Short-term biochemical and anthropometric effects of nutritional education for serum phosphorus control in hemodialysis patients

Kariem M Salem; Hussein Sheashaa; Doaa H El-Sabakhawy; Malak N Amin; Nagy Sayed-Ahmed; Mohammed K Nassar

doi:10.4103/jesnt.jesnt_45_20

ORIGINAL ARTICLE

Year : 2022 | Volume : 22 | Issue : 4 | Page : 183-192

Short-term biochemical and anthropometric effects of nutritional education for serum phosphorus control in hemodialysis patients

Kariem M Salem¹, Hussein Sheashaa², Doaa H El-Sabakhawy³, Malak N Amin⁴, Nagy Sayed-Ahmed⁵, Mohammed K Nassar⁵
¹ Department of Internal Medicine, Fayom University, Cairo, Egypt
² Urology and Nephrology Center, Mansoura University, Mansoura, Egypt
³ National Nutrition Institute, Cairo, Egypt
⁴ Theodor Bilharz Research Institute, Cairo, Egypt
⁵ Mansoura Nephrology and Dialysis Unit (MNDU), Department of Internal Medicine, Mansoura University, Mansoura, Egypt

Date of Submission	22-Dec-2020
Date of Acceptance	25-Jun-2022
Date of Web Publication	22-Sep-2022

Correspondence Address:
Dr. Mohammed K Nassar
Mansoura University Hospital, El Gomhouria Street, Mansoura, Dakahlia Governorate 35511
Egypt

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jesnt.jesnt_45_20

Abstract

Background Hyperphosphatemia is a frequently encountered and difficult-to-manage problem in hemodialysis (HD) patients and is an important risk factor for cardiovascular diseases. This study was carried out to explore the effect of nutritional education on the serum phosphorus level in HD patients. Patients and methods This open-label, single-center randomized controlled trial involved 100 HD patients. Patients were randomly assigned to one of two groups: the education group underwent a 12-week nutritional education program, whereas the control group received standard treatment. Nutritional education was provided by a trained renal dietitian in the form of educational sessions, brochures, audiovisual teaching aids, and patient-tailored dietary recommendations. Detailed nutritional and laboratory tests were done before randomization and 3 weeks after the end of the study. Results Serum phosphorus level and calcium–phosphorus product were significantly lower among the education group (P=0.02 and 0.04, respectively) with a percent reduction of serum phosphorus of -13.8 ± 21.41 after nutritional education. Nutritional education (B: -0.57, 95% confidence interval: -1.13 to -0.01, P=0.04) and the dietary protein intake (B: -0.47, 95% confidence interval: -0.94 to -0.003, P=0.04) were the predictors of serum phosphorus level at the end of the study. Three weeks after termination, BMI, waist circumference, and malnutrition inflammation score were lower (P=0.04, 0.04 and 0.02, respectively), whereas midarm muscle circumference was higher (P=0.004) among the education group. Conclusion Nutritional education can help in controlling the serum phosphorus level in HD patients without causing derangements in the nutritional status and should be provided in each HD unit.

Keywords: Egyptian, hemodialysis, map, nutritional, phosphorus

How to cite this article:
Salem KM, Sheashaa H, El-Sabakhawy DH, Amin MN, Sayed-Ahmed N, Nassar MK. Short-term biochemical and anthropometric effects of nutritional education for serum phosphorus control in hemodialysis patients. J Egypt Soc Nephrol Transplant 2022;22:183-92

How to cite this URL:
Salem KM, Sheashaa H, El-Sabakhawy DH, Amin MN, Sayed-Ahmed N, Nassar MK. Short-term biochemical and anthropometric effects of nutritional education for serum phosphorus control in hemodialysis patients. J Egypt Soc Nephrol Transplant [serial online] 2022 [cited 2023 Jun 8];22:183-92. Available from: http://www.jesnt.eg.net/text.asp?2022/22/4/183/356691

Introduction

Chronic kidney disease (CKD) is a major public health problem that affects more than 500 million people worldwide [1]. Phosphorus retention plays a pivotal role in many CKD-related comorbidities [2]. It commonly occurs because of net intestinal absorption exceeding renal excretion or dialysis removal. The dietary phosphorus load is crucial since the early stages of CKD up to dialysis-dependent end-stage renal disease (ESRD) [3]. The management includes phosphate binders and restriction of phosphorus in diet. These restrictions may limit protein intake, exacerbating malnutrition-inflammation-atherosclerosis syndrome and mortality among hemodialysis (HD) patients, as many phosphorus-rich foods are important sources of protein [4]. Furthermore, the collinearity of phosphorus and protein may be skewed because the phosphorus burden of food is affected by three factors: (a) the presence of phosphate additives, (b) food preparation method, and (c) bioavailability of phosphorus, all of which are frequently overlooked in nutrition assessments [5].

