Vitamin D Status Is a Biological Determinant of Health Disparities

BackgroundIn human beings, dark skin requires more exposure to ultraviolet light to synthesize the same amount of vitamin D as lighter skin. It is has been repeatedly shown that at the latitude of the United States there are vitamin D disparities related to skin color. Although inadequate vitamin D status and health disparities have been associated with many of the same diseases, neither nutrition policy nor public health policy in the United States currently recognizes any role at all for vitamin D as a determinant of health disparities.ObjectiveThis study investigated the relationship between health, skin color, and vitamin D nutriture in the US population.DesignThe design is cross-sectional, correlational, and can be generalized to the population of the United States.ParticipantsWe used data from 12,505 (unweighted) subjects (3,402 non-Hispanic blacks, 3,143 Mexican Americans, and 5,960 non-Hispanic whites), aged 13 years or older, from the continuous National Health and Nutrition Examination Survey 2003-2006.Main outcome measureSelf-rated health, a repeatedly validated indicator of objective health status, was used as a continuous measure of health.Statistical analyses performedUsing software appropriate for the complex survey design of the National Health and Nutrition Examination Survey, the study consisted of six regression models, one predicting vitamin D status and five predicting self-rated health.ResultsControlling for the covariates sex, interview language, country of birth, tobacco use, age, body mass index, and leisure exercise as well as the socioeconomic variables education and family income, remaining disparities in self-rated health are greatly reduced or eliminated by controlling for serum 25-hydroxyvitamin D levels.ConclusionsWe found that socioeconomic factors are the strongest determinant of skin-color based health disparities in the US population, but that it may not be possible to eliminate health disparities in the United States without eliminating the skin-color–related disparities in vitamin D nutriture.