Blood pressure and diet in normotensive volunteers: absence of an effect of dietary fiber, protein, or fat

Abstract

In the course of four controlled experiments on the effect of specific dietary components on cardiovascular risk factors, the effects on blood pressure of various sources of dietary fiber, of type and amount of dietary fat, and of animal versus plant were measured in young normotensive volunteers. In each of the four experiments a group of 50 to 75 healthy student volunteers received a control diet for 11/2 to 21/2 wk. They were then randomized into subgroups which received various test diets for periods ranging from 4 to 12 wk. In each experimental one group received the control diet throughout the whole experimental period. Diets differed between groups in one dietary component only. All foodstuffs were weighed out individually according to each person's energy needs. Body weights and Na intake were controlled. Initial blood pressures were about 120 mm Hg systolic and 70 mm Hg diastolic. Both systolic and diastolic blood pressure decreased during the test period in all four experiments on almost every diet, including the control diets, by about 0 to 5 mm Hg. However, changes in blood pressure over the test period were never significantly different between the test groups and the control groups. Thus, none of the investigated dietary factors had a demonstrable effect on blood pressure in young normotensive persons.

A Clinical Trial of the Effects of Dietary Patterns on Blood Pressure

“…[7][8][9][10][11] However, in trials that tested these nutrients, often as dietary supplements, the reduction in blood pressure has typically been small and inconsistent. [12][13][14][15][16][17][18] There are several possible reasons for the discrepancy between the inconsistent results of trials that modified single nutrients and the generally positive results of trials of vegetarian diets and observational studies of diet and blood pressure. The effect of any individual nutrient in lowering blood pressure may be too small to detect in trials.…”

Lack of effect on blood pressure by low fat diets with different fatty acid compositions

“…[26][27][28][29] In contrast to these findings, several studies have failed to show an effect on BP by increased intake of linoleic acid. 5,[30][31][32][33] In two studies with study periods of 6-8 months, a reduction of BP was observed during a low-fat, high-fibre diet 34 and an American Heart Association Step I diet with moderate fat reduction and equal amounts of SAFA and PUFA. 35 Trials with n-3 fatty acids have indicated that very high intakes of fatty fish and supplementation with fish oil concentrates decrease both SBP and diastolic BP (DBP).…”

Reduction of blood pressure associated with dietary polyunsaturated fat.

“…A recent study 35 suggests that a low fat, high P/S ratio diet did not give a significant lowering of blood pressure in young healthy men and women. The general tendency was that the diet did lower blood pressure, but not significantly.…”