The Lesser-Known Side Effects and Dangers of 8 Popular Herbal Supplements

Side effects of Herbal Supplements
  • Herbal supplements are a popular alternative to conventional prescription drugs.
  • Although there are a number of risks associated with many herbal supplements, the natural medicine industry remains largely unregulated.
  • It is important to be aware of these risks and talk to your doctor before incorporating dietary supplements into your treatment plan.

Pharmaceutical drugs might play a dominant role in Western medicine, but that does not stop a large number of people from seeking alternative remedies.

About 19% of the United States adult population has used a complementary and alternative medicine supplement in the past 12 months, according to research from Washington State University.

Despite their popularity, there are a number of risks associated with taking natural medicines. In contrast to conventional pharmaceutical drugs, the herbal supplement industry is largely unregulated, which increases the incidence of quality control problems during the manufacturing process.

Furthermore, a number of seemingly healthy natural medicines are closely linked to a range of negative side effects that may have a long lasting impact on a patient’s health.

Read on to get more insight into eight potentially dangerous natural medicines.

Are herbal supplements safe and effective?

Alternative medicine certainly has its place in modern medicine and can be an effective form of treatment for some ailments. Many doctors prescribe herbal medicines in conjunction with pharmaceutical drugs to treat a wide variety of health conditions, often to great effect.

“Numerous supplements from Europe that are made by pharmaceutical companies have been shown to be effective for multiple medical problems based on published clinical trials, according to Commission E, the German equivalent of the FDA,” says Dr. Joseph Feuerstein, Director of Integrative Medicine at Stamford Hospital and Assistant Professor of Medicine at Columbia University. “These are natural remedies in clinically effective doses that are given in Europe under the supervision of a physician.”

However, herbal supplements are not without their faults.

“The main issue with herbal products is that they very often do not contain the stated ingredients,” says Dr. Levitan co-founder of Vous Vitamin LLC. “There is no FDA regulation of this industry and many manufacturers are not scrupulous in their production methods. When products are analyzed, many do not contain the herbal substance that is stated on the label.”

Given that medicine typically needs to be taken in precise doses, this is a major concern for patients.

Many natural medicines are yet to gain FDA approval due to a lack of quality scientific evidence showing their medicinal benefits. In addition, some proponents of natural medicine tend to exaggerate the effectiveness of certain products, which confuses patients and detracts from the real medical potential of herbal supplements.

Here are eight potentially dangerous herbal supplements, and their known side effects.


Made from the roots of Piper methysticum, kava has been used in the Pacific Islands for hundreds of years for both recreational and medicinal purposes. Today, it is widely available in health food stores across the United States, and is commonly used as an alternative to prescription anti-anxiety drugs.

However, according to research published in the European Journal of Gastroenterology & Hepatology, heavy kava use is associated with hepatotoxicity (chemically-driven liver damage), particularly when taken in large doses or over a prolonged period of time.

Kava also interacts with a number of drugs, including alprazolam and sedatives, and should not be taken by women who are pregnant or breastfeeding.

Licorice root

The licorice plant is a naturally occurring herb that grows natively in the Mediterranean, Russia, and Asia Minor. It is used in a wide range of foods, tobacco, and herbal medicinal products. Many people use licorice root to reduce stress, combat gastrointestinal problems, and maintain respiratory system health.

However, while licorice is fairly safe when consumed in the amounts found in everyday foods, there are some risks involved with taking licorice in larger amounts for medicinal purposes.

As noted in research published in Regulatory Toxicology and Pharmacology, continuous use of licorice root may result in serious side effects such as high blood pressure and abnormally low levels of potassium.

St. John’s wort

St. John’s wort is a flowering plant that is used to make a variety of herbal products, including pills, teas, and liquid extracts. Research indicates it can be used to effectively alleviate some of the symptoms associated with depression, but it can also interfere with the body’s ability to process other chemicals.

As Dr. Jared Heathman of Houston Psychiatrist explains, this means there are significant risks involved with using St. John’s wort in conjunction with pharmaceutical drugs.

“In mental health,” he explains, “a common problem I see is the use of St John’s Wort and FDA approved antidepressants. Such a combination can lead to a dangerous complication called serotonin syndrome, which would likely require extensive hospitalization.”


Also known as Larrea tridentata, chaparral is a type of herb that grows in parts of North, Central, and South America. Over the years, it has been used to treat a variety of health conditions, including cancer, rheumatism, diabetes, and more. However, its medical benefits have never been proven in clinical trials.

In fact, in a review of 18 case reports of adverse events linked with chaparral use, the FDA found evidence of hepatotoxicity in 13 cases, leading investigators to conclude that “the use of chaparral may be associated with acute to chronic irreversible liver damage.”

Research also suggests that chaparral can cause drug interactions with many medicines, including anti-inflammatories, blood thinners, antidepressants, and more.

Red yeast rice extract

A traditional Chinese medicine, red yeast rice extract is believed to lower cholesterol and can be found in a number of natural supplements.

While there is some evidence that supports this theory, there are significant issues with the level of quality in products containing red yeast rice extract.

“Red yeast rice products are manufactured so that the strength of the product varies from batch to batch, meaning toxicity can occur at any time,” says Dr. Levitan. “These products have the same potential toxicity of statin medications — liver disease and muscle break down — but people taking red yeast rice are typically not monitored with regular blood work in the same way as people taking prescription statin medication.”

Colloidal silver

Colloidal silver is essentially a liquid containing microscopic slivers of silver. Some people claim that it has antibacterial properties and antifungal properties, and it has been used in the treatment of conditions such as cancer, diabetes, and arthritis.

Despite a resurgence in popularity, there is no quality evidence to support the use of colloidal silver as a health supplement or medication.

According to research published in the Dermatology Online Journal, using colloidal silver could lead to argyria, a rare condition that turns the skin a bluish-gray color. Consuming large doses of colloidal silver can also be toxic to bone marrow and may cause coma, pleural edema, and other similarly significant problems.

Garcinia cambogia

Garcinia cambogia is a tropical fruit that is commonly used in the production of weight loss supplements. It is purported that hydroxycitric acid, the active ingredient found in the rind of the fruit, prevents the body from producing fat and decreases appetite.

Although there is some evidence to suggest that garcinia cambogia may have a small impact on weight loss in the short term, a comprehensive review published in the Journal of Obesity found that the effect is more or less negligible.

Researchers also found that most studies on the use of garcinia cambogia reported a range of adverse side effects, including headache, skin rash, common cold, and gastrointestinal issues.

Ginkgo biloba extract

Ginkgo biloba extract is a popular herbal supplement made from the leaves of the ginkgo tree, a plant native to Japan, China, and Korea. Famed for its high level of antioxidants, ginkgo is taken orally to improve cognitive function, and to treat anxiety, glaucoma, and vertigo.

While gingko is generally safe for most people, research published in the Journal of General Internal Medicine has found a possible causal link between ginkgo use and internal bleeding events.

Ginkgo extract is also known to have a severe interaction with blood thinning medicines and selective serotonin reuptake inhibitors (SSRIs).

Choosing the right dietary supplements

It is important to note that while there are definitely some risks associated with using herbal supplements, it does not necessarily mean that you should avoid them entirely.

Many current prescription drugs are derived from natural plants, and many people have experienced positive effects from exploring alternative medicine.

However, it is vital that you consult your healthcare provider before you start taking any herbal supplement to get more insight into the risks, benefits, and how the product may interact with any medication you are currently using or any health conditions you might currently have.

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