(CNN) - Yes, wine may protect our hearts when consumed in moderation -- defined as up to one drink per day for women, and up to two drinks per day for men, according to US dietary guidelines. Five ounces of wine is considered one drink.
Benefits of moderate alcohol consumption such as wine include a 30% reduction in the risk of heart attack compared to non-drinkers, a finding that has been repeated over 30 years and in various countries, according to Eric Rimm, a professor of epidemiology and nutrition who has been researching the effects of alcohol and chronic disease for decades at the Harvard T.H. Chan School of Public Health.
Additionally, alcohol consumption has been associated with a 30% to 40% reduction in the risk of Type 2 diabetes, compared to those who don't drink.
But more is not better. Excessive drinking can increase the risk of diseases, including heart disease, liver disease and certain cancers.
The pattern of drinking matters too, so saving up for a bottle of wine during a Saturday night dinner isn't quite the same as following a 'one-a-day' rule. "The maximum benefit appears to be when alcohol consumption is spread out over the course of a week, or at least every other day," said Rimm.
Isn't red wine better?
Red wine has been praised for its resveratrol content. Resveratrol is a polyphenol (plant chemical) found in the skin of red and purple grapes (less so in green). It has antioxidant properties and it also helps to make arteries more flexible, which lowers blood pressure. The amount of resveratrol in red wine is greater than in white and rosé wines, since grape skins are removed early during the production of white and rosé wines.
According to Rimm, a few studies suggest that consuming red wine may be more beneficial than drinking other alcoholic beverages. But, he adds, the amount of polyphenols in red wine is simply not enough to explain the benefits on health.
"If you are a woman, and you're drinking a glass of red wine each day, the amount of polyphenols is small compared to other sources of polyphenols in your diet, like blueberries, tea, apples and dark chocolate," he said.
For example, if you are consuming a glass of red wine daily and also consuming a healthy, Mediterranean-style diet, the polyphenols from red wine represent less than 5% of the total amount of polyphenols in your diet, according to Rimm.
By comparison, the amount of resveratrol given to mice in studies is equivalent to the amount that you would find in 8 to 10 bottles of red wine -- an amount considered unhealthy for humans.
What's more, research that has looked at resveratrol in humans isn't that promising. One recent study involving close to 800 men and women 65 years or older concluded that resveratrol consumed from dietary sources was not associated with longevity; nor did it decrease the incidence of heart disease or cancer.
"When you consume wine in moderation, most or all of the benefit is coming from the ethanol (alcohol) in wine," said Rimm. "Having a shot of spirits or a can of beer will give you equal benefit as wine."
Specifically, ethanol increases HDL, or "good" cholesterol, improves insulin sensitivity, and slows down the ability of blood to clot. It also helps to decrease inflammation inside of your arteries, according to Rimm.
"That being said, if you enjoy red wine, by all means, go for it," he said.
Compared to other alcoholic beverages, wine is a good choice for those watching their weight, as it has fewer carbs than beer. Unlike beer, most of the calories in wine come from alcohol. (An exception is a sweet wine like a dessert wine, where sugar contributes to the total calorie count). Wine also lacks the sugar calories from mixers used for cocktails and other drinks.
For example, though they are all considered one standard "drink" with equivalent amounts of alcohol, 12 ounces of regular beer (5% alcohol) may have about 150 calories, 5 ounces of wine (12% alcohol) may have about 120 calories, and 7 ounces of a rum (40% alcohol) plus cola may have about 155 calories according to US Dietary Guidelines.
But the higher the alcohol content, the more calories in wine. For example, a red Zinfandel with 15% alcohol is going to have more calories than a Riesling with 8% alcohol. Wines from warm climates often have 14% to 15% alcohol, according to Stephen Mutkoski, professor emeritus of wine education and management at the school of hotel administration at Cornell University.
According to Dwayne Bershaw, who teaches wine making classes in the department of food science at Cornell, most whites and rosés are lower in alcohol than most reds, so they have fewer calories compared to red wines.
And though many whites and rosés do contain a small amount of residual sugar, left over when not all of the sugar in grapes is used up to produce alcohol, the amount is not significant enough to outweigh the greater calorie difference from variations in alcohol content among reds, whites and rosés. "A half a percent of residual sugar will add 4 or 5 calories ... it's not that much," said Bershaw.
Bershaw said low calorie wine seems to be a trending item in some circles; this is simply wine with no residual sugar and a lower percent alcohol by volume (%ABV).
A note of caution
Alcohol consumption increases the risk of cancer. For men, drinking a couple glasses of alcohol a day was associated with 26% increased risk of cancers such as liver, colon and esophagus. Women with a high risk of breast cancer (PDF) should be cautious when consuming wine.
"For someone who is at high risk for breast cancer, due to a strong family history or other risk factors, I wouldn't necessarily tell that woman to stop drinking," said Rimm, "but I would say if you are at high risk, drink a little less."
Rimm said while it's true that women who drink a drink per day have a 10% increased risk of breast cancer, it is nowhere near the 30% reduction in risk of heart disease achieved by consuming alcohol in moderation.
But if you are pregnant, nursing or have other health or medical issues where alcohol consumption is not advised, you should avoid alcohol completely. And drinking wine isn't more important than eating a nutritious diet, engaging in regular exercise, and avoiding smoking.
"Wine should be enjoyed along with other aspects of a healthy lifestyle," said Rimm.
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