Main issues in micronutrient supplementation in phenylketonuria

Potential Micronutrient Deficiencies in the First 1000 Days of Life: The Pediatrician on the Side of the Weakest

PURPOSE OF REVIEW

This study is to examine potential micronutrient deficiencies and any need for supplementation in children following specific diet plans in the first 1000 days of life.

RECENT FINDINGS

Optimal nutrition in the first 1000 days of life has a lifelong positive impact on child development. Specific intrauterine and perinatal factors, pathological conditions, and dietary restrictions can represent potential risk factors for micronutrient deficiencies in the first 1000 days of life, which can have negative systemic consequences. Preterm and low-birth-weight infants are intrinsically at risk because of immature body systems. Children affected by cystic fibrosis are prone to malnutrition because of intestinal malabsorption. The risk of micronutrient deficiency can increase in various situations, including but not limited to children following selective dietary regimens (vegetarian and vegan diets and children affected by specific neuropsychiatric conditions) or specific dietary therapies (children affected by food allergies or specific metabolic disorders and children following restricted diet as a part of therapeutic approach, i.e., ketogenic diet for epilepsy). In light of this situation, the micronutrient status in these categories of children should be investigated in order to tailor strategies specific to the individual's metabolic needs, with a particular focus on deficiencies which can impair or delay the physical and cognitive development of children, namely, vitamin B12, vitamin D and folic acid, as well as oligo-elements such as iron, zinc, calcium, sodium, magnesium, and phosphorus, and essential fatty acids such as omega-3. Identification of micronutrient deficiency in the first 1000 days of life and timely supplementation proves essential to prevent their long-term consequences.

Micronutrient Deficiency in Inherited Metabolic Disorders Requiring Diet Regimen: A Brief Critical Review

Many inherited metabolic disorders (IMDs), including disorders of amino acid, fatty acid, and carbohydrate metabolism, are treated with a dietary reduction or exclusion of certain macronutrients, putting one at risk of a reduced intake of micronutrients. In this review, we aim to provide available evidence on the most common micronutrient deficits related to specific dietary approaches and on the management of their deficiency, in the meanwhile discussing the main critical points of each nutritional supplementation. The emerging concepts are that a great heterogeneity in clinical practice exists, as well as no univocal evidence on the most common micronutrient abnormalities. In phenylketonuria, for example, micronutrients are recommended to be supplemented through protein substitutes; however, not all formulas are equally supplemented and some of them are not added with micronutrients. Data on pyridoxine and riboflavin status in these patients are particularly scarce. In long-chain fatty acid oxidation disorders, no specific recommendations on micronutrient supplementation are available. Regarding carbohydrate metabolism disorders, the difficult-to-ascertain sugar content in supplementation formulas is still a matter of concern. A ketogenic diet may predispose one to both oligoelement deficits and their overload, and therefore deserves specific formulations. In conclusion, our overview points out the lack of unanimous approaches to micronutrient deficiencies, the need for specific formulations for IMDs, and the necessity of high-quality studies, particularly for some under-investigated deficits.

Food or medicine? A European regulatory perspective on nutritional therapy products to treat inborn errors of metabolism

Dietary or nutritional management strategies are the cornerstone of treatment for many inborn errors of metabolism (IEMs). Though a vital part of standard of care, the products prescribed for this are often not formally registered as medication. Instead, they are regulated as food or as food supplements, impacting the level of oversight as well as reimbursed policies. This scoping literature review explores the European regulatory framework relevant to these products and its implications for current clinical practice. Searches of electronic databases (PubMed, InfoCuria) were carried out, supplemented by articles identified by experts, from reference lists, relevant guidelines and case-law by the European Court of Justice. In the European Union (EU), nutritional therapy products are regulated as food supplements, food for special medical purposes (FSMPs) or medication. The requirements and level of oversight increase for each of these categories. Relying on lesser-regulated food products to treat IEMs raises concerns regarding product quality, safety, reimbursement and patient access. In order to ascertain whether a nutritional therapy product functions as medication and thus could be classified as such, we developed a flowchart to assess treatment characteristics (benefit, pharmacological attributes, and safety) with a case-based approach. Evaluating nutritional therapy products might reveal a justifiable need for a pharmaceutical product. A flowchart can facilitate systematically distinguishing products that function medication-like in the management of IEMs. Subsequently, finding and implementing appropriate solutions for these products might help improve the quality, safety and accessibility including reimbursement of treatment for IEMs.

