Are Your Herbal Supplements Safe? Tips for Using Unregulated Remedies

Millions of Americans take herbs and supplements to enhance their health or alleviate ailments ranging from the common cold to arthritis. Many consumers consider these to be safe, accessible complements to conventional medicine, but research suggests some of these products could do more harm than good.

In a new study, University of Michigan scientists revealed that roughly 5% of adults in the United States have taken one or more of six potentially hepatotoxic botanicals — or herbal remedies that can cause liver damage — within the last 30 days.

"I am not surprised at all. Most of the supplements identified in this study have been known to be hepatotoxic (potentially dangerous to the liver) for decades. However, there is a general lack of awareness in the public of the potential dangers of natural products," says Aaron Emmel, founder and director of educational programs at Pharmacy Tech Scholar, based in St. Augustine, Florida.

"It is also not uncommon for health care providers to be unaware of the dangers of some of these products," Emmel continues, saying many patients don't tell their providers they're taking herbs or supplements, so there's a missed opportunity for counseling.

"The most important thing to be aware of is that all medicinal products can have side effects, including potentially serious ones. This is true for prescription drugs, over-the-counter drugs, vitamins, herbal supplements and other natural products," Emmell says, adding that supplements can also interact with other drugs in potentially dangerous ways. "This doesn't mean that some supplements cannot be used safely, or that none may be of benefit, but there needs to be careful consideration of the individual's health conditions, medications and treatment plan."

Here's what you need to know about the latest research and how to select and use supplements safely.

For the study, researchers analyzed data from the National Health and Nutrition Examination Survey (NHANES) that has health information — including details of drug and supplement use — from 9,500 American adults. The average age is 47.5. They discovered that about 5% of survey respondents reported using at least one of six hepatotoxic herbal supplements — turmeric or curcumin, green tea extract, red yeast rice, ashwagandha, black cohosh and Garcinia cambogia — within the past month. Based on these findings, the researchers estimate about 15.6 million adults in the broader U.S. population have been similarly exposed. The findings appeared in JAMA Network Open.

"Hepatotoxicity, to put it simply, means damage to the liver by various harmful substances," says Tetyana Cheairs, M.D., assistant dean for Ph.D. programs and assistant professor of pathology, microbiology and immunology at New York Medical College, a member of Touro University in Valhalla, New York.

Of the many chemicals that can harm the liver, alcohol is by far the worst offender, Emmel says. But some seemingly innocuous substances like acetaminophen and, of course, certain herbs are in the mix, too. "There are many published cases of herbal supplement-induced liver injury in the literature," Cheairs says.

A previous systematic review and meta-analysis of 446 studies found 79 types of herbs or herbal compounds linked to herb-induced liver injury. Among those most likely to cause liver damage were green tea extract, He-Shou-Wu, Herbalife, kava kava, Greater celandine, skullcap, germander, Hydroxycut, Gynura segetum, garcinia cambogia, aloe vera, kratom, ma huang, chaparral, senna and supplements with multiple herbs, authors reported.

The liver regulates most chemical levels in the blood and is responsible for breaking down substances and producing bile, which helps transfer waste out of the body, according to Johns Hopkins Medicine. One of its most crucial roles is to filter toxins. When the liver metabolizes certain substances, including some herbs, toxic metabolites can form that damage liver cells, causing cell death and inflammation, Cheairs explains. She adds that botanicals may also interfere with the liver's ability to metabolize other substances, causing a buildup of harmful compounds, or trigger an immune response that attacks liver cells. This injury can impair liver function and, eventually, lead to scarring (cirrhosis) and liver failure.

Herbs have had a place in traditional medicine for thousands of years, but their popularity has recently resurged, and more than 80,000 herbal and dietary supplements (HDSs) are currently available without a prescription at various retailers, from gas stations to drugstores. According to the University of Michigan study, most HDSs are vitamins, minerals and omega-3 fatty acids, but between 5% and 12% are multi-ingredient botanicals.

Emmel says there are likely several reasons for HDSs' prevalence, including high health care costs and a growing mistrust of medicine and pharmaceuticals in general. 

"There is also increasing evidence that some complementary and alternative medicine (CAM) approaches, such as acupuncture, provide benefit and value to the health care system, and we are now seeing the incorporation of some of these approaches in guidelines and insurance coverage for them," he says. Despite emphatic marketing claims and social media testimonials, Emmel says there's little reliable scientific evidence to back most HDSs. And as no government agencies vet herbal supplements for safety or efficacy, the multi-billion-dollar market is somewhat of a nutritional Wild West. 

"Consumers should be aware that 'natural' does not necessarily mean 'safe.' In fact, some of these supplements have been shown to produce toxic effects," Cheairs says.

The U.S. Food and Drug Administration (FDA) regulates herbs and supplements as food, not medications, under the Dietary Supplement Health and Education Act of 1994 (DSHEA), Cheairs explains. "As a result, the requirements to demonstrate the safety of herbal supplements are much less strict compared to pharmaceuticals," she says, adding that it's up to manufacturers to ensure their products are safe and accurately labeled. "The FDA can only restrict or place a regulatory ban on an herbal supplement if the product is found unsafe after it is already on the market."

