Vegetable intake and blood pressure study

• Register: ANZCTR
• Last refreshed on: 13 January 2020
• Main ID: ACTRN12615000194561
• Date of registration: 27/02/2015
• Prospective Registration: Yes
• Primary sponsor: The University of Western Australia
• Public title: Vegetable intake and blood pressure study
• Scientific title: The effects of daily consumption of vegetables on blood pressure in prehypertensive and stage 1 hypertensive individuals
• Date of first enrolment: 27/04/2015
• Target sample size: 25
• Recruitment status: Completed
• URL: https://anzctr.org.au/ACTRN12615000194561.aspx
• Study type: Interventional
• Study design: Purpose: Treatment; Allocation: Randomised controlled trial; Masking: Open (masking not used);Assignment: Crossover;Type of endpoint: Efficacy;
• Phase: Not Applicable

Countries of recruitment

Australia

Contacts

• Name: Ms Lauren Blekkenhorst

• Name: Ms Lauren Blekkenhorst

Key inclusion & exclusion criteria

Inclusion criteria: Ambulant men and women;
21-75 years; and
Systolic blood pressure 120-160 mm Hg.
Exclusion criteria: Systolic blood pressure less than 120 mm Hg or greater than 160 mm Hg;
Diastolic blood pressure greater than 100 mm Hg;
Diagnosed type 1 or 2 diabetes or fasting glucose greater than 7.0mmol/L;
Consumption of a diet estimated to contain greater than 200 mg/day of nitrate (volunteers willing to limit nitrate-rich vegetables for a period of 4 weeks before their lead in visit may be included);
Consumption of greater than or equal to 5 serves of vegetables per day;
Being vegan or vegetarian;
Body mass index less than 18.5 kg/m2 and body mass index greater than or equal to 35 kg/m2;
Use of antihypertensive medication;
Use of nitric oxide donors, organic nitrites and nitrates, sildenafil and/or related drugs;
Use of antibacterial mouth wash (volunteers willing to cease using antibacterial mouth wash for a period of 4 weeks before their lead in visit may be included);
Use of antibiotics (within previous 2 months);
Current or recent (less than 12 months) smoking;
History of symptomatic cardiovascular or peripheral vascular disease or chronic kidney disease;
Recent history of a psychiatric illness or other major illnesses such as cancer;
A change in drug therapy likely to influence blood pressure or major secondary outcomes within the previous 3 months, and/or the likelihood that drug therapy would change during the study;
Current or recent (within previous 6 months) significant weight loss or gain (greater than 6% of body weight);
Alcohol intake greater than 140 g per week for women or greater than 210 g per week for men and/or binge drinking behaviour;
Reported participation in night shift work during the study period;
Breastfeeding, pregnancy or planning of pregnancy; and
Inability or unwillingness to follow the study protocol.

Age minimum: 21 Years
Age maximum: 75 Years
Gender: Both males and females

Health Condition(s) or Problem(s) studied

Cardiovascular - Hypertension

Mental Health - Studies of normal psychology, cognitive function and behaviour

Cardiovascular disease;Hypertension;
Cardiovascular disease
Hypertension

Diet and Nutrition - Other diet and nutrition disorders

Intervention(s)

A randomised, controlled, cross-over trial will be conducted to investigate the effects of different types of vegetables on blood pressure and arterial stiffness.

Each participant will complete three intervention diets of 4 weeks each in random sequence. The first intervention diet will be preceded by a 4 week lead in (washout) period. The first, second and third intervention diets will be separated by a 4 week wash out period.

The intervention diets are:
1. High nitrate diet (~400 mg per day) – with an increase in high-nitrate vegetables (lettuce – all types, spinach, rocket, Chinese leafy greens, other leafy greens, celery, and beetroot). This will involve the consumption of two blended high-nitrate vegetable juices each day: one before breakfast and one before dinner.
2. Low nitrate diet (~100-150 mg per day) – with an increase in low-nitrate vegetables (cauliflower, capsicum, sweet potato, cucumber, tomato, and parsnip). This will involve the consumption of two blended low-nitrate vegetable juices each day: one before breakfast and one before dinner.
3. Low nitrate diet (control diet, ~100 mg per day) – without an increase in vegetables. This will involve the consumption of two blended juice drinks without vegetables each day, matched in energy to juices in diets 1 and 2: one before breakfast and one before dinner.

Participants will be provided with personal blenders and advised on which vegetables/ingredients to buy and blend themselves (all meals will be maintained as usual with the exception of limiting nitrate-rich vegetables where possible). Adherence to the intervention diets will be monitored using juice checklist diaries; food intake questionnaires; and blood, urine and saliva samples.

Participants will attend 9 visits o

Primary Outcome(s)

Blood pressure response to cognitive stress.

Cognitive stress will be induced using a computerized Cognitive Demand Battery that has been utilized in previous studies and shown to be sensitive to effects of non-pharmaceutical interventions. [Performed at baseline and post visits of each intervention period (total of 6 time points). Continuous blood pressure measurements will be performed for 30 minutes using the Finapres NOVA device during the period of cognitive stress. ]

Home blood pressure measured using an automated brachial cuff sphygmomanometer.[Performed by participants daily throughout the entire study duration (24 weeks).]

24 hour ambulatory blood pressure measured using a Spacelabs Medical Ambulatory Blood Pressure Monitor.[Performed at baseline and post visits of each intervention period (total of 6 time points). ]

Secondary Outcome(s)

Arterial stiffness measured as pulse wave velocity and augmentation index using the SphygomoCor XCEL device.[Performed at baseline and post visits of each intervention period (total of 6 time points).]

Measure of mood assessed using the Bond-Lader Visual Analogue Mood Scale.[Performed at baseline and post visits of each intervention period (total of 6 time points).]

Measures of working memory. This is a composite outcome assessed using the Cognitive Demand Battery which comprises two computerized serial subtraction tasks and a Rapid Visual Information Processing task.[Performed at baseline and post visits of each intervention period (total of 6 time points).]

Secondary ID(s)

Nil

Source(s) of Monetary Support

National Health and Medical Research Council

Ethics review

Status: Approved
Approval date:
Contact:

The University of Western Australia Human Research Ethics Committee