Toxicology Reflections

The Controversy of Caffeine


Author –

There is a lot of debate around whether caffeine is “safe” or not.  There are old wives’ tales regarding coffee stunting children’s growth and leeching calcium from bones.  But does it?  Caffeine is often used as a stimulant to help users stay mentally and physically alert.  What sorts of benefits does it really give?  Nearly all of us have felt our hearts race after an energy drink or an extra strong cup of coffee.  Could caffeine be to blame for heart disease and high blood pressure?  Does it cause cancer?  Is it addictive and can you experience withdrawal?  Some tout it as a cure for hyper activity and/or ADHD.  Since it crosses the blood-brain barrier how much is “safe” for adults?  Could it be a leading cause of infertility? What are its effects after crossing the placental barrier?  Is it “safe” for children? Is caffeine really “good” or “bad”?  For such a ubiquitous substance I feel I have a severe lack of knowledge on the subject.  With the following posts I hope to educate myself and readers on one of my favourite substances.  By discussing findings in the literature hopefully some of the questions asked above can be answered.

So where does dietary caffeine come from?  Caffeine (1,3,7-trimethylxanthine) is a nitrogenous organic compound produced by plants.  It is found in the seeds, fruit and leaves of plants such as coffee (beans), cocoa (beans), tea (leaves), and kola (nut).  When these plants are ingested we inevitably intake some caffeine.  Caffeine compounds are also added to consumables such as soft drinks, chocolate, energy drinks, and medications (cold, headache and pain remedies, over the counter stimulants and other drug products)1,2.  According to Health Canada Canadian adults get approximately 60%, 30% and 10% of their caffeine from coffee, tea and cola beverages/chocolate/medicines respectively.  Children (1-5yrs) get approximately 55%, 30% and 14% from cola drinks, tea and chocolate respectively.

Health Canada1 recommends healthy adults keep caffeine intake to 400 mg/d (about 3 8oz cups of brewed coffee), 300 mg/d for women of childbearing age and 2.5mg/kg for children.  That is approximately 45mg for children 4-6 years old, 62.5mg for children 7-9 and 85 mg for children 10-12.  These ranges encompass about 1-2 12oz cans of cola per day (considering the health effects of caffeine only).  To accurately calculate your daily caffeine intake visit Health Canada’s website where they provide a detailed guide on amounts of caffeine found in various foods.

For some additional information on caffeine consumption visit these websites (accessed September 2013).

Graphs on international coffee consumption

Interesting graphs on Canadian beverage consumption – soft drink industry website

Nawrot P, Jordan S, Eastwood J, Rotstein J, Hugenholtz A & Feeley M (2003) Effects of caffeine on human health.  Toxicological Evaluation Section, Chemical Health Hazard Assessment Division, Bureau of Chemical Safety, Food Directorate, Health Canada.  Food Additive and Contaminants 20,1-30.

Health Canada (2013)  Caffeine: It’s your health. (accessed September 2013).


24 thoughts on “The Controversy of Caffeine

  1. Caffeine clearly has many benefits that aid our performance in modern day society (Glade 2010); however, is it the other constituents (i.e. phenolic compounds) associated with the caffeine from coffee and tea that provide the greater benefit? There appears to be several factors that influence the interaction between caffeine and polyphenols (Couzinet-Mossion 2010), so perhaps by increasing the bioavailability of phenolic compounds in products, as suggested by M. Ferruzzi (2010), you can have your cake the eat it too!

    Couzinet-Morrion, A., S. Balayssac, V. Gilard, M. Malet-Martino, M. Potin-Gautier and P. Behra. 2010. Interation mechanisms between caffeine and polyphenols in infusions of Camellia sinensis leaves. Food Chemistry. 119(1):173-181

    Ferruzzi, M. G. 2010. The influence of beverage composition on delivery of phenolic compounds from coffee and tea. Physiology and Behavior. 100(1):33-41

    Glade, M.J. 2010. Caffeine – not just a stimulant. Nutrition. 26(10):932-938

  2. Another myth you could investigate is whether caffeine is effective at reducing the effects of alcohol intoxication. A study by Marczinski et al. suggests that although caffeine reduces the feeling of fatigue, it does not improve information processing or motor coordination (2012). This could lead to a misconception of ability and increase willingness to engage in dangerous activities such as drinking and driving.

