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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Retrospectively registered

Titles & IDs
Public title
Salt and Hypertension: Is arterial function affected by dietary salt intake?
Scientific title
The impact of dietary salt (NaCl) intake on arterial wall function in hypertensive subjects: a randomised placebo controlled study.
Secondary ID [1] 836 0
Cochrane Renal Group Prospective Trial Register: CRG040700113
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Hypertension 4539 0
Condition category
Condition code
Cardiovascular 4828 4828 0 0

Study type
Description of intervention(s) / exposure
Dietary salt restriction followed by dietary salt loading. 2 week dietary salt restriction (sodium 60mmol/day) then randomised sequencial allocation to 4 weeks intervention A (tomato juice no added salt 500ml/day), intervention B (tomato juice plus 90mmol sodium, 500ml/day) intervention C (tomato juice plus 140 mmol sodium 500ml/day). There is a 4 week wash out phase between each intervention (no tomato juice). All participants remaining on the low salt diet for the duration of the study. Dietary compliance was facilitated by weekly dietitic input with advice about low salt foods, fortnightly 4 day diet records. Compliance was measured by urinary sodium/creatinine ratios at baseline, week 1, week 2 and week 4.
Intervention code [1] 4303 0
Comparator / control treatment
This is a cross over study so each individual acts as their own control. The tomato juice with no added sodium acts as a positive control as the participants remain on their low dietary salt diet (sodium 60 mmol/day) for the entire duration of the study.
Control group

Primary outcome [1] 5690 0
Changes in arterial function as measured by pulse wave velocity
Timepoint [1] 5690 0
Pulse wave velocity is measured at each of the following time points Baseline (start of intervention), week 1, week 2 week 4 (end of intervention). This is repeated for each of the three interventions.
Secondary outcome [1] 241593 0
Systolic and diastolic blood pressure
Timepoint [1] 241593 0
Blood pressure is measured at each at each of the following timepoints Baseline (week 0 of intervention), week 1 week 2 week 4 (end of intervention). This is repeated for each of the three interventions.
Secondary outcome [2] 241594 0
Markers of Oxidative stress in blood including highly sensitive C reactive protein (hsCRP), lipid peroxides, lipofuscin-like flurophoes, nitrates and nitrites.
Timepoint [2] 241594 0
Blood markers of oxidative stress are measured at Baseline (week 0 of intervention), week 1 week 2 week 4 (end of intervention). This is repeated for each of the three interventions.
Secondary outcome [3] 241595 0
Vasoactive hormones including renin, aldosterone, insulin, ANP, BNP N terminal CNP, endothelin 1 will be measured from blood samples.
Timepoint [3] 241595 0
Vasoactive hormones will be measured at each time point for each intervention: Baseline (week 0), week 1 week 2 week 4 (end of intervention).

Key inclusion criteria
Indviduals with prehypertension or hypertension defined as a systolic blood pressure (SBP) > 130 and/or diastolic blood pressure (DBP) >85 mmHg or on antihypertensive medications
Minimum age
18 Years
Maximum age
65 Years
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Smokers, any underlying cardiovascular disease, diabetes, renal impairment

Study design
Purpose of the study
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation of treatment sequence was done by a third paper, contacting the hospital pharmacy who prepared the salt addition to the tomato juice, separate to the investigator. The subjects were then provided with the tomato juice from the pharmacy
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Randomisation sequence was generated by a random number sequence from www.randomisation.com
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?

Intervention assignment
Other design features
Participants and investigators were blinded to sequence allocation. However, clearly the participants will be aware of added salt to daily tomato juice once commenced intervention. Investigator remained blinded. There was a 4 week wash out phase between each intervention with no tomato juice. Participants remained on low salt diet (sodium 60 mmol/day throughout whole study.
Not Applicable
Type of endpoint(s)
Statistical methods / analysis

Recruitment status
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 1705 0
New Zealand
State/province [1] 1705 0

Funding & Sponsors
Funding source category [1] 4730 0
Name [1] 4730 0
National Heart Foundation of New Zealand
Address [1] 4730 0
The National Heart Foundation of New Zealand
P O Box 17-160, Greenlane
9 Kalmia Street, Ellerslie
New Zealand
Country [1] 4730 0
New Zealand
Primary sponsor type
University of Otago
University of Otago
Dunedin School of Medicine
PO Box 913
Dunedin 9054
New Zealand
Secondary sponsor category [1] 4272 0
Name [1] 4272 0
Otago District Health Board
Address [1] 4272 0
Great King Street
Dunedin 9054
Country [1] 4272 0
New Zealand

Ethics approval
Ethics application status
Ethics committee name [1] 6771 0
Lower South Regional Ethics Committee
Ethics committee address [1] 6771 0
Ministry of Health
229 Moray Place
PO Box 5849 Dunedin 9001
Ethics committee country [1] 6771 0
New Zealand
Date submitted for ethics approval [1] 6771 0
Approval date [1] 6771 0
Ethics approval number [1] 6771 0

Brief summary
Epidemiological studies have demonstrated the association between dietary NaCl intake and hypertension and the risk of cardiovascular disease. Reduction in dietary NaCl intake lowers blood pressure significantly, with a subsequent reduction in cardiovascular events. Reducing dietary NaCl increases arterial compliance and reduces arterial stiffness in older people with systolic hypertension. Experimentally, NaCl affects arterial stiffness by altering vascular structure along with smooth muscle cell and endothelial cell function through a variety of mechanisms. There are only a limited number of studies which have examined the effects of dietary NaCl on arterial wall function in vivo in humans. These studies have focused predominantly on large artery compliance. This study proposes to examine the impact of low, normal and high dietary NaCl on arterial function in normal healthy volunteers. Arterial function can be measured non-invasively by pulse wave analysis, pulse wave velocity and markers of endothelial function. Using these different techniques collectively, we will be able to document the impact of dietary NaCl on arterial compliance in mildly hypertensive individuals. This will then allow for subsequent studies investigating the impact of dietary NaCl in greater at risk populations of hypertensive individuals and those with chronic kidney disease.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 29447 0
Address 29447 0
Country 29447 0
Phone 29447 0
Fax 29447 0
Email 29447 0
Contact person for public queries
Name 12694 0
Dr Rob MacGinley
Address 12694 0
Deakin University Medical School Waurn ponds Geelong Australia. 3217
Country 12694 0
Phone 12694 0
+61 414017665
Fax 12694 0
Email 12694 0
Contact person for scientific queries
Name 3622 0
Dr Rob MacGinley
Address 3622 0
Deakin University Medical School Waurn ponds Geelong Australia.3217
Country 3622 0
Phone 3622 0
61 414017665
Fax 3622 0
Email 3622 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary