Cholesterol reduction using manufactured foods high in monounsaturated fatty acids: a randomized crossover study

In two separate studies, the cholesterol-lowering efficacy of a diet high i n monounsaturated fatty acids (MUFA) was evaluated by means of a randomized crossover trial. In both studies subjects were randomized to receive eithe r a high-MUFA diet or the control diet first, which they followed for a per iod of 8 weeks; following a washout period of 4-6 weeks they were transferr ed onto the opposing diet for a further period of 8 weeks. In one study sub jects were healthy middle-aged men (n 30), and in the other they were young men (n 23) with a family history of CHD recruited from two centres (Guildf ord and Dublin). The two studies were conducted over the same time period u sing identical foods and study designs. Subjects consumed 38 % energy as fa t, with 18 % energy as MUFA and 10 % as saturated fatty acids (MUFA diet), or 13 % energy as MUFA and 16 % as saturated fatty acids (control diet). Th e polyunsaturated fatty acid content of each diet was 7 %. The diets were a chieved by providing subjects with manufactured foods such as spreads, 'rea dy meals', biscuits, puddings and breads, which, apart from their fatty aci d compositions, were identical for both diets. Subjects were blind to which of the diets they were following on both arms of the study. Weight changes on the diets were less than 1 kg. In the groups combined (n 53) mean total and LDL-cholesterol levels were significantly lower at the end of the MUFA diet than the control diet by 0.29 (sD 0.61) mmol/l (P < 0.001) and 0.38 ( sD 0.64) mmol/l (P < 0.0001) respectively. In middle-aged men these differe nces were due to a mean reduction in LDL-cholesterol of -11 (sD 12) % on th e MUFA diet with no change on the control diet (-1.1 (sD 10) %). In young m en the differences were due to an increase in LDL-cholesterol concentration on the control diet of +6.2 (sD 13) % and a decrease on the MUFA diet of - 7.8 (sD 20) %. Differences in the responses of middle-aged and young men to the two diets did not appear to be due to differences in their habitual ba seline diets which were generally similar, but appeared to reflect the lowe r baseline cholesterol concentrations in the younger men. There was a moder ately strong and statistically significant inverse correlation between the change in LDL-cholesterol concentration on each diet and the baseline fasti ng LDL-cholesterol concentration (r - 0.49; P < 0.0005). In conclusion, die ts in which saturated fat is partially replaced by MUFA can achieve signifi cant reductions in total and LDL-cholesterol concentrations, even when tota l fat and energy intakes are maintained. The dietary approach used to alter fatty acid intakes would be appropriate for achieving reductions in satura ted fat intakes in whole populations.