Certain herbs can be harmful on their own, especially when consumed in large quantities. But to make matters more complicated, supplements often contain multiple ingredients that can magnify or reduce each other's effects, including undesirable ones, Cheairs says. Plus, several factors can affect a supplement's composition and potency, including what part of the plant was used, where it was harvested from, cultivation conditions and manufacturing methods, she says. "Moreover, harmful contaminants, including heavy metals, can be present in the supplement," she says. She adds that labels don't usually impart all this information, making verifying a product's safety even more challenging.

As Emmel mentioned, not all supplements are bad, and some may be beneficial. However, it's essential to exercise caution — especially if you have a health condition like liver disease. Here are a few tips.

"In order to ensure your safety before taking any supplements, first and foremost, please consult with your health care provider," Cheairs says. Also, be sure to tell your doctor and pharmacist about any supplements or herbal remedies — including teas and essential oils — you're already using. "A qualified health care professional can help you understand the indications for use, recommended dosage, and any potential side effects," Cheairs continues. If you're unsatisfied with your primary care provider's advice, consider seeking a second opinion from an integrative health physician with more in-depth knowledge of natural remedies.

Another reason to tell your health care team about all the products you're taking is that many substances interact in potentially harmful ways, Emmell reiterates. Some can also worsen existing health issues — including liver disease.

"As a pharmacist, I immediately think of the potential for drug interactions," Emmell says. "This is especially problematic because these supplements rarely get incorporated into the patient's health records, so screening for dangerous interactions doesn't occur." One example is St. John's wort, an herbal supplement that may help treat depression, Emmell says. He explains that it increases the activity of some enzymes that metabolize medications, which can render the drugs ineffective as the body breaks them down quickly.

Moreover, taking St. John's wort alongside an antidepressant can lead to serotonin syndrome, a potentially life-threatening condition, he continues. "Green tea extract is another example of this kind of interaction: it can inhibit certain drug transporters and prevent them from being adequately metabolized in the body, leading to toxicity," Emmell says.

Some supplements can also exacerbate medication side effects, Emmell says. "An example is red yeast rice," he says. "It has a side effect profile similar to statins, so combining it with a statin significantly increases the risk for muscle breakdown and toxicity, as well as liver damage."

In one review, which reported nearly a quarter of U.S. adults are taking at least one supplement alongside a prescription medication, authors advise anyone taking prescription drugs to avoid St. John's wort, specifically. That's particularly crucial for folks taking hepatitis C medications, they write, as the herb can reduce liver function in people taking these drugs. 

As previously mentioned, there's little oversight in the supplement industry, and reliable research is lacking. "Without rigorous clinical trials, we have a poor understanding of the risks and benefits of many supplements," Emmel says. "There is also a lack of manufacturing oversight, which leads to the potential for contaminated products to arrive on the market."

One way to mitigate this is only to purchase products that have a seal of approval from an unbiased third-party organization like the United States Pharmacopeia (USP) or NSF International, Emmel says. Harvard Health also recommends Consumer Lab as a reliable vetting source.

Cheairs says consider doing DIY research in addition to consulting your doctor and pharmacist. However, she stresses the importance of leaning on trustworthy sources like government agencies. Although they don't regulate such products, she explains, many provide information on their use, including consumer alerts and recalls. 

She recommends the following:

• Office of Dietary Supplements of the National Institutes of Health (NIH) - Office of Dietary Supplements (ODS)
• The National Center for Complementary and Integrative Health of the NIH- Herbs at a Glance
• The FDA- Information for Consumers on Using Dietary Supplements
• The US Department of Agriculture - Herbal Supplements
• The Botanical Safety Consortium - Useful Resources
• MedlinePlus database - Herbs and Supplements

"Many people tend to overdo it with supplements with a 'more is better mentality,' not realizing that nutrient toxicities exist," Coogan says. It doesn't help that serving suggestions on supplement labels may be inappropriately high, designed with a company's bottom line — not your health — in mind, she adds. "Then if you have someone who thinks twice the serving size would surely be better than one, you could be at a point of toxicity that could lead to some adverse or dangerous effects," she says.

There's not enough rigorous scientific evidence on most HDSs to determine the optimal dosage. Still, Coogan says it's best to purchase the smallest possible dose so you have better control of how much you consume. A pharmacist or other health care provider can also help you determine a safe amount.

More research on HDSs is necessary to determine how specific herbs might benefit or harm people, especially those with existing health issues. In the meantime, always speak with your health care provider before changing your health regimen, and if you are taking supplements of any kind, don't ignore potential side effects.

"If a person notices any side effects after taking a dietary supplement, they must immediately notify their physician and stop using the product," Cheairs says. "The patterns of liver damage from herbal supplements differ a lot, and so does their treatment and diagnosis."

You or your doctor can also notify the FDA using the Safety Reporting Portal or by calling the FDA's toll-free information line 1-888-INFO-FDA, Cheairs adds.

Kate Daniel is a freelance writer and award-winning journalist from the Pacific Northwest specializing in health and wellness, with a particular emphasis on mental health and nutrition. She's written for a broad array of publications, including HealthDay, Everyday Health, Lose It, Nice News, Get Me Giddy, and The Whidbey News-Times. You can find more of her work here. Read More