Caffeine fails to enhance the taste of cola, so what’s it doing there?

I was lecturing today and at one point was exploring some of the adverse effects on health the artificial sweetener aspartame may have with regard to human health (for more about this, see here). One of the attendees was lamenting the fact that she had, for several years, drunk one and a half litres of diet cola a day. She had, mercifully I think, cut this habit out some months ago. I asked her what it was that led to her taking this step, expecting her to mention increasing awareness of the hazards aspartame poses to human health. However, her real motivation turned out to be that she was concerned about what the caffeine in diet cola might be doing to her health.

Actually, out of caffeine and aspartame I generally view the former as the lesser or two evils. But this lady’s focus on caffeine got me thinking about what this stimulant is doing in cola in the first place. You see, according to the manufacturers, caffeine is there because it enhances the flavour of cola beverages. Cola beverages manufacturers for doing extensive taste tests on consumers, so this made me wonder if there was any evidence that caffeinated cola tastes any different or better than non-caffeinated cola.

My search on-line turned up one interesting paper [1]. As part of this research, 30 trained tasters sampled caffeinated and non-caffeinated cola beverages, without knowing which was which. None of them (not one) was able to tell the difference. This wasn’t the biggest sampling exercise ever conducted, but the results were pretty conclusive. Even for trained tasters, the addition of caffeine to cola really doesn’t seem to affect taste.

And if that’s how it is, we can only wonder what caffeine is really doing in cola beverages. The fact that caffeine is a stimulant means that its addition to beverages will help ensure these drinks give individuals a bit of a lift or even positive boost to their energy. Regular cola doesn’t contain, volume for volumne, anything like the caffeine found in energy drinks or even regular coffee and tea. However, it certainly contains enough to give a bit of jolt to some that drink it, and this is especially the case if someone is quite caffeine sensitive. Some individuals have relatively limited capacity to metabolise caffeine in the liver, and can therefore feel ‘wired’ on even quite small amounts of caffeine.

The stimulant effects of caffeine means it has at least some addictive potential. Especially for caffeine-sensitive individuals, withdrawing from caffeine can induce symptoms such as headaches, fatigue and irritability. The discomfort that can come from withdrawal of caffeine will help, of course, to keep punters coming back for more. There is some evidence [2] that caffeine withdrawal can come on after abstaining from a daily dose of only 100 mg of caffeine per day (about what you’d find in 3 cans of cola).

The fact that caffeine withdrawal can induce headaches reminds me also of the fact that caffeine is a sometime component in headache remedies. Yet, caffeine has no painkilling qualities. In a previous column here. I suggested that caffeine may be in these medications to help with the caffeine withdrawal that may have induced the headache in the first place. However, having a painkiller with caffeine in might sort out a headache, but is also likely to lead to caffeine withdrawal. Which, of course, might induce another headache. And so the cycle may go on.

Part of the reason for writing about this is personal: about 10 weeks ago I withdrew from caffeine. I wasn’t having that much (just some coffee in the morning) but I like a bit of self-experimentation and thought I’d bite the bullet on this. I was a bit chicken about it, and opted for gradual withdrawal (over a week) rather than going cold turkey. I avoided the caffeine withdrawal headache, but I definitely missed the caffeine for the first few days after stopping completely. I have a feeling I was more dependent on caffeine then I realised. My girlfriend recently reminded that before kicking the habit, having coffee in the morning was a real priority for me. That’s gone now. And as a result, mornings are easier for me because I no longer have to wonder where I’m going to get my caffeine/coffee fix from when I’m travelling.

But the main thing change I’ve noticed is that my energy levels are that much more stable throughout the day. This may be placebo response, of course, though it mirrors what I hear from a lot of individuals who have withdrawn completely and successfully from caffeine.


1. Keast RS, et al. Caffeine as a flavor additive in soft-drinks. Appetite. 2007;49(1):255-9

2. Juliano LM, et al. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features. Psychopharmacology (Berl). 2004;176(1):1-29

11 Responses to Caffeine fails to enhance the taste of cola, so what’s it doing there?

  1. Jeff 25 November 2008 at 8:48 pm #

    Great post. I was having trouble staying asleep, a problem that plagued me for 5 years or so. For the longest time I thought it was alcohol as I had a glass of wine with dinner a few days a week. After giving that up I found that I still had the trouble. I slept really good one night and later realized that on that day I hadn’t had my afternoon cup of coffee. I experimented by dropping all caffeine after 9am and found I slept considerably better, including remembering my dreams, which I had not done in over a decade.

