Effects of dietary phosphates from organic and inorganic sources on parameters of phosphorus homeostasis in healthy adult dogs

BACKGROUND: The impact of dietary phosphorus (P) excess, especially on renal and cardiovascular health, has been investigated in several species, but little is known in dogs. OBJECTIVE: The aim of this study was to examine effects of different P sources on concentration and postprandial kinetics of selected parameters of P homeostasis in dogs. METHODS: Eight beagles received one control diet (P 0.5% dry matter [DM]) and three high P diets (poultry meal, NaH(2)PO(4,) and KH(2)PO(4); P 1.7% DM) for 18d. Urine samples were collected pre- and postprandially while faeces were collected quantitatively for 5d and analysed for minerals. On day 18, blood was sampled 1h pre- and 0.5, 1, 1.5, 2, 3, 5 and 7h postprandially. RESULTS: Pi (KH(2)PO(4), NaH(2)PO(4)) but not organic P caused an increased apparent P digestibility and significantly influenced kinetics of serum FGF23, parathyroid hormone, P, CrossLaps and bonespecific alkaline phosphatase, demonstrating a disrupted calcium (Ca) and P homeostasis with potential harm for renal, cardiovascular and skeletal health. CONCLUSIONS: Results of feeding Pi to dogs indicate distinct disturbances of Ca and P metabolism, in contrast to organic sources. The use of Pi in food can therefore not be considered as safe. Further research, especially on dose and long-term effects, is warranted.