Energy Drinks Cause Insomnia And Nervousness In Athletes

An increase in the frequency of insomnia, nervousness and the level of stimulation in the hours following competition was seen in a recent study. Analyzing the positive and negative effects of energy drinks on athletes, researchers found that these negative eefects were in spite of theoretical sports performance improvements of between 3% and 7%.

Explains Juan Del Coso Garrigós, one of the authors of the study who is also in charge of the Exercise Physiology Laboratory at Camilo José Cela University (UCJC):

“What is more,”  “they ran further in team competitions, specially at higher intensities, which is related to sports performance."

In the four-year study, conducted by researchers from  UCJC, top footballers, climbers, swimmers and basketball, rugby, volleyball, tennis and hockey players took the equivalent of three cans of energy drink or an energy drink placebo before a sports competition.

Athletic performance was measured with the use of GPS devices to determine the distance and the speed it was covered in during team sports. They also used dynamometers and potentiometers to measure muscle performance in other sports.

Del Coso adds:

“Energy drinks increase jump height for basketball players, muscle force and power for climbers and trained individuals, swimming speed for sprinter swimmers, hit force and accuracy for volleyball players and the number of points scored in tennis."

Insomnia and Nervousness

These studies not only measured objective parameters of sporting performance, but also asked athletes about their sensations after consuming the energy drink and measured the frequency of the side effects in comparison with the placebo drink.

“Athletes felt they had more strength, power and resistance with the energy drink than with the placebo drink,” said Del Coso. “However, the energy drinks increased the frequency of insomnia, nervousness and the level of stimulation in the hours following the competition."

Their consumption produces an increase in the side effects typically found with other caffeinated drinks. They also found no significant differences between male and female athletes in the perception of positive sensations, nor in the apparition of side effects.

“Caffeinated energy drinks are a commercial product that can significantly increase sporting performance in many sports activities,” argues Del Coso. “The increase in their consumption is probably driven by the hard advertising campaigns of energy drink companies related to sports sponsorships."

More Energy?

Energy drinks mainly contain carbohydrates, caffeine, taurine and B vitamins, with little difference in the quantities and ingredients amongst the main energy drink brands.

On the contrary to that indicated by their trade name, energy drinks do not provide more energy than other soft drinks (~40 kcal/100 ml of product), but they do have an ’energising’ effect related to the stimulation provided by caffeine.

In fact, none of the other ingredients present in energy drinks and in the amounts in a can of energy drink actually produces a significant effect on physical or cognitive performance.

The concentration of caffeine (32 mg/100 ml of product) present in energy drinks provides a total of 80 mg of caffeine per 250 ml can, although 500 ml cans are currently being sold.


Juan J. Salinero, Beatriz Lara, Javier Abian-Vicen, Cristina Gonzalez-Millán, Francisco Areces, César Gallo-Salazar, Diana Ruiz-Vicente, Juan Del Coso.
The use of energy drinks in sport: perceived ergogenicity and side effects in male and female athletes.
British Journal of Nutrition, 2014; 1 DOI: 10.1017/S0007114514002189


“The use of caffeine containing energy drinks has dramatically increased in the last few years, especially in the sport context because of its reported ergogenic effect. The ingestion of low to moderate doses of caffeinated energy drinks has been associated with adverse side effects such as insomnia or increased nervousness. The aim of the present study was to assess psycho-physiological changes and the prevalence of side effects resulting from the ingestion of 3 mg caffeine/kg body mass in the form of an energy drink.

In a double-blind and placebo controlled experimental design, ninety experienced and low-caffeine-consuming athletes (fifty-three male and thirty-seven female) in two different sessions were provided with an energy drink that contained 3 mg/kg of caffeine or the same decaffeinated energy drink (placebo; 0 mg/kg). At 60 min after the ingestion of the energy drink, participants completed a training session. The effects of ingestion of these beverages on psycho-physiological variables during exercise and the rate of adverse side effects were measured using questionnaires. The caffeinated energy drink increased self-perceived muscle power during exercise compared with the placebo beverage (6·41 (sd 1·7) v. 5·66 (sd 1·51); P= 0·001).

Moreover, the energy drink produced a higher prevalence of side effects such as insomnia (31·2 v. 10·4 %; P< 0·001), nervousness (13·2 v. 0 %; P= 0·002) and activeness (16·9 v. 3·9 %; P= 0·007) than the placebo energy drink. There were no sex differences in the incidence of side effects (P>0·05). The ingestion of an energy drink with 3 mg/kg of caffeine increased the prevalence of side effects. The presence of these side effects was similar between male and female participants.”

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