Serum lipid profiles in Japanese women and men during consumption of walnuts

Objective: To determine the serum cholesterol, apolipoproteins and LDL oxidizability in young Japanese women and men during walnut consumption and to evaluate its active principle. Design: Experimental study with a randomized design. Subjects: Twenty healthy women and 20 healthy men. Interventions: Subjects were randomly assigned to consume each of two mixed natural diets for 4 weeks in a cross-over design. Reference and walnut diets were designed and the walnut diet had 12.5% of the energy derived from walnuts (44-58 g/day). Results: The total cholesterol and serum apolipoprotein B concentrations, and the ratio of LDL cholesterol to HDL cholesterol was significantly lowered in women and men when fed on the walnut diet, than when on the reference diet (P≤0.05). The LDL cholesterol concentration was significantly lowered in women on the walnut diet (0.22 mmol/l, P=0.0008), whereas this decrease was not significant in men (0.18 mmol/l, P= 0.078). The most prominent change in the fatty acid composition of the cholesteryl esters from serum after the walnut diet was an elevation of α-linolenic acid in women (76%, P <0.001) and men (107%, P<0.001). This elevation was negatively correlated to the change in LDL cholesterol in women (r=0.496, P=0.019) and men (r=0.326, P=0.138). The LDL oxidizability in women was not influenced by the diets (P=0.19). Conclusions: α-Linolenic acid in the walnut diet appears to be responsible for the lowering of LDL cholesterol in women.