In 2020, Americans spent about $55 billion on dietary supplements. That’s no surprise, given that roughly half of all adults take a supplement. What may be a surprise: Many of those people are wasting their money, and some may even be risking their health. Here’s how the industry keeps you buying more.

Pieter Cohen is an associate professor of medicine at Harvard Medical School and an internist at Cambridge Health Alliance. He is an expert on problems with the safety and regulation of dietary supplements. Cohen spoke with Nutrition Action’s Caitlin Dow.

Supplement basics

Q: Can people trust claims for supplements?

A: Not necessarily. The law that authorizes the Food and Drug Administration to regulate supplements gives manufacturers tremendous leeway to market products as if they are beneficial to human health.

Q: Are there any limits on those claims?

A: Supplement makers can’t claim that their products prevent, treat, or cure a disease. But they are free to make what are called structure-function claims, which say that the product supports or maintains some structure or function of the body. There is no requirement that the FDA review those kinds of claims, and it rarely does. 

For example, it would clearly be illegal for a supplement label to claim that ginkgo biloba prevents dementia. But many say something like “supports brain health” or “maintains memory” without facing any consequences.

Yet in a large high-quality government-funded study that randomly assigned some 3,000 older adults to take a placebo or 120 milligrams of ginkgo twice a day for an average of six years, there were no differences between groups in memory, executive function, attention, or any other outcome.

I tell my patients to ignore structure-function claims since they can’t trust that “immune support,” “digestive health,” or any of the others are based on solid evidence.

Q: Are supplements safe?

A: Not necessarily. This may come as a surprise to many people, but the FDA does not review or approve supplements before they get to store shelves.

Every supplement manufacturer is supposed to follow what are called “good manufacturing practices,” but they don’t have to prove that they adhered to them before the product is sold.

That means you could get a supplement that contains too much or too little of an ingredient, that is adulterated with something dangerous, or that was accidentally contaminated.

During a recent inspection of one supplement facility, FDA officials found glass, pieces of hard plastic, rodent feces, peanut shells, and an AA battery in a batch of botanical material.

Q: How often are the ingredients that are listed on the label inaccurate?

A: There may be as many as 80,000 supplements on the market, and no one systematically tests them, so it’s impossible to know.

My colleagues and I have focused on purchasing and analyzing hundreds of samples from four categories of high-risk supplements: weight loss, sports performance, sexual enhancement, and cognitive function. We’ve found mislabeling or adulteration in every category.

Q: What kind of adulteration?

A: There are typically two types. One is where a less-expensive ingredient is used in place of the more-expensive ingredient that’s listed on the label. The other is pharmaceutical adulteration, when a drug is added to a supposed botanical or natural supplement. 

It’s illegal to add any drug—banned or not, dangerous or not—to supplements.

Some sexual enhancement supplements contain Viagra-like drugs. That’s dangerous because those drugs can cause dangerously low blood pressure in people taking medications that contain nitrates. 

But even more concerning is that more than 80 different types of Viagra-like drugs have been found in sexual enhancement supplements. Many of them have never been tested in humans.

Similarly, some weight loss supplements are laced with the now-banned appetite suppressant sibutramine. And weight loss and sports performance supplements may contain dangerous, prohibited amphetamine-like stimulants.

We’ve also found supplements tainted with drugs that are approved in another country but not in the U.S.

Q: Are there problems with vitamin and mineral supplements as well?

A: Yes. In one 2013 study of 12 vitamin D supplements, the actual content of vitamin D ranged from 9 to 140 percent of the dose listed on the label. Mislabeling can affect all categories of supplements.

Q: It’s hard to believe that we can’t be sure of what’s in a supplement.

A: Tell me about it. Our research findings are often so unbelievable. It seems surreal that we would find this absolutely blatant disrespect for the law and consumer health. But that’s what we find time and time again.

Is the FDA asleep at the wheel?

Q: How does the FDA keep track of all the supplements on the market?

A: It doesn’t and can’t. The current law allows products to be introduced at any time without notifying the FDA. The agency has no idea of what’s actually on the market.

Q: Can the FDA do more?

A: Yes. If the agency were using all its enforcement powers under the law, it could test products for accuracy and for dangerous adulterants. It could alert the companies to make sure the adulterant was removed. And if the company didn’t comply, it could refer the case to the Department of Justice to take further action against the company.

Q: How often does that happen?

A: Rarely. There was one case in 2013 when a company called USPlabs reformulated its OxyElite weight loss supplement after the FDA banned the use of DMAA, an illegal stimulant that it contained.

USPlabs replaced the DMAA with a novel combination of lab-made ingredients, including one called aegeline. Investigators suspect that it was the aegeline in the reformulated OxyElite Pro that resulted in dozens of cases of liver injury, including two liver transplants and two deaths.

The CEO was sentenced to 5 years in prison, and USPlabs paid $4.7 million in damages.

USPlabs is a prominent example of a company that continued to violate the law and ended up paying for it.