Compared with other nutrients like protein, sodium, and potassium, HD patients have less awareness of nutrition for phosphorus [6]. Moreover, adherence to these dietary restrictions has been reported in the literature to range from 19 to 57% [7]. Careful dietary management that reduces high phosphate intake is recommended to slow the progression of CKD and prevent its complications [8].

The monitoring of nutritional parameters is an integral part of treatment program of HD patients [9]. Nutritional status of HD patients could be assessed by different methods, such as anthropometric measurements, subjective global assessment, malnutrition inflammation score (MIS), markers of body composition measured by bioelectrical impedance analysis, and predialysis serum creatinine and albumin [10]. Nutrition intervention programs have been reported to have a positive effect on the nutritional status, leading to a decline in BMI and waist circumference (WC), reduction in the risk of cardiovascular disease, and increased satisfaction with current state of health, all of which contribute to improved quality of life [11].

This study was carried out to assess the short-term effect of intensive renal nutritional education provided by trained, dedicated dietitians on the control of serum phosphorus level, followed by performance of nutritional and anthropometric measurements in maintenance HD patients in a single tertiary HD center in Egypt.

Patients and methods

Patients and study design

This was an open-label, single-center, randomized controlled trial. Patients were recruited from the HD unit of New Mansoura General Hospital, Egypt. Patients, nephrologists, and dietitians were not blind to groups’ allocation. Included patients met the following inclusion criteria: (a) age more than or equal to 18 years and (b) on regular HD for more than 3 months. Patients with underlying malignancy or active infection, having difficulty in understanding questions, visual or hearing impairment, those who were pregnant or lactating, and those unwilling to participate were excluded from the study. A total of 50 HD patients from each group were included in the sample. According to the days of HD sessions, the selected patients were randomly divided into two groups (1: 1): the intervention (education) group included patients who had HD sessions on Sunday, Tuesday, and Thursday, whereas the control group included patients who had HD sessions on Monday, Wednesday, and Saturday. This type of randomization was used to avoid knowledge contamination across groups, which is an issue when researching patients who spend a lot of time together in a small space. The education group was subjected to nutritional education program by dedicated renal dietitians for 12 weeks, whereas the control group received the usual care, which was the existing practice in the unit. The study protocol was approved by the Institutional Research Board of the Faculty of Medicine, Mansoura University (code no. MD/16.09.24). The study was explained to all patients, and informed written consents were obtained from them before starting the study.

In addition to regular clinical examinations and essential laboratory testing, all patients had a thorough history taking process that included sociodemographic data, concomitant disorders, and the length of HD. Anthropometric measures, a 24-h diet recall sheet, a MIS [12], and dietary history were used to evaluate nutritional status. These evaluations took place at the beginning and 3 weeks following the study’s termination.

Nutritional education

Nutritional instruction was provided to participants in the education group for 12 weeks by devoted senior nephrologists and an expert renal dietician. Six instructional group sessions were offered at the outset of the trial, in a separate room next to the HD unit. Each session lasted 2 h, and all patients in the educational group attended all six sessions. Then, each patient received a one-to-one discussion with a nephrologist and a dietitian to measure anthropometrics, create a diet plan, and get tailored nutritional instruction. Based on the patient’s nutritional evaluation, a tailored food regimen was devised. The educator attempted to cover many elements of nutritional education but concentrated mostly on phosphorus management and the dangers of hyperphosphatemia, as well as the need of adhering to dietary regimen guidelines. A list of foods with high phosphorus content was supplied, as well as a list of typically low phosphorus-containing substitutes. Patients were urged to consume vegetable-based protein rather than animal-based protein, to limit their intake of processed foods and food additives, and to prepare and cook meals in certain ways to reduce their phosphate level. Easy handouts, which displayed suggested alternate substitutions for favorite foods, were used to ensure that the necessary daily protein intake reached the patient. The Egyptian phosphorus map ([Supplementary Figure 1]), which is an educational material printed in low literacy way, in bold font, and using Arabic language with descriptive photos easy to be understood, was provided for the education group patients. This was adapted from the Italian phosphorus pyramid [3] and modified according to food composition tables for Egypt [13]. This map was used mainly by the dietitian after studying the 24 h recall and the anthropometrics to provide in a simple manner variable diet options and cooking methods for control of phosphorus level without affecting protein intake to avoid malnutrition. Additionally, some audiovisual teaching aids were used: https://www.youtube.com/watch?v=tMKjgMtzjqA; https://www.youtube.com/watch?v=-CNPK_JXc3s; and https://www.youtube.com/watch?v=OzCdFE26RgE.

