Taking berberine by mouth often gives people stomach cramps, constipation, or diarrhea because the body doesn’t absorb it well, so it sits in the gut and irritates it.
Evidence from Studies
Supporting (2)
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Absorption Kinetics of Berberine and Dihydroberberine and Their Impact on Glycemia: A Randomized, Controlled, Crossover Pilot Trial
The study didn’t ask people if they got stomach problems, but it showed that very little berberine gets into the blood after taking it by mouth — which means it’s likely sitting in the gut and irritating it, just like the claim says.
Berberine and health outcomes: An umbrella review
This study found that people who take berberine pills often get stomach problems like constipation and diarrhea, which matches what the claim says. So yes, the study supports it.
Contradicting (1)
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The study found that people taking berberine had less stomach trouble than those taking metformin, which is the opposite of what the claim says—so the claim is not supported.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.