Caffeine

Studies in people

• Open question

  Appetite and food intake²

  In people, caffeine taken 0.5 to 4 hours before a meal may reduce how much you eat at that meal.

• Open question

  Running endurance³

  In people, caffeine helped runners last longer and finish running time trials faster.

• Benefit

  Liver scarring risk⁴

  People who took in more caffeine each day were less likely to show signs of liver scarring.

Study type not stated

• Open question

  Exercise performance⁶

  Caffeine can boost exercise performance, but how much it helps varies from person to person.

• Open question

  Heart and bone health⁷

  Scientists do not yet know whether caffeine causes heart problems or bone loss, or works the same for everyone.

• Open question

  Muscle strength and sprinting⁸

  Caffeine may improve endurance exercise, but results are mixed for strength and sprinting, and it may blunt creatine's benefits.

• Open question

  Physical and mental performance¹⁰

  Caffeine can boost physical and mental performance, but people respond differently depending on how their body breaks it down.

How it’s made and used

• Muscle power and fatigue⁵

  In eight Olympic boxers, caffeine improved jumping and power without changing muscle fatigue.

• Kidney and water balance⁹

  Caffeine makes the kidneys filter more and pull back less salt, so you pass more water.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least two findings in people. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.