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Diet Therapy and Nutritional Management of Phenylketonuria
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Diet Therapy and Nutritional Management of Phenylketonuria

A special issue of Nutrients (ISSN 2072-6643). This special issue belongs to the section "Clinical Nutrition".

Deadline for manuscript submissions: closed (1 December 2021) | Viewed by 94840

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Anita MacDonald

E-Mail Website
Guest Editor
Dietetic Department, Birmingham Children's Hospital, Steelhouse Lane, Birmingham B4 6NH, UK
Interests: phenylketonuria; dietary treatment; protein substitutes; dietary adherence; feeding development
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Phenylketonuria (PKU) is an established inherited amino acid disorder with a very traditional dietary therapy, but there is still more to learn and verify about its nutritional composition, application and overall effectiveness. Although in the 1950s, the first patient successfully treated with diet therapy patently established the role of a low phenylalanine protein substitute, in present times, it is still necessary to characterise the most effective source of artificial protein; defining its optimal amino acid profile; and identifying nutrient modulation that will improve the functionality of protein substitutes. It is also important to understand the impact of a life-long synthetic diet on gut microbiota, metabolomics and inflammatory status.

In early-treated patients with PKU, it is unclear if co-morbidities such as overweight, obesity, hypertension and diabetes are higher than in the general population and if these are associated with increased cardiovascular risk. It is also uncertain if overweight and obesity in PKU is related to early dietary practices, the nutritional composition of protein substitutes and special low-protein foods, impact of the dietary treatment on satiety, disordered eating patterns, non-adherence with the low phenylalanine diet and poor metabolic control, or if this is even a consequence of the disorder. In a generation of ageing patients, the impact of intermittent and suboptimal dietary adherence on nutritional status deserves systematic study.

This Special Issue on dietary management of PKU shall bring together a collection of research articles that will advance knowledge in current areas lacking scientific clarity or with limited and incomplete evidence to support dietary practice.

Prof. Dr. Anita Macdonald
Guest Editor

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Keywords

  • Phenylketonuria
  • Protein substitute
  • Phenylalanine
  • Amino acids

Published Papers (24 papers)

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17 pages, 1557 KiB  
Article
Validation of a Low-protein Semi-Quantitative Food Frequency Questionnaire
by Sharon Evans, Catherine Ashmore, Anne Daly, Richard Jackson, Alex Pinto and Anita MacDonald
Nutrients 2022, 14(8), 1595; https://0-doi-org.brum.beds.ac.uk/10.3390/nu14081595 - 12 Apr 2022
Cited by 3 | Viewed by 2120
Abstract
Analysis of dietary patterns and their role in long-term health is limited in phenylketonuria (PKU). Food frequency questionnaires (FFQ) are commonly used to assess habitual intake. A semi-quantitative 89-item FFQ with a portion size photographic booklet was developed for children with PKU as [...] Read more.
Analysis of dietary patterns and their role in long-term health is limited in phenylketonuria (PKU). Food frequency questionnaires (FFQ) are commonly used to assess habitual intake. A semi-quantitative 89-item FFQ with a portion size photographic booklet was developed for children with PKU as a tool for collecting data on habitual intake of foods, food groups, energy and macronutrient intake. Twenty children with PKU aged 11–16 years, 30 parents of children with PKU aged 4–10 years, and 50 age/gender-matched control children were recruited. To test reproducibility, FFQs were completed twice with a mean interval of 5 weeks (range: 4–10). In order to test validity, FFQs were compared with five 24-h dietary recalls with a mean interval of 10 days (range: 6–18). Energy and macronutrient intake and quantity/week of individual food items were calculated and compared. There was good reproducibility for the FFQ with macronutrient correlations r > 0.6 and good validity data with most correlations r > 0.5. Bland–Altman plots for reproducibility and validity showed mean levels close to 0 and usually within 2 standard deviations. FFQ comparisons of PKU and control groups identified expected differences in % energy from macronutrients (PKU vs. control: carbohydrate 59% vs. 51%, fat 26% vs. 33%, protein 15% vs. 16%). This FFQ for PKU produced comparable data to repeated dietary recalls and is a valid tool for collecting data on habitual food and nutrient intake. It will be useful in assessing changes in dietary phenylalanine tolerance of new pharmacological treatments for PKU. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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13 pages, 263 KiB  
Article
The Challenges and Dilemmas of Interpreting Protein Labelling of Prepackaged Foods Encountered by the PKU Community
by Imogen Hall, Alex Pinto, Sharon Evans, Anne Daly, Catherine Ashmore, Suzanne Ford, Sharon Buckley and Anita MacDonald
Nutrients 2022, 14(7), 1355; https://0-doi-org.brum.beds.ac.uk/10.3390/nu14071355 - 24 Mar 2022
Cited by 4 | Viewed by 2409
Abstract
Phenylketonuria (PKU) can lead to severe intellectual impairment unless a phenylalanine-restricted diet starts early in life. It requires expert user knowledge about the protein content of foods. The ability of adults or caregivers of children with PKU to calculate protein exchanges from food [...] Read more.
Phenylketonuria (PKU) can lead to severe intellectual impairment unless a phenylalanine-restricted diet starts early in life. It requires expert user knowledge about the protein content of foods. The ability of adults or caregivers of children with PKU to calculate protein exchanges from food labels on manufactured foods and any difficulties they encounter in interpreting food labels has not been studied systematically. Individuals with PKU or their caregivers residing in the UK were invited to complete a cross-sectional online survey that collected both qualitative and quantitative data about their experience when calculating protein exchanges from the food labelling on prepackaged foods. Data was available from 246 questionnaire respondents (152 caregivers of patients with PKU aged <18 years, 57 patients with PKU aged ≥18 years or their caregivers (n = 28), and 9 teenagers with PKU). Thirty-one per cent (n = 76/246) found it difficult to interpret food protein exchanges from food labels. The respondents listed that the main issues with protein labelling were the non-specification of whether the protein content was for the cooked or uncooked weight (64%, n = 158/246); labels stating foods contained 0 g protein but then included protein sources in the list of ingredients (56%, n = 137/246); the protein content being given after a product was prepared with regular milk rather than the dry weight of the product (55%, n = 135/246); and the non-clarity of whether the protein content was for the weight of prepared or unprepared food (in addition to non-specification of cooked or uncooked weights on food labelling) (54%, n = 133/246). Over 90% (n = 222/246) of respondents had experienced problems with food labelling in the previous six months. Misleading or confusing protein labelling of manufactured foods was common. The food industry and legislators have a duty to provide accurate and clear protein food labelling to protect populations requiring low protein diets. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
13 pages, 292 KiB  
Article
Hungry for Change: The Experiences of People with PKU, and Their Caregivers, When Eating Out
by Grace Poole, Alex Pinto, Sharon Evans, Suzanne Ford, Mike O’Driscoll, Sharon Buckley, Catherine Ashmore, Anne Daly and Anita MacDonald
Nutrients 2022, 14(3), 626; https://0-doi-org.brum.beds.ac.uk/10.3390/nu14030626 - 31 Jan 2022
Cited by 4 | Viewed by 3209
Abstract
For patients with phenylketonuria (PKU), stringent dietary management is demanding and eating out may pose many challenges. Often, there is little awareness about special dietary requirements within the hospitality sector. This study’s aim was to investigate the experiences and behaviours of people with [...] Read more.
