The Measurement of Caffeine Concentration in Scalp Hair as an Indicator of Liver Function

The study measured caffeine concentration in plasma and scalp hair to assess liver function in individuals consuming normal amounts of caffeine. Six healthy Japanese volunteers had their caffeine intake measured, showing an average consumption of 178.0 mg/day. A larger survey of 121 adults reported a similar average intake of 231.8 mg/day. Plasma caffeine levels were compared between healthy individuals and those with liver disease, revealing higher levels in patients with liver cirrhosis. Caffeine concentration in hair was also higher in cirrhosis patients (26.5 ng/mg) compared to healthy subjects (7.21 ng/mg). These results indicated that caffeine levels in plasma and hair could serve as practical indicators of liver metabolic capacity.