Prevalence of Phosphorus-Based Additives in the Australian Food Supply: A Challenge for Dietary Education?

Phosphate-based additives in processed foods: is excess exposure a cause for concern? A cross-sectional examination of the United States packaged food supply

BACKGROUND

Limiting dietary phosphate intake to slow the progression of chronic kidney disease (CKD) to dialysis and death requires knowledge of the total quantity and forms of phosphate in food, information not currently required on United States food labels. Phosphate additives (P-additives) have more rapid/efficient absorption than naturally occurring dietary phosphate and are not accounted for in nutrient databases despite their greater contribution to total phosphorus intake.

OBJECTIVES

This study aims to examine the presence of P-additives in United States foods and beverages sold by the top 25 United States manufacturers in 2020.

METHODS

Cross-sectional ingredient data for all products from the top 25 manufacturers were sourced from Label Insight (a NielsenIQ company) in May 2021. The presence of inorganic or organic P-additives in each product was determined by reviewing ingredient lists. The number and proportion of products containing P-additives overall and for each phosphate class (inorganic or organic) and individual P-additives were calculated, as well as the revenue derived for each component examined. Sales-weighted proportions were also examined.

RESULTS

P-additives were present in 56% of 39,937 products from the top 25 United States food and beverage manufacturers representing >$120 billion in consumer purchases in 2020. Top P-additives in products included lecithin (32%), sodium phosphate (13%), calcium phosphate (11%), modified starches (10%), and sodium acid pyrophosphate (6%), whereas P-additive numbers per product ranged from 0 to 8 with 21% of foods containing >1 P-additive.

CONCLUSIONS

This study illustrates widespread exposure to P-additives in all packaged food and beverage categories in the United States, with sales-weighted data showing a high volume of purchases even in categories containing a lower percentage of products with P-additives. Research exploring the safety of excessive P-additive exposure in CKD and healthy populations requires the Food and Drug Administration to make labeling of the total phosphorus content on nutrition facts labels mandatory.

The Fate of Phosphate: Assessing Dietary Intake and Urinary Excretion in Swedish Adolescents

Background

A high total phosphorus (P) intake has been proposed to promote endothelial dysfunction and atherosclerosis. A diet rich in foods containing P additives could contribute to an excessive intake, potentially reflected as increased concentration of P in urine.

Objectives

This study aimed to assess the intake of total dietary P, P additives, and its sources and examine their correlation with urinary P in a cross-sectional national study in Swedish adolescents.

Methods

We constructed a database of P additives and applied it to the foods consumed by 3099 participants in the representative school-based dietary survey Riksmaten Adolescents 2016-17. Intake of total dietary P and P additives were assessed using two 24-h recalls. Urinary P was analyzed in a subsample of 756 participants using inductively coupled plasma mass spectrometry. Spearman rank correlation (ρ) was used to assess the association between dietary P intake and urinary P excretion.

Results

The mean (SD) intake of total P was 1538 (±667) mg/d. Food containing P additives were consumed by 92% of adolescents and the median (IQR) intake was 49 (22-97; range: 0.01-947) mg/d, corresponding to 5% (1%-6%; range: 0%-50%) of total P. The main contributing food to P additives was cola drinks, while the main contributing food group was sausage dishes. Total P intake was weakly correlated with urinary P (ρ = 0.12; P < 0.01) but not with intake of P additives.

Conclusions

Nearly, all participants consumed P additives, contributing to an average of 5% of total P intake but ranging up to 50%. The intake of total P, but not P additives, was weakly reflected in the urinary P. Access to more comprehensive information on P additives in foods would improve further evaluation of potential health consequences.

Emulsifiers in ultra-processed foods in the UK food supply

OBJECTIVE

Ultra-processed foods (UPF), including those containing food additive emulsifiers, have received research attention due to evidence implicating them in the pathogenesis of certain diseases. The aims of this research were to develop a large-scale, brand-level database of UPF in the UK food supply and to characterise the occurrence and co-occurrence of food additive emulsifiers.

DESIGN

A database was compiled sampling all products from the food categories contributing to energy intake from UPF in the UK from the National Diet and Nutrition Survey (2008-2014). Every food in these categories were identified from online supermarket provision from the 'big four' supermarkets that dominate the market share in the UK, comprising Tesco, Sainsbury's, Asda and Morrisons.

