Caffeine appears to enhance memory consolidation according to a study published in Nature Neuroscience (“Post-study caffeine administration enhances memory consolidation in humans,” 2014, 17, 201-203).  But before you down an extra cup of coffee or an extra diet Coke, consider the details of the study. 

The subjects were 160 young adults who reported they consume little caffeine each week – < 500 mg, which is less than the equivalent 2-3 cups of coffee per week.  Furthermore, they consumed caffeine pills not coffee.  Participants studied 200 pictures, swallowed the caffeine pill, and returned the next day for a surprise memory test.  Those who had the caffeine were better able to discriminate items similar to those actually seen from different items – familiarity not memory as most of us think of it.

Let’s break down this result.  First, there were three doses of caffeine used, 100, 200, or 300 mg.  The benefit was only for the 200 mg dose.  100 mg was too little and 300 mg was too much –caused side effects such as nausea and headache.  Second, the same findings may not apply to moderate to heavy caffeine users.  Third, the drug had to be administered immediately after the learning experience and testing was the next day. This is called “post-trial facilitation” and also occurs with use of alcohol, benzodiazepines, and norepinephrine – similar to adrenalin.  Fourth, the study used caffeine not coffee, which has hundreds of chemicals in it.

Caffeine is the most used psychoactive drug in the world.  It is used to improve alertness and attention by about 80% of those in the United States (Beckwith, 2008, “A primer of psychopharmacology for clinicians,” Healthforumonline).  As I pursued background for this article, I ran across some interesting studies on coffee.  For example, community dwelling women volunteers aged 65 and older who drank at least three cups of coffee per day showed less decline (does not address the issue of Alzheimer’s) in memory over the course of 4 years than those who drank one cup or less.  There was no association between coffee consumption and memory in men (“the neuroprotective effects of caffeine: a prospective study, Neurology, 2007, 69, 536-545).

There was a special series of articles on caffeine in the Journal of Alzheimer’s Disease (2010, Supplement).  There have been numerous attempts to explore the effects of caffeine/coffee on memory.  The most confident conclusion from these studies is that caffeine has no effect on intentional memory.  Rather it appears to help working memory/multitasking as long as the dose is not too high.  There appears to be no effect on long-term memory and the action seems to result from increasing alertness and counteracting fatigue.

In short, caffeine does not appear to be a pure cognitive enhancer but rather helps improve mood and alertness at the right dose – some people are hypersensitive and too much caffeine impairs performance.  There are no randomized clinical trials from which to draw.  Three to five cups of coffee per day may have potential for slowing and/or treating Parkinson’s disease.  But the caveat is that caffeine may worsen anxiety, induce migraines, cause arrhythmias, interfere with sleep, worsen GERDS, and induce withdrawal.  As with all drugs you must consider the cost-benefit ratio for each individual.

The jury is still out for caffeine and other supplements.  Caffeine’s benefits are probably small rather than profound.  There is no magic bullet.