In the UK, we drink 70 million cups of coffee a day. That is more than the entire population. The question to be answered is ‘Is what we are drinking good for us?’
There is a long version of this and a short version. In short, coffee should be treated more like a drug. One or 2 cups a day is likely to produce more beneficial effects, while too much can lead to short and long term harm
For mainstream media I couldn’t go into as much detail as I would like so will dig a little deeper into the evidence here.
How quickly is coffee absorbed, and when does it pass out of you?
A single cup of coffee has rapid absorption with caffeine uptake to the blood in just over 20 minutes and will stay in the blood stream for over 12 hours. The rate at which caffeine exits your body is dependant on your genetics.
Blood pressure – Blood pressure rises a fraction after drinking, but these effects subside after an hour. This effect is more pronounced in those who are not used to drinking coffee regularly.
Due to an increase in BP, heart rate actually drops. However, more than a few cups of coffee can cause heart rate acceleration
Body – An hour after drinking your cup of coffee, the caffeine stimulates energy expenditure and increases your heat production, thermogenesis, that may help with weight reduction.
Bladder & bowels - Drinking coffee will actually speed up your digestive system, particularly that of your large intestine within 5 minutes of drinking!
it is a common myth that coffee makes you go to the bathroom more than the equivalent amount of water. The diuretic effect of coffee is very small, and it is just as hydrating as water
Gut – Too much coffee can lead to gastric irritation of the stomach lining, therefore anyone with IBS or celiac
Eyes - Within 20 minutes of drinking the caffeine in the coffee causes adrenaline to be released. As a result your pupils will dilate.
Brain function - Recent study showed that coffee can enhance your memory 24 hours after consumption. This may not appear to be long, but most memories are lost within a few hours after learning.
Caffeine is a stimulant and 20 minutes after drinking a coffee you can start to feel more alert with increased concentration and are less likely to make mistakes.
Caffeine has been found to enhance task performance by increasing cortical activation, the rate at which information about a stimulus accumulates and increasing the speed of motor processes via central or peripheral mechanisms
Tiredness - Don’t rush to get your coffee the moment you wake, the best time to drink a cup is about an hour after your get up. Before then your cortisol levels are high and will keep you going until they drop off. Caffeine blocks the adenosine receptors allowing stimulatory molecules to act on the neurons that would otherwise be inhibited by the activated adenosine receptors that cause you to become drowsy
Addiction – By blocking adenosine receptors, dopamine signalling is increased. Dopamine is the ‘feel good’ hormone that can increase the chance of getting you ‘hooked’ wanting more
Sleep – A recent study showed that caffeine has a great impact on our circadian timing, the body clock. Don’t let coffee interfere with your sleep, to be on the safe side do not drink any more after 2pm. This was a great piece of research that showed the effects of cells in culture and in people.
You can also use this to your advantage. If travelling west, have a coffee and this will trick your brain and body to moving more in sync with the local time.
Mood - an hour after drinking there is a reduction in anxiety levels, and increased feelings of contentment. This has been attributed to the theobromine in coffee. Women who are regular coffee consumers have been shown to have less depression
Hippocampus – It is not purely benefits of caffeine on the brain a study from Pusan University showed that caffeine can impact the growth of new neurons in the hippocampus, the brain’s memory centre, and impaired long term learning. This study was in rats, and is very difficult to reproduce this type of of study in humans.
Other risks – Generally associated with large amounts of coffee it can increase anxiety, insomnia, palpitations and increase risk of bone fractures and bone loss increases.
Antioxidant activity – Caffeine doe not has direct antioxidant activity but instead has been shown to increase the concentration of glutathione, a potent antioxidant produced by the body
Overall – Looking at long term studies in a large population set coffee consumption is generally beneficial. However a caveat to this is that to date their has not been enough randomised controlled trials to prove causation. As coffee contains many bioactive molecules not just caffeine, it is diffuclt to ascertain which are having the predominant effects.
The Iowa Women’s Health study showed less death from diseases associated with chronic inflammation in 27000 women followed for 15 years! Also coffee consumption has been correlated with low risk of dementia and Alzheimer's disease.
I’ll drink to that.
Effects of caffeine on the human circadian clock in vivo and in vitro.
Is caffeine a cognitive enhancer
Midlife coffee and tea drinking and the risk of late-life dementia: a population-based CAIDE study.
The effect of coffee on blood pressure and cardiovascular disease in hypertensive individuals: a systematic review and meta-analysis.
Caffeine modulates attention network function.
Central nervous system effects of caffeine and adenosine on fatigue
Inhibitory effects of caffeine on hippocampus neurogenesis and function
Caffeine increases striatal dopamine receptor D2/D3 availability in the human brain
Influence of Caffeine Excess on Activation Patterns in Verbal Working Memory
Chronic coffee and caffeine ingestion effects on the cognitive function and antioxidant system of rat brains
Coffee, but not caffeine, has positive effects on cognition and psychomotor behavior in aging.