SETTING

Major supermarkets in the UK.

RESULTS

A total of 32 719 food products in the UK supermarket food supply were returned in searches. Of these, 12 844 products were eligible and manually reviewed for the presence of emulsifiers. Emulsifiers were present in 6642 (51·7 %) food products. Emulsifiers were contained in 95·0 % of 'Pastries, buns and cakes', 81·9 % of 'Milk-based drinks', 81·0 % of 'Industrial desserts' and 77·5 % of 'Confectionary'. Fifty-one per cent of all emulsifier-containing foods contained multiple emulsifiers. Across emulsifier-containing foods, there were a median of two emulsifiers (IQR 2) per product. The five most common emulsifiers were lecithin (23·4 % of all products), mono- and diglycerides of fatty acids (14·5 %), diphosphates (11·6 %), and xanthan gum and pectin (8·0 %).

CONCLUSIONS

Findings from this study are the first to demonstrate the widespread occurrence and co-occurrence of emulsifiers in UPF in the UK food supply.

Nutritional Epidemiology and Dietary Assessment for Patients With Kidney Disease: A Primer

Nutritional epidemiology seeks to understand nutritional determinants of disease in human populations using experimental and observational study designs. Though randomized controlled trials provide the strongest evidence of causality, the expense and difficulty of sustaining adherence to dietary interventions are substantial barriers to investigating dietary determinants of kidney disease. Therefore, nutritional epidemiology commonly employs observational study designs, particularly prospective cohort studies, to investigate long-term associations between dietary exposures and kidney disease. Due to the covarying nature and synergistic effects of dietary components, holistic characterizations of dietary exposures that simultaneously consider patterns of foods and nutrients regularly consumed are generally more relevant to disease etiology than single nutrients or foods. Dietary intakes have traditionally been self-reported and are subject to bias. Statistical methods including energy adjustment and regression calibration can reduce random and systematic measurement errors associated with self-reported diet. Novel approaches that assess diet more objectively are gaining popularity but have not yet fully replaced self-report and require refinement and validation in populations with chronic kidney disease. More accurate and frequent diet assessment in existing and future studies will yield evidence to better personalize dietary recommendations for the prevention and treatment of kidney disease.

Validation of a Phosphorus Food Frequency Questionnaire in Patients with Kidney Failure Undertaking Dialysis

Nutritional guidelines recommended limiting dietary phosphorus as part of phosphorus management in patients with kidney failure. Currently, there is no validated phosphorus food frequency questionnaire (P-FFQ) to easily capture this nutrient intake. An FFQ of this type would facilitate efficient screening of dietary sources of phosphorus and assist in developing a patient-centered treatment plan. The objectives of this study were to develop and validate a P-FFQ by comparing it with the 24 hr multi-pass recall. Fifty participants (66% male, age 70 ± 13.3 years) with kidney failure undertaking dialysis were recruited from hospital nephrology outpatient departments. All participants completed the P-FFQ and 24 hr multi-pass recalls with assistance from a renal dietitian and then analysed using nutrient analysis software. Bland-Altman analyses were used to determine the agreement between P-FFQ and mean phosphorus intake from three 24 hr multi-pass recalls. Mean phosphorous intake was 1262 ± 400 mg as determined by the 24 hr multi pass recalls and 1220 ± 348 mg as determined by the P-FFQ. There was a moderate correlation between the P-FFQ and 24 hr multi pass recall (r = 0.62, p = 0.37) with a mean difference of 42 mg (95% limits of agreement: 685 mg; -601 mg, p = 0.373) between the two methods. The precision of the P-FFQ was 3.33%, indicating suitability as an alternative to the 24 hr multi pass recall technique. These findings indicate that the P-FFQ is a valid, accurate, and precise tool for assessing sources of dietary phosphorus in people with kidney failure undertaking dialysis and could be used as a tool to help identify potentially problematic areas of dietary intake in those who may have a high serum phosphate.

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.

