The Food and Drug Administration recommends healthy adults not exceed 400 milligrams (mg) of caffeine-; approximately four cups of brewed coffee-; a day. New research out of the New York Institute of Technology finds that staying within these guidelines is more important as people age. The study will be presented this week at the American Physiological Society (APS) annual meeting at Experimental Biology (EB) 2022 in Philadelphia.
"The older rats are more vulnerable than younger rats to caffeine-induced ventricular tachyarrhythmias," researchers wrote.
The research team administered an acute dose of caffeine to four experimental groups of younger (5-month-old) and middle-aged (1-year-old) male and female rats. They also gave saline to control groups of the younger rats. The team then monitored the rats' heart rhythms via electrocardiogram.
Although there is no concrete age conversion of rats to humans, a 5-month-old rat can be considered the rough equivalent of a young adult human. At one year, rats are approximately comparable to early middle age. While similarly, there is no precise conversion for a human equivalent to the rats' caffeine dose, a starting estimate would be about 13 mg per kilogram of weight-;about 880 mg for a person weighing 150 pounds.
After ingesting the caffeine, all except one of the males and all the female middle-aged rats developed ventricular arrhythmias-;i.e., abnormal rhythms in the lower chambers of their hearts. Only two younger males and one female developed abnormal heart rhythms. None of the controls developed abnormal rhythms.
These abnormal heart rhythms are temporary, but can hold serious health risks which increase with frequency of the episodes. Heart arrhythmia can cause lightheadedness, loss of consciousness and cardiac arrest.
"It would be wise to consume caffeine in moderation," the researchers advised.