Lowering Salt Intake in Chronic Kidney Disease: A Pilot Randomized Crossover Trial (BIA)

ABSTRACT

Background:

It is well recognized that excess dietary salt intake plays a major role in the development of hypertension. Chronic Kidney Disease (CKD) is associated with excess salt and water retention (excess volume) which is associated with hypertension.

Hypotheses:

Hypothesis 1:

Dietary salt restriction will improve volume status in subjects with CKD stages 3-4 as assessed by Bioelectrical Impedance Analysis (BIA).

Hypothesis 2:

Dietary salt restriction will result in improved blood pressure control in patients with CKD stages 3-4.

Hypothesis 3:

Dietary salt restriction will decrease albuminuria in patients with CKD stages 3-4.

Patients and Trial Design: This randomized crossover pilot study is designed to assess the effect of salt restriction on volume status in patients with CKD stages 3 and 4.

Subjects will be randomized to a treatment order: (1) 4 weeks of salt restriction of <85 mmol sodium per day, a 2 week washout period, and 4 weeks of usual salt diet, OR (2) 4 weeks of usual diet, 2 weeks washout, and 4 weeks of salt restriction. Patients will receive dietary counseling in person at each study visit and at weekly intervals by phone calls from study dieticians. At weeks 0, 4, 6 and 10, patients will undergo assessments for (i) physical examination with assessments for weight, blood pressure, pulse, anthropometrics and a standardized clinical assessment of volume status. (ii) volume status using bioelectrical impedance analysis (BIA) (iii) 24-hour urine testing for, albumin, creatinine and aldosterone Every 2 weeks throughout the study, a 24-hour urine sodium will be measured for compliance, and serum electrolytes will be assessed for safety.

Data Analysis: BIA measurements in the low salt group will be compared with the regular diet group using the standard linear model analysis for 2x2 crossover trials. Additionally, 24-hour ambulatory and static blood pressure and 24-hour urine aldosterone levels will be compared between the two groups.

Future Implications: A significant reduction in the degree of volume expansion (as assessed by BIA) and blood pressure as a result of a salt restricted diet would have implications for renal and cardiovascular protection and would warrant confirmation by a larger randomized trial.

Study Overview

• Status: Completed
• Conditions: Kidney Disease
• Intervention / Treatment: Dietary supplement: Low Salt Diet; Dietary supplement: Usual Salt Diet

• Study Type: Interventional
• Enrollment (Actual): 35
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • North Carolina
    • Chapel Hill, North Carolina, United States, 27599
      • University of North Carolina

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 85 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

Individuals eligible to participate in this study must meet all of the following criteria:

• Willing and able to provide written, signed informed consent after the nature of the study has been explained, and prior to any research-related procedures.
• Age ≥ 18 years and ≤ 85 years.
• Willing and able to comply with all study procedures.
• Patients with eGFR of 20 to 60 ml/min/173m2 by the abbreviated (4-variable) MDRD equation and a relatively stable clinical course.
• Sitting systolic blood pressure ≥ 100 mmHg prior to study entry (to exclude people at risk from hypotension from dietary salt reduction).

Exclusion Criteria:

Individuals who meet any of the following exclusion criteria will not be eligible to participate in the study:

• Recent acute illness (≤1 month). Minor ailments such as a recovered common cold or allergic rhinitis would not be considered as exclusion criteria but would be left to the site PI's discretion.
• Recent hospitalization (≤1 month) unless clearly for a minor elective procedure unlikely to interfere with BIA measurements. The final decision will be left to the site PI's discretion.
• Any psychological condition (including alcoholism) that could interfere with the patient's ability to comply with the study protocol.
• Subjects with baseline 24-hour urinary sodium excretion ≤100 mmol/day.
• Amputation of a limb other than fingers or toes.
• Pacemaker, defibrillator, implantable pump, artificial joint, pins, plates or other types of metal objects in the body (other than dental fillings).
• Coronary stents or metal suture material in the heart.
• Use of any investigational product or investigational medical device within 30 days prior to screening, or requirement for any investigational agent prior to completion of all scheduled study assessments.
• Weight over 300 pounds (limitation for examination table).
• Pregnancy or lactation.
• Patients with kidney diseases known to be associated with salt wasting (see above).
• Patients with atrial fibrillation as ambulatory blood pressure measurements may not be accurate in this setting.
• Any condition that, in the view of the PI, places the subject at high risk of poor treatment compliance or of not completing the study.

Study Plan

How is the study designed?

Design Details

• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Low Salt Diet; Dietary sodium restriction of ≤2.0 g/day or ≤ 85 mmol/day for two weeks	Dietary supplement: Low Salt Diet; Dietary sodium restriction of ≤2.0 g/day or ≤ 85 mmol/day; Other Names: Low salt diet, CKD, Bioimpedance analysis (BIA)
Placebo Comparator: Ususal Salt Diet; Usual salt intake (approximately >180-200 mmol/day in the average American diet).	Dietary supplement: Usual Salt Diet; Usual salt intake (approximately >180-200 mmol/day in the average American diet).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Primary Outcome: Change in volume status (intracellular, extracellular volume, and total body water) as measured by BIA using both whole body and segmental techniques	12 Weeks

Collaborators and Investigators

• Sponsor: University of Michigan
• Collaborators: Renal Research Institute
• Investigators: Principal Investigator: Rajiv Saran, MD, University of Michigan

Publications and helpful links

General Publications

• McMahon EJ, Campbell KL, Bauer JD, Mudge DW, Kelly JT. Altered dietary salt intake for people with chronic kidney disease. Cochrane Database Syst Rev. 2021 Jun 24;6(6):CD010070. doi: 10.1002/14651858.CD010070.pub3.

Study record dates

Study Major Dates

• Study Start: May 1, 2009
• Primary Completion (Actual): February 1, 2013
• Study Completion (Actual): May 1, 2013

Study Registration Dates

• First Submitted: September 9, 2009
• First Submitted That Met QC Criteria: September 9, 2009
• First Posted (Estimate): September 10, 2009

Study Record Updates

• Last Update Posted (Estimate): August 5, 2015
• Last Update Submitted That Met QC Criteria: August 4, 2015
• Last Verified: August 1, 2015

More Information

Terms related to this study

• Keywords: Kidney Disease; Glomerular filtration rate; Albuminuria; Bioimpedance analysis; Volume status
• Additional Relevant MeSH Terms: Urologic Diseases; Renal Insufficiency; Kidney Diseases; Renal Insufficiency, Chronic
• Other Study ID Numbers: HUM00016384