The effect of body mass index on adequacy of serum 25-hydroxyvitamin D levels in US adults: the National Health and Nutrition Examination Survey 2001 to 2006

Abstract

Purpose: To investigate the relationship between body mass index (BMI) and vitamin D adequacy among US adults.

Methods: We used data for US adults aged 18 years or older (n = 12,927) who participated in the 2001 to 2006 United States National Health and Nutrition Examination Survey. Log-binomial regression was used to estimate the strength of association between BMI categories and the prevalence of serum 25-hydroxyvitamin D [25(OH)D] greater than or equal to 20 ng/mL before and after controlling for selected characteristics. An interaction term between race or ethnicity and BMI categories was tested.

Results: Among US adults, 67.2% had serum 25(OH)D greater than or equal to 20 ng/mL, a cut point suggested by the Office of Dietary Supplements for adequate bone and general health. Overweight and obese adults were 8% (95% confidence interval, 0.89-0.95) and 26% (95% confidence interval, 0.71-0.78), respectively, less likely to have serum 25(OH)D greater than or equal to 20 ng/mL than their normal weight counterparts after controlling for age, gender, race/ethnicity, nativity and marital status, as well as education and income. No heterogeneity of the association between BMI categories and the prevalence of 25(OH)D greater than or equal to 20 ng/mL was observed by race or ethnicity.

Conclusions: The low prevalence of 25(OH)D greater than equal to 20 ng/mL among overweight and obese adults in the US population underscores the need to comparatively assess vitamin D intakes across different BMIs.

Keywords: 25-Hydroxyvitamin D; Body mass index; National Health and Nutrition Examination Survey; Race or ethnicity; Vitamin D.