Editor's Note: Segments of this article have been removed. After publication, further testing revealed the results initially provided to CBC Marketplace were wrong. The CBC regrets the errors. Please see the story here.

When cold season hits, many Canadians reach for Vitamin C. But you're not always getting what you're promised, a CBC Marketplace investigation into vitamins and supplements reveals. Marketplace found a Vitamin C product that makes health claims not allowed by Health Canada.

Canadians spend more than $1.4 billion a year on vitamins and supplements, and many believe the products benefit health and prevent disease.

In the past year, more than 80 per cent of Canadians took a vitamin or supplement or gave one to a family member, according to a survey on vitamin and supplement use commissioned by Marketplace.

Re-testing of samples of popular vitamins and supplements has found that the lab results and analysis provided to Marketplace were incorrect. (CBC)

Health claims break rules

Even though more than half of Canadians who take Vitamin C believe that it helps fight off a cold, Health Canada does not allow manufacturers to make that claim.

That's because that is a myth that the science doesn't back up, says Dr. David Agus, best selling author of The End of Illness, and a professor of medicine at University of Southern California.

"If you have Vitamin C, a cold will last seven days. If you don't have Vitamin C, your cold will last a week," he says.

However, Marketplace found that top-selling brand Jamieson states that its Vitamin C product "is recommended for treatment of the common cold," in violation of Health Canada rules.

Health Canada is investigating Jamieson's Vitamin C claims.

In an email to Marketplace, Jamieson wrote: "We believe very strongly in the importance of providing comprehensive information to consumers. All of the product information on our website is scientifically accurate."

Most believe in health benefits

The Marketplace survey found that almost two thirds of Canadians believe that taking vitamins and supplements helps prevent illness, and more than half believe that it is a good way to get nutrients that are missing from their diet.

The survey was conducted by EKOS in an online panel of 1,080 Canadian adults between Sept. 22 and 28, 2015.

While independent testing is done in the U.S. to verify the accuracy of supplement ingredients, similar testing is not done in Canada.

Although Health Canada sets standards for vitamins and supplements, it's up to manufacturers to make sure their products comply. The agency primarily inspects in response to complaints.