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20th April 2023

5 things you should know about caffeine

By Dr Scott Robinson, PhD MSc SENr

4 Minute Read

Caffeine is the most widely consumed psychoactive substance in the world; often used to boost mood and elevate both mental and physical performance.

If you’re thinking of using caffeine to your advantage, here are five things to keep in mind…

  1. When it comes to caffeine, every ‘body’ responds differently.

    If you’re looking to reap the benefits of caffeine, it’s important to be aware that each person responds differently (often, very differently!). The optimal dose for you is likely to be totally different to that of your significant others, and it often takes a little time and experimentation to find the dose that is most suitable.

    As a general guideline informed by science, a variety of cognitive benefits tend to appear following the consumption of around 0.5mg - 4mg per kg body mass.


    for a 50kg person this is between 25mg - 200mg
    for a 70kg person this is between 35mg - 280mg
    for a 90kg person this is between 45mg - 360mg

    Yep, this is a big range so we always recommend starting low and gradually increasing (as opposed to vice-verse). Too much caffeine can lead to restlessness, anxiety, increased heart rate, GI distress, an inability to focus and insomnia. It’s always better to be safe than sorry, especially when it comes to caffeine.

    If you’re looking to use caffeine as an aid to exercise performance, the research shows that between 3-7mg per kg body mass is effective when consumed within the hour before, during or late into exercise (study here). Yes, another large range!


    for a 50kg person this is between 150mg - 350mg
    for a 70kg person this is between 210mg - 490mg
    for a 90kg person this is between 270mg - 630mg

    Again, when it comes to caffeine there really is no ‘one size fits all’. We all respond differently so be strategic and take the time to find what works best for you (or work with us and let us help you remove the guesswork).

  2. Caffeine's 'half life' is very important!

    The ‘half life’ of caffeine is around 4-6 hours, which means that for most people half of the caffeine will still be in your system 4-6 hours after consumption.

    So, despite not feeling its ‘buzz’ a few hours later, half of it will still be present, which can negatively impact your sleep if you consume caffeine after midday. 

    If you want to fall asleep quickly, and achieve high quality (deep) sleep, try switching to decaf after 12pm - or earlier if you’re highly sensitive to caffeine.

  3. Caffeine ‘trojan horses’ 

    Coffee accounts for over 50% of the world’s caffeine consumption but is also present in other foods and drinks such as teas, dark chocolate and cola.

    Here are a few foods and drinks to be aware of if you’re looking to moderate your caffeine intake (especially if it’s nearing bed time)…

    Coke regular or diet (330ml): ~45mg
    Dark chocolate (45g): ~45mg
    Milk chocolate (45g): ~20mg
    Coffee brewed (300ml): 100-300mg
    Matcha (300ml): 60-120mg
    Decaf coffee (300ml): ~5-50mg
    Energy drinks (250-500ml): 80-350mg
    Tea brewed (300ml): 40-140mg

    *Numbers will vary depending on brand and serving size.

  4. Coffee is unlikely to dehydrate you…

    Coffee contains caffeine and caffeine is a diuretic, which means that it may cause you to urinate more frequently and this may affect your hydration status.

    This has led people, including ourselves and many of our clients, to wonder whether coffee has hydrating or dehydrating effects…

    The answer is ‘it depends’ but in most cases coffee is unlikely to dehydrate you.

    The science shows that drinking coffee in moderation (<400mg per day) is unlikely to dehydrate you as although it may cause you to urinate a bit more, it’s likely that you won’t lose as much fluid as you originally drank.

    *400mg of caffeine is the equivalent of around 3-4 cups of brewed coffee.

    For caffeine to have a mild dehydrating effect, most people would need to be consuming in excess of 500mg of caffeine a day - something we don’t recommend to anybody (study here). 

    Tip: If you really want to play it safe with your hydration, try pairing your coffee with a glass of water. This is an easy habit to get into and is one that many of our high performing clients have adopted and reaped the benefits from.

  5. Caffeine use - insights from high performers 

    When it comes to the high performers we support, some use it, others don’t - but very few rely on it.

    Despite an abundance of research demonstrating the mental and physical benefits of caffeine, over our years of practice it’s been interesting to learn that some of our high performing clients make good use of caffeine, while others have absolutely no interest in using it whatsoever - despite performing at the top of their game day in, day out.

    I suppose this reverts back to what we often preach on our coaching programmes… what works for one person likely won’t work for someone else, and each person has their own unique preferences. This makes especially good sense when it comes to caffeine seeing as it really isn’t the be all and end all of ‘high performance’. In fact, caffeine is only one of many available ‘tools’ in the ‘high performance toolbox’.

Closing thoughts...

If you’re looking to benefit from caffeine, here are the main considerations (albeit not exclusive to!)…

1. The amount - usually determined by your goals and level of caffeine tolerance.

2. The type - keep in mind that different forms contain different amounts.

3. The timing - for several reasons, but mainly so it doesn’t impact your sleep.

Dr Scott Robinson, PhD MSc SENr

Scott is the Founder and Managing Director of The Edge HPL.

An expert on nutrition and metabolism, he has co-authored a number of scientific studies and books.

He is a Registered Nutritionist and holds a Ph.D in Nutrition and Physiology from the University of Birmingham, UK.

Scott's mission with The Edge HPL is to provide high quality, practical solutions that help people thrive - no matter their starting point, goals or ambitions in life.

The Edge HPL is not responsible for any specific health or allergy needs that require supervision nor any adverse reactions you may have to the advice we provide - whether you have followed them as written or have modified them to suit your dietary requirements.

Any nutritional advice and information provided by The Edge HPL is based on our own experiences, research and knowledge. The information provided is not to be used in place of proper medical advice. The Edge HPL and its employees and representatives are not medical professionals, do not hold any type of medical licenses or certifications and do not practice medicine.  If customers have any medical questions regarding any advice or information provided by The Edge HPL, they should consult their physician, or another healthcare professional. Please also refer to our Standard Business Terms and Conditions, which can be found on our website.