Currently Available Handouts for Low Phosphorus Diets in Chronic Kidney Disease Continue to Restrict Plant Proteins and Minimally Processed Dairy Products

A Systematic Review of Online Resources for the Dietary Management of Hyperphosphatemia in People With Chronic Kidney Disease

OBJECTIVE

Internet search engines and social media websites are prominent and growing sources of dietary information for people with chronic kidney disease (CKD) and their healthcare providers. However, nutrition therapy for CKD is undergoing a paradigm shift, which may lead to inconsistent advice for managing hyperphosphatemia. The aim of this study was to summarize and evaluate online resources for phosphorus-specific nutrition therapy.

DESIGN AND METHODS

Patient-facing resources were collected from Google, Yahoo, and Facebook in June-July 2021. Using nine independent search terms, the first 100 hits were reviewed. Dietary advice for food types, food groups, food subgroups, and individual food items was categorized as "restricted," "recommended," "mixed," and "not mentioned." Information on publication date, source, and author(s), phosphorus bioavailability, and demineralization were also collected.

RESULTS

After removing duplicates, 199 resources from Google and Yahoo and 33 from Facebook were reviewed. Resources ranged from 2005 to 2021 and were primarily authored by registered dietitians and medical doctors (65% and 31%, respectively). Dietary advice mostly focuses on restricting high-phosphorus foods and phosphorus additive-based processed foods. Dietary restrictions were generally consistent with the traditional low-phosphorus diet, which targets whole grains, dairy, and plant-based protein foods, although major inconsistencies were noted. Phosphorus bioavailability and demineralization were rarely mentioned (16% and 8%, respectively). Similar findings were found on Facebook, but the limited number of resources limited meaningful comparisons.

CONCLUSION

Results showed that online resources for phosphorus-specific nutrition therapy are highly restrictive of heart-healthy food items and contain significant inconsistencies. Given the widespread and increasing use of online resources by people with CKD and health care professionals to inform dietary choices, efforts are urgently needed to establish consensus for phosphorus-specific nutrition therapy. Until then, the findings of this study provide a basis for increasing awareness of the potential for confusion arising from online resources.

Dietary Phosphate Educational Materials for Pediatric Chronic Kidney Disease: Are Confused Messages Reducing Their Impact?

OBJECTIVE

This study aimed to review the quality and content of phosphate educational materials used in pediatric chronic kidney disease.

METHODS

The quality of text-based (TB) pediatric phosphate educational materials was assessed using validated instruments for health literacy demands (Suitability Assessment of Materials, Patient Education Material Assessment Tool [PEMAT-P]) readability (Flesch Reading Ease, and Flesch-Kincaid Grade Level). Codes were inductively derived to analyse format, appearance, target audience, resource type, and content, aiming for intercoder reliability > 80%. The content was compared to Pediatric Renal Nutrition Taskforce (PRNT) recommendations.

RESULTS

Sixty-five phosphate educational materials were obtained; 37 were pediatric-focused, including 28 TB. Thirty-two percent of TB materials were directed at caregivers, 25% at children, and 43% were unspecified. Most (75%) included a production date, with 75% produced >2 years ago. The median Flesch Reading Easetest score was 68.2 (interquartile range [IQR] 61.1-75.3) and Flesch-Kincaid Grade Level was 5.6 (IQR 4.5-7.7). Using Suitability Assessment of Materials, 54% rated "superior" (≥70), 38% rated "adequate" (40-69), and 8% rated "not suitable" (≤39). Low-scoring materials lacked a summary (12%), cover graphics (35%), or included irrelevant illustrations (50%). Patient Education Material Assessment Tool-P scores were 70% (IQR 50-82) for understandability and 50% (IQR 33-67) for actionability. An intercoder reliability of 87% was achieved. Over half of limited foods are in agreement with PRNT (including 89% suggesting avoiding phosphate additives). Recommendations conflicting with PRNT included reducing legumes and whole grains. Over a third contained inaccuracies, and over two-thirds included no practical advice.

CONCLUSIONS

TB pediatric phosphate educational materials are pitched at an appropriate level for caregivers, but this may be too high for children under 10 years. The inclusion of relevant illustrations may improve this. Three-quarters of materials scored low for actionability. The advice does not always align with the PRNT, which (together with the inaccuracies reported) could result in conflicting messages to patients and their families.

