Coffee's impact on the human body is strongly felt shortly after consumption, but what exactly happens inside our bodies as we ingest this popular beverage?
For many of us, a morning cup of coffee is an essential ritual that boosts focus and provides an energy boost to kickstart the day.
The impact of coffee on the body is rapid and significant. Here, MailOnline breaks down exactly what happens to you when you drink coffee.
How Coffee Affects Your Body
10 Minutes After
Blood pressure and heart rate begin to increase as the caffeine in coffee takes effect.
Dr. Duane Mellor, registered dietitian with the British Dietetic Association, says caffeine is detected in the blood within 10 minutes of consumption, reflecting the rapid rate at which it is absorbed.
The buzz you feel is the result of caffeine blocking the effects of adenosine, a neurochemical in the brain which promotes sleepiness.
20 Minutes After
Alertness, energy, and focus all increase. Productivity soars.
Mellor explains that while caffeine blocking adenosine receptors largely contributes to the increased alertness, it's also responsible for the spike in blood pressure that occurs within half an hour of coffee consumption - an effect that can continue for up to four hours.
The blood pressure spike is caused by caffeine narrowing your blood vessels, increasing the force of your heartbeat.
While this effect is temporary, the NHS warns that regularly drinking more than four cups of coffee a day can contribute to long-term high blood pressure.
45 Minutes After
Caffeine's stimulating effects reach their peak, according to Mellor.
Levels of the neurotransmitter serotonin (the 'happy hormone') rise. It improves motor function in the brain, allowing muscles to contract more powerfully. We feel energized and performance is at its optimum.
However, this doesn't mean more coffee is better. Consuming excessive caffeine can cause feelings of anxiety and restlessness rather than promoting focus.
NHS guidelines state that 400mg of caffeine a day is safe for most adults, equivalent to about four average-sized cups of coffee.
For pregnant women, it's recommended to consume no more than 200mg (two cups) a day. The recommended limit for teenagers is one cup.
60 Minutes After
As the stimulating effects of caffeine begin to wane, you may notice its diuretic effect kicking in after about an hour.
Once caffeine enters the bloodstream, it starts to exert what experts call a 'diuretic effect,' says Mellor.
Put simply, you may find yourself needing to urinate more than usual.
According to the NHS, caffeine in coffee inhibits the production of the anti-diuretic hormone, ADH, which normally helps regulate the amount of water in your body.
This prevents the kidneys from reabsorbing water, leading to increased urine production.
It's not necessary to worry about becoming dehydrated from caffeine's diuretic action, however.
Research indicates that only when consuming more than 500mg of caffeine (over five cups of coffee) a day is the risk of mild dehydration increased.
The NHS also states that moderate coffee consumption actually contributes towards hydration, similar to water and fruit juice.
90 Minutes Onwards
Caffeine's half-life varies from person to person, but for most, the stimulating and diuretic effects start to fade after one to two hours, says Mellor.
Some may experience a lull in energy levels, similar to before they consumed coffee.
However, the fact that you no longer feel wired from caffeine doesn't mean it has completely left your system.
Six hours after consuming caffeine, half of it will still be present in the body. Researchers from the Sleep Foundation state that caffeine can linger in your body for up to 12 hours.
For this reason, sleep experts recommend avoiding caffeine at least eight hours before bed to prevent sleep disruption - meaning afternoon coffee is best avoided.
Summary
Coffee has a significant impact on our bodies, providing an energy boost and increased alertness within 20 minutes.
However, the diuretic effect that occurs within an hour may increase the need to urinate. Most people will experience a decline in caffeine's stimulating effects after 90 minutes to two hours, but it can take up to 12 hours to be completely eliminated from the system.