It's also important to know, that in the case of resveratrol, you can't just look up the literature and get an understanding of how effective it is. There was a fairly large scandal in the field around 2012 which was closely followed by the watchdog site retractionwatch. Now while one researcher publishing fraudulent data does not mean the entire field of research is wrong, it does mean each and every paper needs to be carefully scrutinized to see how heavily it relied on background assumptions made by papers that were later shown to be false. In this case in particular, with the researcher publishing over a hundred of papers a year some highly sited that left a pretty big impact. I can't say for sure how strongly this was felt in the longevity research community, but in the field of cardioprotection, which I was in at the time, it was a big deal.

Even a fairly recent review, which is by in large well and fairly balanced regarding the literature still cites papers from this researcher' publications and doesn't mention that aspect of the field's history at all.