The impact of caffeine: a doctor's POV

“One of the things that people don't realize is, if you think of it as a medicine, then the best way to use it is in small, frequent doses,” said Dr. Kilgore. “So, 20 milligrams to 100 milligrams at a time as opposed to the standard American mug of coffee.

“And then just getting it into your brain a small amount at a time,” she added, noting that “if you're home with the increase of telework and things like that it might be easy to just serve yourself a little bit at a time throughout the day.”

“Then, when you start to feel your mental performance lagging, take it a little bit more—up until 2 p.m.,” Dr. Kilgore said. 

“In low doses, caffeine may help depression,” said Dr. Clark. The reason is because caffeine “stimulates dopamine, which is a chemical in your brain that plays a role in pleasure motivation and learning.”

Low levels of dopamine can make you feel tired, moody and unmotivated, among other symptoms, she said. But “having more dopamine helps patients with depression by improving their mood.”

“Caffeine is rapidly absorbed, typically within 45 minutes, and is metabolized in the liver at rates subject to significant genetic variability,” said Dr. Devries.

“It is highly metabolized with about 3% or less being excreted in the urine,” said Dr. Kilgore. “The half-life of the drug typically is around four to five hours, but it can range dramatically from as quickly as an hour and a half to as much as nine hours, depending on genetic factors and coadministration with other medications, including oral contraceptives, and smoking.

“Smokers have massively increased clearance, so they will keep it around for a shorter time,” she added, noting that “pregnancy gets greatly reduced metabolism, so women need to watch how much caffeine they’re drinking.”

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• Nicole Clark, MD, a neurologist at St. Peter’s Health Medical Group in Helena, Montana, and an AMA delegate for the Montana Medical Association.
• Stephen Devries, MD, a preventive cardiologist and executive director of the educational nonprofit Gaples Institute in Chicago.
• Shannon Kilgore, MD, a neurologist at the Veterans Affairs Health Care System in Palo Alto, California and Stanford University School of Medicine. She is also an AMA delegate for the American Academy of Neurology.