Dietary Phosphate and the Forgotten Kidney Patient: A Critical Need for FDA Regulatory Action

The Relevance of Phytate for the Treatment of Chronic Kidney Disease

Diets high in plant-based foods are commonly recommended for people with CKD. One putative advantage of these diets is reduced intestinal phosphate absorption. This effect has been ascribed to phytic acid (myoinositol hexaphosphoric acid) and its anion, phytate, that are present in many plant foods, particularly in the seeds, nuts, grains, and fruits of plants. This article reviews the structure and many actions of phytate with particular reference to its potential effects on people with CKD. Phytate binds avidly to and can reduce gastrointestinal absorption of the phosphate anion and many macrominerals and trace elements including iron, zinc, calcium, and magnesium. This has led some opinion leaders to label phytate as an anti-nutrient. The human intestine lacks phytase; hence, phytate is essentially not degraded in the small intestine. A small amount of phytate is absorbed from the small intestine, although phytate bound to phosphate is poorly absorbed. Clinical trials in maintenance hemodialysis patients indicate that intravenously administered phytate may decrease hydroxyapatite formation, vascular calcification, and calciphylaxis. Orally administered phytate or in vitro studies indicate that phytate may also reduce osteoporosis, urinary calcium calculi formation, and dental plaque formation. Phytate seems to have anti-inflammatory and antioxidant effects, at least partly because of its ability to chelate iron. Other potential therapeutic roles for phytate, not definitively established, include suppression of cancer formation, reduction in cognitive decline that occurs with aging, and amelioration of certain neurodegenerative diseases and several gastrointestinal and metabolic disorders. These latter potential benefits of phytate are supported by cell or animal research or observational studies in humans. Many of the above disorders are particularly common in patients with CKD. Definitive clinical trials to identify potential therapeutic benefits of phytate in patients with CKD are clearly warranted.

Dietary Needs, Barriers, and Facilitators Among Patients on Hemodialysis and Their Caregivers: The GoodRENal Project in Spain

OBJECTIVE

Dietary restrictions are common in patients undergoing hemodialysis (HD). These restrictions result in a complex diet that becomes difficult for patients to understand and to follow. Therefore, we aimed to identify dietary needs, barriers, and facilitators that influence the adherence to dietary recommendations as perceived by patients on HD and their caregivers.

METHODS

Seventy-two Spanish patients on HD and 57 caregivers participated in this explorative study by replying a questionnaire consisting of 20 and 10 questions respectively. The responses were assessed using a Likert scale varying from 1 to 5 (strongly agree, agree, neither disagree or disagree, disagree, strongly disagree, respectively) to evaluate the perception of patients and caregivers regarding dietary needs, barriers, and facilitators to adhere to the recommended diet. For analysis purposes, the responses were grouped in 3 categories (agree, neither agree or disagree, disagree).

RESULTS

Seventy percent of the patients agreed that knowing the food sources of potassium, protein and phosphate was a need for them to know to be able to adhere to the dietary recommendations. Moreover, patients stated that not being able to eat what they liked, and feeling thirsty, were important barriers. For caregivers, the support of a renal dietitian was mentioned as an important facilitator to assist those they cared for to adhere to the diet.

CONCLUSIONS

Knowing food sources of potassium, phosphate, and protein, exploring foods patients like to eat and adjusting fluid intake to avoid feeling thirsty were identified as important by the patients. These findings can be used to develop strategies and educational material to improve the dietary adherence in patients undergoing HD. Moreover, the presence of a renal dietitian was identified as an important resource by the caregivers.

Ultraprocessing and presence of additives in commercially produced complementary foods in seven Southeast Asian countries: a cross-sectional study

BACKGROUND

There has been a dramatic shift in food systems, and the consumption of commercially processed and packaged foods has grown globally, including among older infants and young children. Many of these products are ultraprocessed and contain additives, with concerning implications for the health and nutrition of children.

OBJECTIVES

The study objectives were as follows: 1) to assess the levels of processing among different commercially produced complementary food product (CPCF) categories marketed in the Southeast Asia region, 2) to compare the nutrient content of CPCF products across levels of processing, and 3) to assess the types of additives present in different CPCF categories.

METHODS

This cross-sectional study involved secondary analysis of a cross-sectional dataset of product label information from CPCF purchased in 2021 in Cambodia, Indonesia, Lao People's Democratic Republic, Malaysia, Philippines, Thailand, and Viet Nam. Ingredient lists were reviewed to determine the level of processing-based on the Nova classification-and the presence of additives. Nutrient declaration panels were reviewed to determine total sugar, sodium, and total fat.

RESULTS

Nearly half of all CPCF were ultraprocessed, with total sugar and sodium content significantly higher among ultraprocessed CPCF than unprocessed/minimally processed products. Almost half of CPCF contained additives, with a median of 6 per product. More than 30% of all CPCF made use of cosmetic additives to enhance the products' appearance, flavor, or texture, with emulsifiers, colors, and thickeners the most prevalent. Almost one-third of products contained additives not permitted in Codex Alimentarius standards and guidelines for CPCF.

CONCLUSIONS

Findings from this study should alert national governments to both adopt and ensure enforcement of Codex guidance on additives and regulations enacted to encourage lower levels of processing for CPCF.

