Study of Dietary Phosphate and Mineral Homeostasis in Early Chronic Kidney Disease

NCT ID: NCT00755690

Last Updated: 2014-02-19

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 32 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2008-09-30
• Study Completion Date: 2010-03-31

Brief Summary

This study is designed to describe the physiological response to increased and decreased dietary phosphate intake on various parameters of mineral metabolism in the blood and urine of individuals with Chronic Kidney Disease stage 3 and 4 with normal serum phosphate levels. This detailed study will give us a far greater understanding of the role of diet in abnormal mineral homeostasis early in the progression of this chronic disease. The findings of this study will help both physicians and dietitians better determine the optimal time to introduce dietary therapy in CKD.

Detailed Description

The potential benefits of implementation of phosphate management earlier in CKD (Stages 3/4) are threefold: 1) prevention of vascular damage early in the progression of CKD thus reducing risk of cardiovascular death 2) Improved management of renal bone disease and resultant co-morbidities and 3) slowing the progression of renal failure lengthening the time required till dialysis is required. Although dietary counseling is currently a normal part of CKD care, the utility and effectiveness of lowering phosphate has not previously been quantified. In part this is due to the difficulty of measurement of serum phosphate as it is so tightly controlled before GFR falls below 30mls/min. No studies have investigated whether is it possible to modulate circulating FGF-23 and phosphate excretion in early stages of renal failure using diet in individuals with normal serum phosphate levels.

Study Objectives ;

1. To measure FGF-23 levels before and after a high phosphate diet, low phosphate diet and a low phosphate diet with phosphate binders.

2. To measure levels of calcium, phosphate, PTH, 25 and 1,25 vitamin D and fractional phosphate excretion before and after a high phosphate diet, low phosphate diet and a low phosphate diet with phosphate binders.

Conditions

Kidney Diseases

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

1

High/ Low Phosphate diet I. A five-day low phosphate diet / A five-day low phosphate diet with the addition of a phosphate binder / A five-day high phosphate diet.

II. A five-day low phosphate diet / A five-day high phosphate diet / A five-day low phosphate diet with the addition of a phosphate binder III. A five-day high phosphate diet / A five-day low phosphate diet with the addition of a phosphate binder / A five-day low phosphate diet.

IV. A five-day high phosphate diet / A five-day low phosphate diet / A five-day low phosphate diet with the addition of a phosphate binder.

V. A five-day low phosphate diet with the addition of a phosphate binder / A five-day low phosphate diet / A five-day high phosphate diet.

VI. A five-day low phosphate diet with the addition of a phosphate binder / A five-day high phosphate diet / A five-day low phosphate diet.

Group Type: ACTIVE_COMPARATOR

High/ Low Phosphate diet

Intervention Type: BEHAVIORAL

Low phosphate diet (750mg/day).

2

High/ Low Phosphate diet

Group Type: ACTIVE_COMPARATOR

High/ Low Phosphate diet

Intervention Type: BEHAVIORAL

Low phosphate diet (750mg/day) with the addition of the phosphate binder aluminum hydroxide (500mg three times per day).

3

High/ Low Phosphate diet

Group Type: ACTIVE_COMPARATOR

High/ Low Phosphate diet

Intervention Type: BEHAVIORAL

III. High phosphate diet (2000mg /day).

Interventions

High/ Low Phosphate diet

Low phosphate diet (750mg/day).

Intervention Type: BEHAVIORAL

High/ Low Phosphate diet

Low phosphate diet (750mg/day) with the addition of the phosphate binder aluminum hydroxide (500mg three times per day).

Intervention Type: BEHAVIORAL

High/ Low Phosphate diet

III. High phosphate diet (2000mg /day).

Intervention Type: BEHAVIORAL

Eligibility Criteria

Inclusion Criteria

• CKD patients with CKD stage 3 and 4 (eGFR < 60 ml/min and > 15 ml/min per 1.73 m2, not requiring dialysis).
• Normal serum phosphate stable over three months (> 0.87 mmol/L and < 1.70 mmol/L)
• Not yet following a low phosphate diet as reported by the patient or the renal dietitian (<1500mg/d)
• Over 19 years of age

Exclusion Criteria

• Body mass index <20 kg/m2
• Current use of phosphate binders or active vitamin D or phenytonin (which induces vitamin D catabolism)
• Primary parathyroid defects
• Diagnosed osteoporosis
• Gut absorption defects
• Liver disease
• Pregnancy or lactation
• Patients hospitalised within the last 4 weeks

• Minimum Eligible Age: 19 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

University of British Columbia

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Adeera Levin, MD

Role: PRINCIPAL_INVESTIGATOR

University of British Columbia

Locations

St. Paul's Hospital

Vancouver, British Columbia, Canada

Countries

Canada

Other Identifiers

H08-01018

Identifier Type: -

Identifier Source: org_study_id