Q: What would the FDA need to do to enforce safety measures?

A: The agency wouldn’t have to go after all the bad actors to make the industry much safer. It would just need to test, recall, and follow up with some manufacturers on a regular basis for companies to realize, “Sure, we can sell illegal products, but we might get busted by the FDA, and that’s not worth the risk.”

Q: What does the FDA do if a company has broken the law?

A: It typically just sends a warning letter.

Q: That doesn’t sound very forceful.

A: It’s not. We recently looked at instances where the FDA sent warning letters to companies that made 31 supplements whose labels blatantly listed a prohibited stimulant.

A few years later, nine of the 31 were still being sold. That’s not necessarily a problem, because the FDA wasn’t saying the companies had to stop selling the supplements; they just needed to remove the prohibited ingredients.

But when we tested the nine products, we found that five contained one or more prohibited ingredients. Sometimes it was the ingredient that the FDA had warned the company about. Other times, the company had swapped out one prohibited ingredient for another.

Q: Did the warning letters get rid of the other 22 supplements?

A: Who knows? Maybe some companies simply rebranded them with a new name in order to fly under the radar.

Q: How often does the FDA follow up on its warning letters?

A: Likely not often. No one has looked at every instance in which the FDA sent a warning letter, but we’ve now done three studies looking into the FDA’s follow up of warning letters regarding illegal stimulants or banned drugs in supplements. And it’s hard to find cases where they did follow up.

A powerful dietary supplement industry 

Q: Why doesn’t the FDA do more to keep supplements in check?

A: The FDA’s Office of Dietary Supplement Programs is sorely understaffed. It’s impossible for them to manage this multi-billion dollar industry.

And very powerful supplement trade associations lobby members of Congress on both sides of the aisle. That often kills any proposals that might hurt the supplement industry’s bottom line.

Q: How do some companies legitimize their supplements?

A: One way is to stack their medical or scientific advisory boards with doctors from reputable institutions. Maybe that board membership pays for a summer vacation for some docs.

Other companies get athlete or celebrity endorsements or pay for social media influencers to tout the supplements.

Q: How does the industry react to whistleblowers?

A: Not well. For example, I was sued by a supplement company in 2015 after I published a study showing that some of its products were laced with an amphetamine-like compound. And our science was rock-solid.

But the company sued me for $200 million for libel and slander. The case went to trial and we won, but I suspect that it set such a high price tag to dissuade others from doing research that calls out fraudulent products.

Q: What could solve these problems?

A: Safeguards should be put in place to protect consumers. Every supplement should have to be listed in an FDA database before it can be sold. And the FDA should review the ingredients and claims and not allow any product to be added to the database if it contains a prohibited ingredient or makes an illegal disease claim like “prevents Covid,” which some supplements actually did. Supplement makers should also have to submit a certificate of analysis to verify that their labels are accurate.

It’s a pretty low bar, but it would help ensure that supplements are in compliance with the current law.

Ideally, Congress would give the FDA the resources and authority to swiftly remove any product that the agency’s tests show contains a prohibited ingredient.

Q: Should structure-function claims be included in the database?

A: They should only be posted—and appear on labels—if the companies can substantiate the claims with evidence from high-quality randomized clinical trials.

Q: How likely is that?

A: Not very. In May, a Senate subcommittee considered a bipartisan bill that would require companies to list their supplements with the FDA and require the FDA to create an online database that lists all the information that appears on the supplements’ labels. It didn’t even require the FDA to ensure that the companies’ information was accurate.

Q: Did the bill pass?

A: As of mid-September, it seemed that some segments of the industry had succeeded in blocking the measure. So it looks like we’re going to be in our current situation for the foreseeable future. 

But this issue isn’t going away, and advocates will continue pushing for reform.

Tips for safe supplements

Feeling a bit lost about how to choose a supplement? Here are some tips.

Look for a quality assurance seal

The FDA doesn’t endorse or verify seals, logos, or quality claims, so ignore statements like “GMP” (good manufacturing practices) or “3rd party lab tested.”

However, you can trust quality assurance seals from USP (U.S. Pharmacopeia), NSF (NSF International), and ConsumerLab. They test to ensure that a supplement’s contents match its label, that it’s free of tested contaminants, and that it disintegrates fast enough to get into your bloodstream. (Whether it’s safe—or effective—is another story.)

Keep in mind that supplements can interact with medications

Just two examples:

• St. John’s wort can reduce the effectiveness of oral contraceptives and some drugs used to treat HIV, cancer, heart disease, depression, and more.
• Ginkgo biloba, high-dose vitamin E (more than 400 IU), and aspirin can thin the blood. So does the prescription drug warfarin. Taking two of them together can raise the risk of internal bleeding or stroke.

To play it safe, tell your doctor or pharmacist about any supplements you’re taking.

Adverse event? Contact the FDA.

If you have (or suspect you’ve had) an adverse reaction to a dietary supplement, stop taking it, seek medical care, and report the event to the FDA at www.safetyreporting.hhs.gov.