As the alcohol-loving Nick Charles said in "The Thin Man," "The problem with putting two and two together is that sometimes you get four, and sometimes you get 22."

And that's precisely what researchers found when they decided to look into how much wine people actually drink when they have "a glass or two."

A serving of wine is, according to the National Institute of Alcohol Abuse and Alcoholism, five ounces. With wine glasses commonly ranging from 12-24 ounces, it's easy to pour yourself two servings at once.

And a new study found glass size isn't the only thing that influences how much you pour: If you're holding the glass in your hand, you pour more; if it's sitting on a table, less; and you pour more white than red wine into a clear glass.

But it pays to get it right. The risks of excessive drinking (three to five glasses of wine a day) include dementia and Alzheimer's, liver disease, cardiovascular problems, high blood pressure, pancreatitis and breast cancer.

The benefits of drinking just one 5-ounce glass a day for women and two a day for men? Fewer heart attacks and strokes, less precancerous skin lesions and a lower risk of prostate cancer, osteoporosis, Type 1 diabetes and Alzheimer's (by 23 percent).

Do white wine and Champagne confer the same benefits as red? Possibly, since it's the alcohol in moderation that's protective. FYI: Think resveratrol in red wine is what's good for you? You'd have to drink 100 bottles to take in a beneficial amount!

© 2013 Michael Roizen, M.D. and Mehmet Oz, M.D.
Distributed by King Features Syndicate, Inc.