Does wine help you live longer?

A glass of wine a day keeps the doctor away — or does it? From the French to the Sardinians, cultures in which people tend to drink wine daily have famously low rates of heart disease and lead longer lives, on average, than Americans do. But does drinking wine actually help you live longer? 

The belief that a daily glass of vino accounts for the health and longevity of those living in wine-centered food cultures goes back to a 1992 paper that called this phenomenon "the French paradox," pointing to wine as an explanation. Today, however, our understanding of wine and its health effects is more nuanced. There is some evidence that drinking wine protects against certain health conditions, but the evidence that it leads to a longer life is thin, said Adrian Baranchuk, a professor of cardiology at Queen's University School of Medicine in Ontario. "Studies of alcohol are limited in their design," he said. 

For starters, much of the research on red wine and mortality don't focus on wine itself. Rather, the research investigates the health effects of polyphenols, a type of antioxidant in wine. These chemicals shield cells from damage caused by unstable molecules called free radicals, which are associated with heart disease and cancer risk, and have been proposed as one potential reason for wine's purportedly positive health effects. 

Related: Is champagne stronger than non-bubbly alcoholic drinks?

When an international team of researchers pooled the results of 22 studies and analyzed them as a whole, they found that people who consumed 800 milligrams of flavonoids —​​ one type of polyphenol found in wine, as well as most fruits and vegetables — per day had a 24% lower risk of death within the study period compared with those who consumed no flavonoids. Their 2017 results, published in the American Journal of Epidemiology, found that this difference dropped by 6% for every 100-milligram decrease in flavonoid consumption. (For example, people who consumed only 700 milligrams had an 18% lower risk of death.)

The problem is that 800 milligrams is a lot of flavonoids. "You'd have to drink gallons and gallons of wine to benefit," said Bill Klein, associate director of the National Cancer Institute's (NCI) Behavioral Research Program. Klein studies behavioral risk factors for cancer and has published papers on the health effects of alcohol. In one study, published in 2001 in The Journal of Nutrition, participants who consumed 750 milliliters of wine (about four 6-ounce glasses) ingested only about 24 milligrams of dietary flavonoids. Based on that result, to get 800 milligrams per day, you'd need to drink 133 glasses of wine. Plus, there are other, potentially healthier sources of polyphenols: The Journal of Nutrition study found that participants ingested more polyphenols when eating onions.

There is some evidence that drinking moderate amounts of wine is heart-healthy, Baranchuk said. Around two glasses, five days per week for men or one glass, five days per week for women — the guidelines recommended by the American Heart Association — seem to raise good cholesterol, reduce the risk of blood clots, help to prevent artery damage caused by bad cholesterol, and improve the function of the layer of cells that line the blood vessels compared with people who don't drink at all, he said. 

Part of that benefit to cardiovascular health may be due to the effects of polyphenols, he wrote in a 2017 review on the subject published in the journal Circulation. But these benefits are more likely attributable to ethanol, which is present in all alcoholic beverages, Baranchuk said. An analysis pooling the results of 42 studies found that 30 milligrams of ethanol per day (around two drinks) increases HDL cholesterol (the good kind) and apolipoprotein AI, a main protein found in HDL. However, "all those benefits get first attenuated and then reversed if you drink above the recommended guidelines," Baranchuk said.

Is a glass of wine a day bad for you?

The problem is that heart disease isn't the only factor in health and longevity. And the alcohol in wine may negate any benefit from polyphenols. "Unfortunately, there isn't much evidence that alcohol provides a protective effect," Klein said. "There's much more evidence that it's a risk factor."

While evidence that wine lowers mortality within a given time period is thin, there's very strong evidence linking any amount of alcohol to breast cancer, liver cancer, prostate cancer and cirrhosis, among other diseases. That might be because alcohol changes the way bodies process estrogen, leading levels of this hormone to rise, Klein said. Another potential explanation: Acetaldehyde, a byproduct of alcohol's breakdown in the body, has been shown to cause DNA damage.

In the end, if you aren't in the habit of drinking a glass of wine a day, or if you just prefer beer, there's no reason to take up the habit for your heart health. Instead, try yoga or meditation, Baranchuk said, as "they have way more solid evidence than what alcohol has."

If you already enjoy a glass of wine most nights, and are unsure about your habit's effects on your health, check in with your doctor — particularly if you have any underlying health conditions. But for most people who drink moderately, there's no need to stop, Baranchuk said. "We balance pros and cons of risks all the time," he said. "For example, let's say your office is 25 minutes from your home. Driving those 25 minutes increases mortality 0.005%. Are you going to say, 'I'm not going to go to work anymore even though I love my job and it brings in income?' You say, 'I accept this risk.'"

This article is for informational purposes only, and is not meant to offer medical advice.

Originally published on Live Science.