Management of Natural and Added Dietary Phosphorus Burden in Kidney Disease
Section snippets
Early Phosphorus Retention in CKD
The pathogenesis of CKD-MBD is multifactorial and, in addition to hyperphosphatemia, includes changes in calcium, calcitriol, parathyroid hormone (PTH), and fibroblast growth factor-23 (FGF23).1 However, the tendency to retain phosphorus, based on an excessive dietary intake relative to residual renal function, plays a central role.6, 7, 8, 9, 10 Higher dietary phosphorus load may inhibit renal 1α-hydroxylase directly and also indirectly through the increase in FGF23; the decrease in the
Dietary Phosphorus
Phosphorus (P) is a nonmetal element with an atomic weight of 31 daltons. It is widely present in nature as phosphate (PO4). Phosphorus is also an essential constituent of all living organism because it plays a role in many fundamental biological and enzymatic reactions to maintain life as a result of its high chemical reactivity. Most of the total body phosphorus (ie, about 80%), is found in bones and teeth in the form of calcium salts, whereas about 20% is present in soft tissues and body
Circulating Level of Phosphorus
In plasma, the normal level of phosphorus is 2.5 to 4.5 mg/dL. Under normal physiologic conditions with an extracellular fluid pH of 7.4, hydrogen ion is bound to phosphate either as one (HPO42−) or dihydrogen structure (H2PO4−) at a 4:1 ratio, which explains why the average phosphate valence is 1.8 in body fluids. Serum phosphorus measurement usually yields the same concentration as plasma. The serum phosphorus level remains within the normal range until the late stages of CKD; therefore, as
Phosphorus Digestibility and Intestinal Absorption
The absorption of phosphate in intestinal epithelial cells occurs via a co-transport mechanism through active sodium/phosphate (Na+/Pi) co-transporters, which involves at least three different types of Na+/Pi (ie, NPT2a, b, and c). This mechanism can be inhibited by nicotinamide, therefore the administration of niacin may be used as an effective approach to reduce the intestinal absorption of phosphorus and to decrease the circulating phosphorus level.20 Upon intake of natural (nonenhanced)
Phosphorus From Unprocessed Food
In natural foods phosphorus is present both as inorganic ions and as a constituent of phosphoproteins, but also as membrane phospholipids, adenosine triphosphate, adenosine diphosphate, DNA, and RNA. In a mixed diet, the phosphorus content usually is proportional to the amount of protein content. Indeed, protein-rich foods are historically and naturally the main source of dietary phosphorus. Several equations have been advanced to estimate the content of phosphorus based on the amount of
Changes of Phosphorus Intake by Industrial Processing: Food Preservatives
In modern society, food and beverages often are consumed a long time after their production or in places far away from the production site. Notwithstanding these facts, the dietary product must satisfy safety guidelines and taste characteristics. This is why the food industry uses progressively more food additives, also known as preservatives, (ie, substances intentionally added to food for dietetic-preservative and financial purposes) (Table 2). A food additive is a substance not normally
Changes of Phosphorus Intake by Homemade Processing: Cooking
The considerations made thus far are based on the composition of foods and refer to the phosphorus content per 100 g of uncooked food, or on the recognition of the presence of phosphorus-containing additives in food. However, many foods are consumed after cooking, and this can result in changes in the natural composition of the nutrients.46 Among the different methods of cooking, some are more favorable for health because they maintain or even improve the nutritional properties of food by
Management of Dietary Phosphorus in Clinical Practice: Need for Education
Dietary assessment of patients with CKD is possible through different methods.42 The calculation of phosphorus intake from dietary recall or interview may be inaccurate and indeed misleading. These estimates generally are based on the nutrient contents of the raw product and do not include any loss occurring via the cooking process. Moreover, they usually do not consider the phosphorus from preservatives, and they do not distinguish between the phytates and other components with differential
Conclusion
A simple and effective approach to reduce the load of dietary phosphorus without reducing protein supply consists of educating patients to mitigate consumption of foods high in absorbable phosphorus (eg, processed cheese and egg yolk), to avoid foods containing additives based on polyphosphates (such as certain types of soft drinks), and to choose vegetable-based foods that have lower phosphorus absorption, and to choose boiling versus other common methods of cooking. Table 4 provides an
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Cited by (119)
Complications in Patients with Chronic Kidney Disease
2022, Critical Care Nursing Clinics of North AmericaBioavailability of phosphorus and kidney function in the Jackson Heart Study
2022, American Journal of Clinical NutritionThe Impact of Phosphorus Management Today on Quality of Life: Patient Perspectives
2022, Kidney MedicineCitation Excerpt :The recommended dietary restrictions do not allow flexibility, and patients might struggle to find foods that they are allowed to eat.10 The lack of nutritional information on food labels makes adhering to dietary restrictions even more confusing and difficult (eg, manufacturers are not required to include the quantity of phosphate due to food additives on labels).10,11 Furthermore, consuming a diet different from others’ diets in the household is difficult because preparing multiple meals within 1 household is expensive and time-consuming.12
Phosphate Absorption and Hyperphosphatemia Management in Kidney Disease: A Physiology-Based Review
2021, Kidney MedicineCitation Excerpt :Moreover, in vivo, each pill can only bind a discrete amount of phosphorus.27,23 Thus, patients typically require many large pills every time they eat (Fig 27,8,15-18,27-34) in an effort to bind a meaningful amount of dietary phosphate. Studies have shown that on average, patients receiving dialysis are prescribed 10.8 phosphate-binder pills per day, accounting for ∼50% of their total daily pill burden (Fig 327-33,35).36
Financial disclosure and conflict of interest statements: AC received honoraria from Shire, Heinz-Plasmon. KKZ has received honoraria from Abbott, Amgen, DaVita, Fresenius, Genzyme, and Shire. KKZ was supported by grants from National Institute of Diabetes, Digestive and Kidney Disease of the National Institutes of Health R01 DK078106, K24 DK091419, a philanthropist grant from Mr. Harold Simmons.