The Interplay Between Nutrition, Metabolic, and Endocrine Disorders in Chronic Kidney Disease

The kidneys are responsible for maintaining our bodies' homeostasis through excretion, biodegradation, and synthesis of different hormones. Therefore, a decline in renal function often results in significant derangements in hormone levels. The most common metabolic and endocrine abnormalities seen in patients with chronic kidney disease include deficiencies in erythropoietin, calcitriol, triiodothyronine, testosterone, and estrogen. In addition, accumulation of hormones such as adiponectin, leptin, triglycerides, and prolactin also is seen. Subsequently, this can lead to the development of a wide range of clinical consequences including but not limited to anemia, hyperparathyroidism, insulin resistance, anorexia-cachexia, infertility, bone disorders, and cardiovascular diseases. These disorders can negatively affect the prognosis and quality of life of patients with chronic kidney disease, and, thus, early diagnosis, nutritional intervention, and pharmacologic treatment is imperative.

High-phosphorus diet controlled for sodium elevates blood pressure in healthy adults via volume expansion

Whether increasing exposure to dietary phosphorus can lead to adverse clinical outcomes in healthy people is not clear. In this open‐label prospective cross‐over study, we are to explore the impact of various dietary phosphorus intake on mineral, sodium metabolisms and blood pressure in young healthy adults. There were 3 separate study periods of 5 days, each with a 5 days washout period between different diets interventions. Six young healthy male volunteers with normal nutrition status were recruited in Phase I Clinical Research Center and sequentially exposed to the following diets: (a) normal‐phosphorus diet (NPD): 1500 mg/d, (b) low‐phosphorus diet (LPD): 500 mg/d, (c) high‐phosphorus diet (HPD): 2300 mg/d. HPD induced a significant rise in daily average serum phosphate (1.47 ± 0.02 mmol/L [4.56 ± 0.06 mg/dl]) compared to NPD (1.34 ± 0.02 mmol/L [4.15 ± 0.06 mg/dL]) and LPD (1.17 ± 0.02 mmol/L [3.63 ± 0.06 mg/dL]) (p < .05). Daily average levels of serum parathyroid hormone and fibroblast growth factor 23 in HPD were significantly higher, and serum 1,25(OH)₂D₃ was remarkably lower than those in LPD. HPD induced a significant decrease in daily average serum aldosterone and an increase in daily average atrial natriuretic peptide level compared to LPD. The 24‐hour urine volume in HPD subjects was less than that in LPD subjects. HPD significantly increased daily average systolic blood pressure by 6.02 ± 1.24 mm Hg compared to NPD and by 8.58 ± 1.24mm Hg compared to LPD (p < .05). Our study provides the first evidence that 5‐day high‐phosphorus diet can induce elevation in SBP in young healthy adults, which may due to volume expansion.

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.

Dietary Phosphate Consumption in Australians With Stages 3b and 4 Chronic Kidney Disease

OBJECTIVE

Dietary phosphate modification is a common therapy to treat hyperphosphatemia in individuals with chronic kidney disease (CKD). However, current dietary intake and common food sources of phosphate typically consumed by individuals with CKD are not well characterized. This study examined a cohort of CKD patients to determine total dietary intake and common food sources of phosphate, including phosphate additives.

DESIGN AND METHODS

Participants with CKD stages 3b and 4 recruited to a substudy of the "IMPROVE-CKD (IMpact of Phosphate Reduction On Vascular End-points in Chronic Kidney Disease) Study" completed a 7-day self-administered diet record at baseline. Diet histories were analyzed and daily phosphate intakes determined using FoodWorks V.9 (Xyris). The proportion of phosphate contributed by each food group was determined using the AUSNUT 2011-2013 Food Classification System. Ingredient lists of packaged food items consumed were reviewed to determine frequency of phosphate-based additives.

RESULTS

Ninety participants (mean eGFR 26.5 mL/min/1.73 m²) completed this substudy. Mean phosphate intake of participants was 1544 ± 347 mg/day, with 96% of individuals exceeding the recommended daily intake of phosphate (1000 mg/day). The highest sources of dietary phosphate were milk-based products (25%) and meat and poultry products/dishes (25%). Phosphate-based food additives were identified in 39% (n = 331/845) of packaged foods consumed by participants.

CONCLUSION

Dietary phosphate intakes of Australians with CKD are high and come from a variety of sources. Managing dietary phosphate intake requires a patient-centered, tailored approach with an emphasis on maintaining nutritional adequacy and awareness of phosphate additives.

Structural and ultrastructural renal lesions in rats fed high-fat and high-phosphorus diets

Background

Foods prone to deteriorate renal function are rich in fat and in phosphorus (P), but the interaction between these two factors is not well studied.

Method

Detailed structural and ultrastructural histopathological studies were performed on the kidneys of rats fed different amounts of fat and P: low (4%) fat (LF) and normal (0.6%) P (NP), LF and high (1.2%) P (HP), high (35%) fat (HF) and NP, HF and HP, and HF with low (0.2%) P (LP) for 28 weeks.

Results

Glomeruli of the HF groups showed segmental areas of retraction, sclerosis and thickening of the Bowman’s capsule and basal membranes, which were more accentuated in the HF–HP group. Ultrastructural lesions in the glomeruli also were prominent in rats fed HF, particularly in the HF–HP group, and included thickening of the capillary membrane, endothelial damage, mesangial matrix hypercellularity and podocyte effacement. P restriction reduced the severity of endothelial damage, mesangial matrix hypercellularity, thickening of capillary basement membrane and podocyte effacement. The kidneys of rats fed HP showed significant tubular atrophy and dilatation, focal tubular hyperplasia, thickening of the tubular basal membrane, interstitial edema, inflammation and calcification. All groups fed HF also showed tubular lesions that were more prominent in the HF–HP group. P restriction had a beneficial effect on inflammation and calcification.

Conclusions

Intake of both HF and HP damages the kidneys and their noxious effects are additive. HF intake was preferentially associated with glomerular lesions, while lesions related to HP intake were located mainly in the tubuli and in the interstitium.

The Role of Fibroblast Growth Factor 23 in Inflammation and Anemia

In patients with chronic kidney disease (CKD), adverse outcomes such as systemic inflammation and anemia are contributing pathologies which increase the risks for cardiovascular mortality. Amongst these complications, abnormalities in mineral metabolism and the metabolic milieu are associated with chronic inflammation and iron dysregulation, and fibroblast growth factor 23 (FGF23) is a risk factor in this context. FGF23 is a bone-derived hormone that is essential for regulating vitamin D and phosphate homeostasis. In the early stages of CKD, serum FGF23 levels rise 1000-fold above normal values in an attempt to maintain normal phosphate levels. Despite this compensatory action, clinical CKD studies have demonstrated powerful and dose-dependent associations between FGF23 levels and higher risks for mortality. A prospective pathomechanism coupling elevated serum FGF23 levels with CKD-associated anemia and cardiovascular injury is its strong association with chronic inflammation. In this review, we will examine the current experimental and clinical evidence regarding the role of FGF23 in renal physiology as well as in the pathophysiology of CKD with an emphasis on chronic inflammation and anemia.

Phosphorus in food: limitations of food composition data

Limiting the amount of phosphorus in the diet is the first line for management of hyperphosphatemia in chronic kidney disease, and it is therefore important that dietitians have access to accurate data on the phosphorus content of foods. However, food composition datasets have several limitations for use. In this article, Julie Hannah and colleagues describe the limitations of food composition data, and call for further research into this area

Should We Recommend Renal Diet-Related Apps to Our Patients? An Evaluation of the Quality and Health Literacy Demand of Renal Diet-Related Mobile Applications

OBJECTIVE

Mobile phone applications (apps) are increasingly being used by patients with chronic kidney disease (CKD). We sought to describe the main purpose of commonly available renal diet apps and to quantify the accuracy of information, technical quality, and health literacy demand of renal diet apps.

DESIGN

The design was content analysis. All eligible renal diet apps in the Australian Apple App Store, Google Play, Windows Phone, and Blackberry App World were evaluated.

SUBJECTS

Eligible apps were in English and were related to kidney disease in humans (of any type or stage). Exclusion criteria included apps which were prohibited because of password protection.

MAIN OUTCOME MEASURE

Renal diet information in the apps was compared with evidence-based guidelines for the management of kidney disease to quantify information accuracy. App information was evaluated using the Silberg Scale. Technical quality and health literacy demand were evaluated using the Mobile Application Rating Scale.