Tenapanor: A Phosphate Absorption Inhibitor for the Management of Hyperphosphatemia in Patients With Kidney Failure

Because of increased risks of cardiovascular disease and death, patients with hyperphosphatemia receiving maintenance dialysis are advised to limit phosphorus consumption and are prescribed phosphate binders in an effort to better control serum phosphate concentrations. Because of large pill size, pill burden, and tolerability issues, phosphate binder adherence is relatively poor. On ingestion, phosphate is absorbed from the intestine via transcellular or paracellular transport. Data show that inhibiting sodium-hydrogen exchanger 3 modulates paracellular phosphate absorption (the predominant pathway in humans). Tenapanor is a first-in-class, minimally absorbed, phosphate absorption inhibitor that selectively inhibits sodium-hydrogen exchanger 3, with a mechanism distinct from, and complementary to, that of phosphate binders. In phase 3 and postregistrational studies, tenapanor conferred statistically significant and clinically meaningful reductions in serum phosphate in patients receiving maintenance dialysis with hyperphosphatemia. Here, we review the available preclinical and clinical data on the effects of tenapanor on controlling intestinal phosphate absorption.

Academy of Nutrition and Dietetics Commentary on the Phosphorus Recommendation in the KDOQI Clinical Practice Guidelines for Nutrition in CKD: 2020 Update

The Kidney Disease Outcomes Quality Initiative Clinical Practice Guidelines for Nutrition in Chronic Kidney Disease: 2020 Update recommends adjusting dietary phosphorus to maintain a serum phosphate goal for hemodialysis patients in the normal range (0.81 to 1.45 mmol/L [2.5 to 4.5 mg/dL]). This is lower than the serum phosphate goal used by many dialysis centers (0.97 to 1.78 mmol/L [3.0 and 5.5 mg/dL]). Although context and clinical judgment must always be considered when providing individualized care to patients, a guideline implementation study conducted from December 2020 to December 2022 found that, based on their documentation, registered dietitian nutritionists from two national dialysis chains are almost universally using dialysis center goals instead of the lower phosphate goal recommended by the guideline. This commentary discusses the possible barriers to implementing the Kidney Disease Outcomes Quality Initiative 2020 nutrition guideline's phosphorus recommendation and proposes a systems level approach to promote and support adoption of the recommendation. Calls to action for potential changes in clinician practices, organizational/institutional culture, and government regulations are put forth.

Phosphate in Cardiovascular Disease: From New Insights Into Molecular Mechanisms to Clinical Implications

Hyperphosphatemia is a common feature in patients with impaired kidney function and is associated with increased risk of cardiovascular disease. This phenomenon extends to the general population, whereby elevations of serum phosphate within the normal range increase risk; however, the mechanism by which this occurs is multifaceted, and many aspects are poorly understood. Less than 1% of total body phosphate is found in the circulation and extracellular space, and its regulation involves multiple organ cross talk and hormones to coordinate absorption from the small intestine and excretion by the kidneys. For phosphate to be regulated, it must be sensed. While mostly enigmatic, various phosphate sensors have been elucidated in recent years. Phosphate in the circulation can be buffered, either through regulated exchange between extracellular and cellular spaces or through chelation by circulating proteins (ie, fetuin-A) to form calciprotein particles, which in themselves serve a function for bulk mineral transport and signaling. Either through direct signaling or through mediators like hormones, calciprotein particles, or calcifying extracellular vesicles, phosphate can induce various cardiovascular disease pathologies: most notably, ectopic cardiovascular calcification but also left ventricular hypertrophy, as well as bone and kidney diseases, which then propagate phosphate dysregulation further. Therapies targeting phosphate have mostly focused on intestinal binding, of which appreciation and understanding of paracellular transport has greatly advanced the field. However, pharmacotherapies that target cardiovascular consequences of phosphate directly, such as vascular calcification, are still an area of great unmet medical need.

From ultra-processed foods towards healthy eating for CKD patients: a proposal of educational infographics

Ultraprocessed food (UPF) is defined as industrialized, packaged and ready-to-eat food produced on a large scale, using sophisticated industrial machinery. Examples of UPFs include salty and sweet snacks, industrialized biscuits and packaged meals, processed meats and sugary drinks. Ultraprocessed food has a long-shelf life, is highly palatable, microbiologically safe, affordable and most of all, easy to consume. For these reasons, its consumption has been increasing worldwide, and is replacing healthy homemade meals. The main concern of this dietary shift is that UPFs come with the addition of salt, sugar, unhealthy fats, and several additives and taste enhancers that contain, among other substances, relevant quantities of potassium, phosphate and sodium. A large proportion of UPF in the diet may carry risks for patients with chronic kidney disease (CKD) since it can worsen blood pressure and glycemic control, and lead to constipation, hyperkalemia and hyperphosphatemia. Acknowledging the importance of UPF in kidney health implies integrating nutritional counseling with information on UPFs, and specific educational material can be helpful for patients, caregivers, and also for health care providers. We developed a set of 3 infographics dedicated to CKD patients, with information on how to identify UPFs, reasons for decreasing consumption, how to compose a healthy CKD plate and tips for reading food labels in supermarkets and grocery shops. We hope that this material can be useful in CKD outpatient clinics and dialysis centers as well as in general practitioners' offices, caring for early stage CKD.

Phosphorus - a scoping review for Nordic Nutrition Recommendations 2023

This scoping review aims to describe the totality of evidence for the role of phosphorus for health-related outcomes as a basis for setting and updating dietary reference values (DRVs). Phosphorus is needed in many biological processes, such as cellular metabolism and bone mineralization. Dietary phosphorus intake exceeds the previous Nordic Nutrition Recommendations (NNR2012) 2-3-fold in the Nordic countries. Intake from food additives is unknown but may play a significant role because the use of phosphate additives is common in the food industry. Bioavailability of phosphorus in plant-based products is lower than animal-based products. Nevertheless, bioavailability of phosphorus additives is higher. The main phosphorus-related health outcomes concern high phosphorus intake mainly from food additives with potential adverse effects on kidney, bone, and cardiovascular health.

