Dietary Phosphorus Load and Postprandial Serum Phosphate in HD Patients

The Effect of Dietary Phosphorus Load and Food Matrix on Postprandial Serum Phosphate in Hemodialysis Patients

This study is to investigate the acute postprandial effect of a modified versus standard low phosphorus diet on serum phosphate, potassium and intact parathyroid levels in prevalent hemodialysis (HD) patients

Background: Potential dietary strategies for controlling hyperphosphataemia include the use of protein sources with lower phosphorus bioavailability such as pulses and nuts, focus on phosphorus to protein ratios and the avoidance of all phosphate additives.

Method: Controlled crossover feeding study in 8 HD patients. On one day, participants were directly observed eating a standard low phosphorous diet and on the other day, a modified low phosphorus diet. The modified diet included beef and less dairy, with a lower phosphorus to protein ratio, as well as plant-based protein, whole grains, pulses and nuts containing phytates which reduces phosphorus bioavailability. Both diets were tailored for each participant to provide 1.1g protein/kg ideal body weight. Participants provided fasting bloods before breakfast, a pre-prandial sample before lunch and samples at one hour intervals for the four hours after the meal, for analysis of phosphate, potassium and intact parathyroid hormone (iPTH).

Inclusion Criteria:

• > 18 years of age;
• on dialysis for > 3 months;
• pre-dialysis serum phosphate < 2.5 mmol/L and
• serum potassium < 6.3 mmol/L on most recent routine monthly blood test;
• urinary outputs of < 200 ml/day by self-report;
• being in their usual state of health

Exclusion Criteria:

• history of diabetes mellitus
• history of parathyroidectomy
• history of calciphylaxis