Thursday, June 2, 2011

Canadians benefit from vitamin D supplementation - through out the year

Canada, stereotypically a cold and wintery place. Except that in summer it is warm and sunny. A study has come out and stated that supplementation works in Canadians. The levels of vitamin D required are as follows:
  • Dietary Reference Intakes (DRIs) for vitamin D are blood levels of 25-hydroxyvitamin D, with deficiency when this is below <30 nmol/L
  • Estimated Average Requirement (40 nmol/L)
  • Recommended Dietary Allowance (RDA; 50 nmol/L)
Amazingly, though not surprisingly the study states "The Canadian population has not yet been assessed according to these recommendations". That is right folks, no body has looked at what actually is happening to Canada's population when it comes to vitamin D levels. What the study found again is amazing, but no surprising. The key statements are:
  • In winter 24.5% of white population had blood levels of <50 nmol/L. That is one quarter of the population are not getting the RDA/RDI in winter. 
  • For none whites, who generate less vitamin D with the same sunlight exposure the percentage was 53.1%. That is half the population are not achieving the RDA/RDI intake. 
  • Supplement users had significantly higher 25(OH)D concentrations than did nonusers, and no seasonal differences were found.
  • The use of vitamin D supplements contributed to a better 25(OH)D status
Therefore if you live in Canada you should be supplementing with vitamin D. I believe that this result to be generalized to countries where in winter people spend a significant amount of time indoors. For example NZ winter most people are cocooning inside in front of a fire engaging with electronic media.

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