Caffeine is a central nervous system stimulant that affects the body in multiple ways:

• Increased alertness and energy: Caffeine blocks adenosine receptors in the brain, which normally promote sleepiness, leading to increased mental alertness, reduced fatigue, and enhanced concentration

. This effect usually starts within 5 to 30 minutes after consumption and can last up to 12 hours depending on the individual

• Physical effects: It increases heart rate and breathing rate, and can raise body temperature

. It also stimulates the bladder, causing more frequent urination, though this diuretic effect is mild and fluid intake from caffeinated drinks still contributes to hydration

• Mood and cognitive function: At low doses, caffeine can improve mood, cognition, learning, and memory. However, higher doses may cause restlessness, nervousness, anxiety, irritability, tremors, headaches, and insomnia

. Caffeine may also have therapeutic potential in conditions like depression, Alzheimer’s, and Parkinson’s diseases due to its complex actions on brain receptors

• Digestive system: Caffeine can increase gastric acid secretion and relax smooth muscles, which might cause gastrointestinal discomfort or exacerbate conditions like irritable bowel syndrome in sensitive individuals

• Tolerance and side effects: Regular consumption can lead to tolerance, requiring higher doses for the same effects. Excessive intake can cause symptoms such as dizziness, rapid heartbeat, dehydration, anxiety, and sleep disturbances

• Other physiological effects: Caffeine influences multiple body systems including cardiovascular, respiratory, immune, and urinary systems. It also exhibits antioxidant and anti-inflammatory properties, which may reduce risk of certain diseases and support liver health

In summary, caffeine stimulates the brain and body to increase alertness and energy but can cause negative effects like anxiety, digestive issues, and sleep problems if consumed in excess. Its effects vary by dose and individual sensitivity