Study of Dietary Additive Phosphorus on Proteinuria and Fibroblast Growth Factor-23 (SODA-POP)

Randomized Cross-over Study Examining the Effects of Phosphorus Additives on Urinary Albumin Excretion and Fibroblast Growth Factor-23

Phosphorus-based food additives are commonly used by food manufacturers for many applications, such as enhancing flavor, in ready-to-eat foods and beverages. While these additives can significantly increase an individual's daily phosphorus intake, little is known about the effect of dietary phosphorus on kidney health. In this study, the investigators will first lower baseline phosphorus intake to about 1000mg/d by educating participants to avoid foods with phosphorus additives. Then, participants will be randomized to a higher phosphorus period (~2gm/d) and a lower phosphorus period (~1gm/d) by providing unaltered, commercially-available food/beverage products with and without phosphorus additives.

The investigators hypothesize that participants will have higher urine albumin excretion and fibroblast growth factor-23 (FGF-23) during the higher phosphorus period compared to the lower phosphorus period.

Study Overview

• Status: Completed
• Conditions: Albuminuria
• Intervention / Treatment: Other: Higher phosphorus period; Other: Lower phosphorus period

Detailed Description

The Study of Dietary Additive Phosphorus on Proteinuria and FGF-23 (SODA-POP) was a single-center, randomized, double-blind, two-period cross-over study that examined the effect of higher vs. lower phosphorus intake for 3 week periods, achieved by addition of commercially available diet beverages and breakfast bars to diet on albuminuria and fibroblast growth factor 23, in adults with presumed early chronic kidney disease (estimated glomerular filtration rate >= 45 ml/min/1.73m2; and urine albumin/creatinine ratio >=17 mg/g for men or >=25 mg/g for women).

• Study Type: Interventional
• Enrollment (Actual): 31
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • Maryland
    • Baltimore, Maryland, United States, 21207
      • ProHealth Clinical Research Unit

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 21 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

Adults at least 21 years of age with at least microalbuminuria

Exclusion Criteria:

Estimated glomerular filtration rate <45ml/min/1.73m2, poorly controlled diabetes or hypertension, nephrotic syndrome, hyperparathyroidism, Paget's Disease, multiple myeloma, uncontrolled thyroid disease, chronic antacid use, use of phosphorus binders, phosphorus supplements, or high-dose vitamin D, inability to complete feeding study, investigator discretion

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Higher phosphorus period; Commercially-available unaltered food/beverage products containing phosphorus additives (~1gm/d of phosphorus) will be given for 3 weeks	Other: Higher phosphorus period; Commercially-available unaltered food/beverage products containing phosphorus additives (~1gm/d of phosphorus) will be given for 3 weeks. All participants at the beginning of the study will receive dietary education to reduce their baseline consumption of phosphorus to a goal of ~1gm/d by receiving education on avoiding phosphorus-based additives.
Placebo Comparator: Lower phosphorus period; Commercially-available unaltered food/beverage products without phosphorus additives (<10mg/d of phosphorus) will be given for 3 weeks	Other: Lower phosphorus period; Commercially-available unaltered food/beverage products without phosphorus additives (<10mg/d of phosphorus) will be given for 3 weeks. All participants at the beginning of the study will receive dietary education to reduce their baseline consumption of phosphorus to a goal of ~1gm/d by receiving education on avoiding phosphorus-based additives.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
24-hour Urine Albumin Excretion	Two 24-hour urine collections will be collected during the 3rd week of each period	3 weeks
Fibroblast Growth Factor-23 (FGF-23)	Plasma FGF-23 will be measured at the end of each 3 week period in the morning after an overnight fast. As this is a small pilot study, we will not adjust for multiple comparisons. A p value<0.05 will be considered statistically significant for both outcomes	3 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Systolic Blood Pressure	Blood pressure was measured at the end of weeks 1, 2, and 3. At each visit, 3 readings were obtained in the seated position by trained and certified observers after 5 minutes of rest with an Omron HEM-907 device (Omron Healthcare Inc, Bannockburn, Ill) using a standardized protocol. We used the average of all blood pressure measurements at the end of weeks 1, 2, and 3 for each period.	2-3 weeks
Diastolic Blood Pressure	Blood pressure measured at the end of weeks 1, 2, and 3. At each visit, 3 readings were obtained in the seated position by trained and certified observers after 5 minutes of rest with an Omron HEM-907 device (Omron Healthcare Inc, Bannockburn, Ill) using a standardized protocol. We used the average of all these readings taken during end of weeks 1, 2, and 3 for each period.	2-3 weeks

Collaborators and Investigators

• Sponsor: Geisinger Clinic
• Collaborators: Johns Hopkins University
• Investigators: Principal Investigator: Alex R Chang, MD, MS, Geisinger Clinic; Study Director: Lawrence J Appel, MD, MPH, Johns Hopkins University

Publications and helpful links

General Publications

• Chang A, Batch BC, McGuire HL, Vollmer WM, Svetkey LP, Tyson CC, Sanguankeo A, Anderson C, Houston J, Appel LJ. Association of a reduction in central obesity and phosphorus intake with changes in urinary albumin excretion: the PREMIER study. Am J Kidney Dis. 2013 Nov;62(5):900-7. doi: 10.1053/j.ajkd.2013.04.022. Epub 2013 Jun 28.

Study record dates

Study Major Dates

• Study Start: January 1, 2014
• Primary Completion (Actual): September 1, 2015
• Study Completion (Actual): September 1, 2015

Study Registration Dates

• First Submitted: December 19, 2013
• First Submitted That Met QC Criteria: December 19, 2013
• First Posted (Estimate): December 25, 2013

Study Record Updates

• Last Update Posted (Actual): June 5, 2019
• Last Update Submitted That Met QC Criteria: February 26, 2019
• Last Verified: February 1, 2019

More Information

Terms related to this study

• Keywords: proteinuria
• Additional Relevant MeSH Terms: Urologic Diseases; Urological Manifestations; Urination Disorders; Proteinuria; Albuminuria
• Other Study ID Numbers: NA_00082089; 13CRP16970085 (Other Grant/Funding Number: American Heart Association); Satellite Dialysis (Other Grant/Funding Number: National Kidney Foundation)