Clinical, genetic, and experimental research of hyperphenylalaninemia

Hyperphenylalaninemia (HPA) is the most common amino acid metabolism defect in humans. It is an autosomal-recessive disorder of the phenylalanine (Phe) metabolism, in which high Phe concentrations and low tyrosine (Tyr) concentrations in the blood cause phenylketonuria (PKU), brain dysfunction, light pigmentation and musty odor. Newborn screening data of HPA have revealed that the prevalence varies worldwide, with an average of 1:10,000. Most cases of HPA result from phenylalanine hydroxylase (PAH) deficiency, while a small number of HPA are caused by defects in the tetrahydrobiopterin (BH4) metabolism and DnaJ heat shock protein family (Hsp40) member C12 (DNAJC12) deficiency. Currently, the molecular pathophysiology of the neuropathology associated with HPA remains incompletely understood. Dietary restriction of Phe has been highly successful, although outcomes are still suboptimal and patients find it difficult to adhere to the treatment. Pharmacological treatments, such as BH4 and phenylalanine ammonia lyase, are available. Gene therapy for HPA is still in development.

Complications of the Low Phenylalanine Diet for Patients with Phenylketonuria and the Benefits of Increased Natural Protein

Phenylketonuria (PKU) is an inherited disorder in which phenylalanine (Phe) is not correctly metabolized leading to an abnormally high plasma Phe concentration that causes profound neurologic damage if left untreated. The mainstay of treatment for PKU has centered around limiting natural protein in the diet while supplementing with medical foods in order to prevent neurologic injury while promoting growth. This review discusses several deleterious effects of the low Phe diet along with benefits that have been reported for patients with increased natural protein intake while maintaining plasma Phe levels within treatment guidelines.

Phenylketonuria

Phenylketonuria (PKU; also known as phenylalanine hydroxylase (PAH) deficiency) is an autosomal recessive disorder of phenylalanine metabolism, in which especially high phenylalanine concentrations cause brain dysfunction. If untreated, this brain dysfunction results in severe intellectual disability, epilepsy and behavioural problems. The prevalence varies worldwide, with an average of about 1:10,000 newborns. Early diagnosis is based on newborn screening, and if treatment is started early and continued, intelligence is within normal limits with, on average, some suboptimal neurocognitive function. Dietary restriction of phenylalanine has been the mainstay of treatment for over 60 years and has been highly successful, although outcomes are still suboptimal and patients can find the treatment difficult to adhere to. Pharmacological treatments are available, such as tetrahydrobiopterin, which is effective in only a minority of patients (usually those with milder PKU), and pegylated phenylalanine ammonia lyase, which requires daily subcutaneous injections and causes adverse immune responses. Given the drawbacks of these approaches, other treatments are in development, such as mRNA and gene therapy. Even though PAH deficiency is the most common defect of amino acid metabolism in humans, brain dysfunction in individuals with PKU is still not well understood and further research is needed to facilitate development of pathophysiology-driven treatments.

Nutritional and metabolic parameters of children and adolescents with phenylketonuria

BACKGROUND AND AIMS

Considering that phenylalanine-poor diets may be monotonous and compromise the development and nutritional status of children and adolescents with phenylketonuria, the aim of this study was to evaluate the anthropometric and biochemical characteristics of children and adolescents with this condition.

METHODS

Retrospective study with anthropometric and biochemical data collection from patients with phenylketonuria in the age group 2-19.9 years. Nutritional status was classified according to the World Health Organization. Biochemical tests were compared to current recommendations.