Industrial Use of Phosphate Food Additives: A Mechanism Linking Ultra-Processed Food Intake to Cardiorenal Disease Risk?

The consumption of ultra-processed food (UPF) keeps rising, and at the same time, an increasing number of epidemiological studies are linking high rates of consumption of UPF with serious health outcomes, such as cardiovascular disease, in the general population. Many potential mechanisms, either in isolation or in combination, can explain the negative effects of UPF. In this review, we have addressed the potential role of inorganic phosphate additives, commonly added to a wide variety of foods, as factors contributing to the negative effects of UPF on cardiorenal disease. Inorganic phosphates are rapidly and efficiently absorbed, and elevated serum phosphate can lead to negative cardiorenal effects, either directly through tissue/vessel calcification or indirectly through the release of mineral-regulating hormones, parathyroid hormone, and fibroblast growth factor-23. An association between serum phosphate and cardiovascular and bone disease among patients with chronic kidney disease is well-accepted by nephrologists. Epidemiological studies have demonstrated an association between serum phosphate and dietary phosphate intake and mortality, even in the general American population. The magnitude of the role of inorganic phosphate additives in these associations remains to be determined, and the initial step should be to determine precise estimates of population exposure to inorganic phosphate additives in the food supply.

Using Potassium Bicarbonate to Improve the Water-Holding Capacity, Gel and Rheology Characteristics of Reduced-Phosphate Silver Carp Batters

To study the use of partial or total potassium bicarbonate (PBC) to replace sodium tripolyphosphate (STPP) on reduced-phosphate silver carp batters, all the batters were composed of silver carp surimi, pork back fat, ice water, spices, sugar, and sodium chloride. Therein, the sample of T1 contained 4 g/kg STPP; T2 contained 1 g/kg PBC, 3 g/kg STPP; T3 contained 2 g/kg PBC, 2 g/kg STPP; T4 contained 3 g/kg PBC, 1 g/kg STPP; T5 contained 4 g/kg PBC, and they were all produced using a bowl chopper. The changes in pH, whiteness, water- and oil-holding capacity, gel and rheological properties, as well as protein conformation were investigated. The pH, cooking yield, water- and oil-holding capacity, texture properties, and the G' values at 90 °C of the reduced-phosphate silver carp batters with PBC significantly increased (p < 0.05) compared to the sample without PBC. Due to the increasing pH and enhanced ion strength, more β-sheet and β-turns structures were formed. Furthermore, by increasing PBC, the pH significantly increased (p < 0.05) and the cooked silver carp batters became darkened. Meanwhile, more CO₂ was generated, which destroyed the gel structure, leading the water- and oil-holding capacity, texture properties, and G' values at 90 °C to be increased and then decreased. Overall, using PBC partial as a substitute of STPP enables reduced-phosphate silver carp batter to have better gel characteristics and water-holding capacity by increasing its pH and changing its rheology characteristic and protein conformation.

New Directions in Phosphorus Management in Dialysis

Current phosphate management strategies in end-stage renal disease (dietary phosphate restriction, dialysis, and phosphate binders) are inadequate to maintain target phosphate levels in most patients. Dietary phosphate restriction is challenging due to "hidden phosphates" in processed foods, and dialysis and phosphate binders are insufficient to match average dietary phosphate intake. As phosphate binders must be taken with each meal, patients need to ingest many, large pills several times a day, negatively impacting quality of life. Recent advances in our understanding of phosphate absorption pathways have led to the development of new nonbinder therapies that block phosphate absorption. This review describes the limitations of current phosphate management strategies and discusses new therapies in development that inhibit phosphate absorption pathways. These new therapies present an opportunity to rethink phosphate management, potentially by prescribing phosphate absorption inhibitors as a primary therapy and adding phosphate binders if needed.

Impact of SARS-CoV-2 Pandemic on food Security in Patients With chronic Kidney Disease

OBJECTIVE

The present study aims to determine the degree of Food Insecurity (FI) in adult patients with CKD during the COVID-19 pandemic, as well as the association between FI and food consumption.

METHODS

A cross-sectional study was conducted on patients with chronic kidney disease (CKD), with and without substitutive treatment, and older than 18 years of age. Food security was measured using the Mexican Food Security Scale (MFSS). Sociodemographic data and a food frequency questionnaire were obtained. Multinomial logistic regression was performed using the 4 categories of food security (food security as reference); principal component analysis was also performed to assess the relationship between food consumption patterns and sociodemographic characteristics.

RESULTS

The prevalence of FI in patients with CKD was 71.6%, the most prevalent degree of FI was moderate. As FI increased, a greater amount of beans, eggs, sweets/desserts, soft drinks, and artificial juices (P < .001) was consumed. The risk factors of FI were diabetes, hypertension, unpaid occupation, living in the country's capital, having children at home, or a decrease in income due to the pandemic. Four main components were identified that were associated with the different degrees of FI.

CONCLUSION

The present study allowed us to conclude that more than 70% of CKD patients in the study cohort had some type of FI, which makes it difficult to adhere to treatment and may increase the risk of advanced CKD. A less healthy food pattern is associated with greater FI.

