In a randomized double-blind parallel study in 36 subjects the effect on serum cholesterol of a daily dose of 2 g lipid extracted from green Arabica and Robusta coffee beans was studied. Arabica oil elevated serum total cholesterol by 1.1 mmol/L (95% CI for the difference from placebo: 0.41, 1.73 mmol/L); the effect of robusta oil (+0.5 mmol/L) was not statistically significant (95% CI: -0.01, 0.92 mmol/L). Arabica oil also raised plasma triglycerides by 0.8 mmol/L (95% CI: 0.26, 1.25 mmol/L). The effect of robusta oil on triglycerides was +0.14 mmol/L and not significant (95% CI: -0.26, 0.42 mmol/L). In the 12 subjects taking arabica oil an average serum alanine amino-transferase elevation of 18 U/L (95% CI: 9.4, 28.4 U/L) was observed. Because only arabica oil contains kahweol and arabica coffee contains more cafestol than does robusta oil, this is further evidence for the role of diterpenes in the rise of serum cholesterol and alanine aminotransferase after consumption of boiled coffee.