How Much Vitamin D Is Absorbed In The Body From Sunlight?

Vitamin D is sometimes called the "sunshine vitamin" because the body makes vitamin D when the skin is exposed to the ultraviolet or UV rays of the sun. Skin type, use of sunscreen and various environmental factors can all affect how much vitamin D your body produces from sunlight.

Considerations

Vitamin D3 is formed in the skin under the influence of UVB in sunshine or artificial UVB light. The sun's energy converts a chemical in your skin into vitamin D3, which is transported to your liver and then the kidneys, where it's changed into active vitamin D.

The primary function of vitamin D is to help maintain bone health by boosting the absorption of calcium and phosphorus. Scientists continue to research other possible functions of vitamin D.

People who live in northern areas may need to take vitamin D supplements during the winter months. Vitamin D deficiency can increase the risk of heart disease, osteoporosis, certain cancers and other diseases.

Variables

The amount of vitamin D3 produced in the body from spending time outdoors depends on the strength of the sun. Environmental factors such as geographic location, season, cloud cover, smog and time of day along with sunscreen, window glass and clothing can all reduce the amount of sunlight that touches the skin, and subsequent vitamin D production.

Effects

Skin color has a significant effect on vitamin D production from the sun. A dark-skinned person may need 3 hours of sunlight to meet their vitamin D needs while someone with light skin may need only 45 minutes, explains Harvard School of Public Health. In many cases a 15-minute daily walk in the sun can ensure you are getting a sufficient daily dose of vitamin D.

A fair-skinned person who spends as little as 10 minutes in the sun during the midday when its rays are most intense, wearing only a sleeveless shirt and shorts will be exposed to enough radiation to produce about 10,000 international units or IU of vitamin D. People with darker skin may need 15 to 20 minutes of sun exposure while those with black skin may require up to one hour in the sun to make the same amount of vitamin D.

Sunscreen

When applied correctly, sunscreen diminishes the body's ability to produce vitamin D by more than 90 percent. Vitamin D should be obtained safely through a healthy diet and possibly supplements instead of from the sun, advises the American Academy of Dermatology. You should apply sunscreen to all exposed areas of skin 15 to 30 minutes before going outdoors.

Supplements/Food Sources

Vitamin D supplements are available as tablets, softgel, capsules and liquid in strengths from 50 to 1,000 mg. Vitamin D is also contained in many multivitamins. The Recommended Daily Allowance for adults is 600 IU daily, according to the Office of Dietary Supplements.Talk to your health care provider about the best dosage for your needs. Dietary sources of vitamin D include cod liver oil; fatty fish like tuna, salmon, sardines and herring; vitamin D-fortified milk; and cereal.