Energy drinks push blood pressure up mid-workout

Caffeinated energy drinks are routinely consumed shortly before training, yet most of what we know about their cardiovascular effects comes from measurements taken at rest. Exercise already raises heart rate and blood pressure, so any extra strain from a stimulant drink lands precisely when the cardiovascular system is working hardest. The review's authors note that the impact of these drinks on the cardiovascular response to exercise has not been well described. This meta-analysis set out to quantify that response using only randomised controlled trials.

The researchers systematically reviewed and meta-analysed randomised controlled trials that tested the acute effects of caffeinated energy drinks on cardiovascular responses during dynamic, aerobic exercise. Twenty-one trials met the inclusion criteria, covering 296 healthy adults, of whom 224 were male and 72 were female. The pooled outcomes were heart rate, systolic blood pressure and diastolic blood pressure during exercise, each compared against control conditions. The team also attempted to assess rate pressure product and exercise-induced arrhythmia.

During exercise, heart rate was 2.86 bpm higher with energy drinks than with controls, a modest difference that was remarkably consistent across trials. Systolic blood pressure rose by a larger 9.02 mmHg on average, with a confidence interval spanning 4.25 to 13.79 mmHg. Diastolic blood pressure, by contrast, was similar with and without the drinks. There were insufficient data to draw any conclusion about rate pressure product or about heart rhythm disturbances during exercise.

The novelty here is the setting: rather than testing cardiovascular effects at rest, this review directly assessed what happens while people are actually exercising, which is when many energy drinks are consumed. The heart rate change is small, but the systolic blood pressure rise is more substantial, and the authors single out its relevance to people prone to hypertension. Important gaps remain, particularly around arrhythmia, where the trial evidence was too thin to analyse. The evidence also skews heavily male, with only 72 of the 296 participants being women.

If you drink an energy drink before training, this review is a reason to think it does more than sharpen your focus: it appears to add measurably to the blood pressure load your heart carries during the session. The participants were healthy adults and the heart rate change was modest, so this is not evidence of harm in that group. It is, however, a reason for anyone with high blood pressure, or a tendency towards it, to know that these drinks' cardiovascular effects show up during exercise itself, not just at rest.