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

Sponsor

University of British Columbia (Other)

Overall Status

Completed

CT.gov ID

NCT00755690

Collaborator

(none)

Enrollment

Location

Arms

17.9

Duration (Months)

1.8

Patients Per Site Per Month

Study Details

Study Description

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.

Condition or Disease	Intervention/Treatment	Phase
Kidney Diseases	Behavioral: High/ Low Phosphate diet Behavioral: High/ Low Phosphate diet Behavioral: High/ Low Phosphate diet	N/A

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 ;

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

Study Design

Study Type:

Interventional

Actual Enrollment :

32 participants

Allocation:

Randomized

Intervention Model:

Crossover Assignment

Masking:

None (Open Label)

Primary Purpose:

Treatment

Official Title:

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

Study Start Date :

Sep 1, 2008

Actual Primary Completion Date :

Mar 1, 2010

Actual Study Completion Date :

Mar 1, 2010

Arms and Interventions

Arm	Intervention/Treatment
Active Comparator: 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.	Behavioral: High/ Low Phosphate diet Low phosphate diet (750mg/day).
Active Comparator: 2 High/ Low Phosphate diet	Behavioral: High/ Low Phosphate diet Low phosphate diet (750mg/day) with the addition of the phosphate binder aluminum hydroxide (500mg three times per day).
Active Comparator: 3 High/ Low Phosphate diet	Behavioral: High/ Low Phosphate diet III. High phosphate diet (2000mg /day).

Arm

Intervention/Treatment

Active Comparator: 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.

Behavioral: High/ Low Phosphate diet

Low phosphate diet (750mg/day).

Active Comparator: 2

High/ Low Phosphate diet

Behavioral: High/ Low Phosphate diet

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

Active Comparator: 3

High/ Low Phosphate diet

Behavioral: High/ Low Phosphate diet

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

Outcome Measures

Primary Outcome Measures

FGF-23 [5 days]

Secondary Outcome Measures

Serum calcium, phosphate, PTH, 25 and 1,25 vitamin D and fractional phosphate excretion. [5 days]

Eligibility Criteria

Criteria

Ages Eligible for Study:

19 Years and Older

Sexes Eligible for Study:

All

Accepts Healthy Volunteers:

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