This week we’re keeping you caffeinated with the impact of coffee on our health, sleep, exercise performance and more.
Google Trends
Health and disease risk
https://pubmed.ncbi.nlm.nih.gov/29276945/
https://pubmed.ncbi.nlm.nih.gov/28853910/
https://pubmed.ncbi.nlm.nih.gov/16507475/
https://pubmed.ncbi.nlm.nih.gov/24671262/
https://pubmed.ncbi.nlm.nih.gov/25156996/
https://pubmed.ncbi.nlm.nih.gov/16685044/
https://pubmed.ncbi.nlm.nih.gov/22591295/
Diuretic effect
Despite the fact that caffeine is a mild diuretic, you don't lose more fluid than you take in by drinking coffee, so it cannot dehydrate you.
While we don’t count coffee towards our fluid targets for the day, it doesn’t throw you into the negatives. It’s a net-neutral sort of scenario.
Coffee and exercise performance
The impact of coffee on exercise performance is related to caffeine’s impact on the CNS. It’s a stimulant meaning it enhances alertness, and also reduces our perception of fatigue and our perception of effort. So you feel like you’re not working as hard, and also feel less tired.
Those that are most likely to benefit from caffeine are those involved in team or intermittent sports so basketball, footy etc, endurance sports and high intensity, short duration sports.
How much do you need?
While research initially focused on high doses of caffeine, more recent research indicates that lower doses can provide similar performance benefits with less negative side effects. Around 1-3 mg caffeine per kg body weight are sufficient to improve performance (so for a 60kg athlete this equates to roughly 1-2 cups of coffee).
Timing is also important - coffee reaches peak concentrations 1hr post intake and will generally last for 3-4hrs. The ideal time to down your coffee is 30-45mins pre-training and often black is best if you’re likely to be sensitive to exercising on a tummy full of milk.
https://www.sportsdietitians.com.au/factsheets/supplements/caffeine/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867441/
Coffee and sleep
We all know the joys of caffeine in perking us up, but does it affect our sleep?
The stimulating effects of caffeine from coffee last 3–5 hours, and depending on individual differences, about half of the total caffeine you consume remains in your body after 5 hours. It’s no surprise that consuming coffee too close to bedtime can cause sleeping problems. Most studies suggest avoiding caffeine for 6 hours prior to bed.
The good news is that a switch to tea in these 6 hrs, including green tea which contains about a third of the caffeine as coffee, will be helpful due to the presence of amino acid L-theanine, which has relaxing and calming properties.
Coffee and waking!
Studies have shown that the ideal time to drink coffee is around 203hrs after waiting. This is because of our hormones.
As we wake up, a hormone called cortisol is at its highest. Cortisol is responsible for balancing our energy levels, blood pressure and how we respond to stress or danger.
So, drinking coffee when cortisol is already at its highest may not be giving you any additional energy. In fact, it may be making you feel more tired and stressed or anxious later in the day.
Science suggests waiting 2-3 hours after waking when cortisol is slowly declining to have your morning coffee for the most bang for your buck.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2257922/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2684472/
Coffee naps
Some research suggests that combining caffeine with naps is more energising than caffeine or sleep alone. Enter the coffee nap. The theory is that if you drink coffee (or anything caffeinated) before sleeping for a short period, you can boost your energy levels by increasing your brain’s capacity to receive caffeine.
This is related to caffeine competing with adenosine for receptors in your brain.
Adenosine is an organic compound whose derivatives are important for energy processes in the body amongst other things. Adenosine circulation increases when we feel tired and the act of sleep brings these levels down. But coffee might give us a double whammy by blocking some of the adenosine being registered in our brain. This can make us feel even less tired when we wake.
Most of the research suggests the best way to take a coffee nap is to have some caffeine right before taking a 15–20 minute nap (and no more than 30mins).
https://pubmed.ncbi.nlm.nih.gov/9401427/
https://pubmed.ncbi.nlm.nih.gov/14652086/
Fun facts