RESULTS

A total of 84 patients (71.8%) were eligible, with a median age of 10.7 years (2.4-19.9 years). There was predominance of adequate (n = 58, 69%) with presence of overweight and obesity in 24 (28.5%) patients. The biochemical tests revealed hyperphosphatemia in 46 (55%), hypertriglyceridemia in 27 (50%), vitamin B12 elevated in 34 (41.2%), selenium deficiency in 10 (13.7%), insufficient zinc in 7 (8.9%), low globulin in 21 (26.9%), low HDL in 35 (59.3%) and elevated phenylalanine level in 28 (34.5%) patients in the sample. Overweight and obesity were correlated with low HDL (p = 0.04) and lowest adequate frequency of LDL (p = 0.09). Higher phosphorus values were associated with lower body weight (r = -0.72) and age (r = -0.75), as well as vitamin B12 in the same parameters (r = -0.67 and r = -0, 68). A positive correlation of phenylalanine with body weight and age (r = 0.62 and r = 0.66) was observed.

CONCLUSION

Most patients presented adequate according to anthropometric parameters and appropriate biochemical tests, except HDL, and moderate metabolic control of the disease. However, attention should be paid to the presence of overweight and need for biochemical monitoring of triglycerides, selenium, zinc, HDL, and phenylalanine.

Casein-derived peptides as an alternative ingredient for low-phenylalanine diets

Introduction: casein-derived peptides can be liberated both in vivo via normal digestion of casein, as well as in vitro via enzymatic hydrolysis. These peptides were suggested to have biological activity. Objectives: the aim of this study was to describe the production and characterization of casein peptides and to explore the potential of these peptides as an option for low-phenylalanine diets. Methods: peptides were produced by tryptic hydrolysis of sodium caseinate and acid precipitation with HCl, followed by precipitation with ethanol or aggregation of CaCl2 or ZnSO4. Results: the amino acid analysis revealed a significant reduction in the amount of phenylalanine from the original protein. Conclusion: casein-derived peptides could be a future alternative of short chain peptides to low-phenylalanine formulations.

Status of nutrients important in brain function in phenylketonuria: a systematic review and meta-analysis

Background

Despite early and ongoing dietary management with a phe-restricted diet, suboptimal neuropsychological function has been observed in PKU. The restrictive nature of the PKU diet may expose patients to sub-optimal nutritional intake and deficiencies which may impact normal brain function. A systematic review of the published literature was carried out, where possible with meta-analysis, to compare the status of nutrients (Nutrients: DHA, EPA phospholipids, selenium, vitamins B₆, B₁₂, E, C, A, D, folic acid, choline, uridine, calcium, magnesium, zinc, iron, iodine and cholesterol) known to be important for brain development and functioning between individuals with PKU and healthy controls.

Results

Of 1534 publications identified, 65 studies met the entry criteria. Significantly lower levels of DHA, EPA and cholesterol were found for PKU patients compared to healthy controls. No significant differences in zinc, vitamins B₁₂, E and D, calcium, iron and magnesium were found between PKU patients and controls. Because of considerable heterogeneity, the meta-analyses findings for folate and selenium were not reported. Due to an insufficient number of publications (< 4) no meta-analysis was undertaken for vitamins A, C and B₆, choline, uridine, iodine and phospholipids.

Conclusions

The current data show that PKU patients have lower availability of DHA, EPA and cholesterol. Compliance with the phe-restricted diet including the micronutrient fortified protein substitute (PS) is essential to ensure adequate micronutrient status. Given the complexity of the diet, patients’ micronutrient and fatty acid status should be continuously monitored, with a particular focus on patients who are non-compliant or poorly compliant with their PS. Given their key role in brain function, assessment of the status of nutrients where limited data was found (e.g. choline, iodine) should be undertaken. Standardised reporting of studies in PKU would strengthen the output of meta-analysis and so better inform best practice for this rare condition.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0839-x) contains supplementary material, which is available to authorized users.

Metabolomic Insights into the Nutritional Status of Adults and Adolescents with Phenylketonuria Consuming a Low-Phenylalanine Diet in Combination with Amino Acid and Glycomacropeptide Medical Foods

BACKGROUND

Nutrient status in phenylketonuria (PKU) requires surveillance due to the restrictive low-Phe diet in combination with amino acid medical foods (AA-MF) or glycomacropeptide medical foods (GMP-MF). Micronutrient profiles of medical foods are diverse, and optimal micronutrient supplementation in PKU has not been established.

