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Canadians using supplements containing vitamin D are more likely to have 25-hydroxyvitamin D (25(OH)D) levels consistent with the Recommended Dietary Allowance, particularly with the low UVB exposure during the winter. This study aimed to determine these users' characteristics and to examine the relationship between dosage and 25(OH)D using the 2007-2009 Canadian Health Measures Survey ( n = 5604, 6-79 years of age). Logistic regression models examined the odds of supplement use within the preceding 30 days. Thirty-one percent used vitamin D supplements; 58.5% were female. In adjusted analyses, females' odds of supplement use were lower for those 12-19 years old (odds ratio (OR), 0.63; 95% CI, 0.41-0.96) and higher for those 60-79 years old (OR, 4.19; 95% CI, 2.69-6.64) and 40-59 years old (OR, 1.56; 95% CI, 1.10-2.20) compared with those 20-39 years old; their odds of supplement use were also higher for those of higher income (OR, 2.29; 95% CI, 1.26-4.16) and middle income (OR, 1.59; 95% CI, 1.03-2.46), those reporting ≥1 chronic disease (OR, 1.48; 95% CI, 1.06-2.06), and those consuming milk ≥1 time·day−1 (OR, 1.35; 95% CI, 1.14-1.60). For males, increased use was associated with age 60-79 years (OR, 2.41; 95% CI, 1.54-3.77) and 6-11 years (OR, 1.77; 95% CI, 1.19-2.64) and higher income (OR, 2.12; 95% CI, 1.49-3.00) and middle income (OR, 1.55; 95% CI, 1.04-2.31). Use did not vary significantly by race, education, season, body mass index, health, or physical activity. A total of 35.7% of Canadians >50 years old took ≥400 IU of vitamin D; 25(OH)D increased with increasing supplement dosage ( r = 0.33) in winter, but differences between 1-399 IU and 400-999 IU were not significant. Usage and nonusage patterns are important to consider as ways of improving vitamin D intake are pursued. [ABSTRACT FROM AUTHOR]

Introduction: There is evidence that 25-hydroxyvitamin D levels are lower in overweight and obese youth. This study examined the relationship between weight status and 25-hydroxyvitamin D, while controlling for confounders, in Canadian youth. Methods: Plasma 25-hydroxyvitamin D from subjects aged 6 to 17 years from the Canadian Health Measures Survey cycles 1 (2007 to 2009) and 2 (2009 to 2011) was used. Sex-specific multiple linear regression and logistic regressions examined the relationship of overweight and obesity (body mass index = 85th percentile) with 25-hydroxyvitamin D levels and the odds of 25-hydroxyvitamin D <40 nmol/L and <50 nmol/L. Results: The prevalence of risk of vitamin D deficiency (25-hydroxyvitamin D < 30 nmol/L) was 6% (95% confidence interval [CI] 3.26% to 10.12%). Vitamin D inadequacy, estimated by levels <40 nmol/L, was 15% (95% CI 10.34% to 20.39%; 19% [95% CI 13.1 to 25.6] for teenagers). Seventy per cent (95% CI 63.59 to 75.17) had levels >50 nmol/L, consistent with achieving the Recommended Dietary Allowance. In adjusted analyses, overweight/obesity (1/3 of subjects) was independently associated with lower 25-hydroxyvitamin D for both sexes after adjustment for age, race, income, season, vitamin D supplementation and daily milk consumption. For 25-hydroxyvitamin D <40 nmol/L, the overweight/obese odds ratio for males was 2.63 (95% CI 1.34 to 5.18). For 25-hydroxyvitamin D <50 nmol/L, overweight/obese odds ratios were 2.19 (95% CI 1.46 to 3.28) for males and 1.39 (95% CI 1.05 to 1.84) for females. Conclusions: This study confirms the inverse association between adiposity and serum concentrations of 25-hydroxyvitamin D in Canadian youth and the independent association of overweight/obesity to 25-hydroxyvitamin D level and vitamin D status after adjustment for other factors. [ABSTRACT FROM AUTHOR]