Soy and Brain Vascular Function

Study Overview
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Brief Summary
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Cognitive performance is negatively related to an impaired glucose metabolism, possibly due to impairments in brain vascular function. Supported by the statement from the American Heart and American Stroke Association that healthy plant-based diets, which consist of soy foods, protect against cognitive decline, we now hypothesize that soy-induced changes in glucose metabolism cause beneficial effects on brain vascular function thereby improving cognitive performance. The primary objective of this intervention study is thus to evaluate in elderly men and women the effect of a 16-week soy intervention on cerebral blood flow, as quantified by the non-invasive gold standard magnetic resonance imaging (MRI) perfusion method Arterial Spin Labeling (ASL). Cerebral blood flow is a robust and sensitive physiological marker of brain vascular function. Secondary objectives are to examine effects on glucose metabolism using the oral glucose tolerance test and cognitive performance as assessed with a neurophysiological test battery.

Official Title
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The Effects of Soy on Brain Vascular Function in Elderly Men and Women

Conditions
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Brain Vascular Function, Cerebral Blood Flow, Glucose Metabolism, Cognitive Performance

Intervention / Treatment
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* Dietary Supplement: Soy nuts


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Aged between 60-70 years BMI between 20-30 kg/m2 Fasting plasma glucose < 7.0 mmol/L Fasting serum total cholesterol < 8.0 mmol/L Fasting serum triacylglycerol < 4.5 mmol/L Systolic blood pressure < 160 mmHg and diastolic blood pressure < 100 mmHg Stable body weight (weight gain or loss < 3 kg in the past three months) Willingness to give up being a blood donor from 8 weeks before the start of the study, during the study and for 4 weeks after completion of the study No difficult venipuncture as evidenced during the screening visit Exclusion Criteria: Allergy or intolerance to soy Current smoker, or smoking cessation < 12 months Diabetic patients Familial hypercholesterolemia Abuse of drugs More than 3 alcoholic consumptions per day Use of soy products or dietary supplements known to interfere with the main outcomes as judged by the principal investigators Use medication to treat blood pressure, lipid or glucose metabolism Use of an investigational product within another biomedical intervention trial within the previous 1-month Severe medical conditions that might interfere with the study, such as epilepsy, asthma, kidney failure or renal insufficiency, chronic obstructive pulmonary disease, inflammatory bowel diseases, auto inflammatory diseases and rheumatoid arthritis Active cardiovascular disease like congestive heart failure or cardiovascular event, such as an acute myocardial infarction or cerebrovascular accident Contra-indications for MRI imaging (e.g. pacemaker, surgical clips/material in body, metal splinter in eye, claustrophobia)

Ages Eligible for Study
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Minimum Age: 60 Years
Maximum Age: 70 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: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Participants will receive, in random order, daily 70 g of soy nuts (soy treatment) or no food products (control treatment) for sixteen weeks, separated by a wash-out period of at least 8 weeks.
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Experimental: Soy nuts<br> | Dietary Supplement: Soy nuts<br>* Study volunteers will receive daily 70 g of soy nuts (roasted soybeans containing approximately 100 mg isoflavones). The amount of soy protein provided by the nuts equals the FDA recommended daily intake of 25-30 g.<br>|
| No Intervention: Control - no soy nuts<br> | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Brain vascular function | Cerebral blood flow as quantified non-invasively by the MRI perfusion method Arterial Spin Labeling (ASL) | Difference between outcomes at the end of a 16-week soy nut intervention and control period. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Glucose metabolism | Oral Glucose Tolerance Test (OGTT) | Difference between outcomes at the end of a 16-week soy nut intervention and control period. | 
| Cognitive performance | Cambridge Neuropsychological Test Automated Battery (CANTAB) | Difference between outcomes at the end of a 16-week soy nut intervention and control period. |