  3. I know this thread is about caffeine but I found Lorelei’s comment interesting. There was a article in Chemistry World, which is published by the Royal Society of Chemistry, titled Chemistry in Every Cup. The article highlighted the variety of compounds present in coffee and indicated that coffee is only one part of the human health “story”. Lorelei mentioned the presence of polyphenol antioxidants but I found it interesting that coffee contains various carcinogens. One of the carcinogens identified was acrylamide. It is also interesting that the concentration of acrylamide various with roasting of the coffee bean, lightly roasted coffees have higher concentrations of acrylamide relative to dark roasts. It has also been shown that the concentrations of acrylamide are twice as higher in Robustas beans as opposed to Arabica beans. So go for the dark roasted Arabica beans:)

    That said, a number of studies have shown that coffee consumption does not increase all-cause mortality rate or incidences rte of cancer and it may even have benefits related to cardiovascular disease mortality (Lopez-Garcia et al. 2008). I think coffee is an interest example of mixture toxicity, a variety of polyphenolic antioxidants mixed with a number of carcinogens and hundreds of other compounds.

    Lopez-Garcia et al. 2008. The relationship of coffee consumption with mortality. Annals of Internal Medicine, 148:904-914.

  4. Interesting topic! When I saw your post I immediately thought of this study: suggesting a link between heavy coffee drinkers and mortality (was on the news this summer). Since caffeine acts as diuretic, perhaps there are some interesting links between the health effects associated with heavy coffee drinking and those associated with dehydration.

  5. Oddly enough when I first think of caffeine toxicity I do not think of coffee but of energy drinks. You mentioned that 10% of caffeine intake in adults is from cola. My question is how this value changes if you include energy drinks and narrow the exposure group to adolescents. Similar to St. John’s Wort, caffeinated energy drinks have subpar regulation compared to prescription medicines1. Children and adolescents alike have easy access to caffeinated energy drinks and they probably find them more appealing to their taste buds than coffee. Reissig et al. makes a valid point in that caffeine consumption via energy drinks may present greater risk to children and adolescents because of intolerance1. In other words, unlike the coffee-crazed adult, children and adolescents may be more prone to caffeine toxicity because their systems are not adapted to daily exposure. I wonder how much the average EDI in children and adolescents increases when you factor in exposure to energy drinks and how this affects the risk.

    Reissig C.J., Strain E.C., Griffiths R.R. (2009). Caffeinated energy drinks – A growing problem. Drug and Alcohol Dependence. 99: 1- 10

  6. I thought this seemed like a very interesting topic. I would like to respond to the article highlighted. I think that the Lui et al (2013) article highlight the importance of considering uncertainty and the significance which can be derived from scientific data to that of human health concerns. The Lui et al (2013) firstly only considers coffee and not caffeine intake. This is done by a measure of cups of coffee per month in a survey which was carried out. Cups of coffee are not actually a good measure of caffeine intake at all. Size can differ dramatically between cups and so can the actual caffeine concentration (what some people call coffee is more sugar and fat than actually coffee). In addition in studying the Lui paper, the risk to human health is only seen in the younger population and not the population as a whole. This follows the findings other studies such as which find that coffee consumption is actually negatively correlated with mortality of all forms. So I think what need to be considered in reading these papers are two questions: 1) is age a significant factor in caffeine toxicity and could this be accounting for the finding of Lui et al (2013) and 2) is there too great of an uncertainty in the data to actually have produced a finding.

  7. Along the lines off the myth Steven mentioned with the alcohol intoxication, are their serious health risks to consider if someone chooses to drink “vodka and red bulls”. I have heard some discussion that it can have negative affects on heart function. Are there additive effects if the two are combined?

  8. Author –
    Caffeine’s Pharmacokinetics, Toxicity and Morbidity – Week 2

    In last week’s introduction I talked a little bit about where caffeine comes from, where we find it in our diets (mainly coffee but also in other beverages and foods), Health Canada’s recommended maximum daily intakes (400mg/day for adults, equivalent to 3 8oz cups of coffee), and some of the myths about caffeine I hope to unravel. This week I will talk a little more about caffeine’s pharmacokinetics and address some of the posted comments regarding coffee and mortality. In later posts I will address some of the other comments regarding caffeine in energy drinks, and mixing caffeine and alcohol.

