Millions of cups of coffee are consumed each day but few people realise the extent to which our morning brew affects our bodies from the first sip. Recent research shows that a late-night shot slows down the internal body clock and prevents sleep - but it does a whole lot more than that.Pulse and blood pressureShortly after drinking coffee, your blood pressure rises a fraction - more so if you don't drink coffee regularly. If you stick to one cup, your heart rate slows due to the increase in blood pressure. "But a few cups of coffee can cause heart-rate acceleration," Dr Owen Bain, of the Gourmet Focus consultancy, says. For healthy people this isn't a problem but it might be an issue for those with problems such as heart disease, high blood pressure or abnormal heart rate.The gutOrdering an espresso after a meal makes physiological sense - caffeine raises acid levels in your stomach, which helps digestion. But avoid coffee on an empty stomach because the more acidic gastric juices could irritate the gut lining, causing pain, bloating and heartburn.Bowel and bladderCompounds in coffee stimulate the bowel and can result in waste being pushed out faster than normal. The same thing occurs with decaffeinated coffee and researchers believe a compound other than caffeine is responsible.Bain says it's a myth that coffee makes you urinate more frequently than drinking the same amount of water.EyesWithin 20 minutes of drinking coffee, caffeine causes adrenaline to be released, activating your "fight-or-flight" mode. The pupils dilate and you have sharper vision.Brain power and memory"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," Bain says. "A recent study showed that coffee could enhance your memory 24 hours after consumption."Studies suggest that drinking it over a lifetime might reduce the risk of developing Alzheimer's disease.Energy"The best time to drink a cup is about an hour after you get up," Bain says. The caffeine increases heat production, which helps with weight reduction . But, after three hours, the effects of the caffeine start to fade and you may have a coffee crash.LungsThe caffeine in coffee is similar to the drug theophylline, given to patients with respiratory problems. It helps open up the lungs, making it easier to breathe.MoodCoffee stimulates the release of the feel-good hormone dopamine. "An hour after drinking coffee there is a reduction in anxiety levels and increased feelings of contentment," Bain says.SleepCoffee drunk late at night resets the internal body clock by delaying a rise in the level of melatonin. Fluctuating levels help determine the natural time to go to sleep and wake up, so a double espresso three hours before bed time could leave you sleepless. ..