CRN Disputes Study Linking Popular Supplements to Liver Damage Risk

Recent research set off alarm bells after the findings suggested millions of Americans are at risk for liver damage from six specific dietary supplements. However, the Council for Responsible Nutrition says some media outlets misinterpreted the study.

The study, published on August 5 in JAMA Network Open, assessed the percentage of people in the United States taking at least one of six potentially hepatotoxic dietary supplements. Hepatotoxic is a medical term used to describe liver damage caused by a drug, chemical, or dietary supplement.

Specifically, the researchers used data from the National Health and Nutrition Examination Survey (NHANES) to determine how many people in the U.S. used turmeric or curcumin, green tea extract, Garcinia cambogia, black cohosh, red yeast rice, or ashwagandha. According to the research team, these six botanicals are more frequently associated with liver issues and are contributing to an overall increase in supplement-related liver toxicity cases.

The results estimated that 15.6 million Americans consumed at least one of these products within the previous 30 days, similar to the number of people taking prescription drugs linked to liver toxicity.

"Given a lack of regulatory oversight on the manufacturing and testing of botanical products, clinicians should be aware of possible adverse events from consumption of these largely unregulated products," the study's authors wrote.

Shortly after JAMA published the study, media headlines warned consumers that these dietary supplements were causing hospitalizations and putting millions at risk for liver damage.

However, in a statement responding to the study, the Council for Responsible Nutrition (CRN), a trade association for the dietary supplement and functional food industry, said the media headlines about the potential hepatotoxicity of these products were misleading, as the study's findings did not show any new risk of liver injury.

"This analysis of existing NHANES survey data doesn't appreciate that the overall risk these ingredients pose is exceedingly low," said Steve Mister, president and CEO of CRN. "Revealing that more than 15 million Americans use at least one of these herbal supplements, when compared to their actual reported risks, only strengthens the case for their safety."

CRN admits that liver injury from botanicals can occur in rare cases, especially in individuals with specific genetics or pre-existing conditions. However, the trade association says that most consumers taking these botanical supplements use them as directed without issue.

What does science say about supplements and liver injury?

A recent review of research suggests that dietary supplements are linked to about 20% of reported liver injury cases. However, the researchers say that it's challenging to determine the actual number of supplement-related liver cases due to variability between supplements and the likelihood that the product may contain ingredients not listed on the label.

A 2022 study investigating turmeric found 10 instances of turmeric-associated liver injury occurred after 2011. Five people were hospitalized, and one individual died of acute liver failure. The scientists suggest that turmeric-related liver injury appears to be rising in the U.S., perhaps reflecting increased use of the spice or combining it with black pepper, which is thought to boost absorption.

Still, the study’s authors note that the small number of cases limits their ability to say for certain that turmeric-related injury is rising.

In addition, while green tea has been linked to liver injury, a 2016 meta-analysis of 34 clinical trials found that liver-related adverse events after consuming green tea extract were rare.

Moreover, a 2023 study found that clinical trials involving over 1,200 participants have not revealed links between black cohosh and liver injury. Still, the researchers say that several cases of black cohosh-related liver toxicity were associated with adulterated products.

The analysis also showed that while no clinical trials have found links between ashwagandha and elevated liver enzymes, a 2021 case series identified five incidences of liver injury related to the herbal supplement.

Garcinia cambogia has been linked to liver injury as well. However, a 2019 overview suggests that liver reactions are uncommon, impacting less than one out of 10,000 people who take the supplement.

According to the National Institutes of Health (NIH), red yeast rice extract supplements have not been associated with liver injury or elevated liver enzymes in controlled trials. However, the NIH notes that isolated cases of liver damage after consuming the supplement have occurred.

Doctors can help bridge the information gap

Moving forward, the CRN says that healthcare providers should consider learning more about the benefits and risks of these six and other popular supplements to provide their patients with accurate information about using them safely.

"What consumers and healthcare practitioners should take away from this study is that there is great — and growing — interest in using herbal supplements to promote health and wellness," Mister said. "Practitioners should encourage candid and open-minded conversations with their patients about supplement usage."

Mister adds that alarmist headlines that mislead doctors and panic consumers hamper those conversations and do a disservice to the millions of people who use these products every day.