According to researchers, light-skinned people who avoid sun exposure are twice as likely to develop vitamin D deficiency. The study followed 6,000 people at the Stanford University School of Medicine.
Interesting to note in the study, using (or not using) sunscreen did not cause any significant difference in the blood levels of vitamin D. The researchers assume this might be due to using too little in the first place.
The study coincides with research pertaining to ongoing research about skin color and vitamin D recommendations. Researchers believe that they need to begin to tailor their recommendations to the skin tones and lifestyles of different people.
Vitamin D is produced by the skin when exposed to the ultraviolet rays in sunlight. If a person receives too little of the vitamin, it can cause bone weakening, rickets and possibly contributes to chronic disease. Small amounts of vitamin D can be taken through diet, such as supplements, fortified foods, and fortified drinks. Experts believe approximately 30 to 40 percent of the United States population may be deficient.
The study analyzed population-base data from the U.S. National Health and Nutrition Examination Survey, which was collected by the Centers for Disease Control and Prevention from 2003 to 2006. The survey included questions that covered sun-protective behavior, such as clothes choices, hats, sunscreen, and retreating to the shade. It also asked them their race and blood levels of a form of vitamin D called 25-hydroxyvitamin D.
The researchers sound found that Caucasians who avoided the sun, either through clothing or the shade had blood levels of vitamin D that were approximately 3.5 and 2.2 nanograms per milliliter lower than those who did not. However, when it came to the vitamin D levels in Hispanic or African-Americans, there seemed to be no association between sun avoidance and vitamin D levels. This may be because of the inherent pigmentation in darker skin, which acts as natural form of sun protection.
In the case of the study, vitamin D deficiency was based on any respondent with blood levels of 20 nanograms per milliliter or below. They discovered that although about 40 percent of the survey participants were, indeed, deficient, the numbers increased to 53 and 56 percent among those who wore long sleeves and stayed in the shade. Caucasians who wore long sleeves and stayed in the shade were twice as likely to be deficient in the vitamin.
In the study, African-Americans who did not make an effort to stay out of the sun had an average vitamin D blood level of about 14.5 nanograms per milliliter. Hispanics had an average level of about 19.7. Caucasians, about 26.4. On the other side, those who frequently stayed in the shade had average levels of 14, 19.2 and 22.8 nanograms per milliliter.
Further, the use of sunscreen did not seem to affect the levels, which is interesting to note, contradicting what researchers previous would have believed. They assume that they are not using it properly, not applying it often enough or generously enough.
The study was published online Nov. 4 in Cancer Causes and Control.