Heart Rate & Blood Pressure
Soon after drinking a cup of coffee, your blood pressure will go up a little. But if you’re not a regular coffee drinker, it will go up even more. If you only drink one cup, your heart rate will actually slow down because of the rise in blood pressure. If you drink several cups of coffee or more, your heart rate will accelerate. If you’re healthy, this won’t be a problem, but if you have an abnormal heart rate, high blood pressure or heart disease, this could be an issue.
Having an espresso after lunch makes sense from a physiological standpoint because it can facilitate digestion since caffeine does raise acid levels in the stomach. But doctors advise against having coffee drinks on an empty stomach as you don’t want gastric acids irritating your gut lining, which would be painful, cause you to be bloated and have heartburn.
Bowel & Bladder
Coffee stimulates the bowel, which can cause waste to be pushed out much faster than usual, which for some is within 5 minutes of having a cup! This actually happens with decaffeinated coffee too, so researchers think that something in coffee other than caffeine causes this. What is a myth about coffee is that it makes you urinate more often than you would if you drank the same amount of water. Coffee does offer a very small diuretic effect, and it is as hydrating to the system as water.
Caffeine causes the body to release adrenaline, which triggers your “fight or flight” response. When this happens, the pupils will dilate a little to give you sharper vision. This occurs within 20 minutes of having a cup of coffee.
Cognition & Memory
Caffeine is definitely a stimulant. Twenty minutes after having a cup of coffee you will feel more alert, have improved concentration and be less apt to make mistakes. Recent research revealed that drinking coffee could increase memory 24 hours after drinking it. This may not seem very long, but most of our memories fade within a few hours of learning. There have been many studies that suggest people who are regular coffee drinkers throughout their lifetime are less likely to develop Alzheimer’s disease.
It may be wise to hold off on that cup of coffee when you first wake up in the morning. This is when your cortisol levels tend to be high so this should sustain you for a while. It’s best to have your coffee about an hour after getting up. Caffeine increases the body’s production of heat, which may help with weight-loss. About 3 hours after drinking coffee, the effects of caffeine will begin to fade and you may have a “coffee crash.” The reason for this is that caffeine doesn’t really make us more energetic, it just makes us less likely to feel tired.
When you have a late evening espresso your internal body clock will reset by delaying the rise in melatonin levels, which is our body’s main sleep hormone. Fluctuating melatonin levels are what determine our natural sleep patterns, when it’s time to go to sleep and when we awaken. This means an espresso a few hours before bedtime would likely leave us staring at the ceiling, unable to fall asleep.