Phosphate intake, hyperphosphatemia, and kidney function

Phosphate is essential in living organisms and its blood levels are regulated by a complex network involving the kidneys, intestine, parathyroid glands, and the skeleton. The crosstalk between these organs is executed primarily by three hormones, calcitriol, parathyroid hormone, and fibroblast growth factor 23. Largely due to a higher intake of ultraprocessed foods, dietary phosphate intake has increased in the last decades. The average intake is now about twice the recommended dietary allowance. Studies investigating the side effect of chronic high dietary phosphate intake suffer from incomplete dietary phosphate assessment and, therefore, often make data interpretation difficult. Renal excretion is quickly adapted to acute and chronic phosphate intake. However, at the high ends of dietary intake, renal adaptation, even in pre-existing normal kidney function, apparently is not perfect. Experimental intervention studies suggest that chronic excess of dietary phosphate can result in sustained higher blood phosphate leading to hyperphosphatemia. Evidence exists that the price of the homeostatic response (phosphaturia in response to phosphate loading/hyperphosphatemia) is an increased risk for declining kidney function, partly due by intraluminal/tubular calcium phosphate particles that provoke renal inflammation. High dietary phosphate intake and hyperphosphatemia are progression factors for declining kidney function and are associated with higher cardiovascular disease and mortality risk. This is best established for pre-existing chronic kidney disease, but epidemiological and experimental data strongly suggest that this holds true for subjects with normal renal function as well. Here, we review the latest advances in phosphate intake and kidney function decline.

High phosphate-induced progressive proximal tubular injury is associated with the activation of Stat3/Kim-1 signaling pathway and macrophage recruitment

Dietary phosphate intake in the Western population greatly exceeds the recommended dietary allowance and is linked to enhanced cardiovascular and all-cause mortality. It is unclear whether a chronic high phosphate diet (HPD) causes kidney injury in healthy individuals. Here, we show that feeding a 2% HPD in C57BL/6N mice for one up to six months resulted in hyperphosphatemia, hyperphosphaturia, increased plasma levels of fibroblast growth factor (FGF) 23, and parathyroid hormone (PTH) compared to mice on a 0.8% phosphate diet. Kidney injury was already noted after two months of HPD characterized by loss of proximal tubular (PT) cell polarity, flattened epithelia, disruption of brush border membranes, vacuolization, increased PT cell proliferation, marked interstitial mononuclear infiltration, and progressive accumulation of collagen fibers. HPD increased Stat3 activation and Kim-1 expression in PT epithelial cells and enhanced renal synthesis of chemokines recruiting monocytes and macrophages as well as macrophage related factors. Enhanced recruitment of F4/80⁺ macrophages around injured PT lesions was timely associated with increased Kim-1 synthesis, tubular MCP-1 expression, and degree of PT injury score. Likewise, tubulointerstitial fibrosis was associated with activation of Stat3/Kim-1 signaling pathway. The stimulation of human proximal tubular cells with high phosphate activated Stat3 signaling and induced HAVCR1 and CCL2 expression. We conclude that high phosphate results in progressive proximal tubular injury, indicating that high dietary phosphate intake may affect kidney health and therefore represents an underestimated health problem for the general population.

The Intake of Phosphorus and Nitrites through Meat Products: A Health Risk Assessment of Children Aged 1 to 9 Years Old in Serbia

This study provides the data on dietary exposure of Serbian children to nitrites and phosphorus from meat products by combining individual consumption data with available analytical data of meat products. A total of 2603 and 1900 commercially available meat products were categorized into seven groups and analysed for nitrite and phosphorous content. The highest mean levels of nitrite content, expressed as NaNO2, were found in finely minced cooked sausages (40.25 ± 20.37 mg/kg), followed by canned meat (34.95 ± 22.12 mg/kg) and coarsely minced cooked sausages (32.85 ± 23.25 mg/kg). The EDI (estimated daily intake) of nitrites from meat products, calculated from a National Food Consumption Survey in 576 children aged 1-9 years, indicated that the Serbian children population exceeded the nitrite ADI (acceptable daily intake) proposed by EFSA (European Food Safety Authority) in 6.4% of children, with a higher proportion in 1-3-year-old participants. The mean phosphorus concentration varied from 2.71 ± 1.05 g/kg to 6.12 ± 1.33 g/kg in liver sausage and pate and smoked meat products, respectively. The EDI of phosphorus from meat products was far below the ADI proposed by EFSA, indicating that the use of phosphorus additives in Serbian meat products is generally in line with legislation.

Fibroblast Growth Factor-23-Klotho Axis in Cardiorenal Syndrome: Mediators and Potential Therapeutic Targets

Cardiorenal syndrome (CRS) is a complex disorder that refers to the category of acute or chronic kidney diseases that induce cardiovascular disease, and inversely, acute or chronic heart diseases that provoke kidney dysfunction. There is a close relationship between renal and cardiovascular disease, possibly due to the presence of common risk factors for both diseases. Thus, it is well known that renal diseases are associated with increased risk of developing cardiovascular disease, suffering cardiac events and even mortality, which is aggravated in those patients with end-stage renal disease or who are undergoing dialysis. Recent works have proposed mineral bone disorders (MBD) as the possible link between kidney dysfunction and the development of cardiovascular outcomes. Traditionally, increased serum phosphate levels have been proposed as one of the main factors responsible for cardiovascular damage in kidney patients. However, recent studies have focused on other MBD components such as the elevation of fibroblast growth factor (FGF)-23, a phosphaturic bone-derived hormone, and the decreased expression of the anti-aging factor Klotho in renal patients. It has been shown that increased FGF-23 levels induce cardiac hypertrophy and dysfunction and are associated with increased cardiovascular mortality in renal patients. Decreased Klotho expression occurs as renal function declines. Despite its expression being absent in myocardial tissue, several studies have demonstrated that this antiaging factor plays a cardioprotective role, especially under elevated FGF-23 levels. The present review aims to collect the recent knowledge about the FGF-23-Klotho axis in the connection between kidney and heart, focusing on their specific role as new therapeutic targets in CRS.

