Your complexion and the quantity of sunshine you get in addition to all you eat, all this can influence the amount of vitamin D that your body has on hand for optimum health.

In a preliminary research, Agricultural Research Service (ARS) physiologist Charles B. Stephensen and fellow workers created a preliminary model, which predicts the vitamin D requirement of an individual.

Stephensen is based at the ARS Western Human Nutrition Research Centre at the University of California-Davis.

Researchers have known since the early 20th century that human bodies get stimulated to make vitamin D when UV rays reach to the skin.

But the quantity of direct sunlight, which a person gets is affected not only by the amount of time spent in the sun, but also by latitude, season, skin pigmentation, and even the amount of protective clothing that one wears.

The current suggested daily allowance of vitamin D for adults, who are below the age of 50, is 200 international units.

To develop the preliminary model, Stephensen and fellow workers worked with 72 young adult volunteers who provided intermittent records of what they ate and, for 7- to 8-week stints, wore photosensitive badges from 7 a. m. to 7 p. m. so scientists could determine their level of sun exposure.

Facts from the volunteers, either African-American or of European ancestry, who had relatively low amounts of sun exposure, said that they may need additional vitamin D to reach a target blood level of 75 nanomoles of vitamin D per litre of plasma, said an ARS release.

But, Stephensen cautions that some vitamin D levels recommended by the model exceed the level currently considered safe.

He said that more research may refine the predictive power of the model.

The study was published in the Journal of Nutrition. (With Inputs from Agencies)