Dr Ruhl and colleagues from Maryland in America designed a study to investigate whether coffee and caffeine consumption reduced the risk of elevated alanine aminotransferase (ALT) activity in persons at high risk for liver injury.
In this national, population-based study the researchers recruited a total of 5944 adult participants from the Third US National Health and Nutrition Examination Survey, 1988–1994.
The participants exhibited excessive alcohol consumption, viral hepatitis, iron overload, overweight, or impaired glucose metabolism.
Liver injury was indicated by abnormal serum ALT activity (>43 U/L).
The researchers found elevated ALT activity in 8.7% of this high-risk population.
In unadjusted analysis, the research team noted that lower ALT activity was associated with increasing consumption of coffee and caffeine.
| Relationships were relatively unchanged when analyses included the entire population |
The researchers performed multivariate logistic regression analyses in order to show that risk of elevated ALT activity declined with increasing intake of coffee and caffeine.
The research team found that on comparing persons who drank more than 2 cups per day with noncoffee drinkers, the odds ratio was .56.
Comparing persons in the highest caffeine quintile with the lowest, the odds ratio was .31.
The researchers found that these relationships were consistent across subgroups at risk for liver injury.
Relationships were relatively unchanged when analyses included the entire population or when limited to persons without impaired liver function or right upper quadrant pain.
Fasting insulin concentrations did not mediate the effects.
Dr Ruhl concluded, "In this large, national, population-based study, among persons at high risk for liver injury, consumption of coffee and especially caffeine was associated with lower risk of elevated ALT activity."