[The impact of known and unknown dietary components to phosphorus intake]

The pathogenesis of CKD-MBD is multifactorial but the tendency towards phosphorus retention due to an excessive dietary intake for the residual renal function plays a central role. The dietary phosphorus is absorbed in the intestine as inorganic free phosphorus. The share of intestinal absorption (about 60% on average) is negligible for plant phosphorus (in the form of phytate), while it is maximal for phosphate or polyphosphates contained in food additives. The latter represent a dangerous extra load of phosphorus because they are poorly recognized by patients and widely used in modern nutrition, in particular in low-cost food. In a free mixed diet, the phosphorus content is directly related to that of proteins. It follows that protein-rich foods are the main source of phosphorus. This is a favorable condition for CKD patients in conservative therapy when a low-protein diet is implemented, while it represents a huge problem for dialysis patients, who need a high-protein diet. A simple and effective approach to reduce the load of dietary phosphorus without reducing protein intake is to educate patients to avoid foods high in phosphorus (cheese, egg yolk, nuts, etc.), and particularly those containing phosphorus additives. In addition, they should prefer boiling (resulting also in a decrease in sodium and potassium) to other methods of cooking. Counseling by a dietician is important for successful patient care. The dietician provides nutritional education, can help the patient with the choice of food, and may favor the adherence to dietary prescriptions, which is a crucial aspect in an integrated approach to CKD-MBD.