Based on new evidence renal dietitians in Ireland are revising the diet sheet that is used to teach patients about reducing blood phosphate. Changes that renal dietitians plan to make to the dietary phosphorus prescription

• Inclusion of some nuts and pulses
• More detailed education re phosphate additives
• More accurate protein prescription
• Inclusion of more whole grains
• Encouraging the use of foods with a low phosphorus to protein ratio

The investigators want to test the two diet prescription to find out, which one is better at reducing blood phosphate and which one is more acceptable to patients. The investigators also want to make sure it is safe.

Background:

Chronic Kidney Disease (CKD) afflicts one in twenty Irish citizens who are over age 45 and is a significant risk factor for cardiovascular disease, premature death and significantly impacts healthcare utilisation. As kidney function deteriorates, phosphorus, upregulates counter regulatory hormones (immunoreactive Parathyroid Hormone (iPTH) and Fibroblast Growth Factor 23 (FGF23), the elevated levels of which are maladaptive. Collectively these abnormalities and their complications are referred to as Chronic Kidney Disease, Mineral & Bone Disorder (CKD MBD). Hyperphosphataemia or high blood phosphate levels is associated with increased mortality, in dialysis patients, in the earlier stages of CKD and even in patients with normal renal function. The use of phosphorus restricted diets in combination with oral phosphate binders has become well established in the management of patients with CKD stages 3-5 (including CKD stage 5D).

Experts have called for research into the dietary management of phosphate in the CKD population. The current evidence base is weak and in a recent Cochrane systematic review the authors concluded that there was limited low quality evidence to indicate that dietary interventions may positively affect CKD-MBD.

In recent years there has been increased focus on dietary phosphorus restriction in the management of CKD-MBD and a number of experts have suggested changes in how we manage dietary phosphorus. Several potential strategies have been suggested and in response the Renal Interest Group (RIG) of the Irish Nutrition & Dietetic Institute (INDI) held a 1 day meeting in Dublin in January 2015 which brought together numerous experts in the field to summarise our current understanding and the recent advances in the field.

Following on from this, RIG set up a working group to translate the new knowledge from the advanced study day and from further literature reviews into a modified low phosphate diet sheet.

Almost all people who have end stage kidney disease (ESKD) and require dialysis to survive, follow a dietary phosphorus restriction, to control high blood phosphate, with the aim of reducing the risk of cardiovascular disease, fractures and death.

Research Hypothesis: The modified low phosphate diet sheet is superior to current treatment in haemodialysis patients

Study Objectives

Primary Objective: To determine if the modified low phosphorus dietary prescription is superior to current management in reducing serum phosphate levels in HD patients

Secondary Objectives To determine if the modified low phosphorus diet is tolerable To determine if the modified low phosphorus diet is safe To determine if the modified low phosphorus diet brings the renal diet closer to healthy eating advice e.g. increased fibre intake.

Inclusion Criteria:

• >18 years
• Self reported urine output less than 2 cups (400mls) / day
• On maintenance haemodialysis for > 3 months
• Phosphate >1.6mmole/L on average of last 3 available routine monthly blood tests

Exclusion Criteria:

• Hyperkalemia, defined as a predialysis serum K on routine monthly blood test of >6mmoles/l in the month preceding the trial.
• Parathyroidectomy
• Corrected serum calcium <2.2 or > 2.6mmol/L or local normal units where ranges varied significantly from 2.2-2.6mmoles/l.
• Acute concurrent illness, requiring hospitalisation in the 2 weeks prior to recruitment.

As with most education based interventions compared to routine care it is difficult to reliably mask either the subjects or the investigators to the proposed intervention. We will attempt to blind patients referring only to the diets as diet A and diet B and avoiding the use of terminology such as old and new. We will reprint the dietary information for both arms so they do not resemble current illustrated formats.