For patients with phenylketonuria (PKU), stringent dietary management is demanding and eating out may pose many challenges. Often, there is little awareness about special dietary requirements within the hospitality sector. This study’s aim was to investigate the experiences and behaviours of people with PKU and their caregivers when dining out. We also sought to identify common problems in order to improve their experiences when eating outside the home. Individuals with PKU or their caregivers residing in the UK were invited to complete a cross-sectional online survey that collected both qualitative and quantitative data about their experiences when eating out. Data were available from 254 questionnaire respondents (136 caregivers or patients with PKU < 18 years and 118 patients with PKU ≥ 18 years (n = 100) or their caregivers (n = 18)). Fifty-eight per cent dined out once per month or less (n = 147/254) and the biggest barrier to more frequent dining was ‘limited choice of suitable low-protein foods’ (90%, n = 184/204), followed by ‘no information about the protein content of foods’ (67%, n = 137/204). Sixty-nine per cent (n = 176/254) rated their dining experience as less than satisfactory. Respondents ranked restaurant employees’ knowledge of the PKU diet as very poor with an overall median rating of 1.6 (on a scale of 1 for extremely poor to 10 for extremely good). Forty-four per cent (n = 110/252) of respondents said that restaurants had refused to prepare alternative suitable foods; 44% (n = 110/252) were not allowed to eat their own prepared food in a restaurant, and 46% (n = 115/252) reported that restaurants had refused to cook special low-protein foods. Forty per cent (n = 101/254) of respondents felt anxious before entering restaurants. People with PKU commonly experienced discrimination in restaurants, with hospitality staff failing to support their dietary needs, frequently using allergy laws and concerns about cross-contamination as a reason not to provide suitable food options. It is important that restaurant staff receive training regarding low-protein diets, offer more low-protein options, provide protein analysis information on all menu items, and be more flexible in their approach to cooking low-protein foods supplied by the person with PKU. This may help people with PKU enjoy safe meals when dining out and socialising with others. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
19 pages, 454 KiB  
Article
Dietetic Management of Adults with Phenylketonuria (PKU) in the UK: A Care Consensus Document
by Louise Robertson, Sarah Adam, Charlotte Ellerton, Suzanne Ford, Melanie Hill, Gemma Randles, Alison Woodall, Carla Young and Anita MacDonald
Nutrients 2022, 14(3), 576; https://0-doi-org.brum.beds.ac.uk/10.3390/nu14030576 - 28 Jan 2022
Cited by 9 | Viewed by 5512
Abstract
There is an increasing number of adults and elderly patients with phenylketonuria (PKU) who are either early, late treated, or untreated. The principal treatment is a phenylalanine-restricted diet. There is no established UK training for dietitians who work with adults within the specialty [...] Read more.
There is an increasing number of adults and elderly patients with phenylketonuria (PKU) who are either early, late treated, or untreated. The principal treatment is a phenylalanine-restricted diet. There is no established UK training for dietitians who work with adults within the specialty of Inherited Metabolic Disorders (IMDs), including PKU. To address this, a group of experienced dietitians specializing in IMDs created a standard operating procedure (SOP) on the dietetic management of adults with PKU to promote equity of care in IMD dietetic services and to support service provision across the UK. The group met virtually over a period of 12 months until they reached 100% consensus on the SOP content. Areas of limited evidence included optimal blood phenylalanine reporting times to patients, protein requirements in older adults, management of weight and obesity, and management of disordered eating and eating disorders. The SOP does not include guidance on maternal PKU management. The SOP can be used as a tool for training dietitians new to the specialty and to raise the standard of education and care for patients with PKU in the UK. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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17 pages, 329 KiB  
Article
Special Low Protein Foods Prescribed in England for PKU Patients: An Analysis of Prescribing Patterns and Cost
by Georgina Wood, Alex Pinto, Sharon Evans, Anne Daly, Sandra Adams, Susie Costelloe, Joanna Gribben, Charlotte Ellerton, Anita Emm, Sarah Firman, Suzanne Ford, Moira French, Lisa Gaff, Emily Giuliano, Melanie Hill, Inderdip Hunjan, Camille Newby, Allison Mackenzie, Rachel Pereira, Celine Prescott, Louise Robertson, Heidi Seabert, Rachel Skeath, Simon Tapley, Allyson Terry, Alison Tooke, Karen van Wyk, Fiona J. White, Lucy White, Alison Woodall, Júlio César Rocha and Anita MacDonaldadd Show full author list remove Hide full author list
Nutrients 2021, 13(11), 3977; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13113977 - 08 Nov 2021
Cited by 12 | Viewed by 3220
Abstract
Patients with phenylketonuria (PKU) are reliant on special low protein foods (SLPFs) as part of their dietary treatment. In England, several issues regarding the accessibility of SLPFs through the national prescribing system have been highlighted. Therefore, prescribing patterns and expenditure on all SLPFs [...] Read more.
