According to the International Food Information Council, the average adult consumes approximately 200 milligrams of caffeine daily — about two to three cups of coffee. Since this legal drug is so widely consumed, I had a few caffeine-related questions for the experts.

Q. Is there any reason we shouldn't drink or eat caffeine?

A. Caffeine sensitivity depends on myriad factors, including weight, gender and age. But most studies agree that a moderate amount — 200 milligrams a day — is safe for most adults.

According to Michael F. Jacobson of the Center for Science in the Public Interest, "The biggest concern is that caffeine may interfere with reproduction. Women who are pregnant or trying to become pregnant simply should avoid caffeine. The average person shouldn't worry about drinking a couple cups of coffee a day, but those who are drinking five, 10 or more should rethink their habit. They probably are addicted."

However Jonathan Scher, a New York City obstetrician, says he doesn't believe pregnant women have to give up coffee completely: "Caffeine does cross the placenta to the baby, but it is believed that only very large amounts of caffeine may have harmful effects."

There are, however, other reasons to avoid caffeine: It increases anxiety and can induce panic attacks. Some even experience caffeine-induced anxiety disorder, characterized by severe stress brought on by caffeine. Another issue is osteoporosis. "Caffeine increases calcium excretion and could conceivably contribute to bone loss and osteoporosis," says Jacobson.

Q. Will caffeine interfere with my sleep cycle?

A. According to Dr. Herbert L. Muncie Jr., professor of family medicine at Louisiana State University, caffeine can affect your ability to fall asleep but not your actual sleep cycle. So why do some people swear they can't have caffeine past 2 p.m.? "It's probably psychological, because it's not physiological. Also, those in their late 50s and beyond start having more difficulties with sleep and look for a reduction in caffeine as their answer," says Muncie.

Still, Harris R. Lieberman of the Military Nutrition Division of the U.S. Army Research Institute of Environmental Medicine (USARIEM) in Natick, Mass., recommends avoiding caffeine too late in the evening. "I wouldn't advise someone to consume caffeine after dinner, although its effect is primarily determined by your caffeine habits. Someone who drinks a lot of coffee regularly will be less affected than someone who isn't used to getting a lot of caffeine. But I would say that three to four cups of coffee at 2 p.m. might interfere with your sleep at 11 p.m."

And, according to Terry D. Blumenthal, a professor of psychology at Wake Forest University, Winston-Salem, N.C., caffeine "can increase sensitivity to stimulation while asleep, so that the person is more likely to wake up if there is noise."

Q. Can caffeine be lethal?

A. "You would have to ingest more than 30 cups of coffee in one sitting," says Blumenthal.

Q. Does caffeine enhance performance during exercise or physical activity?

A. According to Lieberman, "There is good evidence that caffeine will improve your athletic performance." In a lab, a low to moderate caffeine intake (two to three cups of coffee) has been shown to improve the performance of well-trained athletes, so a little coffee might just give you an edge.

As for exercise, most studies conclude that caffeine consumption before working out seems to extend endurance during moderately strenuous aerobic exercise and to decrease the sense of overall exertion. However, the benefits may be reduced once a certain tolerance level is reached. Studies have shown that the caffeine improves athletes' stamina and endurance for long-term exercises as well as their performance in short-term exercise. However, performance in very short-term events, such as a 100-meter dash, is not improved.

Q. Will caffeine enhance memory or mood?

A. "Studies have shown that caffeine does not improve memory, though it can enhance sustained attention, particularly for repetitive or monotonous tasks. There is a continuous debate as to whether these mood or mental performance changes are 'real' or due to a reversal of caffeine-withdrawal symptoms," says Lorenzo Stafford, a caffeine researcher and professor of psychology at the University of Portsmouth in England.

Q. Does caffeine help you lose weight?

A. It's a stimulant, and it makes sense that if your body is stimulated, it should burn more calories. Unfortunately, it doesn't work that way. It may play a minor role in increasing metabolic rates in first-time users, but its effects become muted through chronic use, according to Muncie. And no, caffeine is not an appetite suppressant, so it doesn't reduce hunger.

Q. What are some of the most important health benefits of caffeine?

A. In addition to acting as a pick-me-up, it turns out that a morning cup of java may improve cognitive functions — including learning aptitude, decision-making ability and attention span. Lieberman studied Navy SEALs during their "hell week" training and found that caffeine resulted in significant differences in performance on cognitive tests. His conclusion: Caffeine increases alertness and mental acuity under stressful conditions, particularly sleep deprivation.

"The effect caffeine will have depends on whether you're rested or sleep-deprived," says Lieberman. "If you're rested, caffeine helps you maintain focus during prolonged, boring activities — such as driving or monitoring a computer. If you're sleep-deprived, caffeine will elevate your ability to stay alert and to be functional."

Q. Is drinking coffee a good way to sober up if you're drunk?

A. No. "What you get is a hyperactive drunk person," says Blumenthal.

Charles Stuart Platkin is a syndicated health, nutrition and fitness writer.

Reach Charles Stuart Platkin at info@thedietdetective.com.