Getting your Vitamin D from Sunlight

.Going for a walk during your lunch break is a great way to get your vitamin D for the day according to the text Becoming Vegan. For people with light skin it takes abut 10-15 minutes of sunlight a day on the face and forearms (or an equivalent surface area of skin) to build up previtamin D that can then be converted to vitamin D.

Sun exposure (ultraviolet/UV radiation) beyond about 20 minutes does not seem to provide further benefit. People with dark skin require more exposure to sunlight (3-6 times longer) to get the same degree of vitamin D production, the darkest skin requiring the longest exposure in the sunlight.

The melanin pigment in dark skin absorbs some of the UV radiation and is a protective feature in the typically darker skin of people in sunny climates. It seems that over our evolution, as people moved from sunnier climates to northern latitudes, skin pigmentation decreased, allowing for adequate production of vitamin D in areas with less UV light. Aging lowers the capacity for vitamin D production to about half that of young people. This may be particularly true for senior who are very thin. Here is a situation where those with little fat on their bones (or at least under their skin) have the advantage. These people seem to have more reserves of fat-soluble vitamin D to get them through gray winters.

Sunscreen protection factors (SPF) of 8 and about can prevent vitamin D synthesis. People don't usually put on sunscreen nearly as lavishly as levels recommend; in fact surveys have shown that quantities applied are only about one-quarter of those used to measure their sun protection effectiveness. If this is the case, some vitamin D synthesis may occur using sunscreens about SPF 8.For vitamin D synthesis, the amount of UV light in mid morning sun and through the afternoon is fine.

Vitamin D production varies with the amount of clothing one is wearing, which affects the surface area of skin exposed. Recommended times are based on exposure of face and forearms. If you bare a lot more, time can be reduced considerably. .

Production of vitamin D varies with season and latitude, as these factors affect the amount of UV radiation. A summer day may bring us 16 times the UV rays of a winter day, and even cloudy summer days will stimulate some vitamin D production. Becoming Vegan - Brenda Davis, R.D. and Vesanto Melina, M.S., R.D.

Photo- Bridget Bardot