The Food Medic - Ask Dr Hazel E7: EVENING EXERCISE AND CAFFEINE DILEMMA

Starting point is 00:00:00 What's better than a well-marbled ribeye sizzling on the barbecue? A well-marbled ribeye sizzling on the barbecue that was carefully selected by an Instacart shopper and delivered to your door. A well-marbled ribeye you ordered without even leaving the kiddie pool. Whatever groceries your summer calls for, Instacart has you covered. Download the Instacart app and enjoy $0 delivery fees on your first three orders. Service fees, exclusions, and terms apply. Instacart. Grocer $0 delivery fees on your first three orders. Service fees, exclusions and terms apply. Instacart, groceries that over-deliver. Hi Hazel, so I've been told that you're not supposed to have coffee past 12pm because of its half-life and how it'll affect your sleep. But I'm just wondering for somebody who does an

Starting point is 00:00:41 afternoon workout, is it okay to drink coffee before that? If you're going to be burning off that energy, will it affect the half-life? Thank you. This is a great question and actually I didn't know the answer myself, so I'm really glad that you asked. There are a lot of papers on the effects of caffeine on exercise, but not many the other way around. Caffeine has some pretty powerful effects when it comes to mental and physical performance but the timing and the dose does matter. So first of all before we jump into the question how does caffeine work? So it's a psychoactive stimulant and it works through a variety of mechanisms but mainly through its effects on adenosine. So adenosine

Starting point is 00:01:26 accumulates across the day as we're awake, the more we have the sleepier we feel. Then caffeine comes in and acts by preventing adenosine binding to its receptors so essentially it's elbowing caffeine out of the way and blocking it from doing its job so this increases alertness which of course can be a positive thing depending on the time of the day but it can also have a knock-on effect to your sleep later that night so the half time which is the time taken to eliminate half the caffeine from your body varies from person to person but on average is about five hours although research shows that it can be anywhere from two to ten hours ten hours the half-life varies between people depending on lots of other factors such as age body weight pregnancy status smoking status

Starting point is 00:02:20 medication and also the health of your liver. So the coffee you're having later in the day could very well be affecting your sleep at night. So in general, I would advise having a caffeine cutoff time at around midday, or at least eight hours before you go to bed. But back to your question, can exercise speed this process up? So one paper looking at the effects of exercise on the pharmacokinetics of caffeine, this was in the European Journal of Clinical Pharmacology from 1991, found that exercise reduced the half-life of caffeine from an average of 3.99 hours to 2.29 hours. but this study was only with 12 participants and heavy coffee drinkers had a greater half-life elimination compared to light drinkers. So it seems exercise can speed up

Starting point is 00:03:16 how fast we metabolize caffeine but as the half-life varies so much between people, I can't say for sure that the same results would happen for you or for anyone. I think that does answer your question, but if you are a slow metabolizer and you do feel the effects of caffeine, maybe you should look at alternatives to your pre-workout. So if you're feeling let lethargic I would take a look at your nutrition around training so perhaps add in an afternoon snack close to training or maybe you can look at your lunchtime meal and maybe think about adding in more complex carbohydrates that are going to sustain you over a longer period you could also think about having a pre-workout that doesn't have caffeine or other stimulants but what I would say about that is

Starting point is 00:04:05 they're hugely variable in terms of ingredients and quality so do your research first you could consider creatine which enables you to sustain an all-out effort for longer than usual and recover faster between sets and it can also help reduce mental fatigue. So check out our website for more information on this because we wrote a really detailed article on that. It's www.thefoodmedic.co.uk. Hopefully that helps. Thank you again for your question. That's all from me today.

Starting point is 00:04:37 But if anyone listening would like to ask their own question for a chance to feature on the podcast, please send your voice recorded questions to ellie at thefoodmedic.co.uk and I will see you again next time

The Food Medic - Ask Dr Hazel E7: EVENING EXERCISE AND CAFFEINE DILEMMA

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