At the very beginning of this blog in 2009, I wrote about a compound called resveratrol. I concluded at that time that it was “promising but unproven.” I subsequently reported on a scandal in which a key researcher studying this compound had a large number of papers retracted due to fraud. And last November, I passed along the conclusions of a couple of reviews of the existing evidence to that point concerning resveratrol. The conclusions had changed little from my first report. Resveratrol shows promising properties in the lab and in animal models, but it has not yet been shown to be an effective treatment or preventative health agent in humans or, of course, in pets.
A new study has recently been published which adds to the existing evidence that intake of resveratrol from natural food sources, notably red wine and chocolate, is not associated with a reduced risk of any disease.
Semba RD. Resveratrol in red wine, chocolate, grapes not associated with improved health. JAMA Intern Med. Published online May 12, 2014. doi:10.1001/jamainternmed.2014.1582
This study followed nearly 800 people for nine years and measured the amount of resveratrol metabolites excreted in the urine, which represented how much resveratrol was being consumed in the diet. Though the study had some methodological limitations (it was an observational study, not a clinical trial, so there was no randomization, and it’s not clear from the abstract if there was any blinding for the analysis), it is a piece of data to add to our current understanding. The conclusion, unfortunately, was that
The antioxidant resveratrol found in red wine, chocolate and grapes was not associated with longevity or the incidence of cardiovascular disease, cancer and inflammation.
This does not, of course, mean that we can definitively say dietary resveratrol is of no value or that higher doses provided as a supplement might not have beneficial effects, There iss till some weak clinical trial evidence to suggest some benefits from supplementation might be beneficial in some cases. The bottom line here is that we don’t know for certain, but the compound is looking less promising the more we study it.
This is less surprising than it might once have been since the theoretical reason to expect a benefit from resveratrol is its antioxidant effects. While “antioxidant” is something of a magic word in alternative medicine, science-based medicine has been soberly and carefully investigating the idea that such compounds might have a wide variety of beneficial health effects. As I discussed earlier this year, however, the evidence is becoming more and more convincing that antioxidants have fewer benefits than once supposed and, as should be expected with all therapies that do anything at all, they come with risks.
A recent animal model study actually found evidence suggesting free radicals might in some cases be protective and that the reason they increase with age may be because they are part of the body’s attempt to fight the effects of aging rather than the cause of it. This is, of course, only one lab study, but it is a piece in a growing body of information which suggests that the hype and reality about antioxidants like resveratrol may differ quite a bit. Enthusiastic recommendations for antioxidant supplement products are clearly not warranted, and justifying therapies, including herbal and other alternative treatments, as useful by arguing they provide antioxidant effects is a weak and unconvincing rationale.