Sunlight and Other Determinants of Circulating 25-Hydroxyvitamin D Levels in Black and White Participants in a Nationwide US Study

Abstract

Circulating 25-hydroxyvitamin D (25(OH)D), a marker for vitamin D status, is associated with bone health and possibly cancers and other diseases; yet, the determinants of 25(OH)D status, particularly ultraviolet radiation (UVR) exposure, are poorly understood. Determinants of 25(OH)D were analyzed in a subcohort of 1,500 participants of the US Radiologic Technologists (USRT) Study that included whites (n = 842), blacks (n = 646), and people of other races/ethnicities (n = 12). Participants were recruited monthly (2008-2009) across age, sex, race, and ambient UVR level groups. Questionnaires addressing UVR and other exposures were generally completed within 9 days of blood collection. The relation between potential determinants and 25(OH)D levels was examined through regression analysis in a random two-thirds sample and validated in the remaining one third. In the regression model for the full study population, age, race, body mass index, some seasons, hours outdoors being physically active, and vitamin D supplement use were associated with 25(OH)D levels. In whites, generally, the same factors were explanatory. In blacks, only age and vitamin D supplement use predicted 25(OH)D concentrations. In the full population, determinants accounted for 25% of circulating 25(OH)D variability, with similar correlations for subgroups. Despite detailed data on UVR and other factors near the time of blood collection, the ability to explain 25(OH)D was modest.

Hypovitaminosis D and Associated Risk Factors in Postmenopausal Women

“…In agreement with other reports [21] [25]- [27], an inverse association was found between 25(OH)D and BMI, even after adjusting by several confounders. The finding of a mean BMI in the range of overweight has been systematically observed in our previous studies on postmenopausal women [15]- [17].…”

A prospective randomized controlled trial of the effects of vitamin D supplementation on long-term glycemic control in type 2 diabetes mellitus of Korea

“…The main sources of vitamin D are cutaneous synthesis and dietary ingestion [4,5]. The contribution of dietary intake in serum vitamin D levels is small [6,7]. Therefore, the concentrations are mainly synchronized to sun-exposure or outdoor physical activity.…”

Serum 25(OH)D and vitamin D status in relation to <i>VDR</i>, <i>GC</i> and <i>CYP2R1</i> variants in Chinese

“…Vitamin D deficiency has been related to rickets, diabetes mellitus, metabolic syndrome, hypertension, cardiovascular disease, and cancer [1][2][3][4][5][6]. Sun exposure, dietary and supplementary vitamin D intake, race, age, sex, obesity, skin color, and tea intake have been previously reported to be associated with circulating levels of 25(OH)D [7][8][9][10] Chinese. Nine common variants of VDR, GC and CYP2R1 were genotyped using multiple SNaPshot assay, and serum 25(OH)D was detected by radioimmunoassay.…”