February 11, 2015

Red wine good for your liver?

From the UK press, rather than NZ, but by Twitter request

  • Independent Drinking red wine could help overweight people burn fat better, scientists claim
  • DailyMail How a glass of red wine can be slimming
  • Telegraph: Drinking wine or red grape juice ‘can help burn fat’

From the Oregon State University press release:

“We didn’t find, and we didn’t expect to, that these compounds would improve body weight,”

So, the headlines are misleading at best.

Previous research, about a year ago, showed that feeding grape extracts to mice reduced fat accumalation in the liver. The new research looked at human cells grown in a lab: cells from fat and liver cells, and showed that these extracts made them synthesise less fat, providing some support for the idea that this might work in people as well. The doses are not insane — about a cup and a half of grapes per day.

There are some important reservations (aren’t there always?)

First, the research looked at extracts from muscadine grapes, not ordinary wine or table grapes. The chemical being studied, ellagic acid, isn’t found at any significant level in the type of grapes grown in NZ (or, probably , the UK). There is some ellagic acid in ordinary wine, but only from oak aging and cork corks, so not that much in NZ wines.  There’s nothing in the research about whether you could get relevant amounts of ellagic acid from wine.

Second, while ellagic acid may reduce fat accumulation in the liver, alcohol tends to increase it. The mice and cell cultures got lots of ellagic acid and no alcohol; lots of alcohol and moderate amounts of ellagic acid might not be any good.

Finally, and more technically, the press release speculates about the biochemical mechanism

Shay hypothesizes that the ellagic acid and other chemicals bind to these PPAR-alpha and PPAR-gamma nuclear hormone receptors, causing them to switch on the genes that trigger the metabolism of dietary fat and glucose. Commonly prescribed drugs for lowering blood sugar and triglycerides act in this way, Shay said.

“Commonly prescribed” is pushing it. The best-known PPAR-gamma ligand drug was rosiglitazone (Avandia), famous for having been recalled from market.  There are still drugs that target PPAR-alpha and PPAR-gamma, but they aren’t that widely used. If this is how ellagic acid works, I’d want to see careful human trials before trusting it — it could have nasty side effects.

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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 »

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