A review published in the December 9, 2008 issue of the Journal of the American College of Cardiology describes the involvement of deficient vitamin D levels in common risk factors for cardiovascular disease (including high blood pressure, diabetes, and obesity) and in cardiovascular events.
Vitamin D deficiency is estimated to affect up to half of all adults and 30 percent of children in the United States. While the vitamin’s role in bone health has long been known, a flurry of recent studies have uncovered associations between deficient levels of the vitamin and a number of diseases, including cardiovascular disease. In their review, Michael F. Holick, MD, PhD and colleagues note that insufficient levels of vitamin D activate the renin-angiotensin-aldosterone system, which can lead to hypertension and thickening of the heart and blood vessel walls. Altered hormone levels related to a deficiency of vitamin D (which is also a hormone) increase the risk of diabetes, which is a well known risk factor for the development of cardiovascular disease. In 15,088 subjects from the NHANES III national cohort registry, higher vitamin D levels were related to a lower risk of diabetes as well as hypertension, high triglycerides, and obesity. And among Framingham Heart Study participants who had levels of vitamin D of less than 15 nanograms per milliliter upon enrollment, the risk of subsequent cardiovascular events was twice as great as the risk experienced by those with higher levels of the vitamin.
Chronic vitamin D deficiency is associated with secondary hyperparathyroidism, which increases the risk of inflammation and cardiovascular events. Elevated parathyroid levels were associated with an increased risk of death among older individuals compared to those with normal levels over the course of follow-up in a recent observational study.
"We are outside less than we used to be, and older adults and people who are overweight or obese are less efficient at making vitamin D in response to sunlight," stated review coauthor James H. O'Keefe, MD, who is a cardiologist and director of Preventive Cardiology at the Mid America Heart Institute in Kansas City, Missouri. The authors’ strategy for restoring vitamin D to optimal levels in cardiovascular disease patients includes initial treatment with 50,000 international units (IU) vitamin D2 or D3 weekly for 8 to 12 weeks followed by maintenance with 1,000 to 2,000 IU daily. They also suggest limited sun exposure as a means of increasing vitamin D. They observe that supplementation with vitamin D is safe and that such effects as elevated calcium levels and kidney stone development have only rarely been observed among individuals who consume 20,000 IU per day or more.
"Vitamin D deficiency is an unrecognized, emerging cardiovascular risk factor, which should be screened for and treated," stated Dr O'Keefe. "Vitamin D is easy to assess, and supplementation is simple, safe and inexpensive."
"Restoring vitamin D levels to normal is important in maintaining good musculoskeletal health, and it may also improve heart health and prognosis," Dr. O'Keefe concluded. "We need large randomized controlled trials to determine whether or not vitamin D supplementation can actually reduce future heart disease and deaths."