METHODS

In a crossover design, 30 participants with PKU were randomized to consume AA-MF and Glytactin™ GMP-MF in combination with a low-Phe diet for 3 weeks each. Fasting venipunctures, medical food logs, and 3-day food records were obtained. Metabolomic analyses were completed in plasma and urine by Metabolon, Inc.

RESULTS

The low-Phe diets in combination with AA-MF and GMP-MF were generally adequate based on Dietary Reference Intakes, clinical measures, and metabolomics. Without micronutrient supplementation of medical foods, >70% of participants would have inadequate intakes for 11 micronutrients. Despite micronutrient supplementation of medical foods, inadequate intakes of potassium in 93% of participants and choline in >40% and excessive intakes of sodium in >63% of participants and folic acid in >27% were observed. Sugar intake was excessive and provided 27% of energy.

CONCLUSIONS

Nutrient status was similar with AA-MF and Glytactin GMP-MF. More research related to micronutrient supplementation of medical foods for the management of PKU is needed.

The complete European guidelines on phenylketonuria: diagnosis and treatment

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine metabolism caused by deficiency in the enzyme phenylalanine hydroxylase that converts phenylalanine into tyrosine. If left untreated, PKU results in increased phenylalanine concentrations in blood and brain, which cause severe intellectual disability, epilepsy and behavioural problems. PKU management differs widely across Europe and therefore these guidelines have been developed aiming to optimize and standardize PKU care. Professionals from 10 different European countries developed the guidelines according to the AGREE (Appraisal of Guidelines for Research and Evaluation) method. Literature search, critical appraisal and evidence grading were conducted according to the SIGN (Scottish Intercollegiate Guidelines Network) method. The Delphi-method was used when there was no or little evidence available. External consultants reviewed the guidelines. Using these methods 70 statements were formulated based on the highest quality evidence available. The level of evidence of most recommendations is C or D. Although study designs and patient numbers are sub-optimal, many statements are convincing, important and relevant. In addition, knowledge gaps are identified which require further research in order to direct better care for the future.

Key European guidelines for the diagnosis and management of patients with phenylketonuria

We developed European guidelines to optimise phenylketonuria (PKU) care. To develop the guidelines, we did a literature search, critical appraisal, and evidence grading according to the Scottish Intercollegiate Guidelines Network method. We used the Delphi method when little or no evidence was available. From the 70 recommendations formulated, in this Review we describe ten that we deem as having the highest priority. Diet is the cornerstone of treatment, although some patients can benefit from tetrahydrobiopterin (BH4). Untreated blood phenylalanine concentrations determine management of people with PKU. No intervention is required if the blood phenylalanine concentration is less than 360 μmol/L. Treatment is recommended up to the age of 12 years if the phenylalanine blood concentration is between 360 μmol/L and 600 μmol/L, and lifelong treatment is recommended if the concentration is more than 600 μmol/L. For women trying to conceive and during pregnancy (maternal PKU), untreated phenylalanine blood concentrations of more than 360 μmol/L need to be reduced. Treatment target concentrations are as follows: 120-360 μmol/L for individuals aged 0-12 years and for maternal PKU, and 120-600 μmol/L for non-pregnant individuals older than 12 years. Minimum requirements for the management and follow-up of patients with PKU are scheduled according to age, adherence to treatment, and clinical status. Nutritional, clinical, and biochemical follow-up is necessary for all patients, regardless of therapy.