    Pharmacokinetics and Toxicity

    Caffeine is essentially completely absorbed by the gastrointestinal tract and reaches its maximum concentration in the blood stream within 1 – 1.5hrs after ingestion. Once in the blood it is distributed all over the body, crossing the blood-brain and placental barriers. The liver is the primary site of caffeine metabolism and it is very good at its job. Only 1-5% of caffeine is found unchanged in the urine. However caffeine has been found in breast milk and semen. Infants up to 9 months have a much harder time metabolizing caffeine as 85% of caffeine is found unchanged in their urine. By 6 months most children are slowly approaching adult metabolism and elimination rates. The elimination ½ life in adults is between 3-7hrs. Rate of elimination is affected by many factors such as sex (20-30% shorter ½ life in females), age (50-100hr ½ life in newborns), use of contraceptives (2x faster elimination in users), pregnancy (4 hr elimination in 1st trimester vs 18 hrs in 3rd trimester) and smoking (2x faster elimination in smokers).

    Caffeine’s acute lethal dose in adults is approximately 10g (~75 cups of coffee) however there have been reports of death from 6.5g of caffeine and survival after ingesting 24g of caffeine. Chronic caffeine exposure has been implicated in cases of nervousness, irritability, insomnia, increased heart rate, arrhythmia, elevated respiration, increased urine production and unstable bladder, stomach complaints, dysfunction of the gastrointestinal tract, liver, renal and musculature. Caffeine’s most important effect is the antagonism of adenosine receptors. It releases norepinephrine, dopamine, serotonin and increases circulating catecholamine.


    One discussion started in the comments last week was regarding coffee and heart disease and general mortality. One problem with the Lui et al and Freedman et al papers was that they looked at coffee consumption and disease/death rather than a single component of coffee (i.e. caffeine). As was pointed out by Lorelei there are many different compounds in coffee which have pharmacological effects, not just caffeine. These two studies often did not distinguish between caffeinated and decaffeinated coffee, how the coffees were made (which has a large impact on caffeine and other chemical content), and didn’t seem to dive too deeply into other consumer choices that might have an impact on cardiovascular health and mortality. I also disagree with the papers’ conclusions on coffee/caffeine links to all-cause mortalities. I find it a stretch to link mortalities to any single substance. Interestingly Lui et al found that >7 cups of coffee per day increased all-cause mortality while Freedman et al found >6 cups per day decreased risk of all-cause mortality.

    The review paper by Nawrot et al also strongly highlights the controversy over the benefits/risks of caffeine ingestion. In the interest of the readers time I will just summarize their findings rather than go into details. However keep in mind that in each instance there were numerous studies showing harmful effects, no effects and beneficial effects in caffeine consumption. Nawrot et al found there to be insufficient data to draw conclusions on the effects of > 1000mg caffeine/day (>10 cups coffee) on heart disease or mortality and that current data shows no adverse effect on cardiovascular health from < 400mg caffeine/day (<4 cups coffee). Although there is conflicting evidence physiologically relevant doses of caffeine were not found to cause mutagenic effects in humans. As for the risk of causing cancer evidence indicates that the caffeine found in coffee does not cause breast or bowel cancer, there is inconclusive evidence that it causes urinary bladder or pancreatic cancer and there is insufficient data to conclude on carcinogenic effects at other sites (ex: ovary, stomach, liver). Nawrot et al concluded that it is unlikely that caffeine at <500mg caffeine/day (5 cups coffee) is a carcinogen to humans.

    So it looks as if the old adage of “everything in moderation” holds true for caffeine consumption. Although what form of caffeine consumption (ex: beverages, chocolate, pure caffeine pills) might still be up for debate.

  9. This study by Olini et al 2013 was the subject of a press release today. The authors found a possible linkage between caffeine consumption and brain development at puberty. The study used juvenile rats to look at the maturing brain and found that caffeine and its associated lack of deep sleep caused the brains of rats given caffeine to mature more slowly than those given plain water. I think this study may add some more information to the issues brought up in a previous post. Do you feel that the accessibility to caffeinated beverages for kids needs to be more tightly controlled?

