Serum phosphate concentrations reflect the dynamic balance between dietary phosphorus absorption, urinary phosphorus excretion, and internal exchange with the bone, soft tissue, and intracellular stores [33]. In MHD patients—who possess severely limited urinary phosphorus excretion and still-efficient gut phosphorus absorption—dietary absorption is a critical determinant of serum phosphate concentration. The importance of dietary phosphate intake is further boosted by the widespread use of activated vitamin D analogs, which increase gut absorption of phosphorus [34], and by the relatively poor phosphate clearance provided by standard hemodialysis three times per week. Preventing gut absorption of dietary phosphorus either by restricting intake or prescribing oral phosphorus binders is currently the cornerstone of managing hyperphosphatemia in MHD patients.

Compared to phosphate binders, dietary phosphorus restriction is underutilized in MHD patients. This is likely due to fear of exacerbating protein energy wasting (PEW), the assumption that patients will be poorly compliant with yet another layer of dietary restriction in addition to those already in place (e.g., for fluid, salt) and the logistical challenges of continuous dietary counseling. In support of these concerns, some previous reports suggest that hemodialysis patients are less likely to adhere to a phosphate dietary restriction than to potassium, sodium, or fluid restriction [14, 35].

To help a patient successfully follow phosphate dietary restrictions, dietitians must listen attentively to patients’ concerns and actively identify issues to be solved in order to adequately manage serum phosphorus concentrations. Individual counseling, based on learning needs and preferences, is offered by dietitians to MHD patients with hyperphosphatemia [36,37,38]. This counseling includes advice on avoiding phosphate-rich foods and phosphate additives as shown in Tables 2 and 3. The dietary modification can be achieved through ongoing education from dietitians and other medical team members and through support from family and friends [39]. Towards this end, the Academy of Nutrition and Dietetics in the USA proposed the Nutrition Care Process (NCP). This systematic approach provides high-quality nutrition care through the following four steps: (1) nutrition assessment and reassessment, (2) nutrition diagnosis, (3) nutrition intervention, and (4) nutrition monitoring and evaluation [40, 41]; Fig. 3.

Table 2 Questionnaires about dietary phosphorus for dialysis patients Full size table

Table 3 Self-management survey about dietary phosphorus for patients Full size table

A number of large studies have examined the association between educational attainment and outcomes in patients with kidney disease. In an analysis of 61,457 participants in the Kidney Early Evaluation Program, lower educational attainment was independently associated with reduced kidney function and increased mortality [42]. Several interrelated pathways have been proposed to explain the relationship between educational attainment and health including (a) health knowledge and behaviors, (b) employment and income [43], and (c) social and psychological factors. In particular, education contributes to health by improving health knowledge, affording adequate health literacy, and improving coping and problem-solving skills [44, 45]. These advantages allow patients to make better decisions about their health, engage in healthy behaviors, and self-manage their medical conditions [46].

Successful control of diet is often challenging, and the availability of a variety of educational resources is very beneficial when working with patients and their families [47]. In an ideal situation, patients are allowed to learn at their own speed. Many medical teams have developed an array of educational tools that include written, visual, or auditory programs to instruct patients on how to effectively modify their diets. Dietitians in our hospital also evaluate and educate MHD patients using original question sheets and tools (Additional file 1; Tables 2, 3, and 4; Figs. 4, 5, and 6). Many patients have noted that altering diet behavior is one of the hardest challenges in adjusting to dialysis. A recent survey of nutrition trends in CKD patients showed that the greatest perceived obstacles to positive dietary change included the fear of giving up favorite foods, confusion regarding dietary recommendations, and false beliefs regarding the length of time required to prepare healthy foods.

Table 4 Phosphorus to protein ratio in dairy product Full size table

Fig. 4 Educational leaflets on dietary phosphorus made by the Kyoto working committee on food for dialysis patients. Leaflets address (a) carbonated beverages, (b) Japan McDonald’s, and Kentucky Fried Chicken Japan (c). Food information is published with permission from these companies Full size image

Fig. 5 Leaflet on preparation methods for reducing phosphorus in processed food Full size image

Fig. 6 Recipes on diet supplementation for avoiding PEW Full size image

Additional file 1: Movie of dietitian’s counseling. (MP4 185512 kb)

In addition to education, assessing patients’ knowledge is an important factor in estimating patient compliance to the renal diet [46, 47]. Dietitians initiate the processes of assessment and education in order to (1) establish communication with patients and their families, (2) provide information to address any underlying nutritional issues, and (3) calm the fears that many patients have regarding the implementation of the many changes required in their lives [48]. In support of this approach, Reddy et al. [41] found that an education program significantly improved patients’ general knowledge of phosphorus and phosphate binders and was associated with a significant reduction in serum phosphate in patients with hyperphosphatemia.