Many ailments—such as achy muscles, a weak immune system, lack of sleep, and anxiety—can be alleviated with natural remedies. More than one third of American adults use some form of complementary and alternative medicine (the most common being natural supplements), according to the National Institute of Health . While herbal remedies have grown in popularity in the Western world for some time, native cultures have been using natural cures for centuries. Modern herbs, in general, continue to be safe, however, we may not be harvesting or consuming them like our ancestors, which is where it starts to get dangerous.
The strains of plants that are grown, the method of harvesting, and the dosage at which they’re ingested aren’t necessarily the same as when the plants were first used medicinally, explains Michael Tims, Ph.D. , academic director of the herbal program at Maryland University of Integrative Health. Because the FDA classifies herbs as “dietary supplements,” it only takes responsibility for regulating the safety of each ingredient. This means it is not necessarily monitoring adulterated formulas as closely as with traditional prescription medications.
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“Herbs need a proven record of safety for the FDA to approve their use,” Tims explains. For traditional herbs, their use over thousands of years is enough of an epidemiological trail to earn them the FDA’s GRAS (“generally recognized as safe”) designation or to be accepted under the Dietary Supplement Health and Education Act as “Herbs in Commerce.” New dietary ingredients require a much more robust presentation of data to prove their safety, he adds. While the FDA supervises the safety of individual ingredients, the majority of the responsibility for safety and compliance falls on the manufacturer.
The bigger problem: Some herbs interact with prescription and OTC drugs, something which indigenous cultures never had to worry about, Tims says. While herbs can significantly improve your health, certain combinations can have harmful effects. For example, researchers at Baylor College of Medicine recently found that around 5 percent of people who take a supplement of the herb aristolochia—which has traditionally been used to increase sex drive, boost immune function, and help menstruation—experience side effects as serious as cancer of the kidneys, liver, and bladder. The onus is on supplement manufacturers to report these adverse reactions to the FDA so they know to reconsider their stance.
Luckily, the FDA has banned all products that may contain the harmful aristolochia herb as well as other plants that have been proven toxic. But the study authors from Baylor warn that herbal remedies pose a global health hazard, and indeed there are a handful of all-natural treatments still on shelves in the U.S. that can be bad for your health. Here are four of the biggest threats to watch out for.
1. HERB: Kava
Sometimes called “kava kava,” this herb has been used by the Polynesians for its hypnotic and calming properties for centuries. The Western world caught on to the herb’s ability to alleviate stress, anxiety, and insomnia in the 90’s. A 2007 study published in American Family Physician recommended short-term use of kava for moderate anxiety disorders.
Health hazard(s): As popularity of the herb (often ingested as a drink) increased, so did reports of liver damage—enough that Canada and a handful of European countries banned the supplement in the early 2000’s. The U.S. never did, and some countries, like Germany, have since lifted the ban.
What went wrong: “The issue isn’t necessarily the herb itself, it’s how it is used and being altered from tradition,” Tims says. Growers and producers began to use black kava, which was easier to harvest than the traditional white variety; they started using shavings and parts of the plants that hadn’t been used before; and they began to extract it in a non-traditional way that concentrated less on water-soluble lipids, altering the way our bodies absorb the herb. Plus, the plant was being ingested at such a rate that, when combined with other factors like pharmaceuticals and excessive alcohol intake, it was tearing up people’s livers.
2. HERB: Green Tea Extract
Green tea is one of the best herbs for your health. For the most part, the antioxidants in the drink help reduce your risk of heart disease, obesity, diabetes, and cancer, among other diseases. And the popularity of green tea extract in weight loss supplements has skyrocketed in the past few years.
Health hazard(s): The American College of Gastroenterology released a warning in 2014 that said, when the supplement form is taken at a high dose, the herb can be toxic and actually cause liver failure. The herb can also be dangerous when combined with certain drugs, like amphetamines or prescribed medications such as MAOI antidepressants and quinolone antibiotics, which interact with the natural caffeine in the extract to overstimulate your body, increasing high blood pressure, nervousness, and headaches.
What went wrong: It’s difficult to know because, while the potential issues with green tea have been reported, most remain unverified. “There are natural variations in the tea—whether it was harvested during monsoon season, for example—as well as variations in how it’s extracted,” Tims says. The problem could also be from excessive caffeine (the tea already has some, but weight loss supplements often add more for a metabolism boost) or from an overload of EGCG and other catechins that give the herb its detoxifying power.
3. HERB: St. John’s Wort
St. John’s wort is a highly effective natural antidepressant. Its chemical makeup encourages the uptake of key neurochemicals, including serotonin, dopamine, and norepinephrine.
Health hazard(s): The happiness-inducing herb is also well-known for reducing the efficacy of certain prescription medications. In fact, more than 70 percent of all prescription medications are potentially affected by St. John’s wort in one way or another, according to a 2012 study published in Planta Medica. Plus, an Australian study last year found that St. John’s wort can sometimes cause side effects similar to those seen in people taking Prozac, namely anxiety, panic attacks, dizziness, nausea, and spikes in blood pressure.
What went wrong: St. John’s wort binds to enzymes in the liver, some of which are the same enzymes other drugs bind to. This crossover alters the chemical structure of the second drug, creating potential for you to reach a toxic dose very quickly or, conversely, never reach an effective level, Tims explains. The most prevalent problem: The plant makes birth control less effective. Women taking both St. John’s wort and oral contraception report an increase in irregular bleeding and, much more alarming, an uptick in unplanned pregnancies.
4. HERB: Goldenseal
Extraction of this root is taken for both its anti-inflammatory properties to ease problems, like constipation, and antimicrobial properties to prevent the common cold and upper respiratory tract infections. If you think you’ve never taken it, check out your all-natural allergy med—goldenseal is often formulated with Echinacea.
Health hazard(s): While the herb is great at fighting infections, it also curtails the activity of two major enzymes that help your body remove toxins and drugs, CYP3A4 and CYP2D6, according to the above-mentioned study from Planta Medica. Plus, the Cleveland Clinic warns goldenseal may affect blood pressure and increase your risk of bleeding when you take blood-thinning drugs, like warfarin.
What went wrong: The herb can affect how quickly your body processes and removes active ingredients of medications and other herbs. A 2008 study published in Molecular Nutrition & Food Research found that this remedy affected these enzymes enough that the researchers recommend folks who are on goldenseal steer clear of prescription meds that are metabolized by CYP2D6, like serotonin reuptake inhibitors (SSRIs), beta-blockers, opiates, and antiarrhythmics.