Caffeine, a central nervous system stimulant found in coffee, green tea, and other beverages, has both health benefits and potential risks depending on the amount consumed.

Health benefits:

• Mental alertness and cognitive function - enhance focus in the short term
• Physical performance - by increasing adrenaline levels and releasing fatty acids from fat tissues
• Metabolism and weight loss - caffeine can boost metabolic rate and increase fat burning
• Protective effects - regular consumption of coffee and green tea is associated with a reduced risk of certain chronic diseases, including Parkinson's disease, type 2 diabetes, and liver diseases

Health risks:

• Anxiety and insomnia - sensitivity varies among individuals
• Heart health - large amounts of caffeine can lead to increased heart rate and blood pressure
• Dependency - withdrawal symptoms include headache, fatigue, and irritability

Moderation is key to maximizing the health benefits of caffeine while minimizing its risks. For most people, moderate coffee consumption is defined as about 3 to 4 cups per day (up to 400 milligrams of caffeine), although individual tolerance varies. Green tea contains less caffeine than coffee but is rich in antioxidants, making it a healthy choice for those who are sensitive to caffeine.