Perspective: Plant-based Whole-Grain Foods for Chronic Kidney Disease: The Phytate-Phosphorus Conundrum

Restriction of dietary phosphorus intake is an important component of good clinical practice in kidney failure patients, particularly after dialysis initiation. Greater consumption of predominantly plant-based diets, including phytate-rich foods, is increasingly recommended for health maintenance/disease prevention in this population, with the implicit assumption that phytate-phosphorus in whole-grain cereals, legumes, pulses, and nuts is poorly absorbed. Review of human interventions with diets high in phytate-phosphorus indeed suggests an absorption of at least 50%, still less than animal protein-bound phosphorus, but higher than the generally believed 10-30%. Factors largely ignored up to now, but of potential influence on phytate-phosphorus bioavailability, include effect of food processing in releasing phosphorus, action of colonic bacteria that are able to release inorganic phosphorus, and capacity of the colon to absorb phosphorus. These issues may become increasingly important as new plant-based alternatives to meats, all containing phytate, are being rapidly introduced in the market.

Dialysis Nonadherence and Kidney Transplant Outcomes: A Retrospective Cohort Study

RATIONALE AND OBJECTIVE

Concerns about non-adherent behaviors often prevent dialysis patients from entering waitlists for transplantation, despite an inconsistent association with posttransplant outcomes. We examined the association between plausible metrics of non-adherence related to dialysis treatment and posttransplant outcomes.

STUDY DESIGN

Retrospective cohort. We linked national dialysis treatment data with transplant registry data.

SETTING AND PARTICIPANTS

Adult patients on maintenance hemodialysis from 1/1/2004-12/31/2014 who received a kidney transplant at US centers.

EXPOSURES

We examined five nonadherence metrics: serum potassium (≥5.2 mEq/L), serum phosphorus (>5.5 mg/dL), intradialytic weight gain (IDWG, ≥5 L), shortened treatments (≥30 minutes) and missed treatments (≥1); missed treatment data was only available for 2004-2009. These metrics were characterized as the proportion of time under observation. Dialysis observation time was divided into 3-month intervals (quarters) and the number of "non-adherent" measurements in each domain was calculated for each quarter.

OUTCOMES

Allograft loss; mortality; and acute rejection in the first posttransplant year.

ANALYTICAL APPROACH

Using Cox proportional hazards and logistic regression, we estimated the hazard ratios (HRs) for graft loss and mortality, and odds ratios (OR) for rejection.

RESULTS

9543 patients met inclusion criteria. In our primary model, hyperphosphatemia (aHR 1.27, 05% CI 1.08-1.49), IDWG (aHR 1.39, 95% CI 1.23-1.59) and shortened treatments (aHR 1.54, 95% CI 1.12-2.13) were associated with greater rates of allograft loss but hyperkalemia was not. IDWG (aHR 1.49, 95% CI 1.29-1.73) and shortened treatments (aHR 1.34, 95% CI 1.13-1.58) were associated with mortality while hyperkalemia and hyperphosphatemia were not. Only shortened treatments was associated with an increased risk of acute rejection (aOR 3.88, 95% CI 1.98-7.58). In models limited to the years 2004 to 2009 that included missed treatments, missed treatments were only associated with mortality.

LIMITATIONS

Unmeasured confounding (e.g., dietary data); adherence metrics used may have multiple, complex causes.

CONCLUSIONS

Plausible measures of dialysis nonadherence have long-term associations with allograft and patient survival. Behavioral metrics were more closely associated with outcomes than laboratory markers. The implications of non-adherent behaviors for dialysis patients must be carefully considered before excluding patients from transplantation.

Phosphorus-Containing Food Additives in the Food Supply-An Audit of Products on Supermarket Shelves

OBJECTIVES

Phosphorus (P)-containing food additives pose a risk for chronic kidney disease (CKD) patients. We aimed to investigate the prevalence of P-containing additives in the Finnish food supply across different food categories to evaluate their burden in CKD, reflecting the situation in Europe.

METHODS

The dataset of 6,176 products was obtained in June-August 2019 from the foodie.fi website, which contains all foodstuffs sold in the grocery stores of the S Group (46% of the Finnish market share in 2019). The food category, full product name, type of P additive (inorganic, organic, and natural P-containing), and reporting methods (name or E number) of P additives were recorded. Duplicates and products lacking ingredient information were excluded.

RESULTS

The prevalence of P additives was 36% in the final sample (n = 5,149). Among food categories, the prevalence varied from 4% in dairy-based snacks to 67% in meat products. Altogether 17 different P additives were observed. Inorganic P additives were the most common P additive type, present in 20% of foodstuffs. Natural P-containing additives were observed in 19% and organic P additives in 2% of foodstuffs. The most commonly used P additives were lecithin (E 322), pyrophosphate (E 450), and triphosphate (E 451). E number was used as a reporting method in 49% of foodstuffs, and full name in 44% of foodstuffs. Reporting by E number was particularly common in the products containing inorganic P.

CONCLUSIONS

The use of P additives is common in the Finnish food supply, indicating the situation in Europe. The high prevalence of inorganic, that is, the most absorbable and potentially most harmful P additives in particular food groups, and their usual reporting only by E numbers can create challenges in CKD dietary counseling.

