Oolong tea is a partially fermented, caffeinated tea that is a cross between black and green tea, Drayer said. Senna acts as a laxative and will cause more bowel movements.
"I don't know the amount they use, but yerba mate is known for its caffeine content, which can ... perhaps speed metabolism in the short term," Drayer said. "In large amounts, it certainly can be an issue for those with high blood pressure or any heart issues."
and valerian root
, which are ingredients in many of these weight-loss products, have been associated with drug-induced liver injury
and in some cases liver failure, said Dr. Dina Halegoua-De Marzio
, a gastroenterologist and director of the Jefferson Fatty Liver Center in Philadelphia.
Researchers acknowledge that the liver-damaging potential of garcinia cambogia is debated and warrants further study. Though the exact concentrations of these substances are not listed on the companies' websites, the US National Institutes of Health's National Center for Complementary and Integrative Health
says that taking garcinia cambogia for 12 weeks or less should be safe for most healthy people. The National Institutes of Health
also reports that instances of liver toxicity from valerian root are very rare.
Do detox teas work?
The lack of regulation of the ingredients in these teas is a concern for many doctors.
"The FDA does not regulate these substances," said Halegoua-De Marzio, who is also an assistant professor of medicine at the Sidney Kimmel Medical College at Thomas Jefferson University. "Really, they can put anything they want in these teas. They can make any claim that they want, and it doesn't have to be supported by any evidence. That makes these very, very dangerous."
Adi Arezzini, Teami's co-founder and CEO, maintains that her company is "definitely transparent."
"All of the ingredients are 100% plant based and 100% natural," she wrote in an email to CNN. "All of the ingredients we use are written on our product labels!"
MateFit, Fit Tea, Flat Tummy and Lyfe Tea did not respond to CNN's requests for comment.
The sellers of these supplements tend to use general terms to describe their actions like "supports a healthy digestive system," Drayer said, contrasting that with drugs that have scientific backing that can assert they "lower blood pressure or cholesterol" and other more specific benefits.
Halegoua-De Marzio, who is a liver specialist, has seen an increase in patients asking about ways to detoxify
their bodies, an ability many of these weight loss companies profess to offer.
"And my answer is, it's an organ," she said. "There's no way really to detoxify an organ. The liver does a very good job of it on its own."
Are there any risks to detox teas?
The worst side effect someone may experience is liver failure
, according to Halegoua-De Marzio, but that would be extremely rare. More common side effects include increased heart rate, high blood pressure, nausea, vomiting and diarrhea.
"In my mind, it's not an effective treatment, so it's not worth any potential risk," she said. Users "really should talk to their physicians about any supplements. Because even beyond them not being effective and my safety concerns, some of these supplements can actually interact with other medications
that someone may be on."
Halegoua-De Marzio said valerian root can interact with muscle relaxants, sleep and anxiety medicines, as well as antidepressants. Dried green tea leaves contain vitamin K
, which can increase blood clotting, she said, and large amounts of vitamin K may interfere with some blood thinners.
Nevertheless, Halegoua-De Marzio and Drayer agreed that the average healthy person will probably be fine drinking the teas for a short period of time.
"We know by now that there are no quick fixes when it comes to weight loss
," Drayer said. "You may get a temporary drop in pounds, which can certainly be motivating on a psychological level, but that's as far as it's going to go. In terms of real weight loss, it takes portion control
[and] changing your eating habits
The key to sustained success, Drayer said, is "just making one or two changes a week until it becomes habit."