August 11, 2013

The wine when it is red

An NZ wine maker has produced wines with high levels of the chemical resveratrol. In Stuff’s story

“We can’t say that alcohol is healthy, but we can say resveratrol is,” co-director Kathleen Corsbie said.

Actually, the evidence for health benefits of lowish levels of alcohol consumption compared to none is much, much stronger than the evidence for any benefit of resveratrol, because resveratrol is almost unstudied in human disease.

Stuff’s story is well done, with useful background and expert commentary, eg,

The French, who eat fatty foods such as cheese and pate and also drink a lot of red wine, are the most commonly used example, Holt said.

“They have one of the lower rates of heart disease.”

But saying the wine will protect drinkers against cancer and other diseases is an exaggeration, Holt said.

It’s a respectable, though far from proven, hypothesis that resveratrol has some part in lower French rates of heart disease, but as he points out, that’s not true for cancer (the French actually don’t have low cancer rates compared to the rest of Europe, for example).

If you go to the Southern Wines website, you find more detail about their claim

The human body uses many complex biochemical pathways and reactions to function; but these reactions result in waste products such as free radicals (molecular compounds that contain an extra unpaired electron). These free radicals are the body’s terrorists and cause biological havoc which helps contribute to our degenerative ongoing diseases such as cancer, dementia, diabetes, vascular disease (heart attack and stroke), macular degeneration (most common cause of blindness in people over 65) and arthritis.

So, they are claiming a reduction in a large collection of aging-related diseases, based on anti-oxidant effects.  In this context it’s useful to note that while there have been no large studies of resveratrol in humans, there have been large randomised trials of anti-oxidant vitamins (beta-carotene, vitamin C, vitamin E) that have, by and large, not found benefits.  For cancer, they have sometimes even found harm, perhaps because free radicals are an important part of the immune system’s armory.

This is the sort of case that makes setting advertising standards tricky.  There’s no question that resveratrol is an antioxidant.  Presumably the manufacturer knows how much resveratrol is in their wine, though saying it’s “40 times higher” as they do is harder to defend given the more-than-20-fold range in resveratrol concentrations in regular red wines (PDF).  There’s moderate evidence that resveratrol is good for lab animals. In humans, almost nothing is known directly — there’s slight evidence for reductions in some heart disease risk factors — but there’s strong evidence that some other antioxidants don’t have large benefits.

Southern Wines co-director is quoted as saying

“One glass of our Balancing Act wine is equivalent to consuming the resveratrol contained in around 40 glasses of normal wine, so why would you drink anything else?”

As with chocolate, the StatsChat advice would be that if you are drinking wine primarily for the health benefit, you’re doing it wrong.


Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »