Controlled, randomised trial of the effect of dietary fat on blood pressure.

57 couples living in two communities of North Karelia, aged 30-50 years, were randomly allocated to three groups. After a 2-week baseline period group I followed a diet low in fat (23% of energy) with a high polyunsaturated/saturated (P/S) ratio (1 . 0), group II reduced daily salt intake from 192 mmol to 77 mmol, and group III (control group) continued the usual diet. After the 6-week intervention period groups I and II reverted to their usual diets. In group I systolic blood pressure declined from 138 . 4 to 129 . 5 mm Hg and diastolic blood pressure from 88 . 9 to 81 . 3 mm Hg during the intervention period; the values rose during switch-back. The fall was greater among hypertensive than among normotensive subjects. In groups II and III the mean blood pressure changed very little during the study.