Friday February 7 2014
A bottle of energy drink can contain up to 500ml of caffeine
"Teenagers who consume energy drinks 'are twice as likely to use alcohol and drugs'," the Mail Online warns. Research suggests that US teenagers who regularly consume energy drinks such as Red Bull are more likely to use drugs as well as smoke and drink alcohol.
This new research employed a survey to assess the self-reported use of energy drinks and soft drinks among a large nationally representative sample of almost 22,000 US secondary school students.
It found that roughly a third of adolescents aged 13 to 18 years reported drinking energy drinks daily, and just under half reported drinking regular soft drinks daily.
The use of energy drinks and soft drinks was slightly higher among those in the 8th grade (13 to 14 years) than the 10th or 12th grades.
The researchers found a general trend that increased use of energy drinks was associated with increased use of substances, including alcohol, tobacco, cannabis and amphetamines.
However, a survey of this sort cannot prove cause and effect, and the association could run in both directions. For example, some amphetamine users drink energy drinks to enhance the effect of the drug, and energy drinks are also often mixed with alcohol.
Another theory offered by the researchers is that teenagers with a tendency to take risks are more likely to drink energy drinks and take drugs – but this theory is not proven.
The study does raise the question of whether energy drinks are suitable for teenagers. As the American Academy of Pediatrics stated, "The caffeine and other stimulant substances contained in energy drinks have no place in the diet of children and adolescents."
Where did the story come from?
The study was carried out by researchers from the University of Michigan and was funded by the National Institute on Drug Abuse. It was published in the peer-reviewed open access Journal of Addictive Medicine and is available to read online.
The Mail's reporting of the findings of the study is accurate, but it does not make clear that a cause and effect relationship has not been proven.
What kind of research was this?
This was a cross-sectional study that aimed to see whether drinking energy drinks and soft drinks is associated with substance use among US secondary school students.
They did this by looking at surveys completed by nationally representative samples of 8th, 10th and 12th grade students between 2010 and 2011. In the American school grading system, 8th grade students are around 13 to 14 years old, 10th grade students are around 15 to 16 years old, and 12th grade students are around 17 to 18 years old.
Energy drinks usually have high caffeine content and, as such, the products' marketing claims often boast of increased energy, concentration and mental alertness.
Previous studies are said to have found associations between the use of energy drinks in young adults and increased alcohol, tobacco or cannabis use.
The researchers suggest various theories about why energy drink use may be associated with substance use, including behavioural patterns that may lead to the use of both (for example, sensation-seeking behaviour) and the biological effects on the body, such as high caffeine heightening the body's response to other stimulants.
The main limitation with this cross-sectional study design is that although it can find associations, it cannot prove cause and effect and so prove or disprove any of the researchers' theories.
What did the research involve?
This research used data from the "Monitoring the Future" project, which annually surveys nationally representative samples of 8th, 10th and 12th grade students between the ages of 13 and 18 in the US.
Students self-completed questionnaires during a normal class period in 2010 and 2011, with generally high completion rates (ranging from 90% of the 8th grade to 84% of the 12th grade).
They were asked:
- how many energy drinks they drink per day on average (non-alcoholic drinks containing high amounts of caffeine and sold in 8 or 16oz cans or bottles [equivalent to 237-473ml], including Red Bull, Full Throttle, Monster and Rockstar)
- how many energy "shots" they drink per day on average (small shots containing 2 or 3oz [equivalent to 60-89ml])
- how many regular and diet soft drinks they drink per day (12oz [355ml] cans or bottles of Coke, Pepsi, Mountain Dew, Dr Pepper etc and their diet equivalents)
Response categories were none, less than one, one, two, three, four, five, six and seven or more per day.
They were also asked about daily smoking in the past 30 days (not at all, less than one cigarette per day, one to five per day, about half a pack per day, one pack per day, about one and a half packs, or two packs or more per day).
Questions about the use of alcohol, cannabis and amphetamines in the past 30 days were asked in category frequencies from 0 occasions to 40 or more occasions.
The researchers took possible confounders into account, including self-reported sexual activity, ethnicity, the number of parents they lived with, and parental education (a proxy to indicate family socioeconomic status).
What were the basic results?
The researchers' analyses included a total of 21,995 students.
