitamin D?
Posted Jan 05 2012 5:09pm
New research by Johns Hopkins scientists suggests that vitamin D, long known to be important for bone health and in recent years also for heart protection, may stop conferring cardiovascular benefits and could actually cause harm as levels in the blood rise above the low end of what is considered normal.
Study leader Muhammad Amer, M.D., an assistant professor in the division of general internal medicine at the Johns Hopkins University School of Medicine, says his findings show 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).
Amer and his colleague Rehan Qayyum, M.D., M.H.S., examined data from more than 15,000 adult participants in the continuous National Health and Nutrition Examination Survey, a nationally representative sample, from 2001 and 2006. They found an inverse relationship between vitamin D and CRP in adults without cardiovascular symptoms but with relatively low vitamin D levels. Healthier, lower levels of inflammation were found in people with normal or close to normal vitamin D levels. But beyond blood levels of 21 nanograms per milliliter of 25-Hydroxyvitamin D — considered the low end of the normal range for vitamin D — 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.