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

Highlights

Based on the current cut-offs for vitamin D status, 4% of Canadians are considered as being vitamin D deficient and 10% have level considered inadequate for bone health. Also, 33% of the population has levels above 75 nmol/L, which is the level considered optimal for overall health. However, according to the new Dietary Reference Intakes (DRI) published by the Institute of Medicine (IOM), a level of 25(OH)D above 50 nmol/L (or 20 ng/mL) is sufficient for good bone health for practically all individuals.²

Factors related to low concentrations are:

• Winter season,
• Racial background other than white,
• Less frequent consumption of milk.

Future analysis will investigate additional factors that may influence vitamin D concentrations, such as supplement use, body mass index, pregnancy, fish consumption and sunscreen use.

Introduction

The Canada-wide survey on vitamin D released by Statistics Canada examined serum 25-hydroxyvitamin D [25(OH)D] levels in 5,306 Canadians aged 6 to 79 years as well as factors shown to affect vitamin D status during the period of 2007 to 2009.

The Canadian Health Measures Survey (CHMS), launched by Statistics Canada in 2007 in partnership with Health Canada and the Public Health Agency of Canada, assessed vitamin D status in a representative sample of Canadians.

Concentrations below 37.5 nmol/L were considered inadequate for bone health. Concentrations below 27.5 nmol/L are associated with vitamin D deficiency (defined as high risk of rickets in children or osteomalacia in adults).

There is a growing consensus that much higher concentrations, specifically, those above 75 nmol/L, are desirable for overall health and disease prevention.

Methods

Serum 25(OH)D levels were collected among 5,306 individuals aged 6 to 79 years. Data was collected from all regions by age group, sex, racial background, and within two 6-month periods (April-October, November-March).

In addition to seasonality, other factors such as frequency of milk consumption were also examined. Furthermore, the prevalence of deficiency and the percentage of individuals meeting certain cut-off values were assessed.

Results

• The mean concentration of 25(OH)D among Canadians aged 6 to 79 years was 67.7 nmol/L.
• 4.1% of Canadians (5.2% of males and 3.0% of females) had 25(OH)D levels considered deficient (less than 27.5 nmol/L).
• Just over 10% of Canadians (12.9% of males and 8.3% of females) had concentrations below 37.5 nmol/L (the level considered inadequate for bone health).
• Approximately 1/3 of the population (33% of males and 37.8% of females) had concentrations above 75 nmol/L (the level considered optimal for health).
• The frequency of milk consumption tended to be positively related to 25(OH)D levels.
• People who consumed milk more than once a day had a mean concentration of 75 nmol/L vs. 62.7 nmol/L among those who did so less than once a day.
• The mean percentage of individuals (6 to 79 years) who consume milk more than once per day is low at 25.9% for males and 26.3% for females.
• The percentage of individuals who consume milk more than once a day tends to decreases with age:
  • Among individuals aged 6 to 11 years (67.6% for males, 63.0% for females);
  • Among individuals aged 12 to 19 years (50.9% for males, 40.2% for females);
  • Among individuals aged 20 to 39 years (25.0% for males, 26.3% for females);
  • Among individuals aged 40 to 59 years (15.2% for males, 17.8% for females);
  • Among individuals aged 60 to 79 years (15.8% for males, 21.6% for females).

Main strength of study

• Most comprehensive direct health measures survey undertaken in Canada at the national level.

Main limitations (as identified by the authors)

• Not all factors that may contribute to variations in 25(OH)D levels were examined;
• No direct information on skin pigmentation was collected per se (race was used as a proxy);
• Information on milk consumption pertained to the frequency of consumption, not to the actual amounts consumed;
• Not all regions were represented or compared by date of blood sample collection.

Keywords: vitamin d, survey on vitamin d, data on consumption, statistics canada

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