Efficacy of Dietary Sodium Restriction of Improving Vascular Endothelial Function in Middle Aged and Older Adults

University of Colorado, Boulder17 enrolled

Overview

The investigators hypothesize that reducing salt in the diet will improve the function of blood vessels in middle aged and older adults with moderately elevated systolic blood pressure, by increasing the amount of BH4 and nitric oxide in your blood vessels and reducing the amount of oxidative stress.

The improvement in blood vessel function will be determined over a 10 week period. Subjects will be randomly assigned to either a 'low salt' condition (placebo pills + 1200 mg dietary sodium) or a 'normal salt' condition (2300 mg sodium chloride pills + 1200 mg dietary sodium) and monitored for 5 weeks. After the initial set of 5 weeks, the subjects are switched into the opposite condition, completing the cross-over study design. During weeks 1-4 and 6-9, subjects are monitored weekly with 24 hour urine collections and diet logs. The assessment of the primary outcome (blood vessel function) is completed during weeks 5 and 10. BH4 and ascorbic acid are also administered during weeks 5 and 10 to measure the effects of sodium intake on endogenous BH4 levels and vascular oxidative stress.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

TRIPLE

Enrollment

Conditions

Hypertension

Interventions

Slow sodium tabletsDRUG

The normal salt condition is maintained with 2300 mg / day in the form of slowly released salt (NaCl) tablets.

placeboOTHER

Placebo tablets are administered to maintain the low sodium condition.

Eligibility

Sex: ALLMin age: 50 YearsMax age: 79 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * 50-79 years of age * SBP 130-159 mmHg Exclusion Criteria: * Have been sick with an infection in the past two weeks * Are currently sick or have ongoing health problems such as kidney or CVD * Have lost more than 11 lbs. in the last 3 months * Are taking any type of antioxidants * Smoke or have alcohol problems * Have blood glucose levels higher than 126 mg/dL * Have resting SBP below or less than 100 mmHg or greater than 159 mmHg * Have a resting diastolic blood pressure greater than 99 mmHg * Have a BMI greater than 40 kg/m\^2 * Are presently consuming less than 9 or greater than 18 grams of salt / day * Have a baseline FMD of greater than 6% * Are taking any of the following types of drugs: blood thinners, anti-seizure medications, ant-inflammatory drugs * Participate in any high endurance athletic training * Taking Hormone Replacement Therapy * Have not been post-menopausal for at least 1 year

Locations (1)

Clinical Translational Research Center

Boulder, Colorado, United States

Outcomes

Primary Outcomes

Improved Flow Mediated Dilation

FMD is analyzed at weeks 5 and 10 or after each condition in this cross-over study design. Subjects are randomly assigned to a low salt or normal salt condition for the first set of 5 weeks and then crossed over to the other condition for the second set of 5 weeks.

Time frame: Week 5 (after first condition of low salt or normal salt), Week 10 (after second condition, opposite to first)

Secondary Outcomes

Vascular Oxidative Stress

Change in FMD following acute infusion of ascorbic acid (a dose known to scavenge superoxide) is measured at the end of 5 weeks of sodium condition (low and normal intake) as an index of vascular oxidative.

Time frame: Immediately following acute infusion of ascorbic acid on Weeks 5 and 10

BH4 Bioavailability

Change in FMD following acute oral tetrahydrobiopterin (BH4) is measured at the end of 5 weeks of sodium condition (low and normal intake) as an index of BH4 bioavailability.

Time frame: Immediately following acute administration of BH4 on Weeks 5 and 10

Data from ClinicalTrials.gov

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