Milk Products in the Treatment of Hypophosphatemic Rickets: A Pilot Study

BACKGROUND: Standard treatment of hypophosphatemic rickets (HR) is oral phosphate tablets plus vitamin D. Due to the rapid absorption of phosphate tablets, frequent daily doses are necessary, which is cumbersome and may cause fluctuations in plasma phosphate and risk of secondary hyperparathyroidism. It was hypothesized that phosphate from milk or cheese is less rapidly absorbed, and reduces fluctuations in plasma phosphate. OBJECTIVES: The current randomized, multiple crossover study aimed at investigating if an equivalent phosphate dose given as milk or cheese is comparable to phosphate tablets in patients with HR. METHODS: Seven females with HR were included. They went through three different four-day treatment sessions of either oral phosphate tablets consisting of 800 mg elemental phosphorus divided into five doses over the day or an equivalent phosphorus dose ingested as skimmed milk or cheese divided over five daily doses. Blood and urine samples were taken from patients after each treatment session. Except the usual doses of vitamin D, no phosphate or calcium-modifying treatments were allowed. Statistical analyses were performed using mixed models. RESULTS: Treatment feasibility was independent of the phosphorus source. The study demonstrated reduced plasma levels of parathyroid hormone (PTH), reduced fluctuations in plasma phosphate and plasma PTH, and reduced renal phosphate excretion when ingesting phosphorus supplementation as milk compared to phosphate tablets. The same trend was observed when administering phosphorus as cheese, though not statistically significant. CONCLUSIONS: Phosphorus supplements can be administered as phosphate tablets, milk or cheese when given in equimolar doses. The current study findings indicated that milk may be superior to phosphate tablets as the phosphate source in patients with HR.