Clinical Trial of Dietary Protein and Blood Pressure

Not Applicable

Completed

Conditions: Hypertension
Heart Diseases
Cardiovascular Diseases

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

Registration Number: NCT00046566

Lead Sponsor: Tulane University

Brief Summary: The purpose of this study is to examine the effect of dietary protein supplements on high blood pressure (BP).

Detailed Description: BACKGROUND:

At least 50 million adult Americans have high BP, which is one of the most important modifiable risk factors for coronary heart disease, stroke, and end-stage kidney disease. Nutrient intake has been related to the development of high BP, and nutritional modifications have become an important approach for the treatment and prevention of high BP. While the effect of sodium, potassium, and alcohol on BP has been studied extensively, the effect of dietary macronutrients, such as protein, has not been as well studied. Results from this study may provide justification for recommending protein supplements for the prevention and treatment of high BP in the general population.

DESIGN NARRATIVE:

The study will enroll 280 healthy participants with BP levels higher than optimal or with stage-1 hypertension (systolic BP of 120-159 mm Hg and diastolic BP of 80-95 mm HG). Participants will be recruited by a mass mailing and a worksite/community-based BP screening in New Orleans, Louisiana, and Jackson, Mississippi. Following a two-week screening period, eligible participants will receive either 40 grams of soy protein, 40 grams of milk protein, or 40 grams of complex carbohydrates (control) daily for eight weeks. Following those eight weeks, participants will not receive any supplements for three weeks. Participants will then repeat the process with the other two supplements. The primary outcome will be difference in BP during the soy protein supplementation, milk protein supplementation, and placebo control phases. In addition, changes in serum lipids; waist and hip circumference; and fasting plasma insulin, glucose, leptin, and homocysteine will be monitored and examined in terms of impact on BP level.

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
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.
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.

Primary Outcome Measures

Name	Time	Method
Change From Baseline in Average Systolic Blood Pressure at 8 Weeks	Every 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 two 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	Every 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	Every 8 weeks	Body weight was measured by trained staff using a standard protocol at week 8.