Supplementary Figure 1: Supplementary material: Egyptian phosphorus map.

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Blood sampling and laboratory tests

Blood samples were collected from arteriovenous fistulae just before starting the first HD session of a week. Laboratory tests including complete blood count, serum calcium, phosphorus, intact parathormone, serum albumin, serum cholesterol and triglyceride levels, and iron studies (ferritin and TSAT) were performed at the times of blood sampling using an automated analyzer. In addition, blood urea level was measured at the start and the end of HD session to calculate the urea reduction ratio. All laboratory tests were performed before the study and 3 weeks after termination.

Anthropometric measurements

Height and postdialysis body weight of all patients were measured, and BMI was calculated. Mid-upper arm circumference was measured in centimeters twice using a flexible, inelastic measuring tape in the nonarteriovenous fistula arm, just at the midpoint of upper arm (i.e. between the acromion process of scapula and the olecranon process of ulna), in sitting position, and the average was recorded [14]. Triceps skinfold thickness was measured in millimeters twice using a skinfold caliper at the midpoint of back of upper arm by taking a fold of skin away from muscle while the patient stood upright, with arms hanging down loosely [15]. Then, the midarm muscle circumference (MAMC) was calculated in cm by the following formula: mid-upper arm circumference (cm) – 3.14×triceps skinfold thickness (mm) [14]. WC was measured at the midpoint between the top of the iliac crest and the lower last ribs margin using a stretch-resistant tape [16].

Sample size and statistical analysis

Sample size estimation was based on figures derived from Youkm et al [2]. Using a statistical power of 90% and two-tailed significance level of 5%, the minimum required sample size was 40 patients for each group. Considering a possible dropout of 15%, the sample size was 46 in each group, which was rounded to 50 patients. Data were collected, revised, verified, and analyzed using the Statistical Package for the Social Sciences (SPSS), version 21 for Windows (SPSS Inc., Chicago, Illinois, USA). Medians and interquartile range (Q1–Q3) or means±SD were used for all quantitative values, whereas numbers of cases and percentages (%) were used to describe qualitative variables. After examining the distribution of continuous variables for normality using the Shapiro–Wilk test, the significance of differences between two groups was determined by independent samples t test for normally distributed variables or by Mann–Whitney test for nonparametric variables, as appropriate. χ² or Fisher exact tests were used for comparison between qualitative variables, as appropriate. Pearson correlation was used to correlate normally distributed data, whereas Spearman correlation was used to correlate nonnormally distributed data. Multiple linear regression analysis was done using the Enter approach. All of the potential confounders in the relation between the intervention and serum phosphorus level were included in the model. R² test was done to assess the variance explained by the model. The goodness of fit for the model was tested using χ² goodness-of-fit tests. P values less than 0.05 were considered significant for all statistical analyses in this study.

Results

This study included 100 chronic HD patients. Patients were randomly assigned into two equal groups: the education and control groups. The baseline sociodemographic, clinical, and dietary characteristics of the study patients are shown in [Table 1]. The research groups were clearly well matched in terms of sociodemographic parameters. The education group had a considerably lower percentage of patients with appropriate dietary phosphorus consumption than the control group ([Table 1]).

Table 1: Baseline sociodemographic, clinical, and dietary characteristics

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Of 39 patients with normal phosphorus levels, 13 were overconsumers of dietary phosphate (>17 mg/ideal body weight/day) in the education group, compared with eight out of 11 patients with hyperphosphatemia (>5.5 mg/dl) (P=0.03). Of 38 patients with normal phosphorus levels, six were phosphorus overconsumers in the control group, compared with seven out of 12 patients with hyperphosphatemia (P=0.003) ([Fig. 1]).

Figure 1: Association between dietary phosphorus consumption and phosphorus level among the education and control groups.

