subject: Vitamin D Absorption From the Sun [print this page] Vitamin D Absorption From the Sun Vitamin D Absorption From the Sun
Most of you may know that as little as 15 minutes of sunlight per 24 hours is adequate to allow our skin to manufacture high enough levels of Calcitriol (Vitamin D). What most people may not already know is that the skin production of vitamin D can be hindered by multiple factors and can cause or exacerbate vitamin D deficiency.
Factor #1: Sunscreen: In order for the skin to make Calcitriol, it is necessary that the skin gets UVB rays from sunshine. Consequently, sunscreens that block sunshine's UVB radiation also reduce the ability of 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, which can be caused by the very same rays, including premature aging of the skin and skin malignancy.
Factor #2: Skin Melanin content: The degree of skin pigmentation also largely determines how well the dermal tissues can make Calcitriol from the sun. The darker the pigmentation of the skin, the more difficult it is for your skin to produce vitamin D. This is because melanin is a natural sunscreen that filters out UVB radiation, which is important for vitamin D manufacturing.
Factor #3: Your Weight: Calcitriol is a vitamin soluble in fat, which means it gets deposited in your body fat. The more fat you possess, the more Vitamin D (Calcitriol) 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 demonstrated that there is substantially decreased bioavailability of vitamin D in obese people.
Factor #4: Age: Age also reduces the skin's ability to manufacture vitamin D from sunshine. Scientific studies have demonstrated that a seventy year old individual makes 4x less vitamin D from the sun than a 20 year old. Recognition of this difference is very important for the elderly who spend an insignificant amount of time in the sunshine, and solely rely on daily exposure to the sun for meeting their vitamin D needs.
Although our bodies are capable of producing plenty of vitamin D from the sununder the perfect conditions, the aforementioned factors affect the efficiency of vitamin D synthesis by our skin. It is necessary to understand that vitamin D acquired through dietary sources is not influenced by any of these limiting factors. The FDA daily requirement of vitamin D is only 400IU, however, several scientific studies contest this minimal dosage and recommend a higher daily intake. The National Institute of Medicine officially suggests 2,000IU per day for healthy adults. Due to the fat-solubility of vitamin D, doses larger than 10,000 IU every day may be toxic unless prescribed by a medical physician who has checked your circulating Vitamin D levels.
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