Effects of Inadequate Amino Acid Mixture Intake on Nutrient Supply of Adult Patients with Phenylketonuria

Background: Adult phenylketonuria (PKU) patients often reduce their intake of amino acid mixture (AAM) to less than the prescribed amounts. Effects of reduced AAM intake on nutrient supply were evaluated. Methods: Nutrient intake was calculated in 20 adult PKU patients based on a structured food record and complemented by laboratory assessment of nutritional status. Patients were classified into 2 groups, (A) regular AAM intake, or (B) AAM intake below calculated requirements. Results: Group B consumed a higher proportion of natural protein (60 ± 23 vs. 33 ± 12%, p = 0.002); however, the total protein intake was below the recommended amounts in 60% of patients in group B versus 7% in group A (p = 0.03). Fat intake was higher in group B (39 ± 9% of energy vs. 31 ± 6%, p = 0.03), mainly from saturated fats. Selenium, folate, and vitamin B12 intake was below the recommended intake in group B. However, serum concentrations of these analytes remained within the normal range in both groups, although vitamin B12 levels were lower in group B. Plasma tyrosine correlated with AAM intake, and hydroxyproline correlated with the amount of natural protein consumed. Conclusion: Relaxed AAM intake resulted in insufficient nutrient supply, despite a compensatory increase in consumption of natural protein. Care needs to be taken to ensure adequate nutrition in adults with PKU.

Influence of phenylketonuria's diet on dimethylated arginines and methylation cycle

Phenylketonuria's (PKU) treatment based on low natural protein diet may affect homocysteine (Hcys) metabolic pathway. Hcys alteration may be related to the methylation of arginine to asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), which both modify nitric oxide production. The aim of this work is to evaluate the status of Hcys formation methylation cycle and ADMA and SDMA levels in patients with PKU in order to establish a potential relationship.Forty-two early diagnosed PKU patients under dietary treatment and good adherence to their diets were enrolled in this cross-sectional study. Their nutritional and biochemical profile, as well as Hcys synthesis status, ADMA and SDMA levels were analyzed and compared with a control group of 40 healthy volunteers. ADMA and SDMA were determined by high-performance liquid chromatography system coupled to triple quadrupole mass spectrometer.In this study, 23 classic PKU, 16 moderate PKU, and 3 mild HPA were enrolled. The median age was 10 years old. Median ADMA, SDMA, and Hcys concentration levels (5.1 μM [2.3-25.7], 0.35 μM [0.18-0.57], 0.43 μM [0.26-0.61], respectively) were lower in patients with PKU (P < .001 for ADMA and SDMA) whereas vitamin B12 and folate levels (616 pg/mL [218-1943] and 21 ng/mL [5-51], respectively) were higher comparing with controls. Statistically significant correlations were found between ADMA, and Phe (r = -0.504, P = .001) and Hcys (r = -0.458, P = .037) levels. Several nutrition biomarkers, such as prealbumin, 25-hydroxy vitamin D, selenium, and zinc, were below the normal range.Our study suggests that patients with PKU suffer from poor methylation capacity. Restriction of natural proteins in addition to high intake of vitamin B12 and folic acid supplementation in the dietary products, produce an impairment of methylation cycle that leads to low Hcys and ADMA levels. As a result, methylated compounds compete for methyl groups, and there is an impairment of methylation cycle due to low Hcys levels, which is related to the lack of protein quality, despite of elevated concentrations of cofactors.

Micronutrients, Essential Fatty Acids and Bone Health in Phenylketonuria

INTRODUCTION

In phenylketonuria (PKU), a natural protein-restricted dietary treatment prevents severe cognitive impairment. Nutrient deficiencies may occur due to strict diet. This study is aimed at evaluating the dietary intake and blood concentrations of micronutrients and essential fatty acids (FA), bone mineral density (BMD) and fracture history in patients on long-term dietary treatment.

METHODS

Sixty early diagnosed Dutch patients (aged 1-39 years) were included in a multi-center cross-sectional study. Their dietary intake, blood concentrations of micronutrients, FA, fracture history and BMD were assessed.

RESULTS

Selenium dietary intake and serum concentrations were low in 14 and 46% of patients, respectively. The serum 25-OH vitamin D2 + D3 concentration was low in 14% of patients while 20% of patients had a low vitamin D intake. Zinc serum concentrations were below normal in 14% of patients, despite adequate intake. Folic acid serum concentrations and intake were elevated. Despite safe total protein and fat intake, arginine plasma concentrations and erythrocyte eicosapentaenoic acid were below reference values in 19 and 6% of patients, respectively. Low BMD (Z-score <-2) was slightly more prevalent in patients, but the lifetime fracture prevalence was comparable to the general population.

