Most of us are all too familiar with someone who can be described as a hyperactive or high-energy person.
I'm sure members of my family and my co-workers are thinking this is a self-description. Based on doctor's advice, it's best to limit me to one cup of coffee or pay the price when I become an overzealous taskmaster.
Now, after further research, I've concluded that I may just be hyperactive by nature, regardless of my caffeine intake. The effects of caffeine vary for each individual, but there are some conclusions we can draw from scientific studies.
While research is constantly being done on the health benefits and side effects of caffeine, great controversy and misconception persists. But determining just how caffeine affects us is important, given that about 80 percent of the world's population consumes caffeine on a daily basis.
Caffeine is completely absorbed within 30 to 45 minutes of ingestion, but its effects linger for about three hours. Eventually it is excreted, and there is no accumulation in the body.
Caffeine has been shown to affect mood, stamina and the blood vessels in the brain, as well as stomach and intestinal activity.
However, for most people, when used in moderation - 200 to 300 mg a day, or about two to three cups of coffee - caffeine use is perfectly safe and may offer some health benefits.
Sources of caffeine
Caffeine is a natural substance found in certain leaves, seeds and fruits of more than 60 plants worldwide.
In our culture, the most common dietary sources are coffee, tea leaves, cocoa beans, cola and energy drinks. Caffeine can also be produced synthetically and added to food, beverages, supplements and medications.
Consumption of 130 to 300 mg of caffeine per day is considered minimal to moderate. Amounts exceeding 500 mg are moderate to heavy, and more than 1,000 mg per day is excessive.
The average daily caffeine consumption among Americans is about 280 mg per day, and 20 percent to 30 percent of people consume more than 600 mg per day.
Caffeine content in some of the most popular forms includes: 8-ounce brewed coffee: 133 mg; 8-ounce decaffeinated coffee: 5 mg; 2-ounce Starbucks double espresso: 150 mg; 12-ounce Diet Coke: 47 mg; 8.3-ounce Red Bull: 80 mg; 8-ounce cocoa: 9 mg; 12-ounce Jolt Cola: 72 mg; 8-ounce black tea: 53 mg.
PAUL J. MACKAREY, P.T., D.H.Sc., O.C.S., is a doctor in health sciences specializing in orthopedic and sports physical therapy. He is in private practice and an associate professor of clinical medicine at Commonwealth Medical College. Email: firstname.lastname@example.org.