By Nicole Chiu - Contributing Health Journalist

A recent study published in the December issue of the Journal of the American College of Cardiology (JACC) has sited a growing body of literature, which highlights how low levels of vitamin D may lead to risks of hypertension, obesity, diabetes and cardiovascular disease (CVD) including stroke and congestive heart failure.

"Vitamin D deficiency is an unrecognized, emerging cardiovascular risk factor, which should be screened for and treated," said James H. O'Keefe, M.D., cardiologist and director of Preventive Cardiology at the Mid America Heart Institute, Kansas City, MO. "Vitamin D is easy to assess, and supplementation is simple, safe and inexpensive."

Low levels of vitamin D activates the renin-angiostensin-aldosterone system, which then predisposes the symptoms of hypertension, and heart and blood vessel stiffening and thickening. Vitamin D deficiency also restricts immune function, which is how it increases the risk of diabetes.

The benchmark for what is considered ‘low’ levels of vitamin D is for a measurement of 25(OH)D level of <20ng/ml. It has been estimated that 30% of children and teens and up to half of adults in the United States have vitamin D deficiency.

A separate set of data from the Framingham Heart Study showed that patients with levels below 15ng/ml were twice as likely to experience some form of CVD within the next five years, compared to patients with higher levels of vitamin D. The study eliminated traditional CV risk factors and the results remained conclusive with the fact that vitamin D deficiency posed a significant risk to heart failure.

The controversy and sometimes confusion in common knowledge with vitamin D is that most vitamin D can be manufactured in our bodies through sun exposure – yet, sun exposure for more than 15 to 30 minutes increases the risk of skin cancer. Thus, many people are opting to stay indoors or constantly putting on sunscreen, thus blocking our access to vitamin D.

"A little bit of sunshine is a good thing, but the use of sunscreen to guard against skin cancer is important if you plan to be outside for more than 15 to 30 of intense sunlight exposure,” said Dr. O’Keefe.

Fortunately, the sun is not the only source of vitamin D. Supplements are available which may be consumed orally in tablet form, and also foods such as salmon, sardines, cod-liver oil, milk and some cereals all contain vitamin D.

If you are mature-aged, have darkly pigmented skin, live in cold or winter environments, are a smoker, are obese, have renal or liver disease, or are taking certain medications, then you are more likely to be at risk of vitamin D deficiency.

Sunlight exposure for 10 minutes a day is enough for Caucasians to absorb the recommended amount of vitamin D – a little bit longer for persons with increased skin pigmentation.

A recommended introduction to vitamin D replenishment – only for persons confirmed with vitamin D deficiency – is to start off with 50,000 IU of vitamin D2 or D3 every two weeks, for twelve weeks. Then add 1,000 to 2,000 IU of vitamin D3 daily, plus the daily sun exposure of 10 to 15 minutes.

Vitamin D toxicity is also possible, at levels of more than 20,000 units per day.