Research
Original Research
Vitamin D Status Is a Biological Determinant of Health Disparities

https://doi.org/10.1016/j.jand.2012.12.011Get rights and content

Abstract

Background

In 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.

Objective

This study investigated the relationship between health, skin color, and vitamin D nutriture in the US population.

Design

The design is cross-sectional, correlational, and can be generalized to the population of the United States.

Participants

We 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 measure

Self-rated health, a repeatedly validated indicator of objective health status, was used as a continuous measure of health.

Statistical analyses performed

Using 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.

Results

Controlling 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.

Conclusions

We 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.

Section snippets

Methods

Data for this study come from the continuous National Health and Nutrition Examination Survey (NHANES) conducted by the National Center for Health Statistics,28 which is part of the Centers for Disease Control and Prevention. NHANES data collection protocols were approved by the National Center for Health Statistics Ethics Review Board. Our study was determined to be exempt from review by the Institutional Review Board of Teachers College, Columbia University. The study uses cross-sectional

Results

NHANES provides nationally representative estimates. Because the data were analyzed using complex survey techniques, the sample characteristics of this study reflect the US noninstitutionalized population of non-Hispanic blacks, Mexican Americans, and non-Hispanic whites, aged 13 years and older, during the years 2003 through 2006.34

Figure 1 portrays the relationship between serum 25(OH)D levels and race/ethnicity. For comparison purposes, the graph also includes a normal distribution based on

Discussion

Comparing Model 3 with Model 4, it appears that socioeconomic factors are stronger determinants of health disparities than vitamin D. However, in a comparison of Model 4 and Model 5, it also appears that socioeconomic and serum 25(OH)D levels are largely independent determinants of health disparities, which suggests that ending socioeconomic disparities will not eliminate health disparities unless disparities in serum 25(OH)D levels are also eliminated. These models also support the theory that

Conclusions

Our study supports the hypothesis that—after controlling for covariates and socioeconomic factors—skin-color–related disparities in serum 25(OH)D levels are a biological determinant of health disparities in the United States. Disparities in vitamin D status alone seem to account for about half of the effect of racial health disparities. Disparities in socioeconomic status alone seem to account for about two thirds of the effect. Together, vitamin D and socioeconomic disparities appear to be

Acknowledgements

The authors thank Kathleen A. O'Connell, PhD, RN, FAAN, for her contributions.

T. Weishaar is a student in the Health Education masters degree program, Teachers College, Columbia University, New York, NY.

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    • Cited by (0)

    T. Weishaar is a student in the Health Education masters degree program, Teachers College, Columbia University, New York, NY.

    J. Marcley Vergili is director of the Diabetes Education Program, Columbia Memorial Hospital, Hudson, NY; at the time of the study, she was a visiting professor, Teachers College, Columbia University, New York, NY.

    STATEMENT OF POTENTIAL CONFLICT OF INTEREST No potential conflict of interest was reported by the authors.

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