Too Little Vitamin D Puts Heart at Risk
Research Suggests Vitamin D Deficiency May Be an Unrecognized Heart Disease Risk Factor
Testing for Vitamin D Deficiency
Vitamin D levels can be measured with a blood test that looks at a specific form of vitamin D called 25-hydroxy vitamin D (25(OH)D). Vitamin D deficiency is defined as a blood 25(OH)D level below 20 ng/dL. Normal levels are considered to be above 30 ng/dL.
Researchers recommend 25(OH)D screening for those with known risk factors for vitamin D deficiency including:
- Older age
- Darkly pigmented skin
- Reduced sun exposure due to seasonal variation or living far from the equator
- Kidney or liver disease
The U.S. government's current recommended daily allowance (RDA) for vitamin D is 200 international units (IU) per day for individuals under age 50. For those between 50 and 70, 400 IU per day is recommended, and for those over age 70, the RDA is 600 IU. Most experts believe these doses are too low, and that somewhere between 1,000 and 2,000 IU of vitamin D per day is necessary to maintain adequate vitamin D levels. The safe upper limit of vitamin D consumption is 10,000 IU per day.
Vitamin D supplements are available in two different forms: Vitamin D2 and Vitamin D3. Although both appear effective in raising vitamin D blood levels, Vitamin D3 supplements appear to result in a longer-lasting boost.
Although there are no current guidelines for restoring and maintaining healthy vitamin D levels in people at risk for heart disease, for those who are vitamin D deficient, the researchers recommend initial treatment with 50,000 IU of vitamin D2or D3 once a week for eight to 12 weeks, followed by maintenance with one of the following strategies:
- 50,000 IU vitamin D2or D3 every 2 weeks
- 1,000 to 2,000 IU vitamin D3 daily
- Sunlight exposure for 10 minutes for white patients (longer for people with increased skin pigmentation) between the hours of 10 a.m. and 3 p.m.
Once maintenance therapy has been initiated, rechecking 25(OH)D blood levels is recommended after three to six months of ongoing supplementation.
"Restoring vitamin D levels to normal is important in maintaining good musculoskeletal health, and it may also improve heart health and prognosis," says O'Keefe. "We need large, randomized, controlled trials to determine whether or not vitamin D supplementation can actually reduce future heart disease and deaths."