An NHS doctor has revealed why energy drinks can sometimes make you feel tired instead of, well, energised. While many people rely on these drinks to stay alert – whether for work or before a big event – some find the effect is the opposite.
Instead of feeling awake and full of energy, they feel drowsy and may even need a nap. But there is a good reason for this and it has nothing to do with the drink itself.
Doctor Karan Raj, an NHS GP, explains that this surprising reaction is due to a “glitch” in how our bodies process the drink. Sharing insights on TikTok (@dr.karanr,), he notes that genetic differences play a key role, as people’s bodies metabolize substances at different speeds.
He explains: “If caffeine makes you feel tired, it might be because of a software glitch in your caffeine gene. Broadly speaking, people can have fast or slow caffeine metabolizers and it all depends if you have the fast or slow liver enzyme, CYP1A2.
“This enzyme influences your body’s sensitivity to caffeine. Depending on your metabolism, it could be anywhere from 2 to 8 hours to remove half the caffeine.”
Talking about the thing most often found in drinks like coffee and teas, he explains: “Caffeine keeps you alert by blocking adenosine receptors. Because it shares a similar shape to adenosine, the sleep molecule, people with the fast metabolising mutation, break down caffeine more quickly.”
This allows the adenosine receptors to “free up more allowing the sleep-inducing chemical, adenosine, to bind and make you feel more tired than a slow metabolism.”
Additionally, the doctor notes that if you regularly consume caffeine your body overcompensates. He reveals: “Those adenosine channels are constantly blocked.
“Your body actually does a system update and compensates by producing even more adenosine receptors in your brain.” It does this regulate your sleep cycle so you “don’t glitch out”, he concludes.
Are there any side effects of an energy drink?
According to the British Dietetic Association (BDA), some people may have physical effects from over-consumption of energy drinks and are “mostly related to caffeine.” As noted by Specialist Paediatric Eating Disorder Dietitian, Annabel Gipp, young people in particular are affected by the side effects of some drinks.
They explain that an increase in caffeine consumption in children and adolescents can result in:
- increased blood pressure
- sleep issues
- headaches
- stomach aches
In addition to physical effects, mental health effects due to consumption of energy drinks can include:
- sensation-seeking behaviour
- self-destructive behaviour
- insomnia
- problems with behavioural regulation
- poor lifestyle behaviours – e.g poor diet