  10. Author –
    In the comments of week one it was suggested that I discuss the myth of caffeine increasing sobriety. So here it is.

    An article in Psychology Today uses a neat little equation to sum up the answer: “Caffeine + inebriation = a wide–awake drunk. Only time breaks booze down.” It goes on to explain that alcohol dehydrogenase follows zero order kinetics meaning the process can never be speeded up or slowed down. It just is what it is. However there are 9 variations of the enzyme found in humans which may partially account for varying alcohol tolerances.

    Several studies have investigated the effects of caffeine on alcohol induced impairments. Gulick and Gould (2009) showed that while intoxicated mice given caffeine (equivalent to 8 cups of coffee) were more alert than intoxicated mice not given caffeine, they were still significantly worse at navigating a maze than sober mice. Liguori & Robinson (2001) tested the effect of caffeine and alcohol on driving impairment. 15 adults were given 0, 200, or 400mg of caffeine (remember there is ~80mg in a cup of coffee) and a beverage containing either 0 or 0.6g/kg ethanol. After 45 minutes participants were given a battery of tests. The alcohol only group reported increased dizziness, drug effect and high. Increased body sway, slowed choice reaction time and braking latency were also observed. The caffeine group reported increased alertness and jitteriness. No significant effects on body sway or psychomotor performance were observed. When a mixture of caffeine and alcohol was taken the caffeine counteracted the braking latency effect of the alcohol but not the choice reaction time or body sway. Braking was still significantly (9%) slower than in no alcohol controls. In the Marczinski et al (2012) article mentioned by Steve caffeine again did not improve or alter alcohol induced impairment on dual-task information processing or simple and complex motor coordination tests. However, it did make participants feel less mentally fatigued and increased stimulation versus alcohol alone.

    Next week I will discuss the myth that mixing alcohol and energy drinks (AmED) leads to increased risky behaviour due to increased stimulation and decreased fatigue.

  11. Caffeine is always a riveting topic. I got excited about the caffeine and drinking post so I decided to read up a little on green coffee beans and see what they have to offer in addtion to caffeine.

    Despite containing caffeine, I was unable to find evidence of any adverse human health effects due to their consumption but rather support for products containing them (Heimbach et al. 2010, Ramalakshmi et al. 2009). The 2010 study by Heimback et al. concluded that the NOAEL for a product called CoffeeBerry® would be the highest concentration they tested on rats in the lab, resulting in a TDI of 3446 and 4087 mg/kgbw/day for females and males respectively. I suppose it is good to know that you can consume a fair amount of green coffee bean products because it also appears to be a potential source of antioxidants (Naidu et al. 2008). Furthermore, they suggest it can be used as ‘nutraceuticals as well as preservatives in food formulations’ (Naidu et al. 2008).

    It seems like products using green coffee beans may actually be beneficial because they can give us caffeine plus antioxidants without the negative side effects of roasted coffee; however, they do contain less caffeine per mg. My question is: once you consume large quantities of green bean products wouldn’t you find similar health effects experienced with lower concentrations of roasted coffee? I feel like the information on green coffee is limited despite it being such a popular caffeine product at present but would love to know more if you have come across it.

    Heimbach, J.T., P.A. Marone, J.M. Hunter, B.V. Nemzer, S.M. Stanley, E. Kennepohl. 2010. Safety studies on products from whole coffee fruit. Food and Chemical Toxicology, Volume 48, Issues 8–9, August–September 2010, Pages 2517–2525

    Ramalakshmi, K., L. Jagan Mohan Rao, Yuko Takano-Ishikawa, Masao Goto. 2009. Bioactivities of low-grade green coffee and spent coffee in different in vitro model systems. Food Chemistry, Volume 115, Issue 1, 1 July 2009, Pages 79–85

    Naidu, M.M., G. Sulochanamma, S.R. Sampathu, P. Srinivas. 2008. Studies on extraction and antioxidant potential of green coffee. Food Chemistry, Volume 107, Issue 1, 1 March 2008, Pages 377–384

  12. Author –
    I have not looked into green coffee beans yet but I will try and do so in coming weeks!

  13. Author –
    Thanks for the comments and article suggestions. Effects of caffeine on developing youths will definitely be a topic explored in coming weeks. Maybe next week! Personally I think the control of beverages should fall on parents as the government cannot regulate everything (and it can get super annoying when they try). I think that education in healthy food choices is also important so that teenagers out on there own can make informed decisions for themselves. But perhaps my opinions will change once I read up a little more on the subject.

