Drinking a cup of coffee in the morning is an essential part of daily rituals for many. But have you ever wondered what exactly happens inside your body after the first sip, minute by minute?
**After 10 Minutes**
Dr. Duane Mellor from the British Dietetic Association states that after drinking coffee, caffeine begins to appear in the bloodstream after about 10 minutes. This demonstrates how quickly caffeine is absorbed into the bloodstream through parts of the digestive system. Some caffeine can be absorbed through the mouth and stomach, but in smaller amounts, with most absorption occurring in the first part of the intestine. Once caffeine is absorbed from coffee, individuals feel an increase in energy, but Mellor notes that this boost can be misleading since caffeine doesn't actually provide energy. Instead, it prevents the body from interacting with adenosine, a chemical that causes the feeling of tiredness, as caffeine's chemical structure is quite similar to that of adenosine. This resemblance effectively prevents the sensation of fatigue, making us feel more awake.
**After 20 Minutes**
Dr. Mellor explains that caffeine, which blocks adenosine receptors in the body, not only enhances alertness but also causes an increase in blood pressure within half an hour of drinking coffee, with effects still observable after approximately four hours. He notes that this rise in blood pressure occurs due to caffeine causing blood vessels to constrict, thereby increasing the heart rate. Although this is temporary, the National Health Service warns that consuming more than four cups of coffee a day may raise blood pressure in the long term.
**After 45 Minutes**
Dr. Mellor indicates that caffeine effects peak after 45 minutes, with the stimulating effects of coffee, an increase in heart rate, and enhanced feelings of energy improving concentration and memory. He cautions that drinking too much coffee can have adverse effects, explaining that excessive caffeine intake can lead to feelings of tension and anxiety instead of helping you focus. NHS guidelines suggest that about 400 mg of caffeine per day is safe for adults, roughly equivalent to four regular cups. Pregnant women are advised to consume about half of that amount, while teens should limit their intake to around 100 mg.
**After 60 Minutes**
Dr. Mellor clarifies that after the stimulating effects of caffeine kick in, individuals may notice unwanted side effects. Once caffeine is in the bloodstream, experts refer to a phenomenon called "diuretic effect." This means that consuming enough coffee may make you need to urinate more frequently. When drinking coffee, the caffeine inhibits the production of antidiuretic hormone (ADH), which usually helps regulate the amount of water in the body. Consequently, this results in the kidneys not reabsorbing water and increasing urine output, although dehydration only occurs if an individual consumes excessive amounts of coffee. Research shows that to impact hydration levels, one must consume over 500 mg of caffeine daily, or more than five cups. A study from the University of Birmingham in 2014 found no evidence of dehydration with moderate daily coffee consumption, and the NHS confirmed that moderate caffeine intake is a good way to stay hydrated alongside water and juice. Other studies have shown that coffee can stimulate contractions in the colon and internal muscles, meaning it not only increases the urge to urinate but also stimulates an urge to defecate. A 1998 study pointed out that caffeine increases colon activity by 60 percent, indicating these contractions push contents toward the rectum.
**After 90 Minutes**
Dr. Mellor explains that the time it takes to metabolize caffeine varies from person to person. For most people, this occurs after one to two hours of that first sip of coffee, as the euphoric effects and diuretic attributes begin to fade, potentially causing feelings of fatigue, anxiety, and decreased focus. He mentions that just because one feels a drop in caffeine levels doesn't mean it has completely left the body system. Typically, for most people, caffeine levels drop by about half after six hours, as it is metabolized by the liver. Thus, even though the effects may fade after one or two hours, a significant amount of caffeine remains in the system. Researchers at a sleep foundation have found that as a result, caffeine can stay in the body for up to 12 hours, stressing the importance of avoiding caffeine at least eight hours before bedtime to prevent interference with sleep, implying that it is wiser to skip afternoon coffee.
