6 Potentially Dangerous Herbal Supplements That Could Cause Damage To Your Liver & Kidneys, According To Doctors: Comfrey & More

Herbal supplements are often marketed as natural remedies with a variety of health benefits, but many come with potential risks , especially when it comes to liver health. While some may seem harmless or even beneficial, certain herbs can cause serious damage if consumed in excessive amounts or over long periods of time. The liver, responsible for filtering toxins from the body, can be particularly vulnerable to the effects of these supplements. According to doctors, some popular herbal remedies have been linked to liver inflammation, toxicity, and even failure.

To shed some light on a few supplements you should take with caution, we spoke to Dr. Kubanych Takyrbashev, MD, Health & Wellness Advisor at NAO ; physician Dr. Erik Natkin ; Jesse Feder , RDN, CPT; and Dr. Rimas Geiga. Find all of their warnings and expert insight below.

1. Black Cohosh

Black Cohosh is one supplement that has been associated with liver damage. According to Dr. Natkin, "Black Cohosh has been linked to multiple cases of liver damage, particularly in people with existing liver disease or those taking other hepatotoxic medications." This makes it a risky choice, especially for individuals already managing liver health issues.

2. Senna

Senna is commonly used as a natural remedy for constipation because it stimulates the muscles of the colon. However, Dr. Kubanych Takyrbashev warns that "prolonged or excessive use of Senna can deplete the body of fluids and vital electrolytes." This can lead to dehydration and electrolyte imbalances, placing significant strain on the kidneys. Chronic dehydration and imbalances can ultimately damage the kidneys or worsen existing kidney conditions.

3. Comfrey

Comfrey contains pyrrolizidine alkaloids, which can be highly toxic to the liver. Dr. Erik Natkin points out that "comfrey can cause liver inflammation and veno-occlusive disease," a condition where veins in the liver become blocked. Both the FDA and the European Medicines Agency (EMA) have issued warnings about the hepatotoxic potential of comfrey, urging consumers to avoid it, he says.

4. Green Tea Supplements

Green tea extract, known for its high concentration of epigallocatechin gallate (EGCG) and weight loss benefits , can be harmful in large doses. Dr. Natkin warns that "case studies have linked excessive green tea extract ingestion to liver toxicity and acute liver failure." The liver damage is usually a result of the body's adverse reaction to high levels of catechins, which can cause oxidative stress and inflammation in liver cells.

5. Kava

Kava is a popular anti-stress supplement that many people consume in order to bring a sense of calm to their brain and body. "Kava, which is typically consumed as a tea, is a supplement known to promote relaxation," Feder explains. Unfortunately, though, this relaxation could come with a risk; "Consuming kava regularly has been shown to affect enzyme and antioxidant activity in the liver which can lead to liver damage ." Yikes! On top of this, kava could also pose a risk to your kidneys. "Kava may decrease blood flow to the kidneys and cause increases in harmful metabolites which can also damage them," Feder warns. Like any other supplement, you should always stick to recommended doses when consuming kava. Additionally, it's important to choose high-quality, reputable brands to ensure your safety.

6. Licorice Root

Licorice root, when consumed in large amounts or over extended periods, can cause potassium depletion and elevate blood pressure, potentially leading to kidney damage or worsening existing kidney conditions. "Licorice root can be harmful to kidney health due to its effect on potassium levels and blood pressure," warns Dr. Geiga. For digestive health, consider alternatives like chamomile or fennel tea, which can soothe the stomach without the risks associated with licorice root.