CONCLUSIONS

Dutch patients with PKU on long-term dietary treatment have a near normal nutrient status. Supplementation of micronutrients of which deficiency may be deleterious (e.g., vitamin D and selenium) should be considered. BMD warrants further investigation.

Dietary intervention in the management of phenylketonuria: current perspectives

Phenylketonuria (PKU) is a well-described inborn error of amino acid metabolism that has been treated for >60 years. Enzyme deficiency causes accumulation of phenylalanine (Phe) and if left untreated will lead to profound and irreversible intellectual disability in most children. Traditionally, it has been managed with a low-Phe diet supplemented with a Phe-free protein substitute although newer treatment options mainly in combination with diet are available for some subgroups of patients with PKU, for example, sapropterin, large neutral amino acids, and glycomacropeptide. The diet consists of three parts: 1) severe restriction of dietary Phe; 2) replacement of non-Phe l-amino acids with a protein substitute commonly supplemented with essential fatty acids and other micronutrients; and 3) low-protein foods from fruits, some vegetables, sugars, fats and oil, and special low-protein foods (SLPF). The prescription of diet is challenging for health professionals. The high-carbohydrate diet supplied by a limited range of foods may program food preferences and contribute to obesity in later life. Abnormal tasting and satiety-promoting protein substitutes are administered to coincide with peak appetite times to ensure their consumption, but this practice may impede appetite for other important foods. Intermittent dosing of micronutrients when combined with l-amino acid supplements may lead to their poor bioavailability. Much work is required on the ideal nutritional profiling for special SLPF and Phe-free l-amino acid supplements. Although non-diet treatments are being studied, it is important to continue to fully understand all the consequences of diet therapy as it is likely to remain the foundation of therapy for many years.

Lipid profile status and other related factors in patients with Hyperphenylalaninaemia

BACKGROUND

The mainstay of treating patients with phenylketonuria (PKU) is based on a Phe-restricted diet, restrictive in natural protein combined with Phe-free L-amino acid supplements and low protein foods. This PKU diet seems to reduce atherogenesis and confer protection against cardiovascular diseases but the results from the few published studies have been inconclusive. The aim of our study was to evaluate the relationship between the lipid profile and several treatment-related risk factors in patients with hyperphenylalaninaemia (HPA) in order to optimize their monitoring.

METHODS

We conducted a cross-sectional multicentre study. A total of 141 patients with HPA were classified according to age, phenotype, type of treatment and dietary adherence. Annual median blood phenylalanine (Phe) levels, Phe tolerance, anthropometric measurements, blood pressure (BP) and biochemical parameters [(triglycerides, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), apolipoprotein A (ApoA), apolipoprotein B (ApoB), vitamin B12, total homocysteine (tHcy), Methionine (Met), high sensitivity C-Reactive Protein (hsCRP)] were collected for each patient.

RESULTS

Plasma TC levels were lower in patients with PKU than in the mild-HPA group (150 ± 31 vs. 164 ± 22 mg/dL), and there was a weak inverse correlation between plasma TC and Phe levels. HDL-C, LDL-C, ApoA and ApoB levels were lower in the PKU group than in mild-HPA. Patients with PKU had higher systolic BP than the mild-HPA group and there was found a quadratic correlation between median Phe levels and systolic BP (p = 6.42e(-5)) and a linear correlation between median Phe levels and diastolic BP (p = 5.65e(-4)). In overweight or obese PKU patients (24.11 %), biochemical parameters such as TC, triglycerides, LDL-C, tHcy, hsCRP and BP were higher. By contrast, HDL-C was lower in these patients.

CONCLUSION

Our data show a direct correlation between lipid profile parameters and good adherence to the diet in PKU patients. However, lipid profile in overweight or obese patients displayed an atherogenic profile, in addition to higher hsCRP concentrations and BP. Our study contributes to a better understanding of the relationship between phenotype and treatment in patients with HPA, which could be useful in improving follow-up strategies and clinical outcome.

