Light-skinned people who avoid the sun are twice as likely to suffer from vitamin D deficiency as those who do not

The study adds to a growing debate about how to balance the dangers of sun exposure with the need for appropriate levels of vitamin D to prevent bone diseases such as osteoporosis and rickets. Vitamin D is produced by the skin in response to exposure to the ultraviolet rays in sunlight; too little of the vitamin causes bone weakening and rickets and possibly contributes to many other chronic diseases including cancer. Small amounts of vitamin D can also be acquired by drinking fortified milk, eating fortified breakfast cereals or eating fatty fish such as salmon, tuna and mackerel, as well as from over-the-counter dietary supplements. Although it's not clear exactly how many people may be deficient in the vitamin, experts believe that about 30% - 40% of the United States population may be affected. Researchers have found that whites who avoided the sun with clothing or stayed in the shade had blood levels of vitamin D that were about 3.5 and 2.2 nanograms per milliliter lower than those who did not report such behavior. In contrast, the association between sun avoidance and reductions in vitamin D levels in Hispanic or African-American survey-takers was not statistically significant. The researchers considered any respondent with blood levels of 20 nanograms per milliliter or below to be vitamin D deficient because lower levels have been associated with adverse health outcomes. They found that although about 40% of all survey participants were vitamin D deficient, the prevalence increased to 53% and 56% among those who wore long sleeves and stayed in the shade. Whites who wore long sleeves and stayed in the shade were twice as likely to be deficient in the vitamin as those who did not (odds ratios of 2.16 and 2.11, respectively). Race affects vitamin D production because of differences in skin pigmentation. Highly pigmented skin protects against ultraviolet rays, but also leads to lower overall baseline levels of vitamin D in the blood and frequent vitamin D deficiency. In the current study, African-Americans who rarely took sun-protective measures had an average vitamin D blood level of about 14.5 nanograms per milliliter. Hispanics who didn't avoid the sun had an average level of about 19.7 and sun-loving whites, about 26.4. In contrast, those who frequently stayed in the shade had average levels of 14, 19.2 and 22.8 nanograms per milliliter, respectively.