Effects of Dietary Phosphorus on Phosphorus and Calcium Whole-Body Balance and Kinetics in Moderate CKD

NCT ID: NCT06712719

Last Updated: 2025-12-18

Basic Information

• Recruitment Status: NOT_YET_RECRUITING
• Clinical Phase: NA
• Total Enrollment: 14 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2026-02-01
• Study Completion Date: 2027-05-28

Brief Summary

The aim of the study is to look at the effects of dietary phosphorus on phosphorous and calcium whole-body balance and kinetics in moderate chronic kidney disease (CKD). N = 14 enrolled subjects will be randomly assigned to a cross-over order of (A) Low P Diet, High P Diet. Each cross-over phase will be 19 days and consist of a 7-day outpatient, controlled diet period, followed by a 5- day inpatient, controlled diet, balance, and kinetic study period, followed by a second 7-day outpatient, controlled diet period.

Detailed Description

Chronic kidney disease (CKD) affects approximately 37 million (1 in 7) U.S. adults, most of whom experience mineral and bone disorders (CKD-MBD) that increase risk for cardiovascular events, bone fractures, and death. Dietary and pharmaceutical treatments for CKD-MBD have diverse effects on serum calcium and phosphorus levels, but their effects on the underlying physiological processes of calcium and phosphorus balance are largely unknown. This study aims to determine the effects of a low versus high phosphorus bioaccessibility diet on whole-body calcium and phosphorus balance and kinetics, including measures such as estimated intestinal absorption. This study will be a randomized two-phase cross-over design trial that will include a controlled study diet, a phosphorus isotope as a tracer for kinetic modeling, stool and urine collections, and blood draws. After screening, eligible participants who choose to enroll in the study will be asked to participate in two cross-over sessions, each of approximately 3 weeks (19 days) duration during which time all food will be provided according to the randomized diet intervention assignment. After the first week on the study diet, participants will be asked to stay at the clinical research center when they will be given oral and intravenous doses of phosphorus isotope. Serial blood draws and complete urine and fecal collections will be made for 5 days, then the final week will only include blood draws. Between cross-over sessions, there will be a washout period of 1-3 weeks. Participants will then switch diets and repeat the same study process as the first session. Calcium and phosphorus whole-body balance, intestinal absorption, renal excretion, and movement to and from bone will be determined for both minerals. This project will provide foundational knowledge of calcium and phosphorus physiology in CKD that will support progress towards preventing morbidity and mortality associated with CKD-MBD.

Conditions

CKD

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: DOUBLE

Study Groups

CKD patients group 1

assigned to Low P Diet (LP) then High P Diet (HP),

Group Type: EXPERIMENTAL

LP then HP

Intervention Type: OTHER

Cross-over order of LP then HP diet. Each cross-over phase will be 19 days and consist of a 7-day outpatient, controlled diet period, followed by a 5-day inpatient, controlled diet, balance, and kinetic study period, followed by a second 7-day outpatient, controlled diet period.

CKD patients group 2

assigned to HP, then LP.

Group Type: EXPERIMENTAL

HP then LP

Intervention Type: OTHER

Cross-over order of HP then LP diet. Each cross-over phase will be 19 days and consist of a 7-day outpatient, controlled diet period, followed by a 5-day inpatient, controlled diet, balance, and kinetic study period, followed by a second 7-day outpatient, controlled diet period.

Interventions

HP then LP

Cross-over order of HP then LP diet. Each cross-over phase will be 19 days and consist of a 7-day outpatient, controlled diet period, followed by a 5-day inpatient, controlled diet, balance, and kinetic study period, followed by a second 7-day outpatient, controlled diet period.

Intervention Type: OTHER

LP then HP

Cross-over order of LP then HP diet. Each cross-over phase will be 19 days and consist of a 7-day outpatient, controlled diet period, followed by a 5-day inpatient, controlled diet, balance, and kinetic study period, followed by a second 7-day outpatient, controlled diet period.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Men or women, ages 30-75 years old, any race or ethnicity
• Moderate CKD, defined by KDIGO as eGFR category 3b (30-44 mL/min) or 4 (16-29 mL/min) with albuminuria categories A1-A3
• Serum intact parathyroid hormone above assay normal limit
• Female subjects must be postmenopausal (>12 months since last menstrual period), surgically sterile, or confirmed not pregnant by pregnancy test

Exclusion Criteria

• Willing to discontinue supplements (e.g., vitamin D, calcium, multivitamin/minerals, or others) upon enrollment until completion of the study
• Adequate vitamin D status defined as serum 25D > 20 ng/mL based on National Academy of Medicine (then Institute of Medicine) criteria.

• Plans to initiate dialysis within 6 months
• Hypercalcemia defined as corrected serum calcium >9.8 mg/dL within past 3 months
• Hyperkalemia defined as serum potassium >5.5 mg/dL within past 3 months
• Hyperphosphatemia defined as serum phosphate >5.5 mg/dL within past 3 months
• Intestinal disease that alters absorption or normal intestinal function including celiac disease, small bowel resection, bariatric surgery, or chronic diarrhea/malabsorption
• Serious, uncontrolled underlying systemic disease including diabetes, lupus, hypertension in the opinion of their physician
• Pregnant or breastfeeding
• Prescribed and taken a phosphate binder medication, calcitriol, vitamin D analogs, calcimimetics, PTH analogues, and other medications that may alter Ca and P metabolism within past 4 weeks
• Non-English speaking

• Minimum Eligible Age: 30 Years
• Maximum Eligible Age: 75 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

University of Minnesota

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Kathleen Hill Gallant, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Minnesota

Central Contacts

Kathleen Hill Gallant, PhD

Role: CONTACT

Phone: 612-625-5285

Email: hillkm@umn.edu

Other Identifiers

TBD2

Identifier Type: -

Identifier Source: org_study_id