TRIAL REGISTRATION

Research Ethics Committee of Santiago-Lugo 2015/393. Registered 22 September 2015, retrospectively registered.

Protein substitutes for phenylketonuria in Europe: access and nutritional composition

BACKGROUND/OBJECTIVES

Protein substitutes (PS) are an essential component in the dietary management of phenylketonuria (PKU). PS are available as phenylalanine-free amino-acid mixtures (AAM), glycomacropeptide-based PS (GMP) and large neutral amino acids (LNAA). There is a lack of information regarding their availability in different countries and comparison of their nutritional composition is limited. The objectives of this study were to identify the number of PS available in different European countries and Turkey and to compare their nutritional composition.

SUBJECTS/METHODS

Members of the European Nutritionist Expert Panel on PKU (ENEP) (Portugal, Spain, Belgium, Italy, Germany, Netherlands, United Kingdom, Denmark and Turkey) provided data on PS available in each country. The nutritional composition of PS available in Portugal was analyzed.

RESULTS

The number of PS available in each country varied from 30 (Turkey) to 105 (Germany), with a median of 64. GMP was available only in Portugal, whereas LNAA was an option in Portugal, Italy, Turkey and Denmark. Some PS were designed for weaning. Many PS did not contain added fat and fiber. GMP contained the highest carbohydrate (CHO) and energy content as well as higher LNAA content compared with AAM. Only one AAM contained added fructo-oligosaccharides and galacto-oligosaccharides. AAM designed for the first year of life had the highest CHO, fat and LNAA contribution. Liquid AAM had lower CHO and fat contents compared with powdered AAM, but contained higher LNAA.

CONCLUSIONS

There was widely dissimilar numbers of PS available in different countries. Nutritional composition of different PS was variable and should be considered before prescription.

Special low protein foods for phenylketonuria: availability in Europe and an examination of their nutritional profile

BACKGROUND

Special low protein foods (SLPF) are essential in the nutritional management of patients with phenylketonuria (PKU). The study objectives were to: 1) identify the number of SLPF available for use in eight European countries and Turkey and 2) analyse the nutritional composition of SLPF available in one of these countries.

METHODS

European Nutritionist Expert Panel on PKU (ENEP) members (Portugal, Spain, Belgium, Italy, Germany, Netherlands, UK, Denmark and Turkey) provided data on SPLF available in each country. The nutritional composition of Portuguese SLPF was compared with regular food products.

RESULTS

The number of different SLPF available in each country varied widely with a median of 107 [ranging from 73 (Portugal) and 256 (Italy)]. Food analysis of SLPF available from a single country (Portugal) indicated that the mean phenylalanine content was higher in low protein baby cereals (mean 48 mg/100 g) and chocolate/energy bars/jelly (mean 41 mg/100 g). The energy content of different foods from a sub-group of SLPF (cookies) varied widely between 23 and 96 kcal/cookie. Low protein bread had a high fat content [mean 5.8 g/100 g (range 3.7 to 10)] compared with 1.6 g/100 g in regular bread. Seven of the 12 SLPF sub-groups (58 %) did not declare any vitamin content, and only 4 (33 %) identified a limited number of minerals.

CONCLUSIONS

Whilst equal and free access to all SLPF is desirable, the widely variable nutritional composition requires careful nutritional knowledge of all products when prescribed for individual patients with PKU. There is a need for more specific nutritional standards for special low protein foods.

Vitamin and mineral status in patients with hyperphenylalaninemia

Natural sources of protein and some vitamins and minerals are limited in phenylketonuria (PKU) treated patients, who should receive optimal supplementation although this is not yet fully established. We conducted a cross-sectional observational multicenter study including 156 patients with hyperphenylalaninemia. Patients were stratified by age, phenotype, disease detection and type of treatment. Annual median blood phenylalanine (Phe) levels, Phe tolerance, anthropometric measurements, and biochemical parameters (total protein, prealbumin, electrolytes, selenium, zinc, B12, folic acid, ferritin, 25-OH vitamin D) were collected in all patients. 81.4% of patients had biochemical markers out of recommended range but no clinical symptoms. Total protein, calcium, phosphorus, B12, ferritin, and zinc levels were normal in most patients. Prealbumin was reduced in 34.6% of patients (74% with PKU phenotype and 94% below 18 years old), showing almost all (96.3%) an adequate adherence to diet. Selenium was diminished in 25% of patients (95% with PKU phenotype) and also 25-OHD in 14%. Surprisingly, folic acid levels were increased in 39% of patients, 66% with classic PKU. Phosphorus and B12 levels were found diminished in patients with low adherence to diet. Patients under BH4 therapy only showed significant lower levels of B12. This study shows a high percentage of prealbumin and selenium deficiencies as well as an increased level of folic acid in PKU treated patients, which should lead us to assess an adjustment for standards supplements formulated milks.

