The list of healthy foods that can cause some very unhealthy side effects is long, and often the culprit is too much of a good thing. Even water falls into this category — some is good, more is only sometimes better and too much can kill you. And now you can add green tea to that everything-in-moderation list.
Last year a 16-year-old girl was hospitalized with acute liver failure and hepatitis. The culprit? A green tea drink she'd purchased off the Internet to help her lose weight. She only lost a couple of pounds (par for the course with any weight-loss supplement), but she gained horrible joint pain, dizziness and jaundice. Once she stopped drinking the green tea — which likely contained other ingredients, but she couldn't be sure as the label was entirely in Chinese — her liver function returned to normal and all symptoms of hepatitis disappeared. She was fortunate. In 2005, one woman ended up needing a liver transplant after overdosing on green tea.
And they're not the only ones who have been lured in by the health halo surrounding green tea only to find it makes them anything but healthy. Dozens of patients have shown up in hospitals with liver problems that were later attributed to green tea drinks or supplements, and several have even died.
The main culprit is a type of polyphenols called catechins, says Dr. Herbert Bonkovsky, a gastroenterologist with the Carolinas HealthCare System and one of the authors of a recent study, published in the American Journal of Gastroenterology, that looked at the effects of green tea on liver function. "Just because something is natural doesn't mean it's safe," he says.
Catechins are an antioxidant, and although we’ve all heard about the benefits of polyphenols and antioxidants, you can have too much of a good thing, especially when they're concentrated into green tea supplements or herbal concoctions, Dr. Bonkovsky explains. (Other types of tea also contain catechins, but green tea has the highest concentration.) The catechins target mitochondria, which are the powerhouse of your cells, helping the body to metabolize food and turn it into energy. Damage your mitochondria and you can shut down your whole system.
And it doesn’t take much to do the damage. Dr. Bonkovsky recommends avoiding supplements with green tea extract in them entirely, but if you do decide to take one, limit it to no more than 500 mg per day. This might be harder than it sounds as some of the supplements the researchers tested had up to 700 mg in one capsule, and they recommended taking several a day.
This applies to drinking tea as well. It's harder to overdose with liquid than with supplements, but it can happen. So limit yourself to drinking no more than three 8-ounce cups of tea per day, Dr. Bonkovsky says.
Another factor in how tea affects your health is your diet. A new study from Penn State found that eating iron-rich foods such as meat, nuts and leafy greens while drinking green tea could lessen the health benefits and increase the negative side effects.
"The benefit of green tea depends on the bioavailability of its active components," said Beng San Yeoh, a graduate student in immunology and infectious diseases and the first author of the study. "It is not only a matter of what we eat but also when we eat and what else we eat with it."
Your individual genetics also play a role, according to Dr. Bonkovsky. Some people are naturally more susceptible to liver damage from catechins, but it's hard to know if you're one of them until you're already feeling sick.
Bottom line? Drinking a cup or two of tea with no other ingredients or additives is perfectly safe, and you may also reap health benefits such as a lower risk of cancer and heart disease. But take a hard pass on any cleansing, detox or weight loss teas; tea concoctions (especially ones where you can't read the labels); and green tea supplements.
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