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Regarding the anthropometric measurements at the end of study, the education group patients had significantly lower BMI, WC, and MIS (P=0.04, 0.04, and 0.02, respectively) and higher MAMC (P=0.004). The nutritional education program did not adversely affect the anemia status or dialysis dose. Serum phosphorus level was significantly lower at the end of the study in the education group, with a percent reduction of 13.8 ± 21.41. Regarding the other laboratory measurements, intact parathyroid hormone, serum cholesterol, and triglyceride levels were significantly lower in the education group after the study (P=0.007, 0.03, and 0.006, respectively). Before the trial, the education group’s dietary protein intake was considerably lower (P=0.021); however, there was no significant difference between the two groups at the end of the study. Nutritional education resulted in increased protein intake at the end of the study in group 1 patients (P=0.015) (data not shown). Regarding the treatment characteristics, nutritional education in the intervention group resulted in a lower percentage of consumption of phosphate binders ([Table 2]).

Table 2: Comparison between the education and control groups before and after the study regarding anthropometric and laboratory measurements, dietary protein intake, and medication characteristics

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The incidence rate of hyperphosphatemia after the study was 8 and 22% in the education and control groups, respectively. The relative risk reduction of hyperphosphatemia by nutritional education was 63% [(22-8)/22]. Patients with normal and high serum phosphorus in both groups at the end of the study were matched regarding the sociodemographic characteristics ([Table 3]).

Table 3: Relation between phosphorus category at the end of the study and sociodemographic data

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Serum phosphorus level was significantly correlated with serum creatinine level in the intervention group (P=0.02), but there was no other significant association with the other studied variables in either group ([Table 4]). A multiple linear regression analysis was done including the set of variables (nutritional counseling, sex, age, income, dietary protein intake, and years on HD). The mean phosphorus level was reduced by 0.57 mg/dl for patients receiving educational counseling. In addition, dietary protein was also associated with inverse relation with the phosphorus level at the end of the study. The mean phosphorus decreased by 0.47 mg/dl for every 1 g increase in dietary protein ([Table 5]).

Table 4: Correlation between serum phosphorus and different variables at the end of the study

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Table 5: Multiple linear regression analysis for serum phosphorus level at the end of study in both groups

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Discussion

The burden of CKD with subsequent ESRD requiring renal replacement therapy is increasing globally, especially in nonaffluent countries [17]. Compared with the general population, patients with CKD have significantly increased risks of cardiovascular diseases and all-cause mortality [18]. Both traditional and CKD-specific risk factors contribute to this risk [19]. Abnormal values of serum phosphorus, calcium, parathyroid hormone, and fibroblast growth factor 23 are important CKD-specific risk factors [20].

Management of hyperphosphatemia is complex, and many patients fail owing to a lack of patient awareness. HD patients are hesitant to accept dietary regimens that limit phosphorus consumption in comparison with other nutritional components such as sodium or potassium [6]. Dietary nonadherence in those patients has been reported to range between 9 and 80.4% [21]. This may be owing to the limited knowledge about the diet itself and the hazardous effects of hyperphosphatemia [22]. Appropriate nutritional education may lead to better control of phosphate in patients with CKD, and therefore a better prognosis [23].

In this open-label, single-center, randomized controlled trial, 100 patients with CKD undergoing regular HD in a tertiary care center in Egypt were recruited. The patients were divided into two equal groups: the education group underwent a 12-week nutritional education program, whereas the control group received the unit’s standard treatment. Nutritional education was provided for the education group by a trained renal dietitian in the form of educational sessions, brochures, audiovisual teaching aids, and patient-tailored counseling. Sociodemographic, clinical, nutritional, and laboratory variables were examined in both groups before the trial began and 3 weeks after it ended.

In the present study, there was a significant relation between serum phosphorus level and dietary phosphorus intake in both groups. Noori et al. [24] reported that both higher dietary phosphorus intake and a greater dietary phosphorus-to-protein ratio were associated with an increased risk of mortality in HD patients, and they suggested that the least possible phosphorus content with an adequate protein intake should be recommended to those patients. More than three-quarters of patients in both groups had low-protein diet (<1 g/kg/day). This can be explained by the discrepancy in the dietary protein advice for individuals before and after dialysis begins [25]. Moreover, the high rate of hyperphosphatemia among dialysis patients forces them to reduce their dietary protein intake in a way to reduce the serum phosphorus level [26].

