Vitamin D status of Canadians – Results from the Canadian Health Measures Survey

Introduction

The Canadian Health Measures Survey (CHMS) is a national survey that was launched in 2007 by Statistics Canada in partnership with Health Canada and the Public Health Agency of Canada. It is the most comprehensive survey of direct health measures undertaken in Canada at the national level.

The 2013 report on vitamin D released by Statistics Canada presented findings from cycle 2 of the CHMS. Plasma 25-hydroxyvitamin D [25(OH)D] levels as well as factors affecting vitamin D status were assessed among 6,400 Canadians aged 3 to 79 years based on measures collected from 2009 to 2011.¹ The concentration of 25(OH)D reflects vitamin D in the blood from food, supplements and sun exposure.^1,2 

Methods

Plasma 25(OH)D measures were collected from 6,400 individuals aged 3 to 79 years living in Canada’s 10 provinces and 3 territories. Data was collected from August 2009 to November 2011.

The report on vitamin D investigated the adequacy of vitamin D levels among the Canadian population based on the following defined categories:²

• At levels above the vitamin D cut-off, i.e., ≥50 nmol/L, most Canadians are considered to have sufficient levels of vitamin D for bone health and to meet the Recommended Dietary Allowance for this vitamin;
• At levels below the vitamin D cut-off, i.e., <50 nmol/L, most Canadians are considered to have insufficient levels of vitamin D for bone health and may be at risk of inadequacy relative to bone health;
• Vitamin D levels of <30 nmol/L represent the deficiency level.

The factors associated with vitamin D blood levels, namely age, sex, milk consumption, supplement use, season of sun exposure and body mass index, were also examined.

Results

Adequacy of vitamin D levels

• The national average of plasma 25(OH)D levels was 64 nmol/L;
• Most Canadians (about two thirds) were above the vitamin D cut-off of 50 nmol/L;
• 32% of Canadians were below the vitamin D cut-off of 50 nmol/L;
• 10% of Canadians were considered as being vitamin D deficient (<30 nmol/L).

Age

• The youngest (3 to 5 years) and oldest (60 to 79 years) age groups had the highest levels of vitamin D, at 74 nmol/L and 70 nmol/L, respectively;
• Canadians aged 20 to 39 years had the lowest rates (59%) above the vitamin D cut-off.

Sex

• On average, females had higher vitamin D levels than males (67 nmol/L vs. 61 nmol/L);
• The largest sex difference was observed among adults aged 20 to 39 (66 nmol/L for females vs. 55 nmol/L for males).

Milk consumption

• Those who consumed milk once or more per day had a higher average vitamin D level than those who consumed milk less than once per day (68 nmol/L vs. 59 nmol/L);
• A higher proportion of those who consumed milk once or more per day were above the vitamin D cut-off compared to those who had milk less than once per day (75% vs. 60%).

Supplement use

• 34% of Canadians took a supplement containing vitamin D;
• A greater proportion of Canadians who took supplements containing vitamin D were above the cut-off compared to those who did not (85% vs. 59%).

Season of sun exposure

• More Canadians were below the vitamin D cut-off in winter compared to summer (40% vs. 25%).

Body mass index

• Similar to previous research, it was observed that individuals who are overweight or obese tend to have lower vitamin D blood levels;
• Among children aged 5 to 11 and adolescents aged 12 to 17, those who were overweight or obese had a significantly lower average vitamin D level compared to those who were lean or had a normal weight (61 nmol/L vs. 67 nmol/L).

Conclusions

Although most Canadians have sufficient vitamin D levels, an important proportion (32%) remains below the cut-off of 50 nmol/L deemed optimal for bone health and on which the current recommended intakes are based.

Those who consumed milk at least once per day had a higher average vitamin D level, and more of them were above the vitamin D cut-off for optimal bone health.