Over half of 12-24 year olds have side effects from ...

"Energy drinks 'trigger nasty side effects like heart problems and seizures in half of kids'," is the potentially terrifying, but misleading, headline in The Sun.

This is based on an online survey of more than 2,000 young people aged 12 to 24 years in Canada in 2015. The survey found that more than half of the young people who had ever had caffeinated energy drinks reported at least one side effect after drinking them. Unsurprisingly, the most common side effects were related to the stimulant properties of caffeine-rich energy drinks, such as a fast heartbeat and difficulties sleeping.

About a quarter reported having experienced a fast heartbeat, a similar proportion had difficulty sleeping, and about a fifth experienced headache.

Despite the headline making it sound much more common, actually only 1 in 500 children who drank these drinks reported having had seizures. And we can't be sure these seizures were directly linked to the energy drinks.

Energy drinks are high in caffeine and contain other stimulants that could affect health. They are often also high in sugar and therefore calories. As such there are clearly healthier drinks options for children and young people.

There are no official UK recommendations on caffeine consumption levels in children. The European Food Standards Agency has advised that "daily intakes of caffeine [in children] up to 3mg/kg bw [body weight] do not raise safety concerns". For an average sized UK 14 year old (weighing about 50kg) this would result in an upper daily limit of 150mg of caffeine.

Where did the story come from?

The study was carried out by researchers from the University of Waterloo in Canada and was funded by the Canadian Institutes for Health Research; one of the authors was supported by the Canadian Cancer Society Research Institute.

The study was published in the peer-reviewed Canadian Medical Association Journal (CMAJ) Open. The paper is open access, meaning it can be read in full for free online.

While the side effects of energy drinks in children and young people are clearly a concern, the UK headlines covering this research were overly sensational.

The Sun's headline for example implies that up to half of "kids" who drink energy drinks could experience heart problems and seizures. About a quarter of the young people surveyed reported experiencing a fast heartbeat (the most common heart-related problem), and only a small number (1 in 500) experienced seizures.

The Mail Online reports that the side effects were "devastating". Nobody enjoys side effects such as difficulty sleeping, headaches and vomiting, but most people wouldn't describe these effects as devastating.

What kind of research was this?

This was a cross sectional survey that aimed to assess how common side effects were in children and young people who drink caffeinated energy drinks.

This type of study is good for addressing this type of question, and giving an idea of how common a problem is. Although on its own it can't prove that the drinks caused the effects seen. However, it does help to build up a picture along with what is already known of the effects of caffeine on the body.

The researchers were interested in this because consumption of energy drinks is increasing. They contain stimulants including caffeine, and Health Canada identified them as a "safety concern" in 2010. Children and young people in particular are thought to be more susceptible to their effects.

Many of the adverse effects associated with caffeine are short term (such as difficulty sleeping or headache). However, consuming too much caffeine can be associated with rare serious adverse effects including vomiting, seizures, heart rhythm problems and even death. The US Food and Drug Administration reported more than 30 deaths linked with energy drinks between 2004 and 2012.

What did the research involve?

The researchers surveyed Canadian youths and young people (aged 12 to 24 years old) online in 2015. They asked questions about their habits and knowledge relating to caffeinated energy drinks and caffeinated coffee. This included whether they had experienced any of a number of listed side effects after drinking such drinks. The researchers then looked at how common various side effects were, and how they compared between those who drank coffee or energy drinks.

The survey was carried out through a large existing online panel of consumers. Those who complete the surveys receive cash or other forms of payment. Youths aged 12-17 years old were recruited through their parents, and those aged 18-24 years old were recruited directly. The survey included questions about the participants' age, gender, and where they lived.

The researchers used this information to estimate what the findings might be if the entire Canadian population of young people were surveyed.

What were the basic results?

More than 37,000 individuals were asked to participate, and 2,055 completed the survey. About half were aged 12 to 17 years, and half 18 to 24 years. The researchers did not report their results separately for these age groups.

Overall, almost three quarters (74%) reported having tried an energy drink at least once, and almost 85% had tried coffee.

Just over half (55%) reported experiencing at least one side effect after drinking an energy drink. About half of these individuals (51%) had only had one energy drink before experiencing the reported effect.

Of all the people who responded:

25% reported a fast heartbeat
24% reported difficulty sleeping
18% reported headache
5% reported feeling or being sick, or diarrhoea
4% reported chest pain
0.2% reported seizures (that is, 1 in 500 of those who drank energy drinks)

Just over 1% had sought medical advice because of these side effects, and almost 2% had thought about it. About half of those reporting side effects reported other factors that might have contributed, such as consuming alcohol (22%), other caffeinated products (11%), recreational drugs (8%) or taking medication (6%). Eighteen per cent were taking part in physical activity at the time.

Side effects were more common in those who drank energy drinks than those who drank coffee.

How did the researchers interpret the results?

The researchers concluded: "More than half of youths and young adults who had consumed energy drinks reported adverse outcomes, some serious enough to warrant seeking medical help."

They say that the side effects seen were consistent with what is known about the effects of caffeine on the body. They recommend that wider surveys should be conducted, as well as continuing monitoring through the existing consumer reporting channels.

Conclusion

The potential health impact of caffeinated energy drinks has been a growing concern, particularly among children and young people, as these drinks become more popular. The current survey suggests that it may be relatively common for young people to report some level of side effects after drinking them.

But this study has some limitations:

The survey was carried out in Canada in 2015, and may not be representative of current energy drink consumption habits among young people in the UK.
As the researchers themselves acknowledge, it is difficult to conclusively identify the causes of adverse effects. It's particularly difficult to disentangle the possible direct effect of the energy drink from that of alcohol, pre-existing medical conditions and medications, other substances being consumed or activities carried out at the same time as the drinks were consumed.
The survey was completed on a voluntary basis and based on self-reports, so there may be some inaccuracy based on people's recall. Also, people may be more willing to take part if they have concerns about energy drinks.

In the majority of cases the side effects of caffeinated energy drinks are not likely to be serious. However, given the known effects of caffeine on the body, the number of calories in some energy drinks, and their lack of nutritional value, these drinks can hardly be considered a healthy option.

In the EU energy drinks containing over 150 milligrams of caffeine per litre are required to carry a warning saying that they have high caffeine content and are not recommended for children. Energy drinks may also contain other forms of stimulants, and these may also contribute to the effects seen. The British Soft Drinks Association (BSDA) has a voluntary code of practice on energy drinks which suggests that such drinks should not be promoted or marketed to people under 16 years of age.

No doubt the debate regarding these drinks will continue, with some people calling for additional measures to prevent children from buying and consuming these drinks.