Resveratrol side effects

The main resveratrol side effect we can verify is gastrointestinal upset at high doses. In a 29-day study of 40 healthy volunteers, resveratrol at 0.5 to 5 g a day was called safe, but the 2.5 g and 5 g doses caused mild to moderate gastrointestinal symptoms. Our label's directions work out to about 600 mg of trans-resveratrol a day.

What studies report

Gut symptoms at high doses. In the 2010 repeat-dose study, 40 healthy volunteers took 0.5, 1.0, 2.5 or 5.0 g a day for 29 days. The authors reported it was safe but attributed mild to moderate gastrointestinal symptoms to the two highest doses. The abstract does not name the symptoms, so we do not either (that includes diarrhea, which people ask about; we cannot confirm or rule it out from the abstract).

Effects on medicine-processing enzymes. In a 2010 study, 42 healthy adults took 1,000 mg once a day for 4 weeks. Measures of several liver enzymes that process medicines (CYP3A4, CYP2D6 and CYP2C9) went down, and another (CYP1A2) went up. The authors wrote that doses like this could increase adverse drug reactions or alter how well a drug works. The study tested no prescription drug; the full discussion is on resveratrol and medications.

Everything else. We did not find, in the abstracts we read, a report of dizziness or sleepiness. Abstracts do not list everything, so that is a gap in what we checked, not proof there is none. Kidney and liver questions are on who should not take resveratrol.

What this means for our label

Electric Tiger Resveratrol is directed at one capsule twice a day. By the label's 50% trans-resveratrol figure (arithmetic; no certificate of analysis on file) that is about 600 mg a day, between the lowest tier in the 29-day study (0.5 g) and the 1 g dose in the enzyme study. We know of no study at exactly that dose or in exactly this extract, so we cannot say what side-effect rate to expect. Do not exceed the recommended dose. Label details are on the product page.

Questions people ask

What are the side effects of resveratrol?

Verified: gastrointestinal symptoms at 2.5 g and 5 g a day in healthy volunteers over 29 days, and changes in medicine-processing enzymes at 1 g a day over 4 weeks.

What is the downside of resveratrol?

Beyond side effects: the unchanged compound is poorly retained in blood (only trace amounts in a 6-person study), and trial evidence for benefits is mixed. See what is resveratrol.

Does resveratrol cause diarrhea?

The gut symptoms in the 29-day study were described as mild to moderate; the abstract does not say which. We cannot confirm diarrhea specifically.

Can resveratrol cause dizziness or make you sleepy?

We found no such report in the studies we read. If you feel either after taking a capsule, stop and speak to a healthcare professional.

Are there long-term side effects?

The longest safety data we could verify is 29 days at 0.5 to 5 g a day. We cannot speak to longer use.

When to talk to a doctor

Ask a doctor or pharmacist before taking resveratrol if you take prescription medication, have a health condition, or notice anything unusual after starting it.