The European Food Safety Authority (EFSA) has published a safety assessment of caffeine in 2015. According to it:
- For the healthy adult population, caffeine intake in single doses of up to 200 mg (about 3 mg per kg of body weight) or daily intakes of up to 400 mg (5.7 mg per kg of body weight) is not associated with safety concerns (taking into account total caffeine intake from all sources).
- In adults, consuming 200 mg of caffeine less than two hours before intense physical exercise under normal conditions is considered safe.
- Single doses of 100 mg (about 1.4 mg per kg of body weight), especially when consumed close to bedtime, may adversely affect the ability to fall asleep or the duration of sleep.
- During pregnancy, caffeine intake from all sources of up to 200 mg per day is not associated with safety concerns for the fetus.
- During breastfeeding, caffeine intake from all sources up to 200 mg per day or as a single dose of 200 mg is not associated with safety concerns for the breastfed infant.
- There is insufficient data to establish safe intake levels of caffeine for children and adolescents. However, according to EFSA’s expert assessment, body weight–based values derived from adult data can be applied. Thus, a maximum of 3 mg of caffeine per kg of body weight per day can be set as a guidance value for children and adolescents (aged 1–18 years).
In individuals sensitive to caffeine, as well as in pregnant women and children, even small amounts may cause heart palpitations and tremors. One of the main adverse effects of caffeine is its potential to cause dependence. For example, a person who is accustomed to drinking large amounts of coffee may experience fatigue or headaches if their coffee consumption is suddenly reduced. Other side effects associated with excessive caffeine intake include heart palpitations, arrhythmias, nervousness, restlessness, irritability, gastrointestinal discomfort, and reduced tolerance to stress. People who are sensitive to caffeine may experience symptoms even at low doses.
The EFSA’s 2015 safety assessment of caffeine was preceded by an opinion from the EU Scientific Committee on Food (SCF) on the safety of energy drinks and their stimulating ingredients in 1999 (with the opinion updated in 2003).
In 2009, EFSA issued a scientific opinion on two common ingredients in energy drinks, taurine and glucuronolactone. According to the opinion, the exposure to taurine and glucuronolactone resulting from the regular consumption of energy drinks is not considered a safety concern.
The opinion states that, based on data from human studies, an interaction between taurine and caffeine affecting fluid and sodium balance in the body is unlikely. The opinion also supports the conclusion that an interaction between glucuronolactone and the effects of caffeine, taurine, alcohol, or physical exertion is unlikely. However, it is recommended that energy drinks should not be consumed in conjunction with heavy alcohol use or used as thirst quenchers.