[Effect of phosphorus excess on magnesium metabolism in growing pigs]

This study was designed to assess the influence of dietary P excess on Mg metabolism in normally fed pigs. 22 growing pigs, weighing around 20 kg, received either a high-P (1.2%) or a control P (0.6-0.7%) diet for 7 or 9 weeks. The following parameters were measured: kinetics of plasma levels of Ca, P and Mg, absorption, urinary and fecal excretion, retention of Ca, P and Mg, kidney and bone mineral contents. Dietary P excess decreased absorption, plasma levels and urinary excretion of Mg, but did not change Mg retention or bone mineral contents. It also increased absorption, retention (g/day) and excretion (urinary and fecal) of P, but did not change those of Ca. Nephrocalcinosis appeared on high-P diet. Some Mg metabolism disorders seem to result from direct Mg-P interactions (hypomagnesiuria, for instance), while others (hypomagnesemia) could also be a secondary effect of P excess upon Ca-P metabolism.