Green tea supplements are popular for weight loss, but a new study found that obesity may change how your body processes a key ingredient called EGCG. Researchers gave this compound to obese and lean mice and tracked what happened to it in their bodies. They discovered that obese mice created different types of EGCG byproducts, some of which might be harmful to the liver at high doses. This suggests that people carrying extra weight might need to be more careful about taking large amounts of green tea supplements, though more research is needed to confirm this in humans.

The Quick Take

  • What they studied: Whether obesity changes how the body breaks down and uses EGCG, the main active ingredient in green tea supplements
  • Who participated: Male laboratory mice that were either obese or normal weight, divided into groups receiving different doses of EGCG or a control substance
  • Key finding: Obese mice processed EGCG differently than lean mice, creating more potentially harmful byproducts, especially at higher doses. The obese mice showed significantly higher levels of a compound called cysteinyl EGCG, which could increase liver damage risk.
  • What it means for you: If you’re overweight and considering green tea supplements for weight loss, very high doses might be riskier for your liver than they would be for someone at a normal weight. This doesn’t mean you should avoid green tea, but it suggests talking to a doctor before taking large supplement doses, especially if you have liver concerns.

The Research Details

Researchers used laboratory mice to study how obesity affects the body’s processing of EGCG, the main active compound in green tea. They divided mice into two groups: obese mice and healthy-weight mice. Each group received either a control liquid, a low dose of EGCG (100 mg per kilogram of body weight), or a high dose (750 mg per kilogram). The researchers then collected urine samples and used advanced laboratory techniques called liquid chromatography-mass spectrometry to identify and measure all the different forms of EGCG and its byproducts in the mice’s bodies.

This approach allowed scientists to create a detailed map of how each mouse’s body broke down and processed EGCG. By comparing the metabolite profiles between obese and lean mice at both dose levels, they could see whether obesity changed the way EGCG was handled by the body.

Understanding how obesity affects the body’s processing of supplements is important because it helps explain why some people might experience side effects while others don’t. The liver is responsible for breaking down most substances we consume, and obesity can change how well these systems work. By studying this in mice first, scientists can identify potential safety concerns before testing in humans.

This study used a controlled laboratory setting with carefully measured doses and advanced chemical analysis techniques, which provides reliable data about what happens to EGCG in the body. However, because it was conducted in mice rather than humans, the results may not directly apply to people. The study also doesn’t specify exactly how many mice were used in each group, which would help readers assess the strength of the findings.

What the Results Show

The main discovery was that obese mice and lean mice processed EGCG very differently. When researchers looked at the byproducts created as the body broke down EGCG, they found that obese mice produced higher amounts of certain metabolites, particularly compounds created through glucuronidation (a normal detoxification process) and oxidation (a process that can create harmful molecules).

Most importantly, obese mice had significantly higher levels of a compound called cysteinyl EGCG compared to lean mice. This is concerning because cysteinyl EGCG is thought to be more likely to damage the liver than the original EGCG compound. This difference was especially noticeable at the higher dose (750 mg/kg), suggesting that obese individuals taking large amounts of green tea supplements might face greater liver damage risk.

The lean mice, by contrast, processed EGCG in a way that appeared safer, with lower production of these potentially harmful byproducts even at the higher dose.

The study also showed that the dose of EGCG mattered significantly. At lower doses (100 mg/kg), the differences between obese and lean mice were less dramatic. However, as the dose increased to 750 mg/kg, the differences became much more pronounced. This dose-dependent effect suggests that the risk of problems from EGCG supplements increases with the amount taken, and this risk appears to be amplified in people with obesity.

Previous research has shown that very high doses of EGCG can cause liver damage in both animals and humans. This study adds an important piece to that puzzle by showing that obesity may make the body more vulnerable to this damage. Earlier studies noted that obesity changes how the liver and other organs process medications and supplements, and this research provides specific evidence of that effect with green tea’s main ingredient.

The study was conducted in mice, not humans, so we can’t be certain the same effects occur in people. Mice metabolism can differ from human metabolism in important ways. Additionally, the study doesn’t specify the exact number of mice used in each group, making it harder to assess how reliable the findings are. The research also only looked at male mice, so it’s unclear whether female mice or humans would show the same patterns. Finally, while the study identifies that obesity changes EGCG processing, it doesn’t prove that these changes actually cause liver damage in living organisms—that would require additional research.

The Bottom Line

Based on this research, people with obesity should be cautious about taking high-dose green tea supplements without medical supervision. If you’re interested in green tea for health benefits, moderate consumption of regular green tea (drinking it as a beverage) appears safer than taking concentrated supplements. If you do want to take EGCG supplements, consult with your doctor first, especially if you have liver disease or take medications that affect the liver. Confidence level: Moderate—this is animal research that suggests caution, but human studies are needed for definitive recommendations.

This research is most relevant to people who are overweight or obese and considering green tea supplements for weight loss or other health reasons. It’s also important for anyone with existing liver problems, since they may be at higher risk. People taking medications that stress the liver should also pay attention. However, this doesn’t apply to people simply drinking regular green tea as a beverage—the study focused on concentrated supplements at very high doses.

If liver damage from EGCG were to occur, it could develop relatively quickly with high doses, though the exact timeline isn’t clear from this study. Benefits from green tea for weight loss typically take weeks to months to appear, so there’s time to consult with a healthcare provider before starting supplementation.

Want to Apply This Research?

  • If using a nutrition app, track daily green tea supplement intake (dose and frequency) alongside body weight and any digestive symptoms or unusual fatigue that might indicate liver stress. Note any changes in energy levels or appetite.
  • Instead of taking high-dose EGCG supplements, consider switching to drinking 2-3 cups of regular green tea daily, which provides EGCG in lower, safer amounts. Use the app to log your daily green tea consumption and track how you feel over time.
  • Set monthly reminders to check in on how you’re feeling while taking any green tea supplements. Track energy levels, digestion, and any unusual symptoms. If you have obesity and are taking supplements, schedule regular check-ups with your doctor to monitor liver health through blood tests, especially if taking high doses.

This research was conducted in mice and has not been confirmed in humans. It suggests a potential concern rather than proven harm. If you are overweight or obese and considering green tea supplements, especially at high doses, consult with your healthcare provider before starting, particularly if you have liver disease, take medications affecting the liver, or have a history of liver problems. This information is not a substitute for professional medical advice. Do not stop taking prescribed medications or make major dietary changes without consulting your doctor.