Energy drinks and the heart

An energy drink before training seems like a harmless way to “charge up,” but for the heart this is not always so. The editorial team broke down what energy drinks contain, how they affect blood pressure and rhythm, in what situations complications arise and who should give them up.

What is in the composition of energy drinks

Energy drinks are one of the fastest-growing categories of non-alcoholic beverages. They are drunk by students before exams, drivers on the highway, gym-goers before training. The main active component is almost always caffeine, to which sugar or sweeteners, taurine, B vitamins, glucuronolactone and plant extracts (guarana, ginseng) are added.

The amount of caffeine in a standard 250 ml can is often comparable to a cup of coffee, but popular 500 ml cans contain twice as much. In the EU, drinks with a caffeine content over 150 mg per liter must carry a warning about the high caffeine content and that they are not recommended for children, pregnant women and breastfeeding women (EU Regulation No. 1169/2011).

Guarana is an additional source of caffeine that is not always accounted for in the “figure on the can.” Taurine and B vitamins in the doses present in the drinks have no proven stimulating effect on their own, but their role in combination with caffeine and sugar has not been sufficiently studied.

The editorial team is most often asked whether energy drinks are dangerous for the heart of a person who trains. The answer depends on the amount, frequency, combination with other substances and the state of health. Let us break it down in detail.

How energy drinks affect the heart and vessels

Caffeine stimulates the sympathetic nervous system and raises the level of catecholamines. This increases the heart rate in some people, raises blood pressure and the contractility of the myocardium. In healthy people at moderate doses these changes are small and temporary.

However, energy drinks are not just caffeine. In a randomized study by Shah and colleagues (2019), young healthy volunteers drank about 950 ml (32 ounces) of an energy drink or a control drink with the same amount of caffeine. The energy drink caused a statistically significant prolongation of the QTc interval on the ECG and a more pronounced rise in blood pressure than the control drink. The authors suggested that other ingredients of the drink make their contribution.

QT prolongation is a marker of impaired ventricular repolarization; significant prolongation is associated with the risk of dangerous ventricular arrhythmias. In healthy people the changes in this study were moderate, but for people with congenital long QT syndrome or those taking drugs that prolong the QT, even such shifts may matter.

The large amount of sugar in classic energy drinks also has cardiovascular significance in the long term: the systematic consumption of sweetened drinks is associated with weight gain, insulin resistance and an increased risk of cardiovascular diseases.

Described complications

The medical literature describes many clinical cases of cardiac complications associated with energy drinks: paroxysms of atrial fibrillation, ventricular arrhythmias, myocardial infarctions in young people, sudden cardiac death. Reviews by Higgins, Tuttle and Higgins (2010) and Gunja and Brown (2012) systematized such reports.

It is important to interpret these data correctly. Case reports do not prove a cause-and-effect relationship and do not allow the frequency of complications to be estimated. But they show typical “risk scenarios”: a large number of cans in a short time, combination with alcohol or other stimulants, intense exertion, lack of sleep and the presence of hidden cardiac pathology.

For athletes the combination of “energy drink + pre-workout complex + fat burner” is especially relevant. Each product separately may contain 150–300 mg of caffeine, and together the dose exceeds the daily limit within a few hours even before the start of training.

A separate risk is children and adolescents. The American Academy of Pediatrics (2011) emphasized that energy drinks have no place in the diet of children and adolescents, and Seifert and colleagues (2011) drew attention to cases of caffeine toxicity in this group.

Who is in the group of increased risk

For a healthy adult, one can of ordinary volume is usually not a problem if the total daily caffeine consumption does not exceed the recommended limits. But there are categories of people who should give up energy drinks entirely or discuss them with a doctor.

• people with arrhythmias, long QT syndrome, cardiomyopathies, heart defects;
• patients with arterial hypertension, especially uncontrolled;
• those taking drugs that prolong the QT, stimulants or antidepressants;
• children, adolescents, pregnant women and breastfeeding women;
• people with anxiety disorders and sleep disturbances;
• individuals with a family history of sudden death of relatives at a young age.

If during or after consuming an energy drink you experience strong palpitations, an irregular heartbeat, chest pain, shortness of breath, dizziness or fainting — you should stop the exertion and seek medical help. Such symptoms during training should never be “endured.”

Athletes who train intensively benefit from a basic examination: an ECG and, if indicated, echocardiography. Screening does not eliminate the risk completely, but it helps to detect some hidden conditions.

How to reduce the risks

If energy drinks are part of your life, the editorial team advises a few simple rules. The first is to count the total caffeine from all sources: coffee, tea, energy drinks, pre-workout complexes, fat burners, some cold and headache medicines. For healthy adults, EFSA (2015) sets a benchmark of up to 400 mg per day and up to 200 mg at one time.

The second is not to combine energy drinks with alcohol. The third is not to use them as a substitute for sleep and rest: the fatigue that caffeine “muffles” does not go anywhere, and chronic lack of sleep in itself raises cardiovascular risk.

The fourth is that for training it is smarter to choose a source with a known and moderate dose of caffeine — coffee or a capsule — than a large energy drink with a dozen components and 50 g of sugar. If you still choose an energy drink, a sugar-free option reduces the calorie load but not the caffeine one.

The fifth is to monitor your own body’s reaction. Tremor, anxiety, “jumps” in the pulse at usual loads, worsened sleep are signals that the dose is excessive for you.

Editorial conclusions

Energy drinks increase the strain on the cardiovascular system through caffeine, other stimulants and sugar. Randomized data show that large volumes of an energy drink can prolong the QTc and raise blood pressure more strongly than equivalent caffeine.

The greatest risk is in large amounts, in combination with alcohol or other stimulants and in people with heart diseases, children and adolescents.

For training it is safer to use sources of caffeine with a known dose and to keep daily consumption within the recommended limits.

We also recommend our materials on coffee and training, on pre-workout complexes and the ECG in athletes.

References

1. Shah SA, Szeto AH, Farewell R, et al. Impact of high volume energy drink consumption on electrocardiographic and blood pressure parameters: a randomized trial. J Am Heart Assoc. 2019;8(11):e011318.
2. Higgins JP, Tuttle TD, Higgins CL. Energy beverages: content and safety. Mayo Clin Proc. 2010;85(11):1033–1041.
3. Seifert SM, Schaechter JL, Hershorin ER, Lipshultz SE. Health effects of energy drinks on children, adolescents, and young adults. Pediatrics. 2011;127(3):511–528.
4. Committee on Nutrition and the Council on Sports Medicine and Fitness. Sports drinks and energy drinks for children and adolescents: are they appropriate? Pediatrics. 2011;127(6):1182–1189.
5. Gunja N, Brown JA. Energy drinks: health risks and toxicity. Med J Aust. 2012;196(1):46–49.
6. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific opinion on the safety of caffeine. EFSA J. 2015;13(5):4102.
7. Regulation (EU) No 1169/2011 of the European Parliament and of the Council on the provision of food information to consumers. Official Journal of the European Union. 2011;L304:18–63.