You know vitamin D as the sunshine vitamin. Your body can synthesize it when the sunlight's ultraviolet-B rays hit your skin, and it helps aid in the absorption of calcium, which leads to strong bones. Before it has an impact on the bones, vitamin D is circulating throughout your bloodstream. There it is converted into a prohormone called calcidiol, which may then convert in the kidneys or within the immune system to calcitriol, the biologically active form of vitamin D.
National Surveys
The 2003 to 2006 National Health and Nutrition Examination Survey, or NHANES, and a study published in "The American Journal of Clinical Nutrition" in December 2008 concluded that the majority of people in the United States are not getting adequate levels of vitamin D. This is a serious concern, especially because "adequate intake" suggests only attaining the lowest amount of vitamin D -- as based on the National Institutes of Health's guidelines -- you need to stave off bone diseases like rickets and osteoporosis.
The Vitamin D Council says when you increase your levels of vitamin D beyond what you absolutely need, you may experience a host of health benefits. These benefits include lower rates of depression, cancer and cardiovascular diseases.
Deficiency
People most commonly found to be vitamin D-deficient are the elderly, those with inflammatory bowel diseases like Crohn's, obese individuals, those with darker skin pigmentation, exclusively breastfed infants, those who have limited sun exposure and those with fat malabsorption syndromes like cystic fibrosis.
The Institute of Medicine has determined that North Americans need about 400 IU per day and recommends they get 600 IU. The elderly may actually require as much as 800 IU. It isn't until you consume about 4,000 IU per day that vitamin D may be detrimental, the IOM says.
Beyond the Bones and into the Blood
If you are concerned or just curious about your vitamin D levels, it's easy to get tested through a small blood sample. Ask your doctor specifically for a 25-hydroxyvitamin D test and ask for the exact number value of the results. Although different organizations have different ideas about what constitutes an optimum blood serum level of vitamin D, the Vitamin D Council places the optimum range between 50 and 80 ng/mL. Discuss your results with your doctor, who is in the best position to analyze your numbers in the context of your overall health.
Vitamin D on Cardiovascular Health
Researchers are hard at work in finding the links between Vitamin D deficiency and the blood. In an article published in 2011 in the "Journal of the American College of Cardiology," researchers concluded: "Vitamin D insufficiency is associated with increased arterial stiffness and endothelial dysfunction in the conductance and resistance blood vessels in humans, irrespective of traditional risk burden. Our findings provide impetus for larger trials to assess the effects of vitamin D therapy in cardiovascular disease." This means that although more studies are needed, vitamin D does not simply just travel through the bloodstream but may have an impact on the actual health of the blood and on where the blood travels.
References
- MayoClinic.com: Vitamin D
- Institute of Medicine; Report Brief: Dietary Reference Intakes for Calcium and Vitamin D: Questions About Current Intake; November 2010
- "The Journal of Clinical Endocrinology & Metabolism"; Update in Vitamin D; J. Adams, et al.; February 2010
- "Journal of the American College of Cardiology"; Vitamin D Status Is Associated With Arterial Stiffness and Vascular Dysfunction in Healthy Humans; Ibhar Al Mheid, M.D., et al.; 2011
- "The American Journal of Clinical Nutrition"; Estimation of the Dietary Requirement for Vitamin D in Healthy Adults; Kevin D. Cashman, et al.; December 2008
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