Association between ultrapocessed food and chronic kidney disease

The modern diet is closely linked to the consumption of processed foods, causing an increase in the intake of salt, simple sugars, phosphorus and added potassium. This excess intake is associated with an increased risk of obesity, diabetes, hypertension and chronic kidney disease (CKD). CKD, which according to data from the ENRICA study affects 15% of the population, magnifies its impact due to the higher prevalence of diabetes and hypertension and due to limitations in the management of sodium and phosphorus. The intake of these products far exceeds the established recommendations, assuming 72% of total sodium, 25%-35% of phosphorus, 12%-18% of potassium and exceeding 10% of the caloric intake in simple sugars. Measures are necessary to reduce their contribution through nutritional advice, labeling review, education campaigns on healthy habits, fees and institutional actions that involve food safety agencies, industry, distribution and scientific societies.

The Importance of Phosphate Control in Chronic Kidney Disease

A series of problems including osteopathy, abnormal serum data, and vascular calcification associated with chronic kidney disease (CKD) are now collectively called CKD-mineral bone disease (CKD-MBD). The pathophysiology of CKD-MBD is becoming clear with the emerging of αKlotho, originally identified as a progeria-causing protein, and bone-derived phosphaturic fibroblast growth factor 23 (FGF23) as associated factors. Meanwhile, compared with calcium and parathyroid hormone, which have long been linked with CKD-MBD, phosphate is now attracting more attention because of its association with complications and outcomes. Incidentally, as the pivotal roles of FGF23 and αKlotho in phosphate metabolism have been unveiled, how phosphate metabolism and hyperphosphatemia are involved in CKD-MBD and how they can be clinically treated have become of great interest. Thus, the aim of this review is reconsider CKD-MBD from the viewpoint of phosphorus, its involvement in the pathophysiology, causing complications, therapeutic approach based on the clinical evidence, and clarifying the importance of phosphorus management.

Association between ultrapocessed food and chronic kidney disease

The modern diet is closely linked to the consumption of processed foods, causing an increase in the intake of salt, simple sugars, phosphorus and added potassium. This excess intake is associated with an increased risk of obesity, diabetes, hypertension and chronic kidney disease (CKD). CKD, which according to data from the ENRICA study affects 15% of the population, magnifies its impact due to the higher prevalence of diabetes and hypertension and due to limitations in the management of sodium and phosphorus. The intake of these products far exceeds the established recommendations, assuming 72% of total sodium, 25-35% of phosphorus, 12-18% of potassium and exceeding 10% of the caloric intake in simple sugars. Measures are necessary to reduce their contribution through nutritional advice, labeling review, education campaigns on healthy habits, fees and institutional actions that involve food safety agencies, industry, distribution and scientific societies.

Quality or Quantity of Proteins in the Diet for CKD Patients: Does "Junk Food" Make a Difference? Lessons from a High-Risk Pregnancy

BACKGROUND

How to manage patients with severe kidney disease in pregnancy is still a matter of discussion, and deciding if and when to start dialysis is based on the specialist's experience and dialysis availability. The effect of toxic substances usually cleared by the kidney may be more severe and readily evident. The review, and related case, underlines the importance of considering the presence of additives in food in delicate conditions, such as CKD pregnancy. The Case: A 39-year-old indigenous woman from a low-resourced area in Mexico was referred to the obstetric nephrology at 25 gestational weeks because of serum creatinine at 3.6 mg/dL, hypertension on low-dose alpha-methyl-dopa, and nephrotic-range proteinuria. Kidney ultrasounds showed small poorly differentiated kidneys; foetal ultrasounds detected a female foetus, normal for gestational age. The patient's baseline protein intake, which was estimated at 1.2-1.3 g/kg/day, was mostly of animal-origin (>70%) poor-quality food ("junk food"). In the proposed diet, protein intake was only slightly reduced (1.0-1.2 g/kg/day), but the source of proteins was changed (only 30% of animal origin) with attention to food quality. A remarkable decrease in BUN was observed, in concomitance with adequate dietary follow-up, with rapid rise of BUN when the patient switched temporarily back to previous habits. A healthy female baby weighing 2,460 g (11th centile for gestational age) was delivered at 37 gestational weeks. Discussion and Literature Review: While data on patients with chronic kidney disease are scant, the long list of contaminants present in food, especially if of low quality, should lead us to reflect on their potential negative effect on kidney function and make us realize that eating healthy, unprocessed "organic" food should be encouraged, in delicate conditions such as pregnancy and breastfeeding and for young children, in particular when kidney function is failing. The case herein described gave us the opportunity to reflect on the importance of diet quality and on the potential risks linked to food additives, many of which, including phosphates and potassium, are not declared on food labels, while others, including dyes, antioxidants, thickeners, emulsifiers, and preservatives, are qualitatively, but not quantitatively, reported.