- among 8th graders (13 to 14-year-olds) – 35% reported drinking energy drinks/shots (any frequency), 51% drank regular soft drinks daily, and 23% drank diet soft drinks daily
- among 10th graders (15 to 16-year-olds) – 30% reported drinking energy drinks/shots (any frequency), 46% drank regular soft drinks daily, and 21% drank diet soft drinks daily
- among 12th graders (17 to 18-year-olds) – 31% reported drinking energy drinks/shots (any frequency), 43% drank regular soft drinks daily, and 19% drank diet soft drinks daily
Some of the relationships observed included that:
- energy drink/shot use was significantly higher in the 8th grade than the other two grades
- boys were significantly more likely to drink energy drinks than girls
- having two parents at home and average parental education was associated with lower energy drink/shot use
Looking at substance use, the highest prevalence of use (any frequency) of all types of substance was in the 12th grade (39% for alcohol, 17% for tobacco, 21% cannabis and 4% for amphetamines), with lower use of each for the 10th grade, then lower use again for the 8th grade.
They found that across all grades there was a trend for greater energy drink/shot use in the past 30 days associated with greater use of any substance in the past 30 days.
However, greater consumption of regular soft drinks by all grades was also associated with greater use of any substance, with the exception of amphetamine, which wasn't seen for the 12th grade.
Greater diet soft drink use was also associated with greater tobacco smoking in all grades, as well as with alcohol and cannabis in the 8th and 10th grades, and amphetamine in the 8th grade.
However, the associations between energy drinks/shots and substance use were generally stronger than those for soft drinks and substance use.
How did the researchers interpret the results?
The researchers conclude that their study "indicates that adolescent consumption of energy drinks/shots is widespread and that energy drink users report heightened risk for substance use".
Importantly, though, they do acknowledge that "this study does not establish causation between the behaviours".
The researchers go on to suggest that people should be aware that some groups of adolescents, such as "high sensation-seeking youth", may be particularly likely to consume energy drinks and be substance users.
This cross-sectional survey has assessed the self-reported use of energy drinks and soft drinks among a large nationally representative sample of almost 22,000 US secondary school students.
It found that roughly a third of adolescents aged 13 to 18 years reported drinking energy drinks daily, and just under half reported drinking regular soft drinks daily. The use of energy drinks and soft drinks was slightly higher among those in the 8th grade (13 to 14 years) than the 10th or 12th grades.
The researchers found a general trend that increased use of energy drinks was associated with increased use of substances, including alcohol, tobacco, cannabis and amphetamines. Associations were also found with increasing use of soft drinks, but the links weren't quite so strong.
It is important to be aware, however, that the prevalence of substance use was quite low, particularly when observing that the greatest associations with all substances were found for the youngest in the 8th grade. The 8th grade had the lowest rate of substance use of all the years.
Although a link between the consumption of energy drinks, regular or diet soft drinks was found with amphetamine for the 8th grade, only 1.7% of the 8th grade reported amphetamine use (any frequency). When looking at associations with an outcome that is quite rare, the results may be less reliable.
The important thing to realise is that although the researchers discuss various plausible theories about why there may be an association between energy drink use and substance use – such as behavioural characteristics of the individual – this study cannot prove cause and effect.
Other limitations of the study include the self-reported measures, which may include inaccuracies. It is possible that the adolescents may have had concerns about reporting their use of substances, so this is not reported reliably. The results also cannot be automatically generalised to other populations outside the US.
Overall, the study provides useful information about the self-reported prevalence of energy drinks, soft drinks and substances among 13 to 18-year-old US students.
Both the UK Food Standards Agency and the British Soft Drinks Association recommend that children should only consume caffeine in moderation, and there have been calls to restrict the sale of energy drinks to under-18s.
It is certainly not a good idea for teenagers to frequently consume energy drinks. There is evidence that consuming large amounts of caffeine on a regular basis can cause irritability, nervousness, anxiety and insomnia. This is turn could have a negative impact on behaviour and academic performance.
If you have teenage children, encourage them to look at our teen health bundles. These contain a range of useful advice on drugs, smoking and alcohol and the potential harms linked to all three. See Teen girls' health and Teen boys' health for more information.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.