A study headed by researchers from the University of Barcelona (UB) shows that caffeine has a greater effect on men than women, and that these effects start just 10 minutes after it is drunk. In addition, contrary to what was previously thought, it has also been shown that decaffeinated coffee also produces an increased state of alertness.

“Numerous studies have demonstrated the stimulant effects of caffeine, but none of these have looked at their effects in terms of the consumer’s gender,” Ana Adan, lead author of the study and a researcher in the Psychiatry and Clinical Psychobiology Department of the UB, tells SINC.

Research into the effects of caffeine tends to be carried out using preparations in which the caffeine level is much higher than normal intake. According to Adan, the novelty of this study lies in “the difference seen in the effects on men and women, based on the quantities of caffeine people take in 99% of cases (espresso coffee and decaffeinated espresso coffee, containing 100mg and 5mg of caffeine, respectively)”.

In order to measure the effects, the scientists used a sample of 668 university students (238 male and 450 female) with an average age of 22 years. Measurements were taken before and after the caffeine was ingested (10, 20 and 30 minutes) and were carried out at mid-day (11am to 1pm) and in the afternoon (4pm to 6pm), to act as a control in case of possible differences caused by the time.

“Although both the men and women saw an improvement in their activity levels with the coffee, which increased in later measurements, we observed a greater impact among the males,” the Catalan researcher tells SINC.

When the decaffeinated version was introduced into the study, the authors also found a small subjective improvement in the participants’ state of alertness, which did not rise so strikingly in the later measurements. “Although we can’t say it is a placebo, we did note an effect resulting from drinking a decaffeinated coffee (at a quantity insufficient to actually affect mood),” adds Adan.

The results showed a small impact among both men and women who drank the decaffeinated coffee, although this time the effect was slightly more noticeable among the women. The effect of decaffeinated drinks on alertness had not been previously studied.

As the author says, “if a person cannot drink normal coffee, a decaffeinated one might provide some benefits. It remains to be evaluated whether these effects are simply subjective, or if they do have an impact on performance”.

Coffee produces fast-acting effects

Caffeine has an almost immediate effect. Previous studies had shown that alertness starts to increase 30-45 minutes after consumption, but the new study shows that the effects begin after as little as 10 minutes. According to the researcher “45 minutes is the time needed for maximum caffeine concentration to be reached in the blood, but levels reach half this concentration after just a few minutes”.

The experts say the effects of caffeine last for between two and three hours, although some authors extend this to up to four or five hours according to an individual’s particular sensitivity and metabolic rate, which varies greatly with age.