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5 Supplements That Can Do "The Most Harm"

Stay away from these supplements.
FACT CHECKED BY Emilia Paluszek

They're marketed as "organic" and "all natural"—but how much do you really know about those supplements in your medicine cabinet? "Supplements may interact with other medications you're taking or pose risks if you have certain medical conditions, such as liver disease, or are going to have surgery," says Jeffrey Millstein, MD. "Some supplements also haven't been tested in pregnant women, nursing mothers or children, and you may need to take extra precautions." Here are five supplements that doctors say can do the most harm. Read on—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.


Weight Loss Supplements

weight loss tea

Weight loss supplements may contain dangerous hidden ingredients, experts warn. "Many of our patients try over-the-counter weight loss medications prior to seeking bariatric surgery," says Penn Medicine Bariatric Program Manager, Colleen Tewksbury, PhD, RD. "Unfortunately, what many don't realize is that even those that have some studies to back them up, only a selected few show a couple of pounds' advantage over diet and exercise. If you are a candidate for weight loss medications, speak with your doctor about FDA-approved options that would be best for you. Avoid the OTC options. Most, unfortunately, are marketing ploys preying on people desperate for help."


Caffeine Pills


Caffeine supplements can have serious side effects if too much is taken. "The AAP recommends that adolescents consume no more than 100 mg of caffeine a day; however, one cup of coffee can have anywhere from 95 to 165 mg," says Kathleen Swayne, MD. "Caffeine pills and powders are also being used more often by teens, especially athletes. Even small amounts of powdered caffeine can cause a life-threatening overdose. Just one teaspoon can have the same effect as drinking 25 cups of coffee."


Bodybuilding Supplements

Testosterone boosters

Bodybuilding supplements that contain androgenic anabolic steroids can cause severe liver damage. "Bodybuilding supplements that contain AAS can lead to liver damage, including severe cholestatic hepatitis, which can take months to resolve," says Robert Fontana, M.D., University of Michigan's medical director of liver transplantation. "Additionally, various multi-ingredient nutritional supplements taken to enhance energy, increase performance and facilitate weight loss can lead to potentially severe, or even fatal, liver damage."



kava kava supplement capsules on brown wooden plate
Shutterstock / Iryna Imago

Kava is a highly controversial supplement that can cause liver damage. "Note that kava has been banned in the United Kingdom and within Europe due to liver toxicity," says Robert D. Ashley, MD. "More than 100 cases of liver toxicity related to the use of kava have been identified, some leading to liver transplant and some leading to death. There are many reasons for liver damage. For one, kava depletes glutathione, a chief antioxidant, within the liver. It also inhibits enzymes involved in the metabolism of many drugs. Many of the cases of liver toxicity were seen in people who had prior liver disease or used alcohol in addition to kava."


Green Tea Extract

Green Tea From Kettle

"If you are drinking modest amounts of green tea you're very safe," says Prof Herbert Bonkovsky, director of liver services at Wake Forest University School of Medicine in North Carolina, who has been tracking green tea supplement-related injuries for nearly 20 years. "The greater risk comes in people who are taking these more concentrated extracts… Usually people are taking these green tea extracts trying to lose weight, so they're often not eating. We know from animal studies that fasted animals absorb a much higher percentage of the catechins than do fat animals. There may well be other factors of other drugs, other chemicals, use of alcohol that are also important as modifying factors."

Ferozan Mast
Ferozan Mast is a science, health and wellness writer with a passion for making science and research-backed information accessible to a general audience. Read more about Ferozan