Patients with phenylketonuria (PKU) are reliant on special low protein foods (SLPFs) as part of their dietary treatment. In England, several issues regarding the accessibility of SLPFs through the national prescribing system have been highlighted. Therefore, prescribing patterns and expenditure on all SLPFs available on prescription in England (n = 142) were examined. Their costs in comparison to regular protein-containing (n = 182) and ‘free-from’ products (n = 135) were also analysed. Similar foods were grouped into subgroups (n = 40). The number of units and costs of SLPFs prescribed in total and per subgroup from January to December 2020 were calculated using National Health Service (NHS) Business Service Authority (NHSBSA) ePACT2 (electronic Prescribing Analysis and Cost Tool) for England. Monthly patient SLPF units prescribed were calculated using patient numbers with PKU and non-PKU inherited metabolic disorders (IMD) consuming SLPFs. This was compared to the National Society for PKU (NSPKU) prescribing guidance. Ninety-eight percent of SLPF subgroups (n = 39/40) were more expensive than regular and ‘free-from’ food subgroups. However, costs to prescribe SLPFs are significantly less than theoretical calculations. From January to December 2020, 208,932 units of SLPFs were prescribed (excluding milk replacers), costing the NHS £2,151,973 (including milk replacers). This equates to £962 per patient annually, and prescribed amounts are well below the upper limits suggested by the NSPKU, indicating under prescribing of SLPFs. It is recommended that a simpler and improved system should be implemented. Ideally, specialist metabolic dietitians should have responsibility for prescribing SLPFs. This would ensure that patients with PKU have the necessary access to their essential dietary treatment, which, in turn, should help promote dietary adherence and improve metabolic control. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
13 pages, 261 KiB  
Article
Provision and Supervision of Food and Protein Substitute in School for Children with PKU: Parent Experiences
by Hannah Jones, Alex Pinto, Sharon Evans, Suzanne Ford, Mike O’Driscoll, Sharon Buckley, Catherine Ashmore, Anne Daly and Anita MacDonald
Nutrients 2021, 13(11), 3863; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13113863 - 28 Oct 2021
Viewed by 2070
Abstract
Children spend a substantial part of their childhood in school, so provision of dietary care and inclusion of children with phenylketonuria (PKU) in this setting is essential. There are no reports describing the dietary support children with PKU receive whilst at school. The [...] Read more.
Children spend a substantial part of their childhood in school, so provision of dietary care and inclusion of children with phenylketonuria (PKU) in this setting is essential. There are no reports describing the dietary support children with PKU receive whilst at school. The aim of this cross-sectional study was to explore the experiences of the dietary management of children with PKU in schools across the UK. Data was collected using an online survey completed by parents/caregivers of children with PKU. Of 159 questionnaire responses, 92% (n = 146) of children attended state school, 6% (n = 10) private school and 2% (n = 3) other. Fourteen per cent (n = 21/154) were at nursery/preschool, 51% (n = 79/154) primary and 35% (n = 54/154) secondary school. Sixty-one per cent (n = 97/159) said their child did not have school meals, with some catering services refusing to provide suitable food and some parents distrusting the school meals service. Sixty-one per cent of children had an individual health care plan (IHCP) (n = 95/155). Children were commonly unsupervised at lunchtime (40%, n = 63/159), with snacks (46%, n = 71/155) and protein substitute (30%, n = 47/157), with significantly less supervision in secondary than primary school (p < 0.001). An IHCP was significantly associated with improved supervision of food and protein substitute administration (p < 0.01), and better communication between parents/caregivers and the school team (p < 0.05). Children commonly accessed non-permitted foods in school. Therefore, parents/caregivers described important issues concerning the school provision of low phenylalanine food and protein substitute. Every child should have an IHCP which details their dietary needs and how these will be met safely and discreetly. It is imperative that children with PKU are supported in school. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
11 pages, 1394 KiB  
Article
Nitrogen Balance after the Administration of a Prolonged-Release Protein Substitute for Phenylketonuria as a Single Dose in Healthy Volunteers
by Mika Scheinin, Jouni Junnila, Giorgio Reiner, Anita MacDonald and Ania C. Muntau
Nutrients 2021, 13(9), 3189; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13093189 - 14 Sep 2021
Cited by 6 | Viewed by 4002
Abstract
Nitrogen balance is the difference between nitrogen excreted as urea and nitrogen ingested, mainly in proteins. Increased circulating concentrations of amino acids (AA) in the bloodstream are usually associated with proportional increases in the production and excretion of urea. Previously, we reported results [...] Read more.
Nitrogen balance is the difference between nitrogen excreted as urea and nitrogen ingested, mainly in proteins. Increased circulating concentrations of amino acids (AA) in the bloodstream are usually associated with proportional increases in the production and excretion of urea. Previously, we reported results from a randomized, controlled, single-dose, crossover trial in healthy adult volunteers (n = 30) (Trial Registration: ISRCTN11016729), in which a Test product (prolonged-release AA mixture formulated with Physiomimic Technology™ (PT™)) significantly slowed down the release and reduced the peak plasma concentrations of essential AAs compared with a free AA mixture (Reference product) while maintaining essential AA bioavailability. Here, we report an assessment of the nitrogen balance from the same study. The amount of nitrogen contained in plasma AAs, levels of blood urea nitrogen (BUN) (p < 0.0001) and changes in BUN (p < 0.0001) were smaller after the Test product compared with the Reference product. These findings suggest that the production of urea in proportion to systemic AA availability was significantly smaller after the administration of the Test product compared with the Reference product and that the test product conferred the increased utilization of AAs for protein synthesis and reduced their oxidation and conversion to urea. In the clinical setting, it is possible that the effects of PT™ observed on the disposition of free AAs in this study may translate to health benefits in terms of physiological body composition and growth if used for the treatment of subjects with phenylketonuria (PKU). Further investigation in patients with PKU is warranted. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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13 pages, 953 KiB  
Article
Metabolic Control of Patients with Phenylketonuria in a Portuguese Metabolic Centre Comparing Three Different Recommendations
by Viviane Kanufre, Manuela Ferreira Almeida, Catarina Sousa Barbosa, Carla Carmona, Anabela Bandeira, Esmeralda Martins, Sara Rocha, Arlindo Guimas, Rosa Ribeiro, Anita MacDonald, Alex Pinto and Júlio César Rocha
Nutrients 2021, 13(9), 3118; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13093118 - 06 Sep 2021
Cited by 14 | Viewed by 2583
Abstract
Blood phenylalanine (Phe) is used as the primary marker to evaluate metabolic control. Our study aimed to describe the metabolic control of patients with phenylketonuria (PKU) comparing three different treatment recommendations (European guidelines/US guidelines/Portuguese consensus). This was a retrospective, observational, single centre study [...] Read more.
