The amount of caffeine in a can or bottle of energy drink can range from 80mg to over 500mg. For comparison, an average cup of coffee has 100mg of caffeine. The devil in this detail is the sugar levels between these two. A can of energy drink can have up to 27.5 grams of sugar — that is two heaped tablespoons.
To put it into perspective for your son's drinking habits — if he has three energy drinks he is having six tablespoons of sugar. For reference, the recommended daily amount of added sugar for men is 36 grams or nine teaspoons.
I'll make the assumption you are having milk with your coffee — which means you are having no added sugar at all. Your coffee is not the same as his energy drink — so don't let that little know-it-all try and twist your judgment.
The damaging health effects
There is no safe limit of energy drinks for teenagers. Your son most likely feels energised after he's chugged on one, as a result of the sugar and caffeine. Caffeine effects subside usually after about an hour, and following that the sugar will lose its effect.
Your son would enter an extreme sugar crash, which is why he would have another energy drink later on in the day.
Alongside these energy-boosting effects, energy drinks have been found to increase risk for irregular heart rhythms, disrupt sleep, cause weight gain, cause tooth decay, contribute to mental health problems, and increase risk of diabetes — just to name a few.
In terms of studies that have focused on young people consuming energy drinks, they have found an increased risk of sleep issues, poor learning, and poor performance. In some cases they have been a factor increasing risk of drug and alcohol use.
Your son would be struggling to concentrate in class, and would not be performing at his best level. He would also be struggling to have a proper night's sleep, which would be increasing stress levels and irritability.
I can make the safe assumption that high sugar intake is leading to a fairly serious addiction, and like any other addictive substance, there are consequences. A sugar addiction can lead to diabetes, heart disease, obesity and other related health problems.
Ruth, sometimes we can't wait for our politicians to take action, so I recommend you do so and ban energy drinks in your household. Teach your son why they are bad for him, and introduce him to cups of coffee when he turns 18.
• Dr Zac Turner has a Bachelor of Medicine and Bachelor of Surgery from the University of Sydney. He is both a medical practitioner and a co-owner of telehealth service, Concierge Doctors. He was also a registered nurse and is also a qualified and experienced biomedical scientist along with being a PhD Candidate in Biomedical Engineering.