Substituting polyunsaturated for saturated fat as a single change in a Swedish diet: effects on serum lipoprotein metabolism and glucose tolerance in patients with hyperlipoproteinaemia.

Abstract

Abstract. A diet with a high content of polyunsaturated fatty acids (PUFA) with a ratio between polyunsaturated and saturated fatty acids (P/S) of 20 and a fat content of 44% was worked out. After an initial 2 weeks' period on a control diet (P/S ratio 0–2) the PUFA diet was fed under isoenergetic conditions at a metabolic ward for 2 weeks to thirty patients with hyperlipoproteinaemia type IIa (n= 7), type IIb (n= 5) and type IV (n=18). The two diets were based on ordinary foodstuff and differed only in regard of the quality of the fat, while the amount of fat as well as the content of other nutrients were kept constant. Compared with the control diet the serum cholesterol concentration decreased by 10%, 13% and 12% on the PUFA diet in patients with hyperlipoproteinaemia type IIa, IIb and IV respectively. In hyperlipoproteinaemia Ila the low density lipoprotein cholesterol decreased by 9% (n.s.) and the high density lipoprotein cholesterol by 16% (P < 005). In hyperlipoproteinaemia type lib the very low density lipoprotein cholesterol decreased by 18% (P < 005), the low density lipoprotein cholesterol by 13% (P < 005) and the high density lipoprotein cholesterol by 5% (n.s.). In type IV the very low density lipoprotein cholesterol decreased by 18% (P < 0–01), the low density lipoprotein cholesterol by 7% (P < 0–05)) while the high density lipoprotein cholesterol remained unchanged. The serum triglyceride concentration decreased by 10% (type IIa), 14% (type lib) and 13% (type IV) on the PUFA diet. The serum concentrations of apolipoprotein A‐I and B were reduced by 6% (P < 0–05) and 11% (P < 005) respectively in patients with hyperlipoproteinaemia type IV while the serum apolipoprotein concentration did not change in the patients with hypercholesterolae‐mia. Inverse relationships between very low density lipoprotein triglycerides and high density lipoprotein cholesterol were found before treatment (r= 0–49, P < 0–01) which was altered by the treatment (r= 0–28, P > 005). The very low density lipoprotein triglycerides were also found to be inversely related to low density lipoprotein cholesterol both on the control diet (r= ‐0–65, P < 0001) and the PUFA diet (r= ‐0–56, P < 001). The regression lines of the latter equations were parallel. The intravenous glucose tolerance was improved (P < 0 05) in patients with hyperlipoproteinaemia type IV on the PUFA diet. The fatty acid composition of the serum lipid esters was significantly changed during the treatment. The relative concentrations of oleic acid and saturated fatty acids decreased while the linoleic acid content increased. The effects of the PUFA diet were less pronounced than the effects of conventional lipid lowering diets where also the fat content has been reduced and where complex carbohydrates have been substituted for simple carbohydrates.