Clinical Trial of Protein and Blood Pressure

Not Applicable

Completed

Conditions: Hypertension
Hypercholesterolemia

Interventions: Dietary Supplement: Milk protein-carbohydrate-soy protein
Dietary Supplement: Carbohydrate-soy protein-milk protein
Dietary Supplement: Soy protein-milk protein-carbohydrate

Registration Number: NCT00107744

Lead Sponsor: Tulane University

Brief Summary: The purpose of this randomized, double-blind, controlled trial is to examine the effect of soybean protein supplementation on blood pressure in persons with prehypertension or stage-1 hypertension.

Detailed Description: Background: Epidemiologic studies suggest that vegetable protein intake is inversely related to blood pressure.

Objectives: To examine the effect of soybean protein supplementation on blood pressure in persons with prehypertension or stage-1 hypertension

Design: Randomized, double-blind, controlled trial

Study Participants: 350 participants, aged 35-64 years, with an initial untreated systolic blood pressure of 130-159 mmHg and/or diastolic blood pressure of 80-99 mmHg

Intervention: Study participants will be randomly assigned to take 40-grams of isolated soybean protein supplements per day or complex carbohydrate control for 12 weeks.

Outcomes: Blood pressure measurements will be obtained using random-zero sphygmomanometers at baseline and during the trial at weeks 6 and 12. Net changes in systolic and diastolic blood pressure before and after the intervention is the primary outcome.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 352

Inclusion Criteria

Systolic BP of 120 to 159 mm Hg and diastolic BP of 80 to 95 mm Hg (average of 6 measurements at 2 screening visits)
Willing to participate in all aspects of the study

Exclusion Criteria

Consumption of dietary protein greater than or equal to 1.63 grams/kg per day, as determined by two 24-hour dietary recalls
Stage-2 or higher severe hypertension (systolic BP greater than or equal to 160 mm Hg and/or diastolic BP greater than or equal to 95 mm Hg)
Use of antihypertensive medications or medications that affect BP
History of clinical heart disease (e.g., angina/heart attack, coronary revascularization, heart failure, stroke/transient ischemic attack, peripheral arterial disease)
Kidney disease (serum creatinine level greater than or equal to 1.7 mg/dL for men and greater than or equal to 1.5 mg/dL for women)
Current hypercholesterolemia (fasting serum total cholesterol greater than or equal to 240 mg/dL) or use of cholesterol-lowering medications
Current diabetes (fasting serum glucose greater than or equal to 126 mg/dL) or use of insulin or oral hypoglycemic agents
Severe obesity (body mass index greater than or equal to 40 kg/m²)
Current use of prescription weight loss medications, underwent weight loss surgery, and/or experienced weight loss greater than 15 pounds within the 6 months prior to study entry
Cancer (except non-melanoma skin cancer) that required treatment during the year prior to study entry
Consumption of more than 14 alcoholic beverages per week
Current participation in another medical study
Consumption of milk or soy protein greater than or equal to the 90th percentile of intake in the U.S. general population
Has another member of the household participating in the study
Study employees or living with study employees
Allergy or intolerance to soy protein or milk protein products
Allergy to aspartame
Plans to move out of the study area (greater than or equal to 50 miles from the study site) and has difficulty coming to the study site
Inability or unwillingness to cooperate during the screening visits
Poor compliance during the screening period (intake of less than 85% of supplements)
Pregnant or plans to become pregnant during the study

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Milk protein-carbohydrate-soy protein	Milk protein-carbohydrate-soy protein	Participants received 40 grams of milk protein daily for 8 weeks, 40 grams of carbohydrate daily for 8 weeks, and 40 grams of soy protein daily for 8 weeks.
Carbohydrate-soy protein-milk protein	Carbohydrate-soy protein-milk protein	Participants received 40 grams of complex carbohydrate daily for 8 weeks, 40 grams of soy protein daily for 8 weeks, and 40 grams of milk protein daily for 8 weeks.
Soy protein-milk protein-carbohydrate	Soy protein-milk protein-carbohydrate	Participants received 40 grams of soy protein daily for 8 weeks, 40 grams of milk protein daily for 8 weeks, and 40 grams of carbohydrate daily for 8 weeks.

Primary Outcome Measures

Name	Time	Method
Change From Baseline in Average Systolic Blood Pressure at 8 Weeks	Baseline and 8 Weeks	The change of systolic blood pressure was calculated as the mean of 6 blood pressure values from two 8-week visits minus the mean of 6 values from 2 baseline visits within each intervention phase. At each visit, 3 BP values were measured with a Hawksley random-zero sphygmomanometer by trained and certified observers who were masked to group assignment. BP readings were taken from the right arm with appropriately sized cuffs after the participant had been seated quietly for 5 minutes. The participant was instructed not to eat, smoke, drink alcohol, or exercise for at least 30 minutes before their BP measurements.

Secondary Outcome Measures

Name	Time	Method
Change From Baseline in Serum LDL-cholesterol at 8 Weeks	Baseline and 8 Weeks	Change in serum LDL-cholesterol was calculated as LDL-cholesterol at 8 weeks minus LDL-cholesterol at baseline. Over-night fasting serum LDL-cholesterol was measured with an enzymatic method.
Body Weight at 8 Weeks	Baseline and 8 Weeks	Body weight was measured by trained staff using a standard protocol at week 8.