Murine Fetal Serum Phosphorus is Set Independent of FGF23 and PTH, Except in the Presence of Maternal Phosphate Loading

Fibroblast growth factor 23 (FGF23) appears to play no role until after birth, given unaltered phosphate and bone metabolism in Fgf23- and Klotho-null fetuses. However, in those studies maternal serum phosphorus was normal. We studied whether maternal phosphate loading alters fetal serum phosphorus and invokes a fetal FGF23 or parathyroid hormone (PTH) response. C57BL/6 wild-type (WT) female mice received low (0.3%), normal (0.7%), or high (1.65%) phosphate diets beginning 1 week prior to mating to WT males. Fgf23+/- female mice received the normal or high-phosphate diets 1 week before mating to Fgf23+/- males. One day before expected birth, we harvested maternal and fetal blood, intact fetuses, placentas, and fetal kidneys. Increasing phosphate intake in WT resulted in progressively higher maternal serum phosphorus and FGF23 during pregnancy, while PTH remained undetectable. Fetal serum phosphorus was independent of the maternal phosphorus and PTH remained low, but FGF23 showed a small nonsignificant increase with high maternal serum phosphorus. There were no differences in fetal ash weight and mineral content, or placental gene expression. High phosphate intake in Fgf23+/- mice also increased maternal serum phosphorus and FGF23, but there was no change in PTH. WT fetuses remained unaffected by maternal high-phosphate intake, while Fgf23-null fetuses became hyperphosphatemic but had no change in PTH, skeletal ash weight or mineral content. In conclusion, fetal phosphate metabolism is generally regulated independently of maternal serum phosphorus and fetal FGF23 or PTH. However, maternal phosphate loading reveals that fetal FGF23 can defend against the development of fetal hyperphosphatemia.

Pilot Randomized Controlled Trial of a Standard Versus a Modified Low-Phosphorus Diet in Hemodialysis Patients

INTRODUCTION

The standard low-phosphorus diet restricts pulses, nuts, and whole grains and other high phosphorus foods to control hyperphosphatemia. We conducted a randomized controlled trial to evaluate the effectiveness, safety, and tolerability of the modified diet, which introduced some pulses and nuts, increased the use of whole grains, increased focus on the avoidance of phosphate additives, and introduced the prescription of low-biological-value protein such as bread.

METHODS

We conducted a multicenter, pragmatic, parallel-arm, open-label, randomized controlled trial of modified versus standard diet in 74 adults on hemodialysis with hyperphosphatemia over 1 month. Biochemistry was assessed using monthly laboratory tests. Dietary intake was assessed using a 2-day record of weighed intake of food, and tolerability was assessed using a patient questionnaire.

RESULTS

There was no significant difference in the change in serum phosphate between the standard and modified diets. Although total dietary phosphorus intake was similar, phytate-bound phosphorus, found in pulses, nuts, and whole grains, was significantly higher in the modified diet (P < 0.001). Dietary fiber intake was also significantly higher (P < 0.003), as was the percentage of patients reporting an increase in bowel movements while following the modified diet (P = 0.008). There was no significant difference in the change in serum potassium or in reported protein intake between the 2 diets. Both diets were similarly well tolerated.

CONCLUSION

The modified low phosphorus diet was well tolerated and was associated with similar phosphate and potassium control but with a wider food choice and greater fiber intake than the standard diet.

Effect of Neighborhood Food Environment and Socioeconomic Status on Serum Phosphorus Level for Patients on Chronic Dialysis

BACKGROUND

Elevated blood phosphorus levels are common and associated with a greater risk of death for patients receiving chronic dialysis. Phosphorus-rich foods are prevalent in the American diet, and low-phosphorus foods, including fruits and vegetables, are often less available in areas with more poverty. The relative contributions of neighborhood food availability and socioeconomic status to phosphorus control in patients receiving dialysis are unknown.

METHODS

Using longitudinal data from a national dialysis provider, we constructed hierarchical, linear mixed-effects models to evaluate the relationships between neighborhood food environment or socioeconomic status and serum phosphorus level among patients receiving incident dialysis.

RESULTS

Our cohort included 258,510 patients receiving chronic hemodialysis in 2005-2013. Median age at dialysis initiation was 64 years, 45% were female, 32% were Black, and 15% were Hispanic. Within their residential zip code, patients had a median of 25 "less-healthy" food outlets (interquartile range, 11-40) available to them compared with a median of four "healthy" food outlets (interquartile range, 2-6). Living in a neighborhood with better availability of healthy food was not associated with a lower phosphorus level. Neighborhood income also was not associated with differences in phosphorus. Patient age, race, cause of ESKD, and mean monthly dialysis duration were most closely associated with phosphorus level.

CONCLUSIONS

Neither neighborhood availability of healthy food options nor neighborhood income was associated with phosphorus levels in patients receiving chronic dialysis. Modifying factors, such as nutrition literacy, individual-level financial resources, and adherence to diet restrictions and medications, may be more powerful contributors than food environment to elevated phosphorus.

High Phosphate Induces and Klotho Attenuates Kidney Epithelial Senescence and Fibrosis

Cellular senescence is an irreversible cell growth arrest and is associated with aging and age-related diseases. High plasma phosphate (Pi) and deficiency of Klotho contribute to aging and kidney fibrosis, a pathological feature in the aging kidney and chronic kidney disease. This study examined the interactive role of Pi and Klotho in kidney senescence and fibrosis. Homozygous Klotho hypomorphic mice had high plasma Pi, undetectable Klotho in plasma and kidney, high senescence with massive collagen accumulation in kidney tubules, and fibrin deposits in peritubular capillaries. To examine the Pi effect on kidney senescence, a high (2%) Pi diet was given to wild-type mice. One week of high dietary Pi mildly increased plasma Pi, and upregulated kidney p16/p21 expression, but did not significantly decrease Klotho. Two weeks of high Pi intake led to increase in plasminogen activator inhibitor (PAI)-1, and decrease in kidney Klotho, but still without detectable increase in kidney fibrosis. More prolonged dietary Pi for 12 weeks exacerbated kidney senescence and fibrosis; more so in heterozygous Klotho hypomorphic mice compared to wild-type mice, and in mice with chronic kidney disease (CKD) on high Pi diet compared to CKD mice fed a normal Pi diet. In cultured kidney tubular cells, high Pi directly induced cellular senescence, injury and epithelial-mesenchymal transition, and enhanced H₂O₂-induced cellular senescence and injury, which were abrogated by Klotho. Fucoidan, a bioactive molecule with multiple biologic functions including senescence inhibition, blunted Pi-induced cellular senescence, oxidation, injury, epithelial-mesenchymal transition, and senescence-associated secretary phenotype. In conclusion, high Pi activates senescence through distinct but interconnected mechanisms: upregulating p16/p21 (early), and elevating plasminogen activator inhibitor-1 and downregulating Klotho (late). Klotho may be a promising agent to attenuate senescence and ameliorate age-associated, and Pi-induced kidney degeneration such as kidney fibrosis.

