Usually bound to proteins (such as phytate) that limit their intetsinal absorption
Organic phosphate is hydrolyzed in intestinal lumen, releasing inorganic phosphate, which is then absorbed
Only 60% of intestinal organic phospphate is absorbed
Vitamine D compounds (such as calcitriol): increase intestinal phosphate absorption
Inorganic Phosphorous
Inorganic phosphorus is commonly used as a food additive in many processed foods (chicken nuggets, hot dogs, spreadable cheeses, etc): extends shelf life, enhances flavor, improves color, retains moisture, acts as an emulsifier, etc
Inorganic phosphorus is not protein-bound
Approximately 90-100% of inorganic phosphorus is absorbed
Effects of Hyperphosphatemia
The potential adverse effects of high serum phosphorus (and/or phosphorus accumulation( are observed in end-stage renal disease (CKD-5), CKD-2 to CKD-4, and in the general population
Study: multicenter, open-cohort, observational prospective study in 227 dialysis centers from 20 European countries (n = 6797)
Main Findings
Use of phosphate-binding agents -> 29% lower all-cause mortality
Use of phosphate-binding agents -> 22% lower cardiovascular mortality
All single and combined therapies with phosphate-binding agents (except aluminum salts) showed a beneficial association with survival
References
K/DOQI clinical practice guidelines for nutrition in chronic kidney failure. K/DOQI, National Kidney Foundation. Am J Kidney Dis. 2000;35(6)(suppl 2):S17–S104
The dialysis outcomes and practice patterns study (DOPPS): An international hemodialysis study. Kidney Int. 2000;57(suppl 74):S74–S81
Mortality risk in hemodialysis patients and changes in nutritional indicators: DOPPS. Kidney Int. 2002;62:2238–2245
Hidden sources of phosphorus in the typical American diet: does it matter in nephrology? Semin Dial. 2003;16(3):186–188
K/DOQI clinical practice guidelines for bone metabolism and disease in chronic kidney disease. Am J Kid Dis. 2003;42(4):S1–S201
Hidden phosphorus: where do we go from here? J Ren Nutr. 2007;17(4):e31–e36
Is controlling phosphorous by decreasing dietary protein intake beneficial or harmful in persons with chronic kidney disease. Am J Clin Nutr. 2008;88:1511–1518
Mortality risk for dialysis patients with different levels of serum calcium, phosphorus, and PTH: the Dialysis Outcomes and Practice Patterns Study (DOPPS). Am J Kidney Dis. 2008;52(3):519–530
Understanding sources of dietary phosphorous in the treatment of patients with chronic kidney disease. Clin J Am Soc Nephrol. 2010;5:519–530
Use of phosphate-binding agents is associated with lower risk of mortality. Kidney Int. Published online 3 July 2013; doi:10.1038/ki.2013.185 [MEDLINE]
