An Analysis of Factors Associated with 25-Hydroxyvitamin D Levels in White and Non-White Canadians

Abstract

Vitamin D status was assessed in 19-79 year old whites (8351 participants of European ancestry) and non-whites (1840 participants encompassing all other ancestries) from cycles 1 to 3 (years 2007-2013) of the Canadian Health Measures Survey. Status was assessed using the U.S. Institute of Medicine (IOM) 25-hydroxyvitamin D [25(OH)D] cut point values of 30 and 40 nmol/L. Overall, median 25(OH)D concentrations were significantly higher in whites [58.9 (28.6, 100.1) nmol/L; 5th and 95th percentile] compared with non-whites [43.5 (19.0, 83.2); P < 0.001]. Values were higher in females [58.5 (27.5, 101.3) nmol/L] when compared with males [53.5 (24.2, 92.7) nmol/L] and increased with age. Non-whites were more likely to have 25(OH)D values below IOM established cut points for optimum bone health with 20.1 (16.0, 24.2) and 42.2% (36.8, 47.7) of non-whites having serum 25(OH)D concentrations <30 and <40 nmol/L, respectively. The corresponding values for whites were 5.9 (4.6, 7.2) and 16.1% (14.0, 18.3). Values were lower during the first quarter when compared with the third quarter. Supplement intake was an important factor in determining 25(OH)D levels, but it did not alone account for the difference in status. Equivalent increases in 25(OH)D levels were observed in whites and non-whites during the summer months, suggesting there was no functional difference in sun exposure response. It is apparent that a complex interaction of factors affect 25(OH)D values in free-living Canadians.