  14. I’m enjoying your reflections on caffeine. I have teenagers, so read with interest the article posted about the effects of caffeine on the developing brain. Fortunately, for the most part they have not been interested in energy drinks despite the marketing efforts put into these drinks. My 16 year old seems to be on his way to developing a coffee habit though, so I was curious about the issue of dependence on caffeine. I was a bit surprised at some of the strong language in some literature regarding caffeine dependence (e.g. this article on “Caffeine Use Disorder” by Meredith et al.). I found another review article that made a pretty convincing case for some withdrawal effects of caffeine (Juliano and Griffiths, 2004), some of which I would probably agree I’ve experienced. It would be interesting to investigate the addictive potential of caffeine and whether this might influence health risks.

  15. Caffeine toxicity:

    It was international coffee day on Sunday (29th September). This made finding articles on coffee and caffeine easy this week and by find I mean an article was posted on “Nature news” so we actually emailed to me which was nice. I though this paper was excellent for numerous reasons. Firstly it is open source so is freely available to the public as well as academics. Secondly it focuses on mental health risks, an area of I think risk assessments which I feel could be largely overlooked. Additional Bagwath-Persad, (2011) focuses on Energy drinks.

    In reading Bagwath-Persad’s article I reminded of having recently read about the addition of caffeine withdraw to the American Psychiatric Association’s guidelines on diagnosis. This further highlight the potential negative affects caffeine exposure could have in mental health. I also found it interesting that Bagwath-Persad (2011) questioned the knowledge of the benefits of caffeine, as an area of limited research.

    American Psychiatric Association’s guidelines on diagnosis: URL=

    Bagwath-Persad (2011): URL=

  16. Author –
    A concern about alcohol mixed with energy drinks (AmED) is that these beverages could be a cause of increased alcohol consumption and risky behaviour. Caffeine as the active ingredient in the energy drink heightens stimulation and cancels out the soporific effects of the alcohol and so it is hypothesized to lead to increased alcohol consumption. There is also concern that the lack of fatigue a user feels may lead them to think they are less drunk than they actually are, which in turn may lead to over confidence, bad decision making and subsequent increased risky behaviour (O’Brien et al, 2008). O’Brien et al found that AmED use is associated with increased heavy drinking, weekly drunkenness, and significantly more negative consequences experienced due to impairment (ex: injuries or being taken advantage of sexually). Miller (2008) found that increased energy drink use is positively associated with smoking, marijuana and illicit drug use, drinking, alcohol problems and risk taking behaviour.

    At this point I think a distinction needs to be made between some of the various ways alcohol and caffeine can be mixed. In my mind there are 4 main ways of mixing these substances. 1) “Unintentionally” – at a dessert party (chocolate and alcohol) or by consuming coffee (1/2 life of 3-7 hr) and alcohol (~1hr elimination) closely together. 2) Traditional mixed drinks (ex: rye and coke). 3) Using energy drinks as highball mix (ex: vodka Red Bull or Jagerbombs). 4) Premixed alcoholic energy drinks, often known as “blackout in a can”.

    This last category is of greatest concern. Premixed AmEDs, while most common in the United States, are sold in many countries around the world. Four Loko is a brand frequently making waves in the literature. A typical can is 23.5oz with 12% by volume alcohol and 260mg of caffeine and may be sold for as little as $2-$5. These cans may be drunk within an hour and are roughly the equivalent of a 6 pack of beer and 4-5 cups of coffee. In contrast an 8oz vodka Red Bull mix drink has about ¼ of the alcohol of a Four Loko and 80mg of caffeine. 8oz of cola has approximately 22.7mg of caffeine ( It should be noted that Health Canada has not approved the sale of premixed alcohol energy drinks and in the fall of 2011 the amount of caffeine per can of energy drink has been limited to 180mg for a single serving container. Energy shots (ex: 5Hour Energy) have now been limited to 200mg per shot which is about the same dose as a caffeine pill. While there is concern in the media about AmEDs it is important to understand exactly what is being discussed and where that information is coming from (American vs Canadian news).