    One question: Why didn’t the woman just switch to caffeine free diet soda?

  2. ethyl d 26 November 2008 at 12:08 am #

    I recall reading that when Coca-Cola was first marketed, I think in the late 19th century, maybe early 20th, that it actually contained cocaine, hence the “Coca” portion of the name. Perhaps when people realized adding cocaine to a beverage was not such a good idea, the company compensated by adding caffeine so that the drink still contained a stimulant? I have not researched this at all, so this is just speculation.

  3. Lisa 26 November 2008 at 2:54 pm #

    Hello. I am the lady that Dr Briffa is talking about. In answer to your question, I was having stomach aches and generally feeling unwell. I’d seen the famous ‘penny in a glass of coke’ trick and related that to the lining of my stomach. I am not completely unaware of the ‘evil’ components that make up diet coke but unless they are spelt out (as in Dr Briffa lecture) you do tend to ignore them.
    I had headaches, tiredness, flu like symptoms without and runny nose and generally unwell for about a week. I now feel much better and maybe have one tea a day now. Also sleeping like a baby!

  4. Norma 27 November 2008 at 12:51 am #

    Well I don’t know, I drink one or two cups a day. Never first thing in the morning as I’m not organised enough for that but at some point before noon.

    Sometimes when I’ve had a large meal I really strongly want some coffee but I think that is for the insulin kick to digest food. These days I don’t eat much in the way of carbohydrates and I don’t experience that now. What I do find is that on the rare occasion that I do drink coffee in the evening I find that I have to have it black, as the milk seems indigestible ; I don’t think I have the same problem with cream.

    I usually want tea in the afternoon but for many years I have had the idea that a cup of coffee in the evening helps me get to sleep.

    Caffeine with a painkiller will speed up the painkiller getting round your body, but soluble painkillers are also assimilated quickly, lie the adrenaline in the anaesthetic a dentist gives. However, I don’t think that a cup of coffee with a painkiller would cause a withdrawal headache unless one is already dependent on caffeine. Any more than having one glass of wine will give everyone a hangover.

  5. Norma 28 November 2008 at 6:15 pm #

    Dr Briffa, could you pull together this article with your earlier ones of 13 October and 18th June on the benefits of caffeine?

  6. Dr John Briffa 28 November 2008 at 6:24 pm #

    The blog posts you refer to are on the potential benefits of coffee. Although coffee may contain caffeine, it contains a lot of other things too. Can I suggest you go back and read these posts again.

  7. Daisy 29 November 2008 at 4:11 pm #

    Is decaff alright? I love the taste of coffee & genuinely can’t tell the difference. I usually drink organic decaff with a dash of cinnamon, black, no sugar. Isn’t this OK? And does decaff still have the potential benefits of normal coffee? Thanks for another great post, by the way.

  8. Richard 29 November 2008 at 6:38 pm #

    ethyl d I have heard that caffeine was added to replace cocaine in cola too. Caffeine has addictive qualities and when combined with sugar can have a ‘tonic’ effect in the short term.

  9. Edward 4 December 2008 at 5:36 pm #

    Oh how I envy those people who get a “buzz” out of coffee and the caffeine it contains!

    I like the taste of coffee and drink it black but I’ve never had a buzz from it like some people describe. Maybe I’ve become habituated – but decades ago when I was at college (drinking less coffee) and revising, ProPlus caffeine tablets did nothing for me at all: I still fell asleep in lectures or the library.

    I guess maybe I’m just highly resistant. But I feel it’s a legal “high” I’m missing out on.

  10. Kenneth 31 March 2009 at 5:03 pm #

    Caffeine is highly addictive, thats your reason right there. If a big comapny like Coka-Cola took caffeine out of its drinks then its profits would probably decline. You could apply the same logic to Nicotine and Alcohol.

  11. Ronnie 15 June 2009 at 10:52 pm #

    I am really curious to see the full results of the study. This article mentions that “None of them (not one) was able to tell the difference”. I am wondering what type of test was performed as most sensory tests, such as triangle, duo trio, etc., involve a statistical probability of actually guessing the correct answer, so if “none” of the tasters were able to tell the difference then the test results may actually be invalid. Also the bitterness taste imparted by caffeine is one of the tastes that varies widely from individual to individual. Some people are even unable to taste caffeine bitterness at levels well above that of some energy drinks in just plain water.

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