Dietary Protein and Soluble Fiber Reduce Ambulatory Blood Pressure in Treated Hypertensives

Abstract

Abstract-In population studies, higher blood pressure has been associated with lower intake of protein and, possibly, lower fiber consumption. In the present randomized controlled trial, we sought to determine whether dietary protein and fiber had additive effects on blood pressure reduction in hypertensives. Treated hypertensive patients changed for 4 weeks (familiarization) to a diet low in protein (12.5% energy) and fiber (15 g/d). Patients (nϭ41) were then randomized to 1 of 4 groups in an 8-week factorial study of parallel design in which they continued the low-protein, low-fiber diet alone or had supplements of soy protein to increase protein intake to 25% energy, of psyllium to provide an additional 12 g soluble fiber/d, or of both protein and fiber. The 24-hour ambulatory blood pressure was compared from the end of familiarization to the end of intervention. In the 36 subjects who provided complete data, protein and fiber had significant additive effects to lower 24-hour and awake systolic blood pressure. Relative to control subjects, the net reduction in 24-hour systolic blood pressure was 5.9 mm Hg with fiber and with protein. 8 and have in general proved to be negative. However, increased dietary protein attenuated the pressor effect of salt among young volunteers with a family history of hypertension. 9 Recently, soy protein supplements of 40 g/d were found to lower systolic BP (SBP) by 3 mm Hg and diastolic BP (DBP) by Ϸ2 mm Hg, relative to control subjects, 10 in 35-to 65-year-old Chinese subjects with untreated high-normal BP.Dietary fiber may also be related inversely to BP. 2,11-13 A recent meta-analysis 14 concluded that fiber probably has a small BP-lowering effect. In Chinese populations, BP has been associated inversely with both protein and fiber intake, 2 consistent with additive effects. However, associations with specific nutrients may arise through other dietary or lifestyle differences that affect BP.Given the worldwide prevalence of hypertension, it is important to resolve whether dietary protein and fiber can influence BP alone or additively. We therefore conducted a randomized controlled trial in treated hypertensives in whom protein or fiber intake, or both, was increased against a background of a standardized diet low in both constituents. Methods SubjectsNonsmoking men or women who were Ն20 years old and were receiving drug therapy for hypertension were recruited via advertisement. Inclusion criteria included drug therapy for Ն6 months with Յ2 antihypertensive agents, SBP between 130 and 160 mm Hg, and alcohol intake of Յ210 g alcohol/wk. Exclusion criteria included diabetes, renal disease (creatinine Ͼ130 mmol/L), symptomatic heart disease, regular use of nonsteroidal anti-inflammatory drugs, psychiatric illness, or body mass index of Ͼ33 kg/m 2 for men and Ͼ37 kg/m 2 for women. The study was approved by the University of Western Australia Committee for Human Rights, and all participants gave written consent. Dietary InterventionDuring the initial 4-week period (baseline), subj...

The relationship between dietary protein intake and blood pressure: results from the PREMIER study

“…13 The Intersalt Study, a large cross-sectional international study with 10 020 men and women aged 20-59 years from 54 population-based samples in 32 countries worldwide, also demonstrated that total dietary protein intake had an inverse relationship with BP. 23 Similarly, Liu et al 22 concluded in a metaanalysis report that the inverse association between dietary protein intake and BP was quite convincing in nine population-based cross-sectional studies.…”

“…[11][12][13][14][15] However, it is unclear whether plant and animal proteins have different effects on BP.…”

Long-term effects of advice to consume a high-protein, low-fat diet, rather than a conventional weight-loss diet, in obese adults with Type 2 diabetes: one-year follow-up of a randomised trial

“…It is therefore likely that the higher protein intake in the high-protein diet was responsible for the attenuated rise in blood pressure. Observations from several large epidemiological studies [30,31] and short-term (6-13 week) clinical trials [32,33] have demonstrated that protein intake may be inversely related to blood pressure, although which component of dietary protein might be involved is unclear. The present data also support the hypothesis that a long-term higher protein intake may help to lower blood pressure and CVD risk in people with diabetes.…”

Effects of lupin-enriched foods on body composition and cardiovascular disease risk factors: a 12-month randomized controlled weight loss trial

“…Most previous trials have used a refined carbohydrate as the control. [14][15][16]22 Limited data from human and animal studies suggest that a lupin-enriched diet may benefit serum lipids and lipoprotein. 24,49 However, we previously showed that an ad libitum lupin flour-enriched diet over 4 months also had no benefit on the serum lipid profile.…”

“…13 If consumption of lupin flour-enriched foods has similar effects on energy intake in the longer term, such effects could translate into weight loss. Diets higher in plant protein and fibre may also benefit blood pressure, [14][15][16][17] serum lipids 18,19 and glucose and insulin metabolism. 20,21 In a previous 16-week trial, we showed that consumption of lupin flour-enriched bread reduced 24-h systolic blood pressure by 3.0 mm Hg.…”