Vitamin D stands out as the only essential nutrient that the body can manufacture following exposure to sunlight. Particular cells in the skin produce cholecalciferol, also known as vitamin D3, in response to intense UVB rays. Although small amounts of vitamin D exist in our food, sunshine remains the major source of the nutrient; as a result, supplementation during the winter has become more popular, but confusion still remains over 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. Dr. Joseph Mercola, author of "The No Grain Diet," explains that over 2,000 genes require an ongoing supply of the vitamin to function correctly. Healthy vitamin D levels exert positive effects on bone health, immune system function, cardiovascular risk, insulin sensitivity and mood and energy levels. However, as a fat-soluble nutrient, it is important that you do not take too much vitamin D, as this could result in toxicity.
Official Recommendations
The National Institutes of Health recognize the importance of vitamin D beyond simply protecting bones; they list a range of complaints that may occur from a deficiency of this nutrient. Such conditions include diabetes, seasonal depression and chronic infections. They recommend that adults consume 600 IU per day; they do not specify whether the recommendation is for vitamin D2, also called ergocalciferol, or vitamin D3.
Scientific Studies
Although official concerns exist over higher intakes, scientific studies suggest that your body benefits from a higher intake. A team lead by Dr John Aloia followed 138 volunteers for six months, supplementing them with vitamin D3 and checking their blood levels of the nutrient to establish their exact need. They found that the average adult required 3,800 IU each day to maintain healthy vitamin D status. The results were published in the "American Journal of Clinical Nutrition" in 2008.
Conclusion
Rather that proving too much, 2,000 IU may prove too little for optimum health. Experts such as Dr. Joseph Mercola, author of "The No Grain Diet," advocates using 5,000 IU per day of vitamin D3 throughout the winter as a first step in warding of seasonal colds and flu. Consult with your health practitioner for advice on appropriate supplementation levels.
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