The Physiology of Caffeine
For many people, caffeine is part of their daily routine, whether it comes from coffee, tea, energy drinks, or other products. While it is best known for increasing alertness, caffeine can affect several systems throughout the body.
How Caffeine Affects the Brain
Caffeine is a central nervous system stimulant, meaning it acts directly on the brain to promote alertness and reduce feelings of tiredness. Moderate amounts may also support processing speed and memory.
However, consuming too much can have the opposite effect, contributing to headaches, anxiety, irritability, or other cognitive symptoms. Regular caffeine use can also lead to tolerance, while suddenly stopping can cause withdrawal symptoms such as headaches, drowsiness, and irritability.
Effects on Digestion
Caffeine can increase stomach acid production, which may contribute to heartburn or an upset stomach, particularly in people who already experience digestive problems. The body does not store excess caffeine. Instead, the liver processes it and the kidneys remove it through urine, which can temporarily increase urination.
Heart and Blood Pressure
After being absorbed through the digestive system, caffeine reaches its highest concentration in the bloodstream within about an hour. It can temporarily increase blood pressure, potentially through effects on adrenaline or blood vessels. For most people, this does not appear to cause a lasting increase in blood pressure. However, caffeine may make the heart work harder in people with irregular heart rhythms.
Bones and Muscles
Large amounts of caffeine may interfere with calcium absorption and metabolism, which could contribute to bone thinning. Excessive intake may also cause muscle twitching.
Interestingly, muscle aches can occur when someone experiences caffeine withdrawal.
Caffeine During Pregnancy
Caffeine crosses the placenta, meaning it can reach the fetus. Because it acts as a stimulant, it may increase fetal heart rate and metabolism. Higher caffeine consumption during pregnancy has been associated with slower fetal growth and pregnancy loss. The American College of Obstetricians and Gynecologists recommends limiting intake to 200 mg per day during pregnancy, although some research has raised concerns about lower amounts as well. Anyone who is pregnant should discuss their caffeine intake with a healthcare professional.
How Much Is Too Much?
For most healthy adults, the FDA considers up to 400 mg of caffeine per day to be a safe amount. Individual tolerance can vary depending on factors such as age, body size, and overall health. If you regularly consume caffeine and want to cut back, gradually reducing your intake may help minimize withdrawal symptoms.
The Bottom Line
Caffeine does much more than keep you awake. It can influence the brain, digestive system, cardiovascular system, muscles, and reproductive system. While moderate consumption is generally considered safe for healthy adults, consuming large amounts can produce unwanted effects.
Understanding how caffeine interacts with the body can help put that daily cup of coffee into perspective.
References
Pietrangelo, A. (2023, May 9). The Effects of Caffeine on Your Body. Healthline. https://www.healthline.com/health/caffeine-effects-on-body
Assessed and Endorsed by the MedReport Medical Review Board
