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Those supplements may not be delivering the vitamins they claim

Vitamin supplements have been found to range in potency.

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A U.S. study released this week found a huge variation in the potency of vitamin D supplements from different manufacturers – and even in pills from the same bottle. The supplements ranged from 9 per cent to 140 per cent of the amount listed on the label, according to the findings published in the journal JAMA Internal Medicine.

And in an interview with The Globe, an executive of a Toronto-based supplement manufacturer acknowledged that dose discrepancies sometimes exist in the Canadian market, too.

The U.S. study was led by Erin LeBlanc, an endocrinologist with Kaiser Permanente Center for Health Research in Portland, Ore. She had been planning to do a randomized trial in which some menopausal women took vitamin D supplements and others got placebos. She had a local pharmacy make a batch of identical-looking pills. Before starting the trial, she sent the real vitamin D tablets to an independent lab to confirm their potency. Those results revealed that only a third of the pills contained between 90 to 110 per cent of the active ingredient.

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So LeBlanc decided to test off-the-shelf supplements to see if they might be a better option for her trial. A total of 55 bottles of vitamin D from 12 different manufacturers were purchased at five stores in Portland. The stated doses of the products ranged from 1,000 to 10,000 International Units of vitamin D. In this random sample, the testing lab found almost half the pills could be considered mislabelled – with potency varying from 9 to 140 per cent of the stated amount.

"I admit I was quite surprised. I'm not a pharmacist. So I had assumed that the pills were what [the labels] said they were," said LeBlanc.

"The biggest worry is for someone who has low levels of Vitamin D in their blood. If they are consistently taking a supplement with little vitamin D in it, they could face health risks."

She pointed out that some manufacturers participate in a voluntary quality-verification program run by the U.S. Pharmacopeial Convention, a non-profit group that sets industry standards for supplements. This organization "gives some reassurance that the amount of vitamin D in those pills is close to the amount listed on the label," she said.

But, she added, "there are not many manufacturers" that take part in the program. LeBlanc speculated that the wide variability in potency may be "because there isn't much legislation" regulating U.S. supplements, which don't have to meet the same rigorous standards as pharmaceutical products.

In Canada, vitamins and minerals are regulated as a sub-set of drugs and are governed by the Natural Health Products Regulations. These regulations stipulate that companies must have qualified staff who are responsible for assuring the quality of the product before it is made available for sale. And companies are required to provide detailed information about product quality as part of their product licence applications. Health Canada says it will also investigate complaints that are brought to the department's attention.

"Canada has good strong regulations – on paper," said Gary Leong, vice-president of scientific and technical affairs at Jamieson Laboratories Ltd., a Toronto-based supplement manufacturer.

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"But in order to comply with it as written, it takes a fair bit of effort and not a lot of companies put it in. And the government doesn't have the resources to make sure that the compliance is there."

Mr. Leong acknowledged that product consistency does vary in Canada, but he thinks "we are better" than the situation portrayed in the recent U.S. study.

He said Jamieson conducts tests at each stage of its production process, starting with the raw materials. "To get the product right you have to invest in R&D and the ongoing quality-control support."

He noted that the biggest challenge is making sure the active ingredients are evenly distributed in each batch of pills. "When you have powders and you are mixing particles of different sizes in different quantities, it is hard to get uniformity," he explained. "If you don't understand the science of powder mixing … you get some tablets with very little in it and some with a lot of the active material."

Leong said, "we stand behind the label declaration" of Jamieson products.

However, he said researchers and the medical community should be made aware that supplements may vary in potency.

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Some researchers, he added, wrongly assume that if they purchase a product for use in a study, the label is accurate. "Well, that is a big misconception. They should actually run a test to make sure it is what it says it is," said Leung.

He thinks many clinical trials have produced contradictory results because researchers haven't verified the contents of the supplements under investigation.

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