Targeting specific nutrient deficiencies in protein-restricted diets: some practical facts in PKU dietary management

Among aminoacidopathies, phenylketonuria (PKU) is the most prevalent one. Early diagnosis in the neonatal period with a prompt nutritional therapy (low natural-protein and phenylalanine diet, supplemented with phenylalanine-free amino acid mixtures and special low-protein foods) remains the mainstay of the treatment. Data considering nutrient contents of cooked dishes is lacking. In this study, fourteen dishes specifically prepared for PKU individuals were analysed, regarding the lipid profile and iron and zinc contents. These dishes are poor sources of essential nutrients like Fe, Zn or n-3 fatty acids, reinforcing the need for adequate supplementation to cover individual patients' needs. This study can contribute to a more accurate adjustment of PKU diets and supplementation in order to prevent eventual nutritional deficiencies. This study contributes to a better understanding of nutrient intake from PKU patients' meals, showing the need for dietary supplementation.

The micronutrient status of patients with phenylketonuria on dietary treatment: an ongoing challenge

BACKGROUND

In phenylketonuria (PKU), phenylalanine-free L-amino acid supplements are the major source of dietary micronutrients.

METHODS

Four hundred fifty-two retrospective annual/bi-annual non-fasting blood samples for nutritional markers (plasma zinc, selenium, and serum folate) from 78 subjects aged 1-16 years (median number of blood samples: 6, range 1-14) were analysed over 12 years. Longitudinal blood result data were available for 51 subjects (65%). The dietary intake from supplements was calculated.

RESULTS

The median intakes of all of the micronutrients studied were >200% of the reference nutrient intakes (RNI). There was no statistical correlation between dietary intake and nutritional markers outside of the normal reference range (RR) except for selenium, but there was a correlation between a lower plasma zinc, plasma selenium and haemoglobin status and better blood phenylalanine control in 1- to 4-year-old children. On at least one occasion, the individual plasma concentrations of zinc (71%, n = 54/76) and selenium (21%, n = 16/75) were below the RR; however, the concentrations of selenium (41%, n = 31/75) and serum folate (83%, n = 34/41) were also above the RR. Dietary intakes exceeded the upper tolerable intakes for zinc and copper (32%, n = 25) and folate (65%, n = 51). Individual longitudinal data demonstrated little change in micronutrient status over time.

CONCLUSIONS

In PKU, biochemical micronutrient deficiencies are common despite micronutrient intakes above the RNI. Further study of the nutritional profiling of L-amino acid supplements in PKU is needed.

Micronutrient status in phenylketonuria

Patients with phenylketonuria (PKU) encompass an 'at risk' group for micronutrient imbalances. Optimal nutrient status is challenging particularly when a substantial proportion of nutrient intake is from non-natural sources. In PKU patients following dietary treatment, supplementation with micronutrients is a necessity and vitamins and minerals should either be added to supplement phenylalanine-free l-amino acids or given separately. In this literature review of papers published since 1990, the prevalence of vitamin and mineral deficiency is described, with reference to age of treatment commencement, type of treatment, dietary compliance, and dietary practices. Biological micronutrient inadequacies have been mainly reported for zinc, selenium, iron, vitamin B12 and folate. The aetiology of these results and possible clinical and biological implications are discussed. In PKU there is not a simple relationship between the dietary intake and nutritional status, and there are many independent and interrelated complex factors that should be considered other than quantitative nutritional intake.