Is caffeine a mug's game?

Many of us rely on coffee to wake us up, but do we drink too much? Dr Nick Knight explains the effects and limitations of caffeine

“I'm sittin' on the dock of the bay, Watchin' the tide roll away, ooh”. My eyes open. Then shut. Then open. The hazy outline of the rest of my pillow cuts into view, as my Otis Redding alarm unremorsefully ends my dream where I impressively calculate the restaurant bill in my head while on a date with Rachel Riley. At this moment I am a useless, organic 80 kilogram sack. How then, fast-forwarding 45 minutes, am I tip-toe-dancing over puddles in the busy streets of London, finishing the crossword of my random commuter neighbour, and mentally prioritising the day with ruthless efficiency? Caffeine, first to hit Europe around 1640, is the stimulatory saviour to many dreary, non-functioning mornings.

Whether an essential part to surviving your day, catalyst for a business meeting, or first date, you may be one of the 80 per cent of the UK adult population which find that steaming cup of coffee hitting your lips today.

Now for the science bit. Within about 45 minutes of that first sip, the caffeine from your coffee has been absorbed from your small intestines, far away from your now super-chatty mouth, and entered into your bloodstream. Now from this point, some of the caffeine is transported to your liver where it is broken down ('metabolised') into other active chemicals, while the remainder of the caffeine stays, unaltered, in your blood. Once your liver has done its work, the active chemicals, re-joins the rest of the caffeine in the bloodstream, and together they all commute to their place of work - your brain.

Now there, the key function of caffeine is to block a chemical in the brain called adenosine, which normally stimulates a specific receptor in the brain – a bit like a key fitting perfectly into a lock. The usual role of adenosine is to slow down and dampen your brain activity. Caffeine actively stops this effect for it is a similar shaped 'key' to the adenosine molecule and so can take its place on the receptor (the ‘lock’).

The result is that your adenosine cannot fulfil their normal role; instead, you get a positive build-up of energy-promoting brain processes that boost metabolism and stimulate the release of the energising hormone, adrenaline.

You stare at the bottom of the coffee mug. Empty. The caffeine, now slow-dancing with your brain cells, starts to translate into the positive effects born from caffeine within about 45 minutes of your first ingestion. You feel more alert, vigilant and attentive with the focus of a tight-rope walker over an Ayia Napa pool-party (nobody wants a mouthful of that water). The fatigue that engulfed your body is now lifting and your body and mind begin to start working in tandem with your increased mood and metabolic rate. You can expect to enjoy this for 3 to 5 hours – the half-life of caffeine.

But your cup of coffee hasn’t stopped giving yet. Not satisfied with only improving your cognitive performance, it wants to promote your physical performance too. Apart from the increase in adrenaline, the active chemical (from that earlier caffeine breakdown in the liver) called paraxantine, also helps to mobilise and break down fats by a process called lipolysis. The end result, more fat is used for energy and you spare your precious carbohydrate ‘glycogen’ reserves in your liver and muscles.

Now although helpful for enhancing your endurance performance, it may be perhaps less handy for navigating the two flights of office stairs. What may help with these stairs, however, is the fact that caffeine also reduces the perception of effort, by lowering the ‘neuronal activation threshold’, basically making it easier to recruit muscles for exercise. Before you start pouring boiling water straight into the instant-coffee jar, evidence shows very little benefit of drinking beyond 200 milligrams (mg) to boost your performance – so a mug is fine.

You glance down at the empty coffee mug again. Time for another? The guidelines for caffeine consumption are clear; although, I am aware of the fierce backlash from some coffee drinkers at my next few sentences, standing proud with cups of coffee per day that tip into double figures. The advice, however, is not to exceed 400mg of caffeine daily - about four cups of instant coffee. Pregnant women are the exception – it is half that – sorry.

Well into the day now, you realise you are once again stirring the spoon of yet another coffee. A common occurrence, like many (including myself), you end up having one too many coffees. The negative effects of caffeine excess will vary depending on amount consumed. You may start to find yourself needing to urinate more (thanks to the other caffeine breakdown product, theobromine); your heart palpitates; you develop a tremor; and if I were to take your blood pressure and heart rate, both may be markedly raised. Now if you were to really push the boat out, you may develop caffeine toxicity. This, your prize for drinking seriously excessively concentrated caffeine (500mg at once), includes symptoms of agitation, insomnia, fast breathing and cardiac abnormalities, all due in part to over-stimulation of various control centres in the brain. Over time this may also promote withdrawal.

Of course, caffeine comes in many guises. Apart from coffee (95mg), other common caffeine supplies passing your lips may include plain chocolate bars (up to 50mg), tea (75mg), and a regular can of cola (40mg). Then, there are those sneaky items that insidiously slip a little caffeine into your system – chocolate or coffee flavoured ice-cream (30mg per half cup), weight-loss pills and pain-killers (variable mg), and even DECAF coffee (5mg a cup)! Even so, when totalled up over a day, anecdotally it seems most of us don’t exceed 400 mg per day – so I would not worry too much. Just enjoy it.

