We all know that just 15 minutes of sunlight a day is enough to enable our bodies to make adequate levels of vitamin D. What you may not know is that the skin production of vitamin D can be dampened by several different factors and can cause vitamin D deficiency.
Factor # 1: Sunscreen: In order for the skin to make vitamin D, it requires UVB rays from the sun. For this reason, sunscreens that block UVB radiation also inhibit your skin from making vitamin D. This is an important factor to keep in mind, especially because sunscreen protects us from the sun’s damaging effects, including pre-mature skin aging and skin cancer.
Factor #2: Skin Color: The degree of skin pigmentation also affects how well the skin can make vitamin D from the sun. The darker the skin color, the more difficult it is for your skin to make vitamin D. This is because skin pigmentation is a natural sunscreen that filters out UVB radiation, which is necessary for vitamin D synthesis.
Factor #3: Body Fat: Vitamin D is a fat-soluble vitamin, which means is gets stored in your body fat. The more fat you have, the more vitamin D is deposited in the fat stores, which means less vitamin D makes its way into your circulation, this is called decreased bioavailability. Vitamin D deficiency is strongly correlated with obesity and many studies have shown that there is decreased bioavailability of vitamin D in obese people.
Factor #4: Age: Aging also decreases the skin’s ability to make vitamin D from the sun. Studies have shown that a 70 year old person makes 4 times less vitamin D from the sun than a 20 year old. Recognition of this difference is extremely important for elderly who spend an insignificant amount of time in the sun, and solely depend on sun exposure for their vitamin D nutritional requirements.
Although our bodies are capable of producing plenty of vitamin D from the sun, the aforementioned factors influence the efficiency of vitamin D synthesis by our skin. It is important to understand that vitamin D attained through dietary sources is not influenced by any of these factors. The FDA daily requirement of vitamin D is only 400IU, however, several studies contest this dosage and recommend a higher daily intake. The National Institute of Medicine recommends 2,000 IU a day for healthy adults. Due to the fat-solubilty of vitamin D, doses higher than 10,000 IU daily may be toxic unless prescribed by a physician.
For a more complete list on vitamin D sources, supplementation, and toxicity
These statements and/or products have not been evaluated by the Food and Drug Administration. This information is not medical advice, if you are pregnant, nursing, taking medication, or have a medical condition, consult your physician.
