Alcohol is the Dr. Jekyll and Mr. Hyde of the medical world: Drinking too much causes serious problems, while drinking a little may help many people's health.
How many drinks provide just the benefits and not the harm? It depends on whether a person is most at risk of heart disease, diabetes or breast cancer. But there is one bottom line: Five or six drinks only on Saturday night will provide no benefits, while a drink or two a night might.
So concludes an exhaustive new analysis by the National Institutes of Health that sorts out a plethora of sometimes conflicting research on alcohol's effects.
The review was prompted by cardiologists' complaints that patients suddenly were asking if they should start imbibing, and how much. Other research is overturning the dogma that people at risk of diabetes should abstain; still more links even light drinking to breast cancer.
Adding confusion, people are vulnerable to more than one disease as they age. A 50-year-old woman with breast cancer in the family might get very different advice on alcohol than one who's pre-diabetic with high cholesterol.
Hence NIH's review.
"We are not encouraging anybody to start drinking," stresses Lorraine Gunzerath of the NIH's National Institute on Alcohol Abuse and Alcohol, who led the analysis published last month in the journal Alcoholism: Clinical & Experimental Research.
After all, alcoholism remains a major health problem, and people with liver disease may not tolerate even moderate drinking.
Instead, the report, aimed at people who already drink some, concludes that to get alcohol's potential health benefits, how much those people can consume must be customized by their age, gender and overall medical history.
For many of these diseases, "If you do drink moderately now, fear ... is not a reason to stop," explains Gunzerath. "Some people have said, `Should I stop now because there's diabetes in my family?' Well, if you're a moderate drinker, there's some protection."
As population-wide advice, consuming two drinks a day for men and one a day for women is linked to lower mortality and unlikely to harm, the review found. Men shouldn't exceed four drinks on any day, and women three _ bingeing is simply bad.
But NIH's disease-by-disease findings provide better details:
_Studies consistently show that in people 40 or older, consuming one to four drinks daily significantly reduces the risk of heart disease, the nation's leading killer. In contrast, five or more drinks daily markedly increases heart risk.
However, frequency seems key. Consuming smaller amounts several times a week _ one or two daily or every other day _ is most heart-protective. It apparently takes low, regular alcohol exposure to help raise levels of the body's so-called good cholesterol, the HDL type, and to thin blood.
_The alcohol-breast cancer link remains controversial. Some studies suggest a small increase in risk, that roughly 9 in 100 nondrinkers may get breast cancer by age 80 compared with 10 in 100 women who consume two drinks a day. Per person, that's a tiny risk.
But women whose mothers or sisters had breast cancer, or those taking post-menopausal estrogen replacement, are at greater risk from alcohol. Those women, Gunzerath says, must weigh the fear of breast cancer against their risk of heart disease in deciding whether to avoid alcohol.
_One to two drinks a day several days per week seems to lower the risk of Type 2 diabetes, a disease rising at epidemic proportions.
Low levels of alcohol apparently help the body use insulin to process blood sugar better. The benefit was seen among the overweight and those with "metabolic syndrome," a cluster of pre-diabetic weight-related symptoms that include high blood pressure and poor cholesterol.
_There's no known safe level of alcohol consumption during pregnancy, but what about while breast-feeding? Nursing mothers who want an occasional drink should consume it several hours before the next feeding, enough time to metabolize the alcohol so little reaches the infant. And contrary to folklore, alcohol does not aid lactation but temporarily decreases milk production.
How much is a drink a day? Five ounces of wine, 12 ounces of beer or 1.5 ounces of distilled spirits. To help people add that up, consumer groups are pushing for alcohol containers to list serving sizes and the moderate-drinking advice; the Alcohol and Tobacco Tax and Trade Bureau hasn't yet responded.
Lauran Neergaard covers health and medical issues for The Associated Press in Washington.