Association of dietary patterns with serum phosphorus in maintenance haemodialysis patients: a cross-sectional study

Sources of dietary phosphate differentially contribute to hyperphosphatemia in maintenance haemodialysis (MHD) patients. This cross-sectional study in Malaysia investigated association between dietary patterns and serum phosphorus in MHD patients. Dietary patterns were derived by principal component analysis, based on 27 food groups shortlisted from 3-day dietary recalls of 435 MHD patients. Associations of serum phosphorus were examined with identified dietary patterns. Three dietary patterns emerged: Home foods (HF_dp), Sugar-sweetened beverages (SSB_dp), and Eating out noodles (EO-N_dp). The highest tertile of patients in HF (T3-HF_dp) pattern significantly associated with higher intakes of total protein (p = 0.002), animal protein (p = 0.001), and animal-based organic phosphate (p < 0.001), whilst T3-SSB_dp patients had significantly higher intakes of total energy (p < 0.001), inorganic phosphate (p < 0.001), and phosphate:protein ratio (p = 0.001). T3-EO-N_dp patients had significantly higher intakes of total energy (p = 0.033), total protein (p = 0.003), plant protein (p < 0.001), but lower phosphate:protein ratio (p = 0.009). T3-SSB_dp patients had significantly higher serum phosphorus (p = 0.006). The odds ratio of serum phosphorous > 2.00 mmol/l was significantly 2.35 times higher (p = 0.005) with the T3-SSB_dp. The SSB_dp was associated with greater consumption of inorganic phosphate and higher serum phosphorus levels.

Revising Dietary Phosphorus Advice in Chronic Kidney Disease G3-5D

We summarize how practicing dietitians combined available evidence with clinical experience, to define revised dietary recommendations for phosphorus in chronic kidney disease G3-5D. As well as a review of the evidence base, 4 priority topics were reviewed. These were translated into 3 nutrient level recommendations: the introduction of some plant protein where phosphorus is largely bound by phytate; consideration of protein intake in terms of phosphorus load and the phosphorus to protein ratio; and an increased focus on avoiding phosphate additives. This review summarizes and interprets the available evidence in order to support the development of practical food-based advice for patients with chronic kidney disease.

Intradialytic Nutrition and Hemodialysis Prescriptions: A Personalized Stepwise Approach

Dialysis and nutrition are two sides of the same coin—dialysis depurates metabolic waste that is typically produced by food intake. Hence, dietetic restrictions are commonly imposed in order to limit potassium and phosphate and avoid fluid overload. Conversely, malnutrition is a major challenge and, albeit to differing degrees, all nutritional markers are associated with survival. Dialysis-related malnutrition has a multifactorial origin related to uremic syndrome and comorbidities but also to dialysis treatment. Both an insufficient dialysis dose and excessive removal are contributing factors. It is thus not surprising that dialysis alone, without proper nutritional management, often fails to be effective in combatting malnutrition. While composite indexes can be used to identify patients with poor prognosis, none is fully satisfactory, and the definitions of malnutrition and protein energy wasting are still controversial. Furthermore, most nutritional markers and interventions were assessed in hemodialysis patients, while hemodiafiltration and peritoneal dialysis have been less extensively studied. The significant loss of albumin in these two dialysis modalities makes it extremely difficult to interpret common markers and scores. Despite these problems, hemodialysis sessions represent a valuable opportunity to monitor nutritional status and prescribe nutritional interventions, and several approaches have been tried. In this concept paper, we review the current evidence on intradialytic nutrition and propose an algorithm for adapting nutritional interventions to individual patients.

Strategies for Phosphate Control in Patients With CKD

Hyperphosphatemia is a common complication in patients with chronic kidney disease (CKD), particularly in those requiring renal replacement therapy. The importance of controlling serum phosphate has long been recognized based on observational epidemiological studies that linked increased phosphate levels to adverse outcomes and higher mortality risk. Experimental data further supported the role of phosphate in the development of bone and cardiovascular diseases. Recent advances in our understanding of the mechanisms involved in phosphate homeostasis have made it clear that the serum phosphate concentration depends on a complex interplay among the kidneys, intestinal tract, and bone, and is tightly regulated by a complex endocrine system. Moreover, the source of dietary phosphate and the use of phosphate-based additives in industrialized foods are additional factors that are of particular importance in CKD. Not surprisingly, the management of hyperphosphatemia is difficult, and, despite a multifaceted approach, it remains unsuccessful in many patients. An additional issue is the fact that the supposedly beneficial effect of phosphate lowering on hard clinical outcomes in interventional trials is a matter of ongoing debate. In this review, we discuss currently available treatment approaches for controlling hyperphosphatemia, including dietary phosphate restriction, reduction of intestinal phosphate absorption, phosphate removal by dialysis, and management of renal osteodystrophy, with particular focus on practical challenges and limitations, and on potential benefits and harms.