Effect of polyunsaturated fat on regression of atheroma in the non-human primate

Twenty-seven vervet monkeys were placed on a 'normal' South African diet (polyunsaturated/saturated (P/S) ratio 0.28) for 24 months. Nine animals were then sacrificed to obtain a baseline for percentage atheroma in the aorta and iliac vessels (15.7 +/- 3.6%). The remaining animals were divided into two equal groups. Group A continued on the diet with a P/S ratio of 0.28, while group B was given the same diet, but with the P/S ratio increased to 1.5. After a further 20 months on their respective diets all the animals were sacrificed and the extent of atheroma in the large blood vessels was determined. That for group A was 29.3 +/- 6.5% (almost double the baseline value), while in group B the figure fell to 9.6 +/- 2.7%. The data indicate that: (i) a normal South African diet is highly atherogenic in the vervet monkey; and (ii) simply increasing the P/S ratio of this diet can actually produce regression of atheroma in these animals.