Dear Doctors: I think that, as I get older, I may be developing a sensitivity to caffeine. I have always loved my cup of coffee in the morning, but now I find that it makes me a bit racy. I would love to understand why.
Dear Reader: Whether it’s coffee, tea or other caffeinated beverages, we humans love the lift caffeine gives. Recent data estimate that 85% of adults in the United States consume caffeine in some form each day.
Caffeine stimulates the central nervous system. Due to its physiological effects and its potential for abuse, it’s considered a drug. Caffeine withdrawal — which can cause headache, anxiety, insomnia and depression — is a recognized disorder. Yet research links coffee and tea to a range of physical and cognitive benefits.
It is indeed possible to develop caffeine sensitivity. This becomes more common as we age. Research shows that older adults clear caffeine from the body more slowly than younger people. In one study, coffee drinkers between 65 and 70 took 33% longer to metabolize caffeine than did younger participants. That means the same amount of coffee that someone has been drinking would have an amplified effect. This can cause anxiety, irritability, jumpiness, difficulty with sleep, sleeplessness and the “racy” feeling you describe.
Caffeine is rapidly and completely absorbed by the body. Within 45 minutes of drinking a cup of coffee, 99% of the caffeine in it has been absorbed. In the bloodstream, it can reach peak levels within 15 minutes of consumption.
After a few hours, certain enzymes in the liver begin to break down the caffeine. This occurs gradually. In a healthy young adult, it takes about six hours for the liver to cut the amount of circulating caffeine in half. As people age, the enzymes involved in caffeine metabolism grow less efficient. Other factors, such as pregnancy, certain medications and being a smoker also can slow the rate at which caffeine is metabolized.
An eight-ounce cup of coffee delivers 80 to 100 milligrams of caffeine. Research shows that, for older adults, amounts in the range of 50 to 100 mg are well-tolerated. To manage caffeine sensitivity, limit yourself to one cup a day. If multiple cups are your routine, consider switching to a half-caf blend.
Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.