    A good review (in my opinion) of the literature done by Vester et al (2012) (disclaimer authors have been funded by Red Bull in the past) cautions researchers against finding causality where there are merely associations. They remind readers that people have been mixing alcohol with colas for years without the same stigma attached to mixing alcohol with energy drinks. They made the following 7 conclusions from the currently available literature:

    There is currently insufficient, properly conducted research to make conclusions on the mixing of alcohol and energy drinks
    There is no evidence that AmEDs are more harmful than other forms of alcohol and caffeine mixing (ex: colas) and that only a minority of students are using AmEDs.
    Energy drinks may improve some alcoholic impairments but not all of them (ex: increasing alertness but not speed of decision making)
    The association between AmED and alcohol is not a correlation
    There is no evidence that AmED use initiates drug or alcohol dependence or abuse
    Users may already have higher risk taking personalities and AmED drinking may just be an expression of this lifestyle.
    Personally I think that consuming energy drinks or using it as a highball mix is “safe” in moderation. As a consumer it is important to know the contents of what you ingest and to recognize that some substances are more concentrated than others (ex: caffeine pills vs energy drinks vs coffee or colas). If we want society’s youths to make wise choices concerning caffeine we should educated them on the topic the same as we do with nutrition, exercise and getting a “good night’s sleep”.

  17. I think this is a fascinating topic that a lot of people I know have been talking about for the past several years. I’m wondering if there was any science backing the decision of Health Canada to limit the amount of caffeine per can of energy drink to 180 mg for a single serving container?

    The discussion of causality seems to be a central theme in some of the other student’s discussions. There appears to be limitations in our ability to causally link exposure to an effect if there are confounding factors (i.e., simultaneous exposure to other compounds that have been linked to the same endpoint.

    In addition, I find the point about the lack of previous stigmas concerning rum and cokes a good point. Would this have to do with the comparison in quantities of caffeine and/or the negative outlook on energy drinks alone?

    Lastly, this may be a silly question, but I think there are definitely certain individuals who seem to be more tolerant of caffeine intake (i.e., some students can function normally on 4 cups of coffee a day whereas me on 4 cups of coffee = bonkers!), so do you think this would play a role in the effects of caffeine plus alcohol exposure? A study by Robertson et al. (1981) found that near complete tolerance, in terms of both humoral and hemodynamic variables, developed over the first 1-4 days of caffeine exposure, with no long-term effects observed in humans. More information on caffeine dependence, tolerance, reinforcement and withdrawal was reviewed by Nehlig et al. (1999), which I thought brought up some interesting points worth considering on the topic.

    Nehlig, A. (1999). Are we dependent upon coffee and caffeine? A review on human and animal data. Neuroscience & Biobehavioral Reviews, 23(4), 563-576.

    Robertson, D. A. V. I. D., Wade, D. A. W. N., Workman, R. O. B. E. R. T., Woosley, R. L., & Oates, J. A. (1981). Tolerance to the humoral and hemodynamic effects of caffeine in man. Journal of Clinical Investigation, 67(4), 1111.

  18. Interesting stuff – this paper (I love the name: Club goers and their Trendy Cocktails) reiterates some of what you stated above – mixing caffeine with alcohol results in feeling less intoxicated and leads to a person drinking more than they would otherwise. One of the things pointed out here was that co-consumption of alcohol and caffeine had the potential to impair a person’s perception of intoxication and lead them to drink and drive resulting in more alcohol related car accidents.

    I have really enjoyed following your posts, thanks for all the great information,

  19. I think the concern regarding AmED is centered on young adult use. There has been media attention around the use of energy drinks by people 18 years and younger and the potential adverse health effects including anxiety, heart irregularities, nausea and diarrhea1. The concern here is that young adults are buying and consuming un-safe amounts of these energy drinks and are also using them as mix in alcohol which, as you mentioned, could lead them to drink more1. Recently, there was a call from the Canadian Medical Association for the federal government to ban the sale of energy drink to minors1. However, whether this would actually prevent them from using it is another thing. Alcohol is illegal for purchase by minors in Canada, depending on the province, but they obviously are able to get their hands on it. Several of the links below provide additional information on this topic.

