Potential role of raising dietary protein intake for reducing risk of atherosclerosis

To ascertain the effect on plasma lipoprotein lipids of substituting moderate amounts of protein for carbohydrate in human diets.

Subjects were first stabilized on the desired fat intake for one to two weeks. Using a cross-over design, subjects were randomly allocated to either the high or low protein diet for four to five weeks and then switched to the alternative diet for four to five more weeks. Fasting venous blood was obtained weekly.

Subjects were studied in tertiary care lipid clinic setting.

Studies in two groups of hypercholesterolemic subjects have been completed: group MH - 10 subjects with moderate hypercholesterolemia (5.8 to 8.0 mmol/L) and group FH - five subjects with familial hypercholesterolemia (more than 8.2 mmol/L prior to treatment with cholestyramine). Preliminary findings in Group NL - six normolipidemic subjects (3.5 to 4.9 mmol/L) are also discussed briefly.

Body weight, intakes of fat, fibre and cholesterol and fat composition were constant. Either 11, 17 or 10% of total energy from protein was exchanged for carbohydrate in groups MH, FH and NL, respectively.

Exchange of dietary protein for carbohydrate: significantly reduced mean plasma low density lipoprotein (LDL) cholesterol 6% in group MH and 9% in group NL (P < 0.02); significantly increased mean fasting plasma high density lipoprotein (HDL) cholesterol by 12% in group MH and by 17% in group FH (P < 0.01); significantly reduced the mean value for the ratio of plasma total cholesterol to HDL cholesterol by 15% in group MH and by 16% in group FH (P < 0.05); and significantly reduced fasting total triglycerides by 23% in groups MH and FH and by 18% in NL (P < 0.05).

Substitution of dietary protein for carbohydrate favourable alters human blood cholesterol cardiovascular risk profiles.