The effect of sociodemographic characteristics on the phosphorus level in patients with CKD has previously been studied. Some studies found that among patients with CKD, low socioeconomic status was associated with a higher risk of elevated serum phosphorus level [27,28]. Low income may lead to increased serum phosphorus levels owing to excessive intake of highly absorbable dietary phosphorus additives in the form of cheap, processed foods. Lower attained educational level may play a role owing to lack of understanding regarding a low-phosphorus diet and the importance of phosphate binder use [29]. Other studies suggested that low socioeconomic status and minority race were not associated with worse control of serum phosphorus levels in CKD or dialysis-dependent patients [30–32]. The current study indicated that the analyzed sociodemographic factors had no effect on serum phosphorus levels in either group. In the context of an integrated health-care delivery system like ours, disparities in the management of CKD mineral and bone diseases may be eliminated.

The effect of nutritional education on the control of serum phosphorus was the main scope of this work. Despite the lower prevalence of patients with baseline acceptable phosphorus intake in the education group, those patients had a significantly lower serum phosphorus level and calcium–phosphorus product after the study. Moreover, the percentage of patients with hyperphosphatemia was lower in the education group after study termination. The positive effect of nutritional education on the phosphorus level control was confirmed by a multivariate linear regression analysis. Furthermore, the education group had a significantly lower parathyroid hormone level after termination. These findings match with the results of multiple studies, which found that education could significantly reduce dietary phosphorus intake and increase treatment compliance [4,33–38].

In the current study, reducing processed food consumption and food additives, switching to plant-based protein instead of animal-based protein, and teaching patients how to prepare and cook foods with lower phosphorus contents were all adopted as control measures for hyperphosphatemia and were found to be successful. Another study showed that reducing the intake of processed food was one of the most effective ways of controlling hyperphosphatemia [21]. Guida et al. [39] reported that partial replacement of meat and fish with egg white could represent a useful way to control serum phosphate levels in HD patients without causing protein malnutrition. Despite the fact that more than half of our patients were uneducated, the dietary education program had a positive effect. Similarly, Martins et al. [40] concluded that nutritional education program can achieve excellent results when appropriately applied, and these results can be achieved across different literacy levels. This may be conveyed through visual learning tools such as pamphlets with illustrative images, as well as multimedia resources. All of these strategies made our nutritional information more accessible to all patients and caregivers, as family members could attend learning sessions when they were available.

Anthropometric measurements are valuable tools for assessment of the nutritional status in HD patients. BMI of 23 kg/m² or higher seems to reduce the risk of morbidity and mortality and is associated with improved survival in HD patients [41,42]. MAMC was found to have a stronger association with clinical outcomes than triceps skinfold, a surrogate of fat mass. Higher MAMC is a surrogate of larger lean body mass and an independent predictor of better mental health and greater survival in HD patients [24]. The education group had a lower BMI and WC, as well as a higher MAMC in the current study. However, all of these measurements remained in the acceptable range (e.g. BMI=24.6 ± 3.85). Moreover, the education group had a significantly lower MIS after the study. MIS is a comprehensive scoring system for protein-energy wasting detection and highly linked with hospitalization and mortality in HD patients [12]. These findings denote that the luminous dietary instructions by a professional clinical nutritionist did not adversely affect the nutritional status, a known consequence of the arbitrary dietary phosphate restriction [4]. The reduction in serum phosphorus should not be viewed as the sole outcome of this intervention and should be taken in context of other data, particularly nutritional status. This can help the policy makers to advocate the integrated nutritional programs for patients with ESRD to reduce the economic burden of the disease [43].

Finally, we admit that this study has some limitations, namely, the single-center and open-label nature and the short duration of follow-up. Nevertheless, the availability of a well-matched control group, the detailed assessment of dietary and nutritional characteristics, and the validation of the Egyptian phosphorus pyramid are strengths of this study.

In conclusion, nutritional education provided to HD patients improved hyperphosphatemia management without exposing the patients to the danger of malnutrition caused by injudicious dietary limitations. To meet the education program’s goal, multiple instructional resources that correspond to different reading levels must be available. Every HD center should have brochures showcasing the appropriate meals based on dietary composition tables in each location.

Acknowledgements

The authors are indebted to Dr Osama El Shahat, the past Head of Nephrology Department, New Mansoura General Hospital, Egypt, who provided all of the facilities, together with the nephrology team in arranging the meetings with patients and collection of the patients’ data, which were the backgrounds in the completion of this work.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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