But that explanation has never been completely convincing, either to scientists or to laymen. It fails to explain fully why when men and women of the same size have identical drinks, women tend to get tipsy faster. Scientists have long wondered if there might not be a more compelling biochemical explanation for the drinking puzzle. Last week a team of Italian and American researchers offered what looks to be the answer: women have far smaller quantities of the protective enzyme alcohol dehydrogenase that breaks down alcohol in the stomach.
The enzyme is crucial in curbing intoxication. When a shot of vodka or a beer is swallowed, it travels to the stomach and then to the intestine, where it passes through the organ's wall into the bloodstream. Once there it circulates to the brain, where it finally exerts its inebriating effect. Alcohol dehydrogenase breaks down spirits in the stomach, reducing the amount of pure alcohol that enters the bloodstream about 20%; the rest is eventually metabolized by similar enzymes in the liver.
According to a study of 43 men and women reported in the New England Journal of Medicine, women possess significantly less of the active stomach enzyme. The result is that they absorb about 30% more alcohol into their bloodstreams than men do -- and voila! Taking into account the weight difference between the average man and woman, a mere 2 oz. of liquor has about the same effect on a woman as 4 oz. would on a man. Just why there is such a discrepancy remains a mystery.
The researchers made another startling discovery: men who are alcoholics have about half as much alcohol dehydrogenase as their healthy counterparts, but alcoholic women show almost no enzyme activity at all. The falloff may result from alcohol's injuring the stomach wall, where the enzyme is manufactured. Whatever the cause, "alcoholic women appear to lose all gastric protection," says Dr. Charles Lieber of Mount Sinai School of Medicine in New York City, who collaborated on the study with Dr. Mario Frezza of the University School of Medicine in Trieste, Italy. "For them to drink alcohol is the same as shooting it up directly into their veins."
Experts say this lack of protection may help explain why alcoholic women suffer more heavily from liver damage than do alcoholic men. Women may be more vulnerable to cirrhosis for another reason, says Dr. Jack Mendelson of Harvard Medical School. Studies by a team at Johns Hopkins indicate that women's livers metabolize alcohol faster than men's and thus may be more subject to wear and tear. Mendelson speculates that in female alcoholics a lack of gastric enzyme means that "their livers have to work even harder," accelerating the destruction.
The study supports the common notion that it is better to drink on a full stomach than on an empty one. Booze takes longer to pass through a well-fed stomach, allowing more time for the enzyme to digest the alcohol. Fasting does the opposite: it speeds the stomach's emptying. Taking the popular ulcer medication cimetidine (Tagamet) also appears to interfere with alcohol metabolism by suppressing enzyme activity.
The new findings intensify earlier warnings that drinking holds special risks for women. Labels on liquor bottles and placards in some restaurants and bars already caution that for a pregnant woman to drink can cause serious birth defects in her baby, including physical deformities and mental retardation. The new research indicates that women who are not pregnant need to take heed as well.
"For social drinkers," observes Dr. Lieber, "what is moderate drinking for men is not moderate drinking for women. To reach a given blood-alcohol level, women need to drink only about half of what men drink." Women should be especially aware of their greater sensitivity if they are driving or performing any other task that requires close attention or fine coordination.
What the study emphatically does not suggest is that men now have a green light to drink. Stresses Harvard's Mendelson: "This should not be taken in any sexist way -- that is, 'Men can handle it, women can't.' Men can tolerate alcohol in slightly higher doses than women, but that's about it. There are other factors that might mitigate this difference, for example, how one behaves when drunk." In other words, men may be better enzyme makers, but they are not better drinkers.
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CREDIT: TIME Chart by Joe Lertola
Source: Dr. Charles LieberCAPTION: NO CAPTION