Saturday, May 29, 2010

Does Red Wine Protect the Cardiovascular System?

The 'French paradox' rears its ugly head again. The reasoning goes something like this: French people eat more saturated animal fat than any other affluent nation, and have the second-lowest rate of coronary heart disease (only after Japan, which has a much higher stroke rate than France). French people drink red wine. Therefore, red wine must be protecting them against the artery-clogging yogurt, beef and butter.

The latest study to fall into this myth was published in the AJCN recently (1). Investigators showed that 1/3 bottle of red wine per day for 21 days increased blood flow in forearm vessels of healthy volunteers, which they interpreted as "enhanced vascular endothelial function"*. The novel finding in this paper is that red wine consumption increases the migration of certain cells into blood vessels that are thought to maintain and repair the vessels. There were no control groups for comparison, neither abstainers nor a group drinking a different type of alcohol.

The investigators then went on to speculate that the various antioxidant polyphenols in red wine, such as the trendy molecule resveratrol, could be involved. Even though you have to give animals 500 bottles' worth of resveratrol per day to see any effect. But there's another little problem with this hypothesis...

Ethanol-- plain old alcohol. You could drink a 40 oz bottle of malt liquor every night and it would probably do the exact same thing.

No matter what the source, alcohol consumption is associated with a lower risk of cardiovascular disease out to about 3-4 drinks per day, after which the risk goes back up (2, 3)**. The association is not trivial-- up to a 62% lower risk associated with alcohol use. Controlled trials have shown that alcohol, regardless of the source, increases HDL cholesterol and reduces the tendency to clot (4).

Should we all start downing three drinks a day? Not so fast. Although alcohol does probably decrease heart attack risk, the effect on total mortality is equivocal. That's because it increases the risk of cancers and accidents. Alcohol is a drug, and my opinion is that like all drugs, overall it will not benefit the health of a person with an otherwise good diet and lifestyle. That being said, it's enjoyable, so I have no problem with drinking it in moderation. Just don't think you're doing it for your health.

So does red wine decrease the risk of having a heart attack? Yes, just as effectively as malt liquor. It's not the antioxidants and resveratrol, it's the ethanol. The reason the French avoid heart attacks is not because of some fancy compound in their wine that protects them from a high saturated fat intake. It's because they have preserved their diet traditions to a greater degree than most industrialized nations.

I do think it's interesting to speculate about why alcohol (probably) reduces heart attack risk. As far as I know, the mechanism is unknown. Could it be because it relaxes us? I'm going to ponder that over a glass of whiskey...


* It may well represent an improvement of endothelial function, but that's an assumption on the part of the investigators. It belongs in the discussion section, if anywhere, and not in the results section.

** The first study is really interesting. For once, I see no evidence of "healthy user bias". Rates of healthy behaviors were virtually identical across quintiles of alcohol intake. This gives me a much higher degree of confidence in the results.

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