RESULTS

A total of 21 apps were eligible for evaluation. The main purpose of these apps was to provide food and nutrition information (57.1%) or for educative purposes for CKD patients (38.1%). Only 47.6% (10/21) of apps contained accurate evidence-based information. Overall, app technical quality was considered acceptable (mean Mobile Application Rating Scale score 3.19 ± 0.35 out of 5), with 80.9% of apps scoring acceptable or greater for app technical quality. Scores for health literacy demand also indicated that most apps (15/21, 71.4%) were acceptable.

CONCLUSIONS

A range of apps currently exist that may provide individuals with CKD with useful food and nutrition information or increase their knowledge of the renal diet. These apps are also mainly of acceptable technical quality and health literacy demand. However, caution is required when using renal diet apps because more than half of the apps evaluated were not accurate and evidence based.

Stirring the Pot: Can Dietary Modification Alleviate the Burden of CKD?

Diet is one of the largest modifiable risk factors for chronic kidney disease (CKD)-related death and disability. CKD is largely a progressive disease; however, it is increasingly appreciated that hallmarks of chronic kidney disease such as albuminuria can regress over time. The factors driving albuminuria resolution remain elusive. Since albuminuria is a strong risk factor for GFR loss, modifiable lifestyle factors that lead to an improvement in albuminuria would likely reduce the burden of CKD in high-risk individuals, such as patients with diabetes. Dietary therapy such as protein and sodium restriction has historically been used in the management of CKD. Evidence is emerging to indicate that other nutrients may influence kidney health, either through metabolic or haemodynamic pathways or via the modification of gut homeostasis. This review focuses on the role of diet in the pathogenesis and progression of CKD and discusses the latest findings related to the mechanisms of diet-induced kidney disease. It is possible that optimizing diet quality or restricting dietary intake could be harnessed as an adjunct therapy for CKD prevention or progression in susceptible individuals, thereby reducing the burden of CKD.

Beyond Sodium, Phosphate and Potassium: Potential Dietary Interventions in Kidney Disease

People with kidney disease are advised to restrict individual nutrients, such as sodium, potassium, and phosphate, in line with current best practice guidelines. However, there is limited evidence to support the efficacy of single nutrient strategies, and compliance remains a challenge for clinicians to overcome. Many factors contribute to poor compliance with dietary prescriptions, including conflicting priorities for single nutrient restriction, the arduous self-monitoring required, and the health-related knock-on effects resulting from targeting these nutrients in isolation. This paper reviews the evidence base for the overall pattern of eating as a potential tool to deliver a diet intervention in which all the nutrients and foods work cumulatively and synergistically to improve clinical outcomes. These interventions may assist in kidney disease management and overcome these innate challenges that single nutrient interventions possess. Healthy dietary patterns are typically plant-based and lower in sodium and animal proteins. These patterns may have numerous mechanistic benefits for cardiovascular health in kidney disease, most notably through the increase in fruit, vegetables, and plant-based protein, as well as improved gut health through the increase in dietary fiber. The evidence to date on optimal dietary patterns points toward use of a predominantly plant-based diet, and suggests its adoption may improve clinical outcomes in dialysis patients. However, clinical trials are needed to determine whether these diet interventions are feasible, safe, and effective in this patient population.

The role of phosphate in kidney disease

The importance of phosphate homeostasis in chronic kidney disease (CKD) has been recognized for decades, but novel insights - which are frequently relevant to everyday clinical practice - continue to emerge. Epidemiological data consistently indicate an association between hyperphosphataemia and poor clinical outcomes. Moreover, compelling evidence suggests direct toxicity of increased phosphate concentrations. Importantly, serum phosphate concentration has a circadian rhythm that must be considered when interpreting patient phosphate levels. Detailed understanding of dietary sources of phosphate, including food additives, can enable phosphate restriction without risking protein malnutrition. Dietary counselling provides an often underestimated opportunity to target the increasing exposure to dietary phosphate of both the general population and patients with CKD. In patients with secondary hyperparathyroidism, bone can be an important source of serum phosphate, and adequate appreciation of this fact should impact treatment. Dietary and pharmotherapeutic interventions are efficacious strategies to lower phosphate intake and serum concentration. However, strong evidence that targeting serum phosphate improves patient outcomes is currently lacking. Future studies are, therefore, required to investigate the effects of modern dietary and pharmacological interventions on clinically meaningful end points.