    CBC News. Energy Drink Ban for Minors Urged by Doctors. August 22, 2013 (Accessed October 9, 2013)

  20. I liked the approach you presented in my topic regarding our lack of understanding resulting in unjustified assumptions about risk. Do you think there is an appropriate amount of awareness about this topic and is it justified and based on science? I know we discusses in class some of the difficulties in properly communicating science. Is there an effective way to educate young people who may be more susceptible to drinking these alcohol plus energy drinks more often? It may be two sided since a lot of young people like the idea of the “negative” aspects of alcohol, in that they are letting loose and having fun so if they think these mixed drinks will achieve this faster through miscommunication it may be hard to truly help individuals make good decisions. Do you think enough young people are asking these questions or is it media and parental figures that are driving the concern?

  21. Agree, really really interesting topic, and definitely one packed with uncertainty. You guys have pointed out a few factors that make it hard to properly address the issue, one of them being different social approaches to traditional cola mixes and these new mixes. A little bit abut mixture toxicity has also been dealt with, but i am really interested on this aspect of the issue. Many of this drinks contain large amounts of other substances, such as Taurine, which in many cases are un concentrations orders of magnitude higher to those of caffeine (Finnegan, 2003). After reading the literature for these reflections, do you think the presence of these other substances in the drinks will have an impact on a potential risk assessment of the drink itself compared to a solely caffeine-based assessment?

  22. I was doing a little looking into the energy drinks and what surprised me was that a lot more than caffeine is in some of these drinks. Some contain taurine, vitamin B6 and B12, ginseng, ginkgo biloba and St. John’s Wort (McLellan and Liberman 2012). I found this interesting especially since St. John’s Wort was another reflection from the class. Made me wonder if like mentioned in a lot of the posts are there interactions? If someone is taking a prescription and having these mixture energy drinks could a problem be brewing? So then I came across another paper that found that caffeine, taurine and guarana had cytotoxic effects on neuronal cell lines with signs of apoptosis, degeneration, swelling and morphological changes. The effects were also more detectable when in mixtures (Zeidan-Chulia et al. 2013). Maybe the concerns people have with the energy drinks is not solely due to caffeine but the other components.

    McLellan TM, Liberman HR. 2012. Do energy drinks contain active components other than caffeine? Nutrition Review 70: 730-744.

    Zeidán-Chuliá F, Gelain DP, Kolling EA, Rybarczyk-Filho JL, Ambrosi P, Terra SR, Pires AS, Teixeira da Rocha JB, Behr GA, Moreira JCF. 2013. Major Components of Energy Drinks (Caffeine, Taurine, and Guarana) Exert Cytotoxic Effects on Human Neuronal SH-SY5Y Cells by Decreasing Reactive Oxygen Species Production. Oxidative Med Cellular Longevity. 2013: 1-22.

  23. Author –
    Caffeine, as discussed previously, is a stimulant with psychoactive properties which arouses the central nervous system. It has known health effects on the cardiovascular and neurological systems and its main mode of action is antagonizing adenosine receptors (Clinical Report, 2011; Temple, 2009). While it does have dose dependent effects the exact doses are still under debate as effects vary greatly among individuals. Adult studies show it to be relatively safe (Temple, 2009), however as we learned in class children and adolescents are among the most susceptible to toxicants as they are smaller, have a higher metabolism and are still developing. Many of you have asked about caffeine’s effects on children unfortunately this age group has gone largely unstudied. However, with increasing youth caffeine use (up 70% since 1977) (Temple, 2009) and concern over new caffeinated beverages this is likely to change in future. So what has been seen so far?

    Physiologically children respond similarly to adults. There have been no studies done on the long term developmental effects of caffeine on children. Adolescent brains are still developing in areas containing many adenosine receptors so caffeine has the potential to affect this. Caffeine also acts in the reward and addiction centres of the brain so there is concern that it will reinforce dietary (ex: increased sweet tooth from sodas) and behavioural choices (ex: sensation or risk seeking) but there are currently no studies to validate this (Temple, 2009). There is concern that caffeine in sodas (the largest source of caffeine in youths, (Clinical Report, 2011)) may be causing dehydration (caffeine is a diuretic), decreasing hours spent sleeping (teens need 8-10hrs a night (Cox, 2012)), and replacing other healthier beverage options (ex: water, milk, fruit juice). There is a link between childhood obesity and soda intake but whether that is because of the caffeine, increased sweet tooth or decreased parental attention to a healthy diet is still unknown (Temple, 2009). Overall there is no evidence directly linking caffeine to negative health effects in children but doctors recommend avoiding giving caffeinated beverages to children or adolescents are there is absolutely no need for them (Clinical Report 2011; Cox, 2012; Goldman, 2013; Morganstein, 2010; Temple, 2009).

