From Resveratrol Partners’ press release:
“Once mega-doses of resveratrol (more than 500 mg) began to be employed, side effects like anemia, Achilles heel tendonitis, anxiety reactions, numbness in the fingers, began to be reported,” says Bill Sardi, spokesperson for Longevinex® (long-jev-in-ex), a leading brand resveratrol dietary supplement. “This is probably because resveratrol is a copper chelator and excessive chelation will impair the availability of copper which is needed for collagen formation and nerve regeneration,” he says. “Resveratrol is relatively safe, but not absolutely safe at any dosage. There are drawbacks,” he adds.
Some online suppliers of resveratrol pills, who have no medical training, irresponsibly recommend up to 7000 milligrams of resveratrol a day. There is also evidence that supra-high dose resveratrol inhibits the absorption of folic acid (vitamin B9), an essential nutrient needed for DNA repair. [European Journal Nutrition 46: 329-36, 2007] High doses have not been tested in humans for long-term use.