Dietary Nitrate and Physiological Aging

Not Applicable

Completed

Conditions: Aging

Interventions: Dietary Supplement: Super Beets
Dietary Supplement: Super Beets Placebo

Registration Number: NCT02593305

Lead Sponsor: Darren P Casey

Brief Summary: The main purpose/s of this study is to examine the effects of 4 weeks of dietary nitrate supplementation on peripheral chemoreceptor sensitivity, spontaneous baroreflex sensitivity, and blood pressure responsiveness to a variety of physiological stressors in older healthy adults. We will also examine the effect of dietary nitrate supplementation on measures of central artery stiffness and aortic blood pressure in older adults. Lastly, we will also recruit a group of young subjects in order to help characterize the age-related changes associated with the physiological outcome measures of the present study.

Detailed Description: 1 in 3 adults in the U.S. have hypertension which is known to increase the risk of heart disease and stroke. Blood pressure regulation is mediated by many factors including but not limited to metabolic factors, pressure/stretch sensing receptors located in the aorta and carotid arteries, endothelial cell function, and kidney function (via water and sodium absorption/excretion). It has been shown that many of these regulatory mechanisms are altered and/or become dysfunctional with aging. Specifically older adults commonly demonstrate a decreased sensitivity in pressure receptors and/or endothelial dysfunction. Additionally with aging, there is an increase in sympathetic nervous system activity and arterial stiffness which can contribute to higher blood pressure. The important vasodilator, nitric oxide (NO), has been implicated as a key signaling molecule involved in several of the mechanisms in blood pressure regulation outlined above. A decreased NO production or bioavailability is thought to contribute to several of the physiologic changes that come with aging. Therefore, the overall aim of this study is to use a randomized, double-blind crossover, placebo controlled study to examine the effects of acute dietary nitrate supplementation (to boost bioavailable NO) on various parameters of blood pressure regulation and responsiveness in normal healthy older adults. Our main hypothesis is that 4 weeks of dietary nitrate supplementation will decrease the blood pressure responses in older adults in response to a variety of physiological stressors.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 23

Inclusion Criteria

Healthy young adults 18-35 years of age (comparison group)
Healthy older adults 60-85 years of age (intervention group)

Exclusion Criteria

Hypertension, hyperlipidemia, current smoker or smoker within the last year, heart disease, diabetes, Chronic obstructive pulmonary disease, asthma, sleep apnea, Raynaud's disease, body mass index (BMI) > 30 kg/m2, allergy medication, clinical depression, autonomic disorders and other conditions or medications that might normally alter cardiovascular function, exercise tolerance, and/or blood pressure responses.

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Placebo, then beetroot crystals (nitrate)	Super Beets Placebo	Participants will receive a beetroot powder placebo (no nitrate) for 4 weeks. After a 4 week washout period, they will receive the nitrate rich beetroot powder for 4 weeks.
Placebo, then beetroot crystals (nitrate)	Super Beets	Participants will receive a beetroot powder placebo (no nitrate) for 4 weeks. After a 4 week washout period, they will receive the nitrate rich beetroot powder for 4 weeks.
Beetroot crystals (nitrate), then placebo	Super Beets	Participants will receive a nitrate rich beetroot powder (10g/day) for 4 weeks. After a washout period of 4 weeks, they will then receive the placebo (beetroot powder, no nitrate) for 4 weeks.
Beetroot crystals (nitrate), then placebo	Super Beets Placebo	Participants will receive a nitrate rich beetroot powder (10g/day) for 4 weeks. After a washout period of 4 weeks, they will then receive the placebo (beetroot powder, no nitrate) for 4 weeks.

Primary Outcome Measures

Name	Time	Method
Change in Carotid Chemosensitivity Following 4 Weeks of Dietary Nitrate Supplementation and Placebo in Older Adults	Pre and post 4 weeks dietary nitrate supplementation and pre and post 4 weeks of placebo.	Carotid chemosensitivity examined by measuring hypoxia ventilatory responsiveness in older adults before and after 4 weeks of beet root juice supplementation and placebo. Chemoreflex sensitivity was quantified as the change in ventilation in relation to the change in pulse oxygen saturation.
Change in Systolic Blood Pressure During Metaboreflex Testing Following 4 Weeks of Dietary Nitrate Supplementation and Placebo in Older Adults.	Pre and post 4 weeks dietary nitrate supplementation and pre and post 4 weeks of placebo.	Muscle metaboreflex examined by measuring systolic blood pressure responses to ischemic isometric muscle contraction in older adults before and after 4 weeks of beet root juice supplementation and placebo.

Secondary Outcome Measures