    In researching caffeine and children my biggest concern has become why youths are turning to caffeinated beverages. According to the American Academy of Pediatrics “many children and adolescents perceive the need to increase or boost energy levels” (Clinical Report, 2011). It is hoped the extra energy will increase either athletic or academic performance (Temple, 2009). In a survey of 16,000 Canadians 11-18 years old 27% use caffeine to boost athletic performance with 13% being encouraged to do so by coaches (Temple, 2009). The fact that the pressure for increased academic or athletic success is being felt so acutely by students is worrying to me. Perhaps instead of addressing the effects of stimulant use our culture should address the demands put on youths that are so affecting their sleep patterns and nutrition.

    Through the course of this discussion I have learned about caffeine sources, its pharmacokinetics, its inability to increase sobriety, that moderation is key, and that the scientific jury is still out on caffeine’s negative health effects. The data is muddled due to a number of factors including the complex mixtures caffeine is consumed in, the extreme variation of individual reactions and the lack of targeted studies. I feel that more work needs to be focused youths. I also think that education regarding caffeine and its possible effects need to be more widespread so that the public can make informed decisions. Targets should include information on the effects of excessive partying and alcohol mixed energy drink use for young adults, childhood nutritional and sleep requirements for parents, and the benefits of healthy lifestyle choices for adolescents.

    Thank you to everyone for the thoughtful comments, input and kind words of encouragement.

    If you would like to know more 2 extensive review articles covering a variety of topics are:

    Temple, J. L. (2009). Caffeine use in children: What we know, what we have left to learn, and why we should worry. Neuroscience & Behavioral Reviews 33, 6, 793-806.

    Nawrot, P., Jordan, S., Eastwood, J., Rotstein, J., Hugenholtz, A. & Feeley, M. (2003). Effects of caffeine on human health. Food Additives and Contaminants 20, 1, 1-30.

  24. Author –
    “Self-medication” with caffeine to combat drowsiness and increase alertness has been a common theme throughout my research on caffeine (see posts on AmEDs and Youth Use) and personal experience at work and school has very much validated these findings. Along these lines research has been conducted into using caffeine as a tool to improve occupational safety.

    A study done in Australia found that consumption of caffeine by long distance (>200km) commercial drivers decreased their risk of crashing by 63% compared to drivers who did not use caffeine to stay awake (Sharwood et al, 2013). This study was done by surveying 530 long distance drivers within 4 months of a crash to which police were called but no serious injuries were sustained and 517 control drivers who had not crashed in 12 months. Caffeine consumption was self-reported. I feel confident in the results of this study as many factors were controlled for, including but not limited to: exposure to kilometers driven, sleep patterns, shift (day vs night), breaks taken, health disorders, exercise and age.

    Soldiers in the American army are issued caffeinated gum in some of their rations and other caffeine products are readily available to them. According to the article by Lieberman et al (2012) caffeine has been shown to increase mental and physical performance during long duty and that is the main reason for use among soldiers. The US and Canadian Departments of Defense have both suggested that 1,000 mg/d limits pose little risk, with an Institute of Medicine panel (USA) concluding that a single dose of 100-600 mg can maintain cognitive performance and poses little risk. More than 1,000 mg/d may cause adverse behavioural effects. Health Canada on the other hand recommends limits of 400 mg/d for civilians. For me this throws a lot of uncertainty on to both limits. Perhaps the military limit of 1,000 mg/d has more to do with the performance benefits than personal risk as military personnel are already at such great risk. Ker et al (2010) found that caffeine makes shift workers more alert however it does not guarantee fewer injuries on the job.

    Based on these three studies it appears that caffeine may be a useful tool for increasing worker alertness and possibly performance, however proper sleep and nutrition are essential.

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