Ah, the kettle has just boiled, so I must wrap this up. Caffeine is a mild psycho-active stimulant that is an integral part of many people’s daily grind – mine included. It is still however, a drug, and we should respect this fact; for beyond the positive cognitive and physical effects with healthy, moderated consumption - excess can be dangerous. As always – if you have concerns about your caffeine drinking then do have a chat to your GP. Now, where is the milk…

Dr Nick Knight is a junior doctor based in London with a PhD background in human performance. His blog on life as a doctor can be read at: https://drnickknight.wordpress.com/

Or follow him via Twitter: @Dr_NickKnight

News
Ben Little, right, is a Labour supporter while Jonathan Rogers supports the Green Party
general election 2015
News
The 91st Hakone Ekiden Qualifier at Showa Kinen Park, Tokyo, 2014
news
Life and Style
Former helicopter pilot Major Tim Peake will become the first UK astronaut in space for over 20 years
food + drinkNothing but the best for British astronaut as chef Heston Blumenthal cooks up his rations
News
Kim Wilde began gardening in the 1990s when she moved to the countryside
peopleThe singer is leading an appeal for the charity Thrive, which uses the therapy of horticulture
Life and Style
ebookNow available in paperback
ebooks
ebookPart of The Independent’s new eBook series The Great Composers
Sport
Alexis Sanchez celebrates scoring a second for Arsenal against Reading
football
Life and Style
health
Voices
An easy-peel potato; Dave Hax has come up with an ingenious method in food preparation
voicesDave Hax's domestic tips are reminiscent of George Orwell's tea routine. The world might need revolution, but we like to sweat the small stuff, says DJ Taylor
News
i100
News
Japan's population is projected to fall dramatically in the next 50 years (Wikimedia)
news
Life and Style
Buyers of secondhand cars are searching out shades last seen in cop show ‘The Sweeney’
motoringFlares and flounce are back on catwalks but a revival in ’70s car paintjobs was a stack-heeled step too far – until now
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?

ES Rentals

    Independent Dating
    and  

    By clicking 'Search' you
    are agreeing to our
    Terms of Use.

    iJobs Job Widget
    iJobs General

    Recruitment Genius: Project Implementation Executive

    £18000 - £23000 per annum: Recruitment Genius: They work with major vehicle ma...

    Recruitment Genius: Chiropractic Assistant

    £16500 per annum: Recruitment Genius: A Chiropractic Assistant is needed in a ...

    Recruitment Genius: Digital Account Executive - Midlands

    £18000 - £26000 per annum: Recruitment Genius: They work with major vehicle ma...

    Recruitment Genius: Web Developer

    £28000 - £30000 per annum: Recruitment Genius: This company provides coaching ...

    Day In a Page

    NHS struggling to monitor the safety and efficacy of its services outsourced to private providers

    Who's monitoring the outsourced NHS services?

    A report finds that private firms are not being properly assessed for their quality of care
    Zac Goldsmith: 'I'll trigger a by-election over Heathrow'

    Zac Goldsmith: 'I'll trigger a by-election over Heathrow'

    The Tory MP said he did not want to stand again unless his party's manifesto ruled out a third runway. But he's doing so. Watch this space
    How do Greek voters feel about Syriza's backtracking on its anti-austerity pledge?

    How do Greeks feel about Syriza?

    Five voters from different backgrounds tell us what they expect from Syriza's charismatic leader Alexis Tsipras
    From Iraq to Libya and Syria: The wars that come back to haunt us

    The wars that come back to haunt us

    David Cameron should not escape blame for his role in conflicts that are still raging, argues Patrick Cockburn
    Sam Baker and Lauren Laverne: Too busy to surf? Head to The Pool

    Too busy to surf? Head to The Pool

    A new website is trying to declutter the internet to help busy women. Holly Williams meets the founders
    Heston Blumenthal to cook up a spice odyssey for British astronaut manning the International Space Station

    UK's Major Tum to blast off on a spice odyssey

    Nothing but the best for British astronaut as chef Heston Blumenthal cooks up his rations
    John Harrison's 'longitude' clock sets new record - 300 years on

    ‘Longitude’ clock sets new record - 300 years on

    Greenwich horologists celebrate as it keeps to within a second of real time over a 100-day test
    Fears in the US of being outgunned in the vital propaganda wars by Russia, China - and even Isis - have prompted a rethink on overseas broadcasters

    Let the propaganda wars begin - again

    'Accurate, objective, comprehensive': that was Voice of America's creed, but now its masters want it to promote US policy, reports Rupert Cornwell
    Why Japan's incredible long-distance runners will never win the London Marathon

    Japan's incredible long-distance runners

    Every year, Japanese long-distance runners post some of the world's fastest times – yet, come next weekend, not a single elite competitor from the country will be at the London Marathon
    Why does Tom Drury remain the greatest writer you've never heard of?

    Tom Drury: The quiet American

    His debut was considered one of the finest novels of the past 50 years, and he is every bit the equal of his contemporaries, Jonathan Franzen, Dave Eggers and David Foster Wallace
    You should judge a person by how they peel a potato

    You should judge a person by how they peel a potato

    Dave Hax's domestic tips are reminiscent of George Orwell's tea routine. The world might need revolution, but we like to sweat the small stuff, says DJ Taylor
    Beige is back: The drab car colours of the 1970s are proving popular again

    Beige to the future

    Flares and flounce are back on catwalks but a revival in ’70s car paintjobs was a stack-heeled step too far – until now
    Bill Granger recipes: Our chef's dishes highlight the delicate essence of fresh cheeses

    Bill Granger cooks with fresh cheeses

    More delicate on the palate, milder, fresh cheeses can also be kinder to the waistline
    Aston Villa vs Liverpool: 'This FA Cup run has been wonderful,' says veteran Shay Given

    Shay Given: 'This FA Cup run has been wonderful'

    The Villa keeper has been overlooked for a long time and has unhappy memories of the national stadium – but he is savouring his chance to play at Wembley
    Timeless drama of Championship race in league of its own - Michael Calvin

    Michael Calvin's Last Word

    Timeless drama of Championship race in league of its own