Results of a study said to be the first population-based research to estimate human caffeine intakes in more than 10 years suggest that overall mean caffeine intakes in the United States remain driven by the consumption of coffee and, to a lesser extent, tea and carbonated soft drinks. Diane Mitchell, at al., “Beverage Caffeine Intakes in the U.S.,” Food and Chemical Toxicology, November 1, 2013. The study, which analyzed data from seven-day diet records of 37,602 Americans, indicated that caffeine intakes from so-called energy drinks—shots and beverages—contributed “minimally,” or less than 2 percent, to total caffeine intakes.

The study showed that the greatest proportion (9-10 percent) of caffeinated beverage consumers consuming energy drinks were teenagers (13-17 years old) or young adults (18-24 years old); only 5 percent of total caffeine intake, however, was attributable to energy drink consumption in these groups. Meanwhile, the mean daily intake of those who did consume caffeine was 165 mg/day and mean intakes were highest in the 50-64-year age range at 226 mg/day. According to the study, even the heaviest caffeine consumers were not drinking huge amounts; intakes at the 90th percentile from all caffeinated beverages were slightly above 400 mg/day for adults age 35 years and older. Although the United States has no specific recommendations for caffeine intakes, the U.S. Food and Drug Administration has indicated, that for healthy adults, caffeine intake up to 400 mg/day is not associated with adverse health effects.