Vitamin D stands out as the only essential nutrient that your body can manufacture following exposure to sunlight. Particular cells in the skin produce cholecalciferol, also known as vitamin D3, in response to ultraviolet rays. Although small amounts of vitamin D may be present in your food, sunshine is the major source and stimulus for production of this nutrient. As a result, supplementation during the winter months has become more popular. Confusion still remains, however, regarding the optimal dosage.
Vitamin D Function
A fat-soluble nutrient, vitamin D plays an important role in the operation of many of the body's systems. It is required for efficient calcium absorption. Many of your genes also require an ongoing supply of vitamin D to function correctly, according to a clinical study published in a 2013 issue of "PLoS One." Healthy vitamin D levels exert positive effects on bone health, immune system function, cardiovascular health, insulin sensitivity and mood and energy levels. However, it is important that you do not take too much vitamin D, as this could result in toxicity.
The National Institutes of Health recognize the importance of vitamin D beyond simply protecting bone health, and they list a range of problems that could arise from a deficiency of this nutrient. Such conditions include diabetes, seasonal depression and chronic infections. The recommended dietary allowance for vitamin D from the Food and Nutrition Board at the Institute of Medicine is 600 IU per day for adults up to age 70. However, some experts recommend getting up to 2,000 IU a day from combined sunlight and dietary sources, according to the Harvard School of Public Health.
Although official concerns exist over higher intakes, scientific studies suggest that your body may benefit from a higher intake. A clinical study published in the June 2008 issue of "The American Journal of Clinical Nutrition" followed 138 volunteers for six months. Diets were supplemented with vitamin D3 to establish the dietary vitamin D requirement to obtain optimal blood vitamin D levels. The study found that the average adult required 3,440 IU each day to maintain a healthy blood vitamin D status.
Consult with your health practitioner for advice on appropriate vitamin D supplementation levels. The Food and Nutrition Board has established a tolerable upper intake level of 4,000 IU of vitamin D per day. Vitamin D intakes of less than 10,000 IU per day for several months have not been linked to toxicity. However, your chance of getting too much vitamin D increases with prolonged periods of high-dose supplementation. High blood levels of vitamin D may increase tissue calcification and your risk of some types of cancer, cardiovascular disease and death from any cause.
- American Journal of Clinical Nutrition: Vitamin D Intake to Attain a Desired Serum 25-Hydroxyvitamin D Concentration
- Harvard School of Public Health: Vitamin D - How Much is Enough?
- National Institute of Health: Dietary Supplement Fact Sheet – Vitamin D
- PLoS One: Influence of Vitamin D Status and Vitamin D3 Supplementation on Genome Wide Expression of White Blood Cells - A Randomized Double-Blind Clinical Trial
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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.