Effects of Acute Dietary Sodium on Cerebrovascular Reactivity and Blood Pressure Reactivity

Study Overview
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Brief Summary
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Americans eat more salt than is recommended by the American Heart Association. This is important because consuming a high-salt diet is associated with an increased risk of cardiovascular events, like strokes and heart attacks. In fact, consuming one high-salt meal temporarily reduces blood vessel function and it is not uncommon for Americans to consume high-salt meals. Therefore, our laboratory is interested in determining if a single high-salt meal affects 1) brain blood vessel function at rest and 2) blood pressure responses during exercise.

Detailed Description
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Excess dietary salt increases the risk of cardiovascular events like strokes and heart attacks, independent of resting blood pressure. Recent data found that consuming one high-salt meal temporarily reduces endothelial function in the periphery. This decrease in endothelial function can lead to an exaggerated blood pressure response during exercise and may also attenuate cerebrovascular reactivity at rest. This is essential, because an exaggerated cardiovascular response to exercise and a decrease in brain blood vessel function at rest are risk factors for future cardiovascular events. The long-term goal is to determine how dietary salt adversely affects BP and cerebrovascular regulation. The objective of this proposal is to evaluate the impact of an acute dietary salt meal on BP response during exercise and cerebrovascular reactivity at rest. The investigators have 2 specific aims: 1) Aim 1 will test the hypothesis that high dietary salt will reduce cerebrovascular reactivity, 2) Aim 2 will test the hypothesis that high dietary salt will augment blood pressure reactivity during exercise. The findings of this project will shed light on how acute dietary salt affects the risk of cardiovascular events during a bout of exercise and long-term risk for cardiovascular disease and stroke.

Official Title
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Effects of Acute Dietary Sodium on Cerebrovascular Reactivity and Blood Pressure Reactivity

Conditions
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Blood Pressure, Cerebrovascular Reactivity

Intervention / Treatment
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* Other: Low Sodium Meal (138 mg sodium)
* Other: High Sodium Meal (1,495 mg sodium)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: normal blood pressure males, females, minorities Exclusion Criteria: high blood pressure body mass index (BMI > 30 kg/m2) smokers or nicotine users those who are pregnant or planning to become pregnant allergy to the tomato soup

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Cerebrovascular Reactivity<br>Cerebrovascular reactivity (CVR) will be assessed using transcranial Doppler ultrasound with carbon dioxide as the vasoactive stimuli. The intervention is to provide subjects with either a low sodium meal (138 mg sodium) and high sodium meal (1,495 mg sodium), in a randomized order. The CVR test will be performed prior to soup consumption as well as after soup consumption. | Other: Low Sodium Meal (138 mg sodium)<br>* One Low Sodium Meal<br>Other: High Sodium Meal (1,495 mg sodium)<br>* One High Sodium Meal<br>|
| Experimental: Blood Pressure Reactivity<br>Blood pressure responses during dynamic exercise will be assessed. The intervention is to provide subjects with either a low sodium meal (138 mg sodium) and high sodium meal (1,495 mg sodium), in a randomized order. Blood pressure reactivity during dynamic exercise will be assessed after soup consumption. | Other: Low Sodium Meal (138 mg sodium)<br>* One Low Sodium Meal<br>Other: High Sodium Meal (1,495 mg sodium)<br>* One High Sodium Meal<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from Baseline Cerebrovascular Reactivity post soup consumption | Middle Cerebral Artery/ End-tidal Carbon Dioxide (cm/s/mmHg) | Prior to and 60 minutes after soup consumption | 
| Blood Pressure Reactivity- Dynamic Exercise | Change in Blood Pressure during dynamic exercise (mmHg) | 80 minutes after soup consumption |