I tried resveratrol from Costco. I was tolerating ok for first few days then developed severe abdominal cramping and vomiting. There was an article published in NY Times that sent large number of supplements to independent lab for testing. Not surprisingly, quality was major issue. Amount of active ingredient can vary widely and numerous unwanted substances found. In my opinion, CFS / ME population tends to be "desperate" and may actually suffer from trying too many supplements. In many cases, there is very little science to warrant their use.