Understanding Sources of Dietary Phosphorus in the Treatment of Patients with Chronic Kidney Disease

Abstract

In individuals with chronic kidney disease, high dietary phosphorus (P) burden may worsen hyperparathyroidism and renal osteodystrophy, promote vascular calcification and cardiovascular events, and increase mortality. In addition to the absolute amount of dietary P, its type (organic versus inorganic), source (animal versus plant derived), and ratio to dietary protein may be important. Organic P in such plant foods as seeds and legumes is less bioavailable because of limited gastrointestinal absorption of phytate-based P. Inorganic P is more readily absorbed by intestine, and its presence in processed, preserved, or enhanced foods or soft drinks that contain additives may be underreported and not distinguished from the less readily absorbed organic P in nutrient databases. Hence, P burden from food additives is disproportionately high relative to its dietary content as compared with natural sources that are derived from organic (animal and vegetable) food proteins. Observational and metabolic studies indicate nutritional and longevity benefits of higher protein intake in dialysis patients. This presents challenges to providing appropriate nutrition because protein and P intakes are closely correlated. During dietary counseling of patients with chronic kidney disease, the absolute dietary P content as well as the P-to-protein ratio in foods should be addressed. Foods with the least amount of inorganic P, low P-to-protein ratios, and adequate protein content that are consistent with acceptable palatability and enjoyment to the individual patient should be recommended along with appropriate prescription of P binders. Provision of in-center and monitored meals during hemodialysis treatment sessions in the dialysis clinic may facilitate the achievement of these goals.

Acute Effects of Very-Low-Protein Diet on FGF23 Levels

“…At the first visit, all patients were recommended to minimize added salt to keep daily sodium and phosphorus intake (16,17). As an additional difference, the two diets contained a different percentage of vegetable proteins that was equal to 48% in LpD and 66% in VLPD (14,15).…”

Effects of Dietary Phosphate and Calcium Intake on Fibroblast Growth Factor-23

“…This is well below the amount in a typical Western diet, which contains 1500 mg of phosphate (7)(8)(9)(10). During the second study period, dietary phosphate and calcium intake was high: 2880 and 1700 mg, respectively (10).…”

“…The two dietary interventions led to significant changes in 24-hour urinary urea content (P ϭ 0.003 for change from regular to phosphate-restricted diet, and P ϭ 0.0006 from regular to phosphate-enriched diet), indicating reasonable separated levels of protein intake ( Figure 2). The tight correlation between protein intake and phosphorous intake is well established (10).…”

A Patient with CKD and Poor Nutritional Status

“…An important consideration regarding strategies to improve dietary protein intake in patients with ESRD is the potential increase in the intake of several potentially harmful elements, especially phosphorus (28). Dietary recommendations to improve protein intake should take into account the phosphorus content of the specific protein sources (i.e., vegetarian diets tend to be low in phosphorus) and other phosphorus sources, such as additives and preservatives in processed food (29,30).…”