'Phos'tering a Clear Message: The Evolution of Dietary Phosphorus Management in Chronic Kidney Disease

Phosphorus is a vital nutrient, but disturbances in phosphorus homeostasis are central to chronic kidney disease-mineral and bone disorder. To minimize disturbances, traditional dietary guidance focused on a numerical phosphorus target leading to the exclusion of many healthy foods and implementation challenges. Contemporary phosphorus guidance focuses on dietary source, avoiding additives, and emphasizing low-phosphorus bioaccessibility foods, leading to a more liberal approach. Additional work is needed to demonstrate the efficacy of these contemporary approaches and understand the influence of specific foods, processing, and cooking methods. Unfortunately, patient education using traditional and contemporary strategies may give mixed messages, particularly related to plant-based foods. Thus, greater clarity on the effects of specific foods and dietary patterns may improve phosphorus education. This review aims to discuss the evolution of dietary phosphorus management while highlighting areas for future research that can help move the field toward stronger evidence-based guidance to prevent and treat hyperphosphatemia.

Dysregulated phosphate metabolism in autism spectrum disorder: associations and insights for future research

Studies of autism spectrum disorder (ASD) related to exposure to toxic levels of dietary phosphate are lacking. Phosphate toxicity from dysregulated phosphate metabolism can negatively impact almost every major organ system of the body, including the central nervous system. The present paper used a grounded theory-literature review method to synthesise associations of dysregulated phosphate metabolism with the aetiology of ASD. Cell signalling in autism has been linked to an altered balance between phosphoinositide kinases, which phosphorylate proteins, and the counteracting effect of phosphatases in neuronal membranes. Glial cell overgrowth in the developing ASD brain can lead to disturbances in neuro-circuitry, neuroinflammation and immune responses which are potentially related to excessive inorganic phosphate. The rise in ASD prevalence has been suggested to originate in changes to the gut microbiome from increasing consumption of additives in processed food, including phosphate additives. Ketogenic diets and dietary patterns that eliminate casein also reduce phosphate intake, which may account for many of the suggested benefits of these diets in children with ASD. Dysregulated phosphate metabolism is causatively linked to comorbid conditions associated with ASD such as cancer, tuberous sclerosis, mitochondrial dysfunction, diabetes, epilepsy, obesity, chronic kidney disease, tauopathy, cardiovascular disease and bone mineral disorders. Associations and proposals presented in this paper offer novel insights and directions for future research linking the aetiology of ASD with dysregulated phosphate metabolism and phosphate toxicity from excessive dietary phosphorus intake.

Phosphorus Additives and Their Impact on Phosphorus Content in Foods-An Analysis of the USDAs Branded Foods Product Database

OBJECTIVES

The frequency of phosphate additives reported in the United States Department of Agriculture Branded Foods Product Database and how these additives impact phosphate content is unknown.

METHODS

All products included in the Branded Foods Product Database reporting phosphorus content were reviewed for presence of phosphate salts and/or lecithin additives.

RESULTS

Phosphorus content information was available for 3,466 (1.45%) food items, of these 1791 (51.6%) contained additives. Median phosphorus content was lowest in products with lecithin only compared to products without phosphorus additives (86 [54-200] vs. 145 [77-351] mg per 100 g, P < .01), which was not different from products with phosphate salts (176 [101-276] mg per 100 g, P = .22) or products with both phosphate salts and lecithin (161 [99-285] mg per 100 g, P = 1.00). The impact of a phosphorus salt on phosphorus content (mg per 100) was explored among ultra-processed products grouped by similar phosphorus contents. The phosphorus content of in in nondairy alternatives, dairy, plant proteins, and grains were significantly higher when the product contained a phosphate salt compared to products without a phosphate salt. For all products phosphorus and potassium content were correlated, but the relationship was stronger for when a potassium phosphate additive was present compared to absent (rho = 0.81 vs. 0.53, P < .05). Similar patterns were seen for sodium, calcium, and iron with stronger correlations with phosphate content for products with additives than those without (calcium phosphate: rho = 0.47 vs. 0.32; iron phosphate: rho = 0.47 vs. 0.33; sodium phosphate: rho = 0.45 vs. 0.07. All P < .05). The relationship between phosphate and sodium for products without phosphate additives was weak.

CONCLUSIONS

Lecithin may not be associated with increased phosphorus content. Calcium, potassium, sodium, and iron phosphorus salts appear to be associated with increases in the composite mineral and phosphorus content, with the strongest correlation between potassium and phosphorus content.