Characteristics of users of supplements containing vitamin D in Canada and associations between dose and 25-hydroxvitamin D

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.