Moderate drinking is difficult to define because it means different
things to different people. The term is often confused with "social
drinking," which refers to drinking patterns that are accepted by the
society in which they occur. However, social drinking is not necessarily
free of problems. Moderate drinking may be defined as drinking that
does not generally cause problems, either for the drinker or for
society. Since there are clearly both benefits and risks associated with
lower levels of drinking, this Alcohol Alert will explore potentially
positive and adverse effects of "moderate" drinking.
It would be useful if the above definition of moderate
drinking were bolstered by numerical estimates of "safe" drinking
limits. However, the usefulness of quantitative definitions of moderate
drinking is compromised by the likelihood that a given dose of alcohol
may affect different people differently. Adding further complexity, the
pattern of drinking is also an important determinant of alcohol-related
consequences. Thus, while epidemiologic data are often collected in
terms of the "average number of drinks per week," one drink taken each
day may have different consequences than seven drinks taken on a
Saturday night (1).
Despite the complexity, numerical definitions of
moderate drinking do exist. For example, guidelines put forth jointly by
the U.S. Department of Agriculture and the U.S. Department of Health
and Human Services (2) define moderate drinking as no more than one
drink a day for most women, and no more than two drinks a day for most
men. A standard drink is generally considered to be 12 ounces of beer, 5
ounces of wine, or 1.5 ounces of 80-proof distilled spirits. Each of
these drinks contains roughly the same amount of absolute
alcohol--approximately 0.5 ounce or 12 grams (3).
These guidelines exclude the following persons, who
should not consume alcoholic beverages: women who are pregnant or trying
to conceive; people who plan to drive or engage in other activities
that require attention or skill; people taking medication, including
over-the-counter medications; recovering alcoholics; and persons under
the age of 21 (2). Although not specifically addressed by the
guidelines, alcohol use also is contraindicated for people with certain
medical conditions such as peptic ulcer.
The existence of separate guidelines for men and women
reflects research findings that women become more intoxicated than men
at an equivalent dose of alcohol (4). This results, in part, from the
significant difference in activity of an enzyme in stomach tissue of
males and females that breaks down alcohol before it reaches the
bloodstream. The enzyme is four times more active in males than in
females (5). Moreover, women have proportionately more fat and less body
water than men. Because alcohol is more soluble in water than in fat, a
given dose becomes more highly concentrated in a female's body water
than in a male's (6).
Since the proportion of body fat increases with age,
Dufour and colleagues recommend a limit of one drink per day for the
elderly (7).
Benefits of Moderate Drinking
Psychological benefits of moderate drinking. A review
of the literature (8) suggests that lower levels of alcohol consumption
can reduce stress; promote conviviality and pleasant and carefree
feelings; and decrease tension, anxiety, and self-consciousness. In the
elderly, moderate drinking has been reported to stimulate appetite,
promote regular bowel function, and improve mood (7).
Cardiovascular benefits of moderate drinking. There is
a considerable body of evidence that lower levels of drinking decrease
the risk of death from co ronary artery disease (CAD). This effect has
been demonstrated in a broad range of older epidemiologic studies (9).
More recently, Boffetta and Garfinkel (10) found that white American men
who reported in 1959 that they consumed an average of fewer than three
drinks per day were less likely to die during the next 12 years than men
who reported abstinence. This finding was due primarily to a reduction
in CAD. In a similar study using a wide range of ethnic groups, De Labry
and colleagues (11) found that rates of overall mortality were lowest
for men who consumed fewer than three drinks per day over a 12-year
period.
Similar results have been obtained with female
subjects. Stampfer and colleagues (12) analyzed data on middle-aged
women and determined that consumption of approximately one drink per day
decreases the risks of coronary heart disease. Razay and colleagues
(13), using a random population sample, found consumption of up to two
drinks per day to be associated with lower levels of cardiovascular risk
factors in women. In postmenopausal women, the apparent protective
effect of alcohol may be explained in part by an alcohol-induced
increase in estrogen levels (14).
Various researchers have suggested that moderate
drinking is not protective against CAD, arguing that higher mortality
among abstainers results from including among them people who have
stopped drinking because of ill health. Higher mortality among these
"sick quitters" would explain the comparative longevity of moderate
drinkers (15,16,17). However, studies investigating the "sick quitter"
effect do not support that conclusion; including "sick quitters" in the
abstinent category cannot completely explain the apparent protective
effect of moderate drinking against CAD (10,18,19,20).
Risks of Moderate Drinking
There are risks that might offset the benefits of
moderate drinking. Research shows that adverse consequences may occur at
relatively low levels of consumption (1).
Stroke. A review of epidemiologic evidence concludes
that moderate alcohol consumption increases the potential risk of
strokes caused by bleeding, although it decreases the risk of strokes
caused by blocked blood vessels (21).
Motor vehicle crashes. While there is some evidence to
suggest that low blood alcohol concentrations (BACs) bear little
relationship to road crashes, impairment of driving-related skills by
alcohol has been found to begin at 0.05 percent BAC or lower, with
rapidly progressing deterioration as the BAC rises (22). A man weighing
140 pounds might attain a BAC of 0.05 percent after two drinks.
Interactions with medications. Alcohol may interact
harmfully with more than 100 medications, including some sold over the
counter (23). The effects of alcohol are especially augmented by
medications that depress the function of the central nervous system,
such as sedatives, sleeping pills, anticonvulsants, antidepressants,
antianxiety drugs, and certain painkillers. There is a consequent
increased danger of driving an automobile after even moderate drinking
if such medications are taken (24). In advanced heart failure, alcohol
may not only worsen the disease, but also interfere with the function of
medications to treat the disease (25).
Cancer. Although most evidence suggests an increased
risk for certain cancers only among the heaviest drinkers, moderate
drinking may be weakly related to female breast cancer. In one study
(26), breast cancer was approximately 50 percent more likely to develop
in women who consumed three to nine drinks per week than in women who
drank fewer than three drinks per week. Although evidence concerning
large bowel cancer is conflicting, one study suggests the possibility of
a weak relation to consumption of one or more drinks per day (27).
Birth defects. Several ongoing studies are exploring
the fetal risks associated with low levels of alcohol consumption. In
one study (28), chil dren whose mothers reported consuming an average of
two to three drinks per day during pregnancy were smaller in weight,
length, and head circumference and had an increased number of minor
physical anomalies when examined at intervals through the age of 3. In
addition, mothers' self-reported consumption of as few as two drinks per
day during pregnancy was found to be related to a decrease in IQ scores
of 7-year-old children (29).
The question of whether moderate drinking is a risk
factor for the fetus is not altogether settled, because mothers'
self-reports of alcohol consumption may be underestimates (30). However,
animal research provides additional evidence for adverse fetal effects
from low levels of drinking. Nervous system abnormalities occurred in
monkeys whose mothers were exposed weekly to low doses of alcohol. An
effect occurred at a maternal BAC as low as 0.024 percent (31). A
120-pound woman might attain this BAC after one drink. Similarly, low
prenatal alcohol doses produced biochemical and physiological changes in
rat brains (32,33).
Shift to heavier drinking. Recovering alcoholics, as
well as people whose families have alcohol problems, may not be able to
maintain moderate drinking habits (2). Once a person progresses from
moderate to heavier drinking, the risks of social problems (for example,
drinking and driving, violence, trauma) and medical problems (for
example, liver disease, pancreatitis, brain damage, reproductive
failure, cancer) increase greatly (34).
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