Blood phenylalanine (Phe) is used as the primary marker to evaluate metabolic control. Our study aimed to describe the metabolic control of patients with phenylketonuria (PKU) comparing three different treatment recommendations (European guidelines/US guidelines/Portuguese consensus). This was a retrospective, observational, single centre study in patients with PKU collecting data on blood Phe levels from 2017. Nutritional intake data and sapropterin (BH4) prescription were collected at the last appointment of 2017. The final sample studied included 87 patients (48% females) [13 hyperphenylalaninemia; 47 mild PKU; 27 classical PKU] with a median age of 18 y (range: 1–36 y). The median number of blood Phe measurements for patients was 21 (range: 6–89). In patients aged < 12 y, the median blood Phe level was 300 μmol/L (range 168–480) and 474 μmol/L (range 156–1194) for patients ≥ 12 y. Overall, a median of 83% of blood Phe levels were within the European PKU guidelines target range. In patients aged ≥ 12 years, there was a higher median % of blood Phe levels within the European PKU guidelines target range (≥12 y: 84% vs. <12 y: 56%). In children < 12 y with classical PKU (n = 2), only 34% of blood Phe levels were within target range for all 3 guidelines and 49% with mild PKU (n = 11). Girls had better control than boys (89% vs. 66% median Phe levels within European Guidelines). Although it is clear that 50% or more patients were unable to achieve acceptable metabolic control on current treatment options, a globally agreed upper Phe target associated with optimal outcomes for age groups is necessary. More studies need to examine how clinics with dissimilar resources, different therapeutic Phe targets and frequency of monitoring relate to metabolic control. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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10 pages, 1881 KiB  
Article
Current Practices and Challenges in the Diagnosis and Management of PKU in Latin America: A Multicenter Survey
by Soraia Poloni, Bruna Bento dos Santos, Ana Chiesa, Norma Specola, Marcela Pereyra, Manuel Saborío-Rocafort, María Florencia Salazar, María Jesús Leal-Witt, Gabriela Castro, Felipe Peñaloza, Sunling Palma Wong, Ramsés Badilla Porras, Lourdes Ortiz Paranza, Marta Cristina Sanabria, Marcela Vela Amieva, Marco Morales, Amanda Rocío Caro Naranjo, Antonieta Mahfoud, Ana Rosa Colmenares, Aida Lemes, José Fernando Sotillo-Lindo, Ceila Perez, Laritza Martínez Rey, Georgina María Zayas Torriente, Lilia Farret Refosco, Ida Vanessa Doederlein Schwartz and Veronica Cornejoadd Show full author list remove Hide full author list
Nutrients 2021, 13(8), 2566; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13082566 - 27 Jul 2021
Cited by 7 | Viewed by 3862
Abstract
This study aimed to describe the current practices in the diagnosis and dietary management of phenylketonuria (PKU) in Latin America, as well as the main barriers to treatment. We developed a 44-item online survey aimed at health professionals. After a pilot test, the [...] Read more.
This study aimed to describe the current practices in the diagnosis and dietary management of phenylketonuria (PKU) in Latin America, as well as the main barriers to treatment. We developed a 44-item online survey aimed at health professionals. After a pilot test, the final version was sent to 25 practitioners working with inborn errors of metabolism (IEM) in 14 countries. Our results include 22 centers in 13 countries. Most countries (12/13) screened newborns for PKU. Phenylalanine (Phe) targets at different ages were very heterogeneous among centers, with greater consistency at the 0–1 year age group (14/22 sought 120–240 µmol/L) and the lowest at >12 years (10 targets reported). Most countries had only unflavored powdered amino acid substitutes (10/13) and did not have low-protein foods (8/13). Only 3/13 countries had regional databases of the Phe content of foods, and only 4/22 centers had nutrient analysis software. The perceived obstacles to treatment were: low purchasing power (62%), limited/insufficient availability of low-protein foods (60%), poor adherence, and lack of technical resources to manage the diet (50% each). We observed a heterogeneous scenario in the dietary management of PKU, and most countries experienced a lack of dietary resources for both patients and health professionals. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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16 pages, 2507 KiB  
Article
A Three-Year Longitudinal Study Comparing Bone Mass, Density, and Geometry Measured by DXA, pQCT, and Bone Turnover Markers in Children with PKU Taking L-Amino Acid or Glycomacropeptide Protein Substitutes
by Anne Daly, Wolfgang Högler, Nicola Crabtree, Nick Shaw, Sharon Evans, Alex Pinto, Richard Jackson, Catherine Ashmore, Júlio C. Rocha, Boyd J. Strauss, Gisela Wilcox, William D. Fraser, Jonathan C. Y. Tang and Anita MacDonald
Nutrients 2021, 13(6), 2075; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13062075 - 17 Jun 2021
Cited by 8 | Viewed by 3316
Abstract
In patients with phenylketonuria (PKU), treated by diet therapy only, evidence suggests that areal bone mineral density (BMDa) is within the normal clinical reference range but is below the population norm. Aims: To study longitudinal bone density, mass, and geometry over 36 months [...] Read more.
In patients with phenylketonuria (PKU), treated by diet therapy only, evidence suggests that areal bone mineral density (BMDa) is within the normal clinical reference range but is below the population norm. Aims: To study longitudinal bone density, mass, and geometry over 36 months in children with PKU taking either amino acid (L-AA) or casein glycomacropeptide substitutes (CGMP-AA) as their main protein source. Methodology: A total of 48 subjects completed the study, 19 subjects in the L-AA group (median age 11.1, range 5–16 years) and 29 subjects in the CGMP-AA group (median age 8.3, range 5–16 years). The CGMP-AA was further divided into two groups, CGMP100 (median age 9.2, range 5–16 years) (n = 13), children taking CGMP-AA only and CGMP50 (median age 7.3, range 5–15 years) (n = 16), children taking a combination of CGMP-AA and L-AA. Dual X-ray absorptiometry (DXA) was measured at enrolment and 36 months, peripheral quantitative computer tomography (pQCT) at 36 months only, and serum blood and urine bone turnover markers (BTM) and blood bone biochemistry at enrolment, 6, 12, and 36 months. Results: No statistically significant differences were found between the three groups for DXA outcome parameters, i.e., BMDa (L2–L4 BMDa g/cm2), bone mineral apparent density (L2–L4 BMAD g/cm3) and total body less head BMDa (TBLH g/cm2). All blood biochemistry markers were within the reference ranges, and BTM showed active bone turnover with a trend for BTM to decrease with increasing age. Conclusions: Bone density was clinically normal, although the median z scores were below the population mean. BTM showed active bone turnover and blood biochemistry was within the reference ranges. There appeared to be no advantage to bone density, mass, or geometry from taking a macropeptide-based protein substitute as compared with L-AAs. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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12 pages, 693 KiB  
Article
Growth and Body Composition in PKU Children—A Three-Year Prospective Study Comparing the Effects of L-Amino Acid to Glycomacropeptide Protein Substitutes
by Anne Daly, Wolfgang Högler, Nicola Crabtree, Nick Shaw, Sharon Evans, Alex Pinto, Richard Jackson, Boyd J. Strauss, Gisela Wilcox, Júlio C. Rocha, Catherine Ashmore and Anita MacDonald
Nutrients 2021, 13(4), 1323; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13041323 - 16 Apr 2021
Cited by 12 | Viewed by 2799
Abstract
Protein quality and quantity are important factors in determining lean body (muscle) mass (LBM). In phenylketonuria (PKU), protein substitutes provide most of the nitrogen, either as amino acids (AA) or glycomacropeptide with supplementary amino acids (CGMP-AA). Body composition and growth are important indicators [...] Read more.
