Reproducibility of the serum lipid response to coffee oil in healthy volunteers

The serum lipid response of 32 healthy volunteers was measured twice in separate five-week periods in which coffee oil was administered (69 mg cafestol / day).Total cholesterol levels increased by 24% in period 1 (range:0;52%) and 18% in period 2 (1;48%), LDL cholesterol by 29 % (-9;71%) and 20% (-12;57%), triglycerides by 66% (16;175%) and 58% (-13;202%), and HDL cholesterol did not change significantly: The range of the HDL response was -19;25% in period 1 and -20;33% in period 2.The correlation between the two responses was 0.20 (95%CI -0.16, 0.51) for total cholesterol, 0.16 (95%CI -0.20, 0.48) for LDL, 0.67 (95%CI 0.42, 0.83) for HDL, and 0.77 (95%CI 0.56, 0.88) for triglycerides.The responses of total and LDL cholesterol to coffee oil were poorly reproducible within subjects. The responses of HDL and triglycerides, however, appeared to be highly reproducible. Therefore, investigating the genetic sources of the variation in the serum-lipid response to coffee oil is more promising for HDL and triglycerides.The effect of dietary changes on serum lipid levels differs significantly between individuals [1-5]. The differences in response may be caused by variation in genes regulating serum lipid levels [6-8]. Identification of genes regulating the lipid response may help to clarify the mechanism by which diet raises serum lipid levels. It also might provide leads for dietary and pharmacotherapeutical means of lowering serum cholesterol. Cafestol, a cholesterol-raising substance in coffee oil, can be used to study lipid metabolism and the genes involved [9-11] because it greatly affects serum lipid levels in humans [9-11]. Therefore, coffee oil can be used to affect serum lipid levels without the need to provide a fully controlled diet. The effect of coffee oil on the expression of genes in humans, however, is difficult to study in relevant tissues like liver or intestinal epithelium.An alternative approach is to study the response of serum lipids to coffee oil in ind