Final answer:
CKD patients should start restricting phosphorus intake at stage 3 of the disease due to the risk of hyperphosphatemia as renal function decreases, becoming more important as CKD progresses to stages 4 and 5.
Step-by-step explanation:
Patients with chronic kidney disease (CKD) should start restricting phosphorus intake when they reach stage 3, which is characterized by a moderate reduction in glomerular filtration rate (GFR) between 30 to 59 mL/min/1.73 m². As CKD progresses to stage 4 and stage 5, phosphorus restriction becomes even more crucial due to severely reduced GFR levels and the risk of developing hyperphosphatemia, which is abnormally increased levels of phosphates in the blood. Hyperphosphatemia can occur when there is decreased renal function, and it can lead to bone and heart problems among other complications.
Phosphorus is present in nearly all foods, with dairy products, cereals, egg yolk, meat, beans, and nuts being particularly rich sources. The goal of dietary phosphorus restriction in CKD patients is to prevent or treat hyperphosphatemia and associated complications such as secondary hyperparathyroidism and cardiovascular disease. Management typically includes dietary modification and the use of phosphate binders to reduce phosphate absorption.