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Providing perspectives on recent research into vitamins and nutritionals


Do All Vitamin Supplements Have the Same Quality?

By Julia Bird

A question that recently came up on our Twitter feed was about whether vitamin supplements differ by quality*. Does it matter which brand of dietary supplement that people choose? Ideally, the actual contents of dietary supplements would match the label information – no more and no less, with no added surprises in the mix. The degree to which this occurs depends on a surprising number of different factors.

The manufacturing process used to produce the dietary supplements is very important. Specific requirements vary by country, and it is difficult to generalize, however national regulations can have a considerable impact on the quality of vitamin supplements. Findings on vitamin quality in one country may not be an issue in other countries due to differences in how vitamin supplements are regulated.

Even so, all manufacturers of dietary supplements and dietary supplement ingredients should have checks and balances in place during their product process to ensure the quality of the final product. For example, production process control programs such as Good Manufacturing Practice standardize and  document the manufacture of dietary ingredients. Other programs like HACCP, while intended for the production of food products, can also be used for dietary supplements to identify risks through the entire chain of production, from the supplier of bulk vitamins to the final product as it is used by the consumer. This helps avoid introducing contaminants such as heavy metals, or unwanted microbes, and can reduce variability between batches. Ideally, manufacturers should test their finished product to make sure that it is safe for consumption and contains what it is supposed to.

The example of dietary supplement marketer Gary Null shows what can go wrong (Gregorian). After consuming his own dietary supplement that contained vitamin D for a month, Null started to develop “excruciating fatigue and bodily pain”. Apparently, the contractor that was responsible for mixing the product had made a mistake that resulted in one thousand times more vitamin D in the product than what was intended.  This meant that the final product contained 2,000,000 IU per serving of vitamin D! 10 other consumers of the same product were also affected. Adequate testing by the contractor or the dietary supplement manufacturer, or a better controlled manufacturing process, may have prevented this accident.

Vitamin supplement manufacturers may agree to voluntary certification by an organization such as the US Pharmacopeial Convention (USP) or National Sanitation Foundation (NSP) have requirements for product testing that help consumers choose a product that conforms to the label. These organizations set standards for maximum variations that can be found in dietary supplements between the labelled dose and actual dose. A publication by LeBlanc and co-workers found that the vitamin D content of over-the-counter supplements contained 9% to 146% of the labelled dose: the single USP-certified manufacturer in the study tended to achieve better results in terms of product quality compared to the other manufacturers.

Vitamins also have a shelf life, as with other food products. Each vitamin has a different profile in terms of stability in the final product: they each react differently to light, other components in the product, humidity, and heat to affect the amount in the product. The form of packaging affects shelf life, as does the form of the vitamin supplement (vitamins in a hard capsule are likely to be more stable than in a powder, for example).  Fortification Basics: Stability provides comprehensive information on factors affecting shelf life of the product. Consuming a vitamin supplement after its use-by date carries an added risk that the product may no longer meet its specifications.

Dietary supplement consumers may be complacent in assuming that the amount of vitamins in a product agrees with what is stated  on the label. Local regulations, the manufacturing process, quality systems that are in place, and the final shelf life affect the final quality of vitamins. Certain brands may be superior to others. Consumers should inform themselves about whether vitamin supplement manufacturers follow quality control programs and whether there are any inherent risks due to the regulatory environment that may affect vitamin supplement quality.

*@joanmckennaTV asked “Anyone know if all brands of #vitamin supplements are the same quality or is there a preferred brand?” on April 13

Supporting citations

DSM Nutritional Products. Fortification Basics: Stability.

Gregorian, D. Putting the “die” in diet. New York Post. April 28, 2010.

LeBlanc ES, Perrin N, Johnson JD, Ballatore A, Hillier T. Over-the-Counter and Compounded Vitamin D: Is Potency What We Expect?. JAMA Intern Med. 2013;173(7):585-586. doi:10.1001/jamainternmed.2013.3812.

Levy, SH. Dietary Supplement Popularity, Quality, Safety, and Efficacy – General information. Last updated January 12, 2014.

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