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Phosphorus. Mineral bone abnormalities begin early in the course of CKD and lead to high-turnover bone disease, adynamic bone disease, fractures, and soft-tissue calcification. Careful monitoring of calcium, intact parathyroid hormone, and phosphorus levels is required throughout all stages of CKD, with hyperphosphatemia of particular concern.
In CKD stages 1 and 2, dietary phosphorus should be limited to maintain a normal serum level. 2 As CKD progresses and phosphorus retention increases, 800 to 1,000 mg/d or 10 to 12 mg of phosphorus per gram of protein should be prescribed.
Even with the limitation of dietary phosphorus, phosphate-binding medications may be required to control serum phosphorus in later CKD stages and in HD and PD patients. 2 Limiting dietary phosphorus can be difficult for patients because of inorganic phosphate salt additives widely found in canned and processed foods; they are also added to dark colas and to meats and poultry to act as preservatives and improve flavor and texture. Phosphorus additives are 100% bioavailable and therefore more readily absorbed than organic phosphorus. 4
Fluid. Lastly, CKD patients need to think about their fluid intake. HD patients with a urine output of > 1,000 mL/24-h period will be allowed up to 2,000 mL/d of fluid. (A 12-oz canned drink is 355 mL.) Those with less than 1,000 mL of urine output will be allowed 1,000 to 1,500 mL/d, with anuric patients capped at 1,000 mL/d. PD patients are allowed 1,000 to 3,000 mL/d depending on urine output and overall status. 2 Patients should also be reminded that foods such as soup and gelatin are counted in their fluid allowance.
The complexities of the “renal diet” make patient education by an RD critical. However, a recent article suggested that MNT for CKD patients is underutilized, with limited referrals and lack of education for primary care providers and RDs cited as reasons. 5 This is mystifying considering that Medicare will pay for RD services for CKD patients.
The National Kidney Disease Education Program, in association with the Academy of Nutrition and Dietetics, has developed free professional and patient education materials to address this need; they are available at http://nkdep.nih.gov/.
Luanne DiGuglielmo, MS, RD, CSR
DaVita Summit Renal Center
Mountainside, New Jersey
REFERENCES
1. McMahon GM, Preis SR, Hwang S-J, Fox CS. Mid-adulthood risk factor profiles for CKD. J Am Soc Nephrol . 2014 Jun 26; [Epub ahead of print].
2. Byham-Gray L, Stover J, Wiesen K. A Clinical Guide to Nutrition Care in Kidney Disease . 2nd ed. The Academy of Nutrition and Dietetics; 2013.
3. Crews DC. Chronic kidney disease and access to healthful foods. ASN Kidney News . 2014;6(5):11.
4. Moe SM. Phosphate additives in food: you are what you eat—but shouldn’t you know that? ASN Kidney News. 2014;6(5):8.
5. Narva A, Norton J. Medical nutrition therapy for CKD. ASN Kidney News . 2014;6(5):7.