Caffeine is found in many drinks, coffee, and foods. It is a substance naturally present in the leaves and seeds of many plants, providing an energy boost when consumed. Caffeine stimulates the central nervous system, increasing alertness, and is classified as a drug. Moderate caffeine consumption (200 to 300 milligrams per day) is generally safe, but excessive intake can lead to health problems. In the short term, caffeine can boost energy and improve mood, but it may also cause withdrawal symptoms. Long-term excessive caffeine intake can lead to osteoporosis, especially in postmenopausal women. The effects of caffeine can be felt about 15 minutes after consumption, peak in the blood after 1 hour, and about half of the caffeine remains in the body after 6 hours. It takes up to 10 hours for caffeine to be fully cleared. For health reasons, it is recommended to consume caffeine in moderation and be aware of foods and medications that may contain caffeine.