Clouds reduce sun exposure by approximately 50 percent.
The 13 different vitamins to grow and develop normally. Foods in the diet serve as the main source of vitamins. The body produces some vitamins itself, such as vitamins D and K. The production of vitamin D by the body requires UVB radiation supplied by the sun.
Production
The skin contains sebaceous glands that produce cholesterol. Upon production, the cholesterol immediately converts to a substance called 7-dehyrocholesterol. UV light from the sun provides energy that rearranges the chemical structure of 7-dehydocholesterol, turning it into pre-vitamin D3. Heat then coverts the pre-vitamin D3 to vitamin D.
Exposure
According to the Vitamin D Council, skin receiving 20 to 30 minutes of summer sun exposure produces 10,000 IU of vitamin D. Unlike vitamin D supplements that can accumulate in the body and cause toxicity if levels get too high, the body naturally rejects vitamin D from the skin when it has had a sufficient amount. Showering or bathing washes away any excess vitamin D.
Factors Influencing Production
According to the National Institutes of Health Office of Dietary Supplements, cloud cover and shade reduce UV energy by 50 percent and 60 percent, respectively. Geographic latitude, season of the year, amount of skin pigment, time of day and sunscreen also influence vitamin D production. Since UVB radiation does not penetrate glass, sun exposure received indoors through windows does not make vitamin D.
Requirements
The Office of Dietary supplements suggests that sun exposure, without sunscreen, to the face, arms, legs or back for 5 to 30 minutes during the hours of 10AM and 3 PM twice a week provides sufficient vitamin D synthesis. Tanning beds that give off 2 to 6 percent UVB radiation are effective, as well. Individuals not receiving adequate amounts of sunlight should increase their dietary intake of vitamin D or take supplements.
Tags: body requires, Office Dietary