12/12/2011 02:09 pm ET Updated Feb 11, 2012

Mixed Data for Those Who Cheer Wine, Liquor (For Holiday Imbibing)

The next time you're toasting your health for the holidays, should you raise a glass of water instead of a finely crafted vintage? It may be superstitious bad luck, but the science on the merits and risks of wine have become increasingly murky the more we learn.

Red wine, seen by some simply as a small guilty pleasure or indulgence, had received virtual health food status. It's been lauded for its antioxidants; potential to prevent heart disease by raising "good" cholesterol; and reducing the formation of clots. But if you listened carefully beyond all the cork-popping, physicians, as well as the American Heart Association and National Heart, Lung and Blood Institute, would point out that this was only good news for those who drink moderately; these sources didn't recommend that anyone start drinking just to prevent heart disease.

Now, red wine is looking less rosy for its touted health attributes. Recent studies offer mixed results. The good news: Resveratrol, a chemical found in trace amounts in red wine, gets some backing for its hype, based on a study published this month. Tests on mice showed the substance seems to protect against obesity and diabetes; it boosted the test animals' endurance; and it extended their lives. It's speculated to be the secret ingredient that allows the French to eat in decadent fashion but to still live as long as everyone else. A new study, which gave 11 obese men 150 milligrams of resveratrol or placebo for 30 days, indicated it worked as well in humans as in mice. Metabolism improved, the accumulation of fat in the liver was cut, blood pressure, blood sugar and inflammation reduced, and muscles were more efficient.

That dosage level, however, is available only through supplements. You'd have to drink two gallons of red wine daily to consume the equivalent -- and even the most glowing, positive scientific reviews of libation clearly frown on such excess.

In the meantime, two other studies, one from Harvard Medical School and one from the United Kingdom's Million Women study, both found that even modest consumption of wine increases cancer risk for women.

The Harvard research, published in the Journal of the American Medical Association this month, looked at 105,986 women enrolled in the Nurses' Health Study, which followed women from 1980 to 2008. Even a single drink a day -- which women are allowed under the Dietary Guidelines for Americans (two a day for men) -- can lead to increased risk. Those in the study who reported drinking 5 to 10 grams of alcohol daily -- about three to six glasses of wine per week -- were 15 percent more likely than women who do not drink to be diagnosed with breast cancer. It didn't matter what variety of alcohol, whether a fine red wine, Kentucky bourbon or beer. Keep in mind, however, that the actual number of cancer cases were still relatively small, though statistically significant.

The 2009 British study, looking at nearly 1.3 million middle-aged women, found similar results. The study, the largest ever to examine alcohol and cancer in women, also indicated that even a single drink a day increases the risk of cancer of the breast, liver and rectum. For every additional drink regularly consumed per day, the study projects the increase in incidence of breast cancer in developed countries is about 11 cases per 1,000 women up to age 75.

To imbibe or not? That depends on individuals and their medical history.

There is something of a gender gap to consider. More risks have been associated with moderate drinking for women than for men. But, even among men, context counts. A 2009 Japanese study found that light or moderate alcohol consumption could reduce risks of coronary heart disease and cardiovascular disease. These effects were enhanced by social support.

So, that might be a reason to pair a wine with your holiday dinner, or a champagne toast at midnight with loved ones. It doesn't work as well as an excuse to hit the bar with buddies for boozing bouts: The same study still found that heavy alcohol consumption is linked to increased risk of stroke.

The choice to drink moderately will depend on who you are. A fit 25-year-old marathon runner with no family history or cardiac disease and no additional risk factors who doesn't drink now probably won't gain anything by joining a wine of the month club. Meanwhile, a man well into his AARP membership with little risk of cancer and some concerns about heart disease, may as well keep his nightly glass of wine with dinner if that's his lifelong custom.

Women with reason for concern about breast cancer might wish to stick to the sparkling cider on special occasions. Women at some risk of cardiovascular disease, but at remarkably low risk of cancer, might make a different choice.

The pattern of your drinking also matters. Light intake on a steady basis can be reasonable for many people. But don't save up a week's worth of drinks and down them all on Saturday night or guzzle the whole bottle of wine you've saved for a special occasion. That would be binge drinking, which is never considered healthy.

Like everything we consume, portion size matters. Most wine glasses hold multiple servings -- so filling that fat goblet to the brim doesn't tally as one serving; it's more like three. A single serving of wine is about five ounces; a bottle typically holds five servings. A standard beer is 12 ounces per serving, a little less for more alcoholic brews. For 80 proof spirits, 1.5 ounces is a serving, so watch those holiday cocktails carefully. Fortified wines -- those postprandial sherries and ports -- should be kept to 304 ounces, 2 to 3 ounces for cordials, liqueurs and apertifs. There are handy calculators for cocktail content, drink size and calories here.

As alcohol has been swigged throughout human history, complete and universal abstinence has been rare. Even cave dwellers had stone beer jugs. So, as you arrange your holiday plate -- hopefully heaping on the vegetables and lean turkey breast alongside judicious amounts of mouth-watering stuffing -- think carefully about those beverage choices. Alcohol is calorie-dense. Paired with food, that alcohol brings out more than just subtleties in the wine's flavor -- it brings on a tendency to eat more, too. Second helpings? Well, then, stick to water with dinner. And of course, because one of every three car-crash deaths is alcohol related, please don't drink and drive.