Researchers tested 12 common ingredients found in weight loss supplements to see if they could damage human cells. They discovered that one ingredient called EGCG (found in green tea extract) caused significant damage to liver and intestinal cells in laboratory tests. The damage got worse when combined with certain medications. While the other 11 ingredients tested didn’t show problems on their own, scientists warn that most weight loss supplements contain multiple ingredients mixed together, and we don’t yet know if these combinations are safe. This study highlights why we need better safety testing for supplements before people take them.

The Quick Take

  • What they studied: Whether 12 common plant-based chemicals used in weight loss supplements could damage or kill human cells in laboratory conditions
  • Who participated: This was laboratory research using human liver and intestinal cancer cells grown in dishes—no actual people participated in the study
  • Key finding: EGCG, a compound from green tea, killed 18-25% of liver and intestinal cells tested. This damage increased when the cells were exposed to EGCG alongside a common antibiotic (rifampicin), suggesting dangerous interactions are possible
  • What it means for you: If you take weight loss supplements containing EGCG or green tea extract, especially alongside certain medications, there may be a risk of cell damage. However, this was lab research—actual effects in your body may differ. Talk to your doctor before using weight loss supplements, particularly if you take other medications

The Research Details

Scientists selected 12 active plant chemicals commonly found in weight loss supplements. They grew human liver and intestinal cells in laboratory dishes and exposed them to these chemicals to see what would happen. First, they used a standard test called the MTT assay to measure whether the chemicals killed the cells. Then, they used a sophisticated technique called 1H NMR spectroscopy—think of it as a special scanner that identifies different molecules—to see exactly what changes happened inside the cells when exposed to these chemicals.

For one particularly concerning chemical (EGCG), they also tested what happened when it was combined with rifampicin, an antibiotic that activates certain liver enzymes. This mimics what might happen in a real person’s body if they took the supplement while on this medication.

This approach allowed researchers to identify not just whether cells died, but how and why they died by looking at the chemical changes inside the cells.

Laboratory cell studies are an important first step in safety testing because they can quickly identify which substances might be dangerous before testing in animals or people. By using two different cell types (liver and intestinal), researchers could see if the chemicals affected different parts of your body differently. The 1H NMR analysis was particularly valuable because it revealed the specific ways cells were being damaged—showing problems with protein breakdown, energy production, and fat metabolism—which helps scientists understand the actual mechanism of harm.

This study has several strengths: it tested multiple chemicals systematically, used established laboratory methods, and looked at how drug interactions might increase danger. However, there are important limitations: laboratory cells behave differently than cells in a living body, cancer cells (which they used) may respond differently than normal healthy cells, and the study didn’t test what happens when multiple supplement ingredients are combined, which is how people actually use these products. The study also didn’t include human testing, so we can’t be certain these results apply to real people taking these supplements.

What the Results Show

Of the 12 plant chemicals tested, only EGCG (a compound from green tea) caused significant damage to cells. It reduced the survival of liver cells by about 25% and intestinal cells by about 19%. This was the only chemical that showed this level of toxicity in the initial screening.

When researchers added rifampicin (which activates liver enzymes that break down many substances), the damage from EGCG got worse. This is important because it suggests that if someone takes a weight loss supplement containing EGCG while also taking certain antibiotics or other medications that activate these same liver enzymes, the risk of cell damage could increase significantly.

The detailed analysis of what happened inside the cells showed that EGCG caused problems with protein breakdown, disrupted the cells’ energy production systems, and interfered with how cells process fats. These are serious disruptions to basic cellular functions.

The other 11 plant chemicals tested did not show significant toxicity when tested individually. However, the researchers emphasized that this doesn’t mean they’re completely safe—it just means they didn’t cause obvious cell death in this particular test. The researchers noted that most weight loss supplements contain multiple ingredients combined together, and we don’t know if these ingredients might interact with each other in harmful ways. Some combinations might be safer, while others might be more dangerous than any single ingredient alone.

Previous research has raised concerns about EGCG (green tea extract) safety, particularly at high doses and when combined with other substances. This study adds to that concern by showing specific cellular damage mechanisms. The finding that drug interactions can increase toxicity aligns with what scientists already know about how supplements can interact dangerously with medications. However, most previous studies on weight loss supplements have focused on a few ingredients—this study’s systematic testing of 12 common ingredients provides a broader safety picture than many earlier studies.

The biggest limitation is that this research used cancer cells in laboratory dishes, not normal healthy cells in a living body. Cancer cells may respond to toxins differently than your actual liver or intestinal cells would. Additionally, the study tested each ingredient separately; real supplements contain multiple ingredients that might interact in unpredictable ways. The study also didn’t determine safe doses—EGCG might be safe at very low doses even though it caused problems at the doses tested. Finally, laboratory results don’t always translate to what happens in actual human bodies, where stomach acid, digestion, and the immune system all affect how supplements work.

The Bottom Line

If you’re considering weight loss supplements: (1) Talk to your doctor first, especially if you take any medications—this is important because supplements can interact dangerously with drugs. (2) Be cautious with supplements containing green tea extract or EGCG, particularly if you take antibiotics or medications that affect liver function. (3) Avoid supplements with multiple herbal ingredients when possible, since we don’t know how these combinations affect your body. (4) Remember that ’natural’ doesn’t automatically mean safe—many natural substances can be toxic. Confidence level: Moderate—this is solid laboratory evidence, but human studies are needed to confirm these findings apply to real people.

This research is most relevant to: people considering weight loss supplements, especially those taking medications; people with liver disease or liver problems; anyone taking antibiotics or other medications that affect liver function; and healthcare providers advising patients about supplement safety. People who already take weight loss supplements shouldn’t panic, but should discuss their use with their doctor. This research is less immediately relevant to people who don’t take supplements or who only use well-established, regulated supplements with proven safety records.

If cell damage is occurring from these supplements, it would likely develop gradually over weeks to months of regular use, not immediately. However, severe reactions could happen faster in people taking supplements alongside certain medications. There’s no specific timeline for when you’d notice symptoms, which is why prevention through careful selection and medical consultation is important.

Want to Apply This Research?

  • If users take weight loss supplements, they should track: (1) which specific supplements and ingredients they’re taking, (2) any medications they’re on, (3) any symptoms like unusual fatigue, nausea, or digestive problems, and (4) liver function test results if their doctor orders them. This creates a clear record to share with healthcare providers.
  • Users should implement a ‘supplement safety check’ before starting any new weight loss supplement: verify the ingredient list, cross-check ingredients against this research, note any medications they take, and schedule a conversation with their doctor. The app could provide a simple checklist for this process and send reminders to discuss supplements with healthcare providers.
  • For long-term tracking, users should: (1) maintain an updated list of all supplements and medications in the app, (2) log any unusual symptoms or health changes, (3) set reminders for regular check-ins with their doctor about supplement use, and (4) track any lab work results related to liver function. This creates accountability and helps identify problems early.

This research describes laboratory findings in cells, not effects in actual human bodies. These results do not prove that weight loss supplements are dangerous for everyone, but they do suggest potential risks that warrant caution. If you currently take weight loss supplements, do not stop without consulting your doctor. If you’re considering starting a weight loss supplement, especially if you take any medications or have liver problems, consult with your healthcare provider before use. This article is for educational purposes and should not replace professional medical advice. Always discuss supplement use with your doctor, as individual risk factors vary significantly.