Food and diet

Energy drink warning

“Energy drinks ‘need caffeine alert on cans’”, is the headline in the Daily Mail . The newspaper reports on a study that looked at 28 energy drinks and showed some have up to 14 times the caffeine content of a can of cola. Doctors have warned that these drinks should “carry health warnings”, so young people do not overdose on caffeine, says the newspaper.

The study is a review of the history and regulatory background of caffeine-based energy drinks in the US, including some of the “top selling US energy drinks”, which are also marketed in the UK. The authors discuss the potential for caffeine dependence and withdrawal problems that could be associated with energy drinks. This study did not measure the caffeine content of the drinks directly and did not investigate directly the effect of caffeine intake from these drinks on the body. The problems of toxicity and dependence that can follow caffeinated drink consumption, as discussed by the authors, will need further investigation before there is any proposed change in regulation.

Where did the story come from?

Dr Chad J. Reissig and colleagues from the Department of Psychiatry and Behavioral Sciences at the John Hopkins University School of Medicine in Baltimore, US, carried out this research. The authors declare conflicts of interests in that they own stock in soft drinks companies. The study was supported by grants from the National Institute on Drug Abuse. It was published in the peer-reviewed medical journal: Drug and Alcohol Dependence .

What kind of scientific study was this?

This was a narrative review that included data about drink volumes and caffeine content sourced from the manufacturer’s product label, the product website or by asking the manufacturer representatives directly. In only one case did the manufacturer’s representative refuse to disclose the caffeine content and the data for this drink was sourced from an alternative website.

Several aspects of caffeinated energy drinks and their consumption are discussed. The authors give the background to Red Bull sales in the US, describing the introduction of the drink in Austria in 1987. It was marketed in the US in 1997 and consumption since then has grown “exponentially”. The total US market for energy drinks was estimated to be $5.4 billion in 2006, the analysis shows an annual growth rate of between 47% and 55% per year.

A source, referenced in the article, says that the annual consumption worldwide of these drinks is estimated to be 906 million gallons, with Thailand leading the world in consumption per person and the US leading the world in total volume of sales, i.e. consumption per country. Many different brands are now marketed, and the researchers took a selection of these and reported their published caffeine content. They comment that the regulation of energy drinks, including the labelling of their contents and health warnings differ across countries. The authors suggest that some of the most “lax regulatory requirements [occur] in the US”.

The authors discuss that in the US caffeine tablets are regulated by the FDA (the Food and Drug Administration) and over-the-counter stimulant drug products, usually tablets, must contain the following warnings and directions on the product label:

  • The recommended dose of this product contains about as much caffeine as a cup of coffee. Limit the use of caffeine containing medications, foods or beverages while taking this product because too much caffeine may cause nervousness, irritability, sleeplessness and, occasionally, rapid heartbeat.
  • For occasional use only. Not intended for use as a substitute for sleep. If fatigue or drowsiness persists or continues to recur, consult a (select one of the following: “physician” or “doctor”).
  • Do not give to children under 12 years of age.
  • Directions: adults and children 12 years of age and over: oral dosage is 100–200mg not more often than every 3–4h.

The authors note that it is inconsistent that a 100mg caffeine tablet is required to carry these warnings but a 500mg caffeine drink does not.

What were the results of the study?

The caffeine content of energy drinks marketed in the US ranged from 50–505mg per can or bottle. This compares with the 77–150mg caffeine content of an average 6oz (170ml) cup of brewed coffee, and with 34.5–38mg per can of Coca-Cola Classic or Pepsi Cola.

The higher-caffeine energy drinks (Wired X505, Fixx, BooKoo Energy, Wired X344, SPIKE Shooter, Viso Energy Vigor, Cocaine Energy Drink, Jolt Cola, NOS, Redline RTD and Blow Energy Drink Mix) contained over 11mg/oz of caffeine (the highest was 35.7mg/oz). Some of the top-selling brands in the US (Red Bull, Monster, Rockstar, Full throttle, No Fear, Amp, SoBe Adrenaline Rush and Tab Energy) contained between 9 and 10.9mg/oz.

The total amount of caffeine depends on the size of the can, which was also very variable. Some high-concentration caffeine drinks, such as Ammo, come in tiny cans of 1oz and contain very concentrated caffeine (171mg/oz). This is 17 times the strength of Red Bull (9.6mg/oz).

The content of UK brands is variable. While Red Bull has around 80mg of caffeine per can, Rockstar has around 160mg in a can, and a can of Spike Shooter contains 300mg. The Cocaine Energy Drink, which the newspapers say is about to be launched in the UK, has around 280mg of caffeine in a 250ml can.

What interpretations did the researchers draw from these results?

The researchers state that the absence of regulatory involvement has resulted in the aggressive marketing of energy drinks, and that this is targeted primarily toward young males, for psychoactive, performance-enhancing and stimulant drug effects. They note increasing reports of caffeine intoxication from energy drinks, and say that it seems likely that problems with caffeine dependence and withdrawal will also increase.

The authors say that the combined use of caffeine and alcohol is also increasing sharply, and secondary sources also suggest that such combined use may increase the rate of alcohol-related injury. They also propose, based on other research, that energy drinks may serve as a gateway to other forms of drug dependence. They suggest that the regulation of labelling should be improved and that new restrictions on advertising, particularly regarding children and adolescents, are considered.

What does the NHS Knowledge Service make of this study?

This review of caffeinated energy drinks highlights an important trend in society. It is useful to have access to data that provides some evidence for the content of these drinks although this study did not measure the content of these drinks independently and has relied on other research and media reports in the area to support the author’s arguments.

The problem of caffeinated drink consumption and discussions regarding appropriate regulation for this growing problem will need further investigation. A systematic review of published studies evaluating the toxicity and risk of dependence will be important. As these authors have said, caffeine intoxication can present with a range of symptoms including, nervousness, anxiety, restlessness and sleeplessness. It can also lead to tummy upsets, shaking, heart irregularities, agitation and, in rare cases, death. For the development of rational policy on this topic, the extent of these problems will need to be known and quantified.

NHS Attribution