The dietary supplement business is booming, with about 80% of US adults taking these products to improve their health. USP, also known as the US Pharmacopeia, is working to protect consumer health by helping supplement manufacturers maintain quality. Jaap Venema, executive vice president and chief science officer for USP, shares his perspective.

What quality issues surrounding dietary supplements should consumers be aware of?

People often think that because supplements can be naturally derived products, they are of good quality. But, there are many steps needed to make that a reality. To produce quality supplements, manufacturers have to consider many factors, ranging from the complexity and identity of the product’s ingredients to its potency, and contaminant control. In terms of identity, many different plants can be used to make herbal dietary supplements and even plants that look similar and are closely related can have very different effects. For example, black cohosh is an herbal supplement women have taken for symptoms of menopause. But there have been incidents in the US and Canada where consumers suffered liver damage after taking products that contained a different plant species with a similar name. That’s why proper testing to make sure a supplement product consistently meets quality standards for identity, strength, composition and contaminant limits is so important.

Jaap Venema, executive vice president and chief science officer for USP. Credit: USP

It sounds like defining quality for supplements is more complex than for pharmaceuticals. Why is that?

Depending on the product, it can be. The first reason, which is perhaps counterintuitive, is that dietary supplements can be very complex, often containing dozens or even hundreds of different substances, many derived from botanical or natural sources. Medicines can be purified to comprise as much as 99.9% of one substance with a few impurities. The second is that potency is often not established for dietary supplements and herbal products in the same way it is for medicines.

What does this complexity mean for consumers?

Consumers should know that in many cases, it’s very difficult, if not impossible, to pinpoint the active ingredient. Sometimes it could be a combination of certain substances that have the particular effect that is being claimed. Also, people often don’t realize that there can be interactions between supplements or herbal medicines they take and the medications their doctors may prescribe. For example, some supplements may change liver enzyme activity, which could change the way you metabolize your prescription medicine. This altered metabolism can increase the concentration of the medicine in the bloodstream, which may cause adverse reactions, or lower its concentration, which may make it ineffective.

What kind of tools does USP recommend for assessing the quality of a supplement?

The current gold-standard test for quality is chromatography, which can evaluate the components of a supplement. But you can only get so much information from the data when you’re testing a complex product. Newer techniques like liquid chromatography-mass spectrometry, coupled with certain types of analysis, can capture more precise results. But before these techniques can be widely adopted and incorporated into standards, they must be validated, and we need to make sure they can be implemented in a fairly routine setting—prohibitive equipment cost may sometimes be a barrier to that.

Can DNA testing confirm whether a supplement is what it claims to be?

It really depends on what’s being tested. Dietary supplements come from many different sources. There are vitamins, minerals, herbs and extracts.  DNA-based testing is a very important part of the toolbox for identification of certain types of supplements, but there are many products on the market for which DNA testing is not a consistently valid measure of identity. Extracts are a perfect example because they don’t always contain DNA. In addition, while DNA technology may help in identification, it doesn’t determine strength, because DNA is not the active ingredient.

How does federal oversight work for supplements in the US?

Dietary supplements are regulated under the umbrella of ‘foods’ and are required to meet legal requirements to ensure a safe supply. While dietary supplement manufacturers and suppliers are responsible for ensuring the safety of the products they sell, many of these products have not been reviewed by the FDA. The Dietary Supplement Health and Education Act (DSHEA), the law regulating dietary supplements came into effect in 1994, and dietary supplements on the market before that date do not require review by FDA.

What kind of safeguards are in place for monitoring manufacturers?

The law requires industry to manufacture supplements using current good manufacturing practices that are specifically developed for dietary supplement products. Additionally, FDA conducts random inspections of manufacturing sites or products. But it’s important to note that resources available for inspections are quite limited compared to the vast number of products on the market. If you compare the amount of dietary supplements being consumed relative to drugs, it’s about an order of magnitude greater. And the ingredients for supplements are sourced from many companies—sometimes large companies, but also quite often from very small ones, and their quality systems vary widely.

How is USP working with supplement manufacturers to ensure product quality?

About a decade ago, we started the USP Dietary Supplements Verification Program—a stepwise process for companies to work with USP to assess the quality of their facilities, processes and products. If they reach the final ‘step’ in this process, qualifying products can carry a USP verification mark. We are also looking to expand this program globally. Some countries are interested in increasing their regulation and quality control. In Latin America, we are seeing a real push for quality improvements, and the verification program may help promote this.

Do you think consumers are aware of the importance of quality standards for supplements?

Consumers may see the USP Verified mark, and understand it means ‘quality’, but I don’t think there’s good awareness of what that really means as it relates to standards. Also, people often mistake ‘natural’ for ‘safe,’ and they think that because something is natural that it must be good. That is simply wrong —some of the most toxic known substances are natural. Consumers who would like to learn more can find helpful information on the National Institutes of Health website.

To learn more about the need for quality standards in medicines, visit The Science of Quality.