It would seem that the resolution to the caffeine
debate, at least in terms of short-term effects, is simple moderation.
Drunk to excess, coffee literally verges on poison; drunk in moderation,
it is still the beloved tonic of tradition, a gentle aid to thought,
labor, and conversation.
But just how much is enough and how much is too
much? No study will commit itself. One can estimate based on inference.
Few, if any, studies report negative effects from doses of caffeine
under 300 milligrams a day. Since the average cup of coffee (or
single serving of espresso) contains about 100 milligrams of caffeine,
one could infer from this evidence that anyone should be able
to drink about three cups of coffee a day and enjoy the benefits
of caffeine with none of the drawbacks. Such a figure assumes,
of course, that you do not also consume quantities of cola drinks,
chocolate bars, and headache pills. This is a conservative estimate,
however. One could infer from other studies that five cups a day
is safe for most people. Furthermore, reaction to caffeine varies
greatly from individual to individual; some people cannot consume
any amount comfortably.
So much for the short-term effects. Researchers
in the last 30 years or so have tried to implicate coffee, specifically
the caffeine in coffee, in heart disease, birth defects, pancreatic
cancer, and a half-dozen other less publicized health problems.
So far, the evidence is, at most, inconclusive. Clinical reports
and studies continue to generate far more questions than answers,
and for every report tentatively claiming a link between caffeine
and disease, there are several others contradicting it.
If anything, the medical evidence currently is
running in favor of exonerating caffeine rather than further implicating
it in disease. Some evidence even points to modest long-term health
benefits for coffee drinkers.
One example of the way medical establishment has
tended to see-saw on caffeine, condemning on partial evidence
then backing off on further evidence, is the purported connection
between heavy caffeine intake by pregnant women and birth defects.
In the mid-1970s, experiments indicated that the equivalent of
12 to 24 cups of coffee (or equivalent bottles of cola) per day
may cause birth defects -- in rats. Although human beings metabolize
caffeine differently from rats (and other researchers had questioned
some of the conditions of the experiments), the United States
Food and Drug Administration issued a widely publicized warning
about the possible ill effects of caffeine on the fetus. Subsequently,
an analysis by Harvard researchers of coffee drinking among 12,000
women early in their pregnancies failed to find a significant
link between coffee intake and birth defects. The upshot of the
debate? The official position, if there is one, came from a committee
of the National Academy of Sciences, which recommended what common
sense dictates, what this book recommends, and what coffee lovers
through the ages have argued: Pregnant women, according to the
NAS committee, should exercise "moderation" in their
intake of caffeine.