Protein quality and quantity are important factors in determining lean body (muscle) mass (LBM). In phenylketonuria (PKU), protein substitutes provide most of the nitrogen, either as amino acids (AA) or glycomacropeptide with supplementary amino acids (CGMP-AA). Body composition and growth are important indicators of long-term health. In a 3-year prospective study comparing the impact of AA and CGMP-AA on body composition and growth in PKU, 48 children were recruited. N = 19 (median age 11.1 years, range 5–15 years) took AA only, n = 16 (median age 7.3 years, range 5–15 years) took a combination of CGMP-AA and AA, (CGMP50) and 13 children (median age 9.2 years, range 5–16 years) took CGMP-AA only (CGMP100). A dual energy X-ray absorptiometry (DXA) scan at enrolment and 36 months measured LBM, % body fat (%BF) and fat mass (FM). Height was measured at enrolment, 12, 24 and 36 months. No correlation or statistically significant differences (after adjusting for age, gender, puberty and phenylalanine blood concentrations) were found between the three groups for LBM, %BF, FM and height. The change in height z scores, (AA 0, CGMP50 +0.4 and CGMP100 +0.7) showed a trend that children in the CGMP100 group were taller, had improved LBM with decreased FM and % BF but this was not statistically significant. There appeared to be no advantage of CGMP-AA compared to AA on body composition after 3-years of follow-up. Although statistically significant differences were not reached, a trend towards improved body composition was observed with CGMP-AA when it provided the entire protein substitute requirement. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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13 pages, 274 KiB  
Article
Accidental Consumption of Aspartame in Phenylketonuria: Patient Experiences
by Ella Newbould, Alex Pinto, Sharon Evans, Suzanne Ford, Mike O’Driscoll, Catherine Ashmore, Anne Daly and Anita MacDonald
Nutrients 2021, 13(2), 707; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13020707 - 23 Feb 2021
Cited by 10 | Viewed by 4885
Abstract
Aspartame is a phenylalanine containing sweetener, added to foods and drinks, which is avoided in phenylketonuria (PKU). However, the amount of phenylalanine provided by aspartame is unidentifiable from food and drinks labels. We performed a cross-sectional online survey aiming to examine the accidental [...] Read more.
Aspartame is a phenylalanine containing sweetener, added to foods and drinks, which is avoided in phenylketonuria (PKU). However, the amount of phenylalanine provided by aspartame is unidentifiable from food and drinks labels. We performed a cross-sectional online survey aiming to examine the accidental aspartame consumption in PKU. 206 questionnaires (58% female) were completed. 55% of respondents (n = 114) were adults with PKU or their parent/carers and 45% (n = 92) were parents/carers of children with PKU. 74% (n = 152/206) had consumed food/drinks containing aspartame. Repeated accidental aspartame consumption was common and more frequent in children (p < 0.0001). The aspartame containing food/drinks accidentally consumed were fizzy drinks (68%, n = 103/152), fruit squash (40%, n = 61/152), chewing gum (30%, n = 46/152), flavoured water (25%, n = 38/152), ready to drink fruit squash cartons (23%, n = 35/152) and sports drinks (21%, n = 32/152). The main reasons described for accidental consumption, were manufacturers’ changing recipes (81%, n = 123/152), inability to check the ingredients in pubs/restaurants/vending machines (59%, n = 89/152) or forgetting to check the label (32%, n = 49/152). 23% (n= 48/206) had been prescribed medicines containing aspartame and 75% (n = 36/48) said that medicines were not checked by medics when prescribed. 85% (n = 164/192) considered the sugar tax made accidental aspartame consumption more likely. Some of the difficulties for patients were aspartame identification in drinks consumed in restaurants, pubs, vending machines (77%, n = 158/206); similarities in appearance of aspartame and non-aspartame products (62%, n = 127/206); time consuming shopping/checking labels (56%, n = 115/206); and unclear labelling (55%, n = 114/206). These issues caused anxiety for the person with PKU (52%, n = 106/206), anxiety for parent/caregivers (46%, n = 95/206), guilt for parent/carers (42%, n = 87/206) and social isolation (42%, n = 87/206). It is important to understand the impact of aspartame and legislation such as the sugar tax on people with PKU. Policy makers and industry should ensure that the quality of life of people with rare conditions such as PKU is not compromised through their action. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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Graphical abstract

10 pages, 589 KiB  
Article
Protein Labelling Accuracy for UK Patients with PKU Following a Low Protein Diet
by Dilyana Kraleva, Sharon Evans, Alex Pinto, Anne Daly, Catherine Ashmore, Kiri Pointon-Bell, Júlio César Rocha and Anita MacDonald
Nutrients 2020, 12(11), 3440; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12113440 - 10 Nov 2020
Cited by 5 | Viewed by 3035
Abstract
A phenylalanine (protein)-restricted diet is the primary treatment for phenylketonuria (PKU). Patients are dependent on food protein labelling to successfully manage their condition. We evaluated the accuracy of protein labelling on packaged manufactured foods from supermarket websites for foods that may be eaten [...] Read more.
A phenylalanine (protein)-restricted diet is the primary treatment for phenylketonuria (PKU). Patients are dependent on food protein labelling to successfully manage their condition. We evaluated the accuracy of protein labelling on packaged manufactured foods from supermarket websites for foods that may be eaten as part of a phenylalanine-restricted diet. Protein labelling information was evaluated for 462 food items (“free from”, n = 159, regular, n = 303), divided into 16 food groups using supermarket website data. Data collection included protein content per portion/100 g when food was “as sold”, “cooked” or “prepared”; cooking methods, and preparation instructions. Labelling errors affecting protein content were observed in every food group, with overall protein labelling unclear in 55% (n = 255/462) of foods. There was misleading, omitted, or erroneous (MOE) information in 43% (n = 68/159) of “free from” foods compared with 62% (n = 187/303) of regular foods, with fewer inaccuracies in “free from” food labelling (p = 0.007). Protein analysis was available for uncooked weight only but not cooked weight for 58% (n = 85/146) of foods; 4% (n = 17/462) had misleading protein content. There was a high rate of incomplete, misleading, or inaccurate data affecting the interpretation of the protein content of food items on supermarket websites. This could adversely affect metabolic control of patients with PKU and warrants serious consideration. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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12 pages, 284 KiB  
Article
A 3 Year Longitudinal Prospective Review Examining the Dietary Profile and Contribution Made by Special Low Protein Foods to Energy and Macronutrient Intake in Children with Phenylketonuria
by Anne Daly, Sharon Evans, Alex Pinto, Catherine Ashmore, Júlio César Rocha and Anita MacDonald
Nutrients 2020, 12(10), 3153; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12103153 - 15 Oct 2020
Cited by 16 | Viewed by 3043
Abstract
The nutritional composition of special low protein foods (SLPFs) is controlled under EU legislation for ‘Foods for Special Medical Purposes (FSMP)’. They are designed to meet the energy needs of patients unable to eat a normal protein containing diet. In phenylketonuria (PKU), the [...] Read more.
The nutritional composition of special low protein foods (SLPFs) is controlled under EU legislation for ‘Foods for Special Medical Purposes (FSMP)’. They are designed to meet the energy needs of patients unable to eat a normal protein containing diet. In phenylketonuria (PKU), the macronutrient contribution of SLPFs has been inadequately examined. Aim: A 3-year longitudinal prospective study investigating the contribution of SLPFs to the macronutrient intake of children with early treated PKU. Methods: 48 children (27 boys) with a mean recruitment age of 9.3 y were studied. Semi-quantitative dietary assessments and food frequency questionnaires (FFQ) were collected three to four times/year for 3 years. Results: The mean energy intake provided by SLPFs was 33% (SD ± 8), and this figure was 42% (SD ± 13) for normal food and 21% (SD ± 5) for protein substitutes (PS). SLPFs supplied a mean intake of 40% carbohydrate (SD ± 10), 51% starch (SD ± 18), 21% sugar (SD ± 8), and 38% fat (SD ± 13). Fibre intake met 83% of the Scientific Advisory Committee on Nutrition (SACN) reference value, with 50% coming from SLPFs with added gums and hydrocolloids. Low protein bread, pasta and milk provided the highest energy contribution, and the intake of sweet SLPFs (e.g., biscuits, cakes, and chocolate) was minimal. Children averaged three portions fruit/vegetable daily, and children aged ≥ 12 y had irregular meal patterns. Conclusion: SLPFs provide essential energy in phenylalanine restricted diets. Optimising the nutritional quality of SLPFs deserves more attention. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
13 pages, 299 KiB  
Article
The Impact of the Use of Glycomacropeptide on Satiety and Dietary Intake in Phenylketonuria
by Anne Daly, Sharon Evans, Alex Pinto, Richard Jackson, Catherine Ashmore, Júlio César Rocha and Anita MacDonald
Nutrients 2020, 12(9), 2704; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12092704 - 04 Sep 2020
Cited by 13 | Viewed by 3862
Abstract
Protein is the most satiating macronutrient, increasing secretion of gastrointestinal hormones and diet induced thermogenesis. In phenylketonuria (PKU), natural protein is restricted with approximately 80% of intake supplied by a synthetic protein source, which may alter satiety response. Casein glycomacropeptide (CGMP-AA), a carbohydrate [...] Read more.
Protein is the most satiating macronutrient, increasing secretion of gastrointestinal hormones and diet induced thermogenesis. In phenylketonuria (PKU), natural protein is restricted with approximately 80% of intake supplied by a synthetic protein source, which may alter satiety response. Casein glycomacropeptide (CGMP-AA), a carbohydrate containing peptide and alternative protein substitute to amino acids (AA), may enhance satiety mediated by its bioactive properties. Aim: In a three-year longitudinal; prospective study, the effect of AA and two different amounts of CGMP-AA (CGMP-AA only (CGMP100) and a combination of CGMP-AA and AA (CGMP50) on satiety, weight and body mass index (BMI) were compared. Methods: 48 children with PKU completed the study. Median ages of children were: CGMP100; (n = 13), 9.2 years; CGMP50; (n = 16), 7.3 years; and AA (n = 19), 11.1 years. Semi-quantitative dietary assessments and anthropometry (weight, height and BMI) were measured every three months. Results: The macronutrient contribution to total energy intake from protein, carbohydrate and fat was similar across the groups. Adjusting for age and gender, no differences in energy intake, weight, BMI, incidence of overweight or obesity was apparent between the groups. Conclusion: In this three-year longitudinal study, there was no indication to support a relationship between CGMP and satiety, as evidenced by decreased energy intake, thereby preventing overweight or obesity. Satiety is a complex multi-system process that is not fully understood. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
11 pages, 402 KiB  
Article
An Observational Study Evaluating the Introduction of a Prolonged-Release Protein Substitute to the Dietary Management of Children with Phenylketonuria
by Anita MacDonald, Catherine Ashmore, Anne Daly, Alex Pinto and Sharon Evans
Nutrients 2020, 12(9), 2686; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12092686 - 03 Sep 2020
Cited by 8 | Viewed by 3706
Abstract
Dietary restriction of phenylalanine combined with a protein substitute prevents intellectual disability in patients with phenylketonuria (PKU). However, current protein substitutes are associated with low adherence owing to unpalatability and burdensome administration regimens. This prospective, observational acceptability study in children with PKU assessed [...] Read more.
Dietary restriction of phenylalanine combined with a protein substitute prevents intellectual disability in patients with phenylketonuria (PKU). However, current protein substitutes are associated with low adherence owing to unpalatability and burdensome administration regimens. This prospective, observational acceptability study in children with PKU assessed the use of a prolonged-release protein substitute designed with an ethyl cellulose and arginate coating masking the bitter taste, smell and reducing the osmolarity of free amino acids. The study product was mixed with the subject’s food or drink and replaced ≥1 dose per day of the subject’s usual protein substitute for 7 days. Seven of 13 subjects were able to take their prescribed dose over the 7 day period. Most subjects mixed the test protein substitute with food or fruit juice. Reduced blood phenylalanine levels (n = 5) and improved phenylalanine/tyrosine ratio (n = 4) were recorded from baseline to Day 7, respectively. Four subjects reported fewer gastrointestinal symptoms compared to baseline. There were no cases of diarrhoea, constipation, bloating, nausea or vomiting. No adverse reactions were reported. In conclusion, the novel prolonged-release protein substitute was taken in a different way to a typical protein substitute and enabled satisfactory blood phenylalanine control. The study product was well tolerated; subjects experienced fewer gastrointestinal symptoms than with their previous treatment. Although the results of this pilot study provide reassuring data, longer-term studies evaluating adherence and blood phenylalanine control are necessary. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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13 pages, 455 KiB  
Article
Preliminary Investigation to Review If a Glycomacropeptide Compared to L-Amino Acid Protein Substitute Alters the Pre- and Postprandial Amino Acid Profile in Children with Phenylketonuria
by Anne Daly, Sharon Evans, Alex Pinto, Richard Jackson, Catherine Ashmore, Júlio César Rocha and Anita MacDonald
Nutrients 2020, 12(8), 2443; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12082443 - 14 Aug 2020
Cited by 6 | Viewed by 3526
Abstract
In Phenylketonuria (PKU), the peptide structure of the protein substitute (PS), casein glycomacropeptide (CGMP), is supplemented with amino acids (CGMP-AA). CGMP may slow the rate of amino acid (AA) absorption compared with traditional phenylalanine-free amino acids (Phe-free AA), which may improve nitrogen utilization, [...] Read more.
In Phenylketonuria (PKU), the peptide structure of the protein substitute (PS), casein glycomacropeptide (CGMP), is supplemented with amino acids (CGMP-AA). CGMP may slow the rate of amino acid (AA) absorption compared with traditional phenylalanine-free amino acids (Phe-free AA), which may improve nitrogen utilization, decrease urea production, and alter insulin response. Aim: In children with PKU, to compare pre and postprandial AA concentrations when taking one of three PS’s: Phe-free AA, CGMP-AA 1 or 2. Methods: 43 children (24 boys, 19 girls), median age 9 years (range 5–16 years) were studied; 11 took CGMP-AA1, 18 CGMP-AA2, and 14 Phe-free AA. Early morning fasting pre and 2 h postprandial blood samples were collected for quantitative AA on one occasion. A breakfast with allocated 20 g protein equivalent from PS was given post fasting blood sample. Results: There was a significant increase in postprandial AA for all individual AAs with all three PS. Postprandial AA histidine (p < 0.001), leucine (p < 0.001), and tyrosine (p < 0.001) were higher in CGMP-AA2 than CGMP-AA1, and leucine (p < 0.001), threonine (p < 0.001), and tyrosine (p = 0.003) higher in GCMP-AA2 than Phe-free AA. This was reflective of the AA composition of the three different PS’s. Conclusions: In PKU, the AA composition of CGMP-AA influences 2 h postprandial AA composition, suggesting that a PS derived from CGMP-AA may be absorbed similarly to Phe-free AA, but this requires further investigation. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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12 pages, 256 KiB  
Article
Uniformity of Food Protein Interpretation Amongst Dietitians for Patients with Phenylketonuria (PKU): 2020 UK National Consensus Statements
by Sharon Evans, Sarah Adam, Sandra Adams, Heather Allen, Catherine Ashmore, Sarah Bailey, Janette Banks, Harriet Churchill, Barbara Cochrane, Jennifer Cook, Clare Dale, Anne Daly, Marjorie Dixon, Carolyn Dunlop, Charlotte Ellerton, Anita Emm, Sarah Firman, Suzanne Ford, Moira French, Joanna Gribben, Anne Grimsley, Ide Herlihy, Melanie Hill, Shirley Judd, Karen Lang, Jo Males, Joy McDonald, Nicola McStravick, Chloe Millington, Camille Newby, Catharine Noble, Rachel Pereira, Alex Pinto, Louise Robertson, Abigail Robotham, Kathleen Ross, Kath Singleton, Rachel Skeath, Allyson Terry, Karen Van Wyk, Fiona White, Lucy White, Jo Wildgoose, Alison Woodall and Anita MacDonaldadd Show full author list remove Hide full author list
Nutrients 2020, 12(8), 2205; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12082205 - 24 Jul 2020
Cited by 13 | Viewed by 4558
Abstract
In phenylketonuria (PKU), variable dietary advice provided by health professionals and social media leads to uncertainty for patients/caregivers reliant on accurate, evidence based dietary information. Over four years, 112 consensus statements concerning the allocation of foods in a low phenylalanine diet for PKU [...] Read more.
In phenylketonuria (PKU), variable dietary advice provided by health professionals and social media leads to uncertainty for patients/caregivers reliant on accurate, evidence based dietary information. Over four years, 112 consensus statements concerning the allocation of foods in a low phenylalanine diet for PKU were developed by the British Inherited Metabolic Disease Dietitians Group (BIMDG-DG) from 34 PKU treatment centres, utilising 10 rounds of Delphi consultation to gain a majority (≥75%) decision. A mean of 29 UK dietitians (range: 18–40) and 18 treatment centres (range: 13–23) contributed in each round. Statements encompassed all foods/food groups divided into four categories based on defined protein/phenylalanine content: (1) foods high in protein/phenylalanine (best avoided); (2) foods allowed without restriction including fruit/vegetables containing phenylalanine ≤75 mg/100 g and most foods containing protein ≤0.5 g/100 g; (3) foods that should be calculated/weighed as an exchange food if they contain protein exchange ingredients (categorized into foods with a protein content of: >0.1 g/100 g (milk/plant milks only), >0.5 g/100 g (bread/pasta/cereal/flours), >1 g/100 g (cook-in/table-top sauces/dressings), >1.5 g/100 g (soya sauces)); and (4) fruit/vegetables containing phenylalanine >75 mg/100 g allocated as part of the protein/phenylalanine exchange system. These statements have been endorsed and translated into practical dietary management advice by the medical advisory dietitians for the National Society for PKU (NSPKU). Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
19 pages, 924 KiB  
Article
Special Low Protein Foods in the UK: An Examination of Their Macronutrient Composition in Comparison to Regular Foods
by Georgina Wood, Sharon Evans, Kiri Pointon-Bell, Júlio César Rocha and Anita MacDonald
Nutrients 2020, 12(6), 1893; https://0-doi-org.brum.beds.ac.uk/10.3390/nu12061893 - 25 Jun 2020
Cited by 14 | Viewed by 4586
Abstract
Special low protein foods (SLPFs) are essential in a low phenylalanine diet for treating phenylketonuria (PKU). With little known about their nutritional composition, all SLPFs on UK prescription were studied (n = 146) and compared to equivalent protein-containing foods (n = [...] Read more.
Special low protein foods (SLPFs) are essential in a low phenylalanine diet for treating phenylketonuria (PKU). With little known about their nutritional composition, all SLPFs on UK prescription were studied (n = 146) and compared to equivalent protein-containing foods (n = 190). SLPF nutritional analysis was obtained from suppliers/manufacturers. Comparable information about regular protein-containing foods was obtained from online UK supermarkets. Similar foods were grouped together, with mean nutritional values calculated for each subgroup (n = 40) and percentage differences determined between SLPFs and regular food subgroups. All SLPF subgroups contained 43–100% less protein than regular foods. Sixty-three percent (n = 25/40) of SLPF subgroups contained less total fat with palm oil (25%, n = 36/146) and hydrogenated vegetable oil (23%, n = 33/146) key fat sources. Sixty-eight percent (n = 27/40) of SLPF subgroups contained more carbohydrate, with 72% (n = 105/146) containing added sugar. Key SLPF starch sources were maize/corn (72%; n = 105/146). Seventy-seven percent (n = 113/146) of SLPFs versus 18% (n = 34/190) of regular foods contained added fibre, predominantly hydrocolloids. Nine percent of SLPFs contained phenylalanine > 25 mg/100 g and sources of phenylalanine/protein in their ingredient lists. Stricter nutritional composition regulations for SLPFs are required, identifying maximum upper limits for macronutrients and phenylalanine, and fat and carbohydrate sources that are associated with healthy outcomes. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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Review

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15 pages, 1583 KiB  
Review
The Impact of the Quality of Nutrition and Lifestyle in the Reproductive Years of Women with PKU on the Long-Term Health of Their Children
by Maria Inês Gama, Alex Pinto, Anne Daly, Júlio César Rocha and Anita MacDonald
Nutrients 2022, 14(5), 1021; https://0-doi-org.brum.beds.ac.uk/10.3390/nu14051021 - 28 Feb 2022
Cited by 1 | Viewed by 3171
Abstract
A woman’s nutritional status before and during pregnancy can affect the health of her progeny. Phenylketonuria (PKU), a rare disorder causing high blood and brain phenylalanine (Phe) concentrations, is associated with neurocognitive disability. Lifelong treatment is mainly dietetic with a Phe-restricted diet, supplemented [...] Read more.
A woman’s nutritional status before and during pregnancy can affect the health of her progeny. Phenylketonuria (PKU), a rare disorder causing high blood and brain phenylalanine (Phe) concentrations, is associated with neurocognitive disability. Lifelong treatment is mainly dietetic with a Phe-restricted diet, supplemented with a low-Phe protein substitute. Treatment adherence commonly decreases in adolescence, with some adults ceasing dietary treatment. In maternal PKU, elevated blood Phe is harmful to the fetus so a strict Phe-restricted diet must be re-established preconception, and this is particularly difficult to achieve. A woman’s reproductive years introduces an opportunity to adopt healthier behaviours to prepare for successful pregnancies and positive health outcomes for both themselves and their children. Several factors can influence the health status of women with PKU. Political, socioeconomic, and individual food and lifestyle choices affect diet quality, metabolic control, and epigenetics, which then pre-condition the overall maternal health and long-term health of the child. Here, we reflect on a comprehensive approach to treatment and introduce practical recommendations to optimize the wellbeing of women with PKU and the resultant health of their children. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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17 pages, 353 KiB  
Review
Glycomacropeptide in PKU—Does It Live Up to Its Potential?
by Anne Daly, Alex Pinto, Sharon Evans and Anita MacDonald
Nutrients 2022, 14(4), 807; https://0-doi-org.brum.beds.ac.uk/10.3390/nu14040807 - 14 Feb 2022
Cited by 10 | Viewed by 3611
Abstract
The use of casein glycomacropeptide (CGMP) as a protein substitute in phenylketonuria (PKU) has grown in popularity. CGMP is derived from κ casein and is a sialic-rich glycophosphopeptide, formed by the action of chymosin during the production of cheese. It comprises 20–25% of [...] Read more.
The use of casein glycomacropeptide (CGMP) as a protein substitute in phenylketonuria (PKU) has grown in popularity. CGMP is derived from κ casein and is a sialic-rich glycophosphopeptide, formed by the action of chymosin during the production of cheese. It comprises 20–25% of total protein in whey products and has key biomodulatory properties. In PKU, the amino acid sequence of CGMP has been adapted by adding the amino acids histidine, leucine, methionine, tyrosine and tryptophan naturally low in CGMP. The use of CGMP compared to mono amino acids (L-AAs) as a protein substitute in the treatment of PKU promises several potential clinical benefits, although any advantage is supported only by evidence from non-PKU conditions or PKU animal models. This review examines if there is sufficient evidence to support the bioactive properties of CGMP leading to physiological benefits when compared to L-AAs in PKU, with a focus on blood phenylalanine control and stability, body composition, growth, bone density, breath odour and palatability. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
25 pages, 3148 KiB  
Review
Protein Substitute Requirements of Patients with Phenylketonuria on BH4 Treatment: A Systematic Review and Meta-Analysis
by Fatma Ilgaz, Cyril Marsaux, Alex Pinto, Rani Singh, Carmen Rohde, Erdem Karabulut, Hülya Gökmen-Özel, Mirjam Kuhn and Anita MacDonald
Nutrients 2021, 13(3), 1040; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13031040 - 23 Mar 2021
Cited by 15 | Viewed by 6940
Abstract
The traditional treatment for phenylketonuria (PKU) is a phenylalanine (Phe)-restricted diet, supplemented with a Phe-free/low-Phe protein substitute. Pharmaceutical treatment with