Millions of Americans are taking dietary supplements containing plant-based ingredients that may be harmful to the liver, a study by researchers at the University of Michigan has found. The study isn’t meant to alarm, but it does suggest that the amounts of plant-based supplements being consumed may not be well-studied for their effectiveness and safety.
What are nutritional supplements?
A dietary supplement is defined as a product intended to supplement the diet and containing one or more dietary components, including vitamins, minerals, herbs or other plants, amino acids, and other substances or their components. It should be noted that these dietary supplements are not subject to the same laws that regulate the use of drugs and there are not necessarily adequate studies on them.
National Survey
The study, published in JAMA on August 5 and based on data from the National Health and Nutrition Examination Survey conducted between 2017 and 2020, found that 4.7% of adults surveyed took herbal or dietary supplements containing one of the following plants: turmeric, green tea, ashwagandha, black cohosh, garcinia cambogia, and products containing fermented red rice.
Billions in sales and unproven benefits
According to researchers, turmeric-containing products have been commonly used for joint health or arthritis because of the belief that turmeric may have antioxidant and anti-inflammatory properties. However, several human trials have failed to demonstrate any effectiveness of turmeric-containing products for osteoarthritis.
Green tea-containing products have been used mostly as energy supplements. However, multiple studies have failed to demonstrate any objective evidence of weight loss and sustained improvements in mood or energy levels with products containing high levels of catechins or polyphenols found in green tea extract.
The research indicated that there are more than 80,000 unique supplement products available for purchase worldwide, and that supplement sales exceeded $150 billion in the United States in 2023, a number comparable to sales of prescription drugs.
“We’re not trying to alarm,” said Dr. Robert Fontana, a hepatologist at the University of Michigan, professor of medicine and lead author of the study. “We’re just trying to raise awareness that the supplements that people take and buy over the counter haven’t necessarily been tested or proven safe.”
Dietary supplements are a source of concern.
“We became interested when we saw cases of liver toxicity from herbal and dietary supplements in people participating in a previous study,” said Dr. Alyssa Lekhitsub, MD, assistant professor at the University of Michigan Medical School and the study’s first author.
The study was unable to prove a causal relationship between the consumption of the six plants and the development of liver disease, as it was intended to assess supplement consumption in the general US population. However, the researchers hope to raise awareness among doctors and patients about how little we know about these supplements.
Supplements are of particular concern to researchers for several interrelated reasons, according to EurekAlert, including lack of government regulation, insufficient attention to medical testing, and frequent labeling manipulation.
Researchers say labels are easy to manipulate because of the lack of regulation. “In a previous study, we found that there was a lot of manipulation in some of these products,” said Dr. Robert Fontana.
“We did chemical analyses and found about a 50% discrepancy between the ingredients claimed on the label and what they actually contain, which is very concerning,” he added. “If you buy a supplement and it says it contains a certain ingredient, it’s like a game of chance to determine whether that’s true or not.”
Most users reported taking the plants on their own and not on the advice of a doctor. The most common reason for taking the plants was to improve or maintain health. Because their effects are not well understood, doctors often do not ask patients about the supplements they are taking.