TORONTO - Canadians should consult with their doctors before rushing to their neighbourhood stores and pharmacies to snap vitamin D off of the shelves, a Canadian Cancer Society official said Tuesday.
The caveat was part of the organization's recommendation last week which advised adult Canadians to consider boosting their intake of the so-called sunshine vitamin in fall and winter by supplementing their diet with 1,000 international units.
"The reason the recommendation is for fall and winter is because of where we live in Canada, almost all Canadians are at risk of vitamin D deficiency during the fall and winter because we don't produce any vitamin D from exposure when you live as north as we do in Canada," said Heather Logan, director of cancer control policy at the Canadian Cancer Society.
Adults who are older, dark-skinned, don't go outside often and wear clothing covering most of their skin are at risk of having lower vitamin D levels and should consider maintaining the recommended intake level all year long, the organization said. The Cancer Society's recommendation does not apply to children.
But overall, the prompt to increase intake in vitamin D supplements for many Canadians is just for the fall and winter months, Logan said.
"They don't need to rush out, if there's none in the stores, they can certainly wait until September or October to go and buy their vitamin D," she said.
Pat Chapman, director of communications for Shoppers Drug Mart, said there has been a spike in sales for vitamin D since the Cancer Society released its recommendation.
"Certainly, as with any product, if the demand increases over time, and we see a trend, then we do our best to meet the needs of the customer by increasing the supply of that particular product," she said.
The reason for choosing 1,000 international units a day takes into account that individuals get some of their daily dose of vitamin D from other sources, including diet, Logan said.
Food and drink intake would account for between 250 and 400 international units of vitamin D per day, she said.
"If in addition to that, someone is taking a multivitamin, most of those already contain 400 international units of vitamin D, so those two things alone already put Canadians at about 650-800 international units a day," she said.
"We would not want Canadians to take more than 1,000 units (of supplements) because they would then be approaching that 2,000 upper safety limit."
There have been cases of people who have been on high doses, well beyond 2,000 international units, where they have seen calcium buildup around the kidneys, which may result in kidney stones, Logan said, and some suggest calcium buildup in other areas of the body is a possibility.
"People who take very high doses of vitamin D or are particularly susceptible may experience some nausea, vomiting, constipation, weakness," she said.
"That's particularly why we wanted Canadians to speak with their doctor and have a conversation with them about this recommendation and through a regular discussion with their doctor as they're changing their diet."
The Cancer Society is not alone in grappling with how to address vitamin D deficiencies in Canadians.
A Health Canada official said Tuesday it is going to recommend to the Institute of Medicine of the National Academies in Washington, D.C., that it reassess Vitamin D as a "high priority."
The institute sets dietary reference intakes (DRIs) for both Canada and U.S., and is slated to hold a workshop in September aimed at informing future activities related to DRI development in both countries.
The levels for vitamin D, set in 1997, are general recommendations based on age. Those aged 1-50 are advised to have a daily intake of 200 international units. That figure doubles to 400 for adults between 51-70, and is 600 international units for those aged 70 and over.
"We are aware there's evidence suggesting vitamin D insufficiency may be a concern in Canada," Health Canada spokesman Paul Duchesne said from Ottawa.
"We want to make sure that the (Institute of Medicine) takes a look at all the evidence that's out there to see whether there should be a change in their recommendations or not."
Duchesne said Health Canada bases its decisions with respect to setting DRIs on the Washington institute's research and work, and will hold to its current recommendations until the meeting.
The Canadian Cancer Society based its recommendation on an expanding body of evidence linking the vitamin to reduced risk for colorectal, breast and prostate cancers.
