The Caffeine Debate Goes on but, Says An FDA Scientist, It's Nothing to Lose Sleep Over
updated 09/10/1984 AT 01:00 AM EDT
•originally published 09/10/1984 AT 01:00 AM EDT
Why is caffeine so popular?
We like it for the mild high. It clears your head when you're tired. To my knowledge it's the only substance we add to the food supply specifically as a stimulant.
How does it affect the body?
No one is certain how caffeine works in the body. One thing we do know is that it stimulates the adrenal glands. Generally speaking, the effect is to cause your blood vessels to constrict, and in some individuals the blood pressure can increase by as much as 10 percent. There is a very slight slowing of the pulse rate, except in cases of "caffeinism"—a caffeine overdose—when the pulse rate becomes faster.
How much caffeine is in various beverages and pills?
The average cup of coffee will contain 100 milligrams of caffeine, but it can range from 40 mg in weak coffee to 200 mg in espresso. There's only about 3 mg in decaffeinated coffee. Teas range between 40 and 80 mg, while hot cocoa rarely has more than 10 mg. An average 12-ounce soft drink will contain 40 mg, although various brands range from 30 to 60 mg. Aspirin has zero, but other nonprescription drugs like Anacin and Midol contain 32 mg per tablet. Medicines with the most caffeine are appetite-suppressants like Dexatrim—about 200 mg each.
How harmful is caffeine to one's health?
It's relatively safe. The range between the dose at which you get a kick and the dose at which it causes acute toxicity is very large. A lethal dose is approximately 10,000 mg. You'd have to drink more than 100 cups of coffee within a few minutes to reach that.
Are some people more sensitive to caffeine than others?
Yes, responses to caffeine vary enormously. Doses that produce sleeplessness in healthy adults can range from less than the amount in one cup of coffee to as much as the amount in eight cups.
What are some of the signs of caffeine overdose?
They are very similar to an anxiety attack—a cold sweat, the shakes, heart palpitations—usually associated with a feeling of impending doom. I remember when my daughter was a high school senior trying to stay up all night for final exams, she suddenly yelled, "Come here quickly, I'm dying." I ran in to find her pale, in a cold sweat, with her heart racing. She had had four cups of coffee in two hours and was suffering from caffeinism. I told her to lie down and relax a while to let the caffeine become metabolized.
Is caffeine an addictive drug?
There is that risk, but researchers differ on how much caffeine constitutes addiction. In general, anyone who drinks more than five cups a day will develop a physical dependency, meaning they'll go through some withdrawal symptoms if they stop.
What are the withdrawal symptoms?
Headache, nervousness, irritability and sometimes nausea. These may develop after several days without caffeine. Usually these symptoms don't last more than a few days.
Is there a link between caffeine and heart disease?
In the early '70s two studies by researchers at the Boston University Medical Center reported that coffee drinkers had a higher risk for heart attacks. But other scientists later disagreed with these findings because the researchers overlooked personality traits in choosing their subjects. Studies in Georgia, Illinois and Massachusetts found no connection between coffee drinking and heart disease. Still, anyone with high blood pressure should consult his doctor about coffee. The same advice goes for people with an irregular heartbeat.
Can coffee drinking cause ulcers?
Though we know caffeine increases the production of stomach acids, no one has proved that it causes ulcers. On the other hand it is known that if you already have an ulcer, drinking coffee can make it worse.
How about caffeine and cancer?
Again, some researchers say yes, some say no. The real problem with any aspect of caffeine research is that there's usually something wrong with the control group: It's difficult to find populations of people who are as homogeneous as laboratory rats. You can breed 200 generations of rats to create a genetically similar group. You can't do that with people, who tend to breed with whomever they want.
Why do some women apparently develop benign lumps in the breasts from coffee drinking?
Caffeine has been associated with fibrocystic diseases, but there's no consensus among researchers that it's more than a suggestive link. As yet the evidence isn't conclusive.
Can the same be said about research into caffeine and birth defects?
Yes. Between 1978 and 1980, an FDA-backed study found that the caffeine equivalent of 12 to 14 cups of coffee a day produced deformed litters in laboratory rats. At high doses the offspring had low birth weights and missing toes; at low doses the offspring showed slow skeletal development. But again we aren't sure if an animal model is valid for humans because of the different way each species metabolizes caffeine. Moreover, a 1982 Harvard study of 12,205 pregnant women concluded that no link could be found between coffee consumption and birth defects. But there was a problem here too. The kinds of birth defects that may be associated with caffeine consumption are relatively rare, and the size of the sample group studied at Harvard simply wasn't large enough to detect small deviations from the norm.
Then why did the FDA issue its warning to pregnant women about caffeine?
We have to distinguish between scientific truth and public health need. With caffeine we have a substance that may cause heart disease or cancer or birth defects. There isn't enough scientific proof to take regulatory action, but there is enough to be concerned. We wanted people to remember caffeine is a drug and treat it like one. If you're pregnant, our advice is either to avoid caffeine or reduce your intake to a reasonable level, no more than a couple of cups of coffee a day.
For others, is there a safe level of caffeine consumption?
No more than 10 mg per kilogram of body weight, or about seven cups of coffee a day for a 150-pound person. For a child I'd cut that ratio in half. If a child weighs 70 pounds, I'd say no more than three colas a day. It's when a kid drinks 10 or 12 soft drinks a day that things get out of hand.
Do decaffeinated coffees and noncola soft drinks help?
If you're a person with a low sensitivity threshold to caffeine, those are good alternatives. Although it's a small step, the FDA is preparing to remove formally by the end of this year the 1966 requirement that cola drinks, by definition, include caffeine as one of their ingredients.
Aside from being a stimulant, are there other benefits from caffeine?
A recent study published in the Journal of the American Medical Association concluded that caffeine in the right dose makes an analgesic [a pain-killing drug such as aspirin] more effective. The report said you need 40 percent less analgesic when combined with caffeine to get the same pain-reducing effect. However, the results have yet to be completely evaluated by the medical community, so it's best to reserve judgment.
Can caffeine sober up a drunk?
Not really. Coffee can act as a diuretic to help you expel the alcohol in your blood. It can also keep you conscious so you can metabolize the alcohol more rapidly. But if you're drunk, a cup of coffee isn't going to make you a better driver. And it isn't going to help you with your headache.