Phosphorus and the Kidney: What Is Known and What Is Needed

Abstract

A major role of the kidneys is to maintain phosphorus homeostasis. High serum phosphorus has been linked to all-cause and cardiovascular mortality in chronic kidney disease (CKD) both before and after initiation of renal replacement therapy. Considering the clinical implications of uncontrolled hyperphosphatemia, maintenance of phosphorus concentrations within an optimum range is standard of care in this patient population. Recently, the epidemiologic associations between serum phosphorus and worse outcome have been extended to the general population. This becomes even more important in view of the increasing dietary phosphorus intake in the American diet due in large part to the greater consumption of foods processed with phosphate additives. A greater understanding of mechanisms and epidemiology of altered phosphorus metabolism and disease in CKD may help clarify the possible role of excess dietary phosphorus as a health risk factor in the general population. Adv. Nutr. 5: 98-103, 2014.

Stirring the Pot: Can Dietary Modification Alleviate the Burden of CKD?

“…Inorganic phosphate additives are found in many processed foods including frozen meals, snack bars, French fries, spreadable cheeses, instant food products and beverages such as sodas, flavoured water, juices and sport drinks [122]. The phosphorous content in a typical Western diet has increased substantially during the past few decades [123] and in many countries dietary phosphorus exceeds the recommended daily allowance [124]. A recent Australian study found that phosphate additives were present in 44% of the most commonly purchased grocery foods, and were particularly prevalent in small goods (96%), bakery products (93%) and frozen meals (75%) [125].…”

“…Whilst many studies have shown an association between serum phosphate levels and risk of CVD death in CKD patients, it has been noted that there is a dearth of randomised controlled trials with an intervention that modifies dietary phosphate and assesses mortality as an outcome [123]. Whilst this evidence may be lacking for mortality outcomes, the current guidelines recommend maintaining serum phosphate within a normal range for CKD stages 3–5 and dialysis patients, by dietary restriction and the use of phosphate binders [14], with insufficient evidence for recommending dietary phosphate restriction for early CKD patients (stages 1–3) [61].…”

Inorganic Phosphate Effect of on Human Dental Pulp Cell Cultures

“…It was shown that a high-phosphate diet would significantly improve bone mineralization and play a role in formation of secondary ossification centers, but hypophosphatemia caused a delay in ossification [5]. Conversely, patients who undergo hyperphosphatemia which is a common manifestation of advanced chronic kidney disease (CKD), are disposed to cardiovascular morbidity and mortality due to increased vascular calcifications and are susceptible to bone diseases [6,7]. Few studies have been conducted to test the effect of inorganic phosphate (Pi) on osteoblasts.…”

A promising materials approach to combatting renal hyperphosphatemia:Fe(II)-montmorillonites

“…The mixtures were centrifuged and then the concentration of phosphate in the supernatant was determined by UV-vis spectroscopy at λ max = 700 nm. Similarly, the experiments were carried out to determine the optimum pH and maximum adsorption of phosphate onto Fe(II)-MMT at pH of 1,2,3,4,5,6,7,8,9, and 10 and the initial amounts were 9.9, 11.5, 13.1, 14.8, 16.4, 18.1, 19.7, 21.4, 23, and 26.3 mg, respectively. All the experimental data were repeated three times and the relative errors ranged within ±3%.…”

“…8,9 DOPPS studies have shown that the prevalence of hyperphosphatemia in hemodialysis patients was 57.4% and the prevalence of hyperphosphatemia in peritoneal dialysis patients was 47.7%, while the success rate of blood phosphorus control was only 38.5%. 10 The main treatment for hyperphosphatemia was food intake control 11,12 and reduction of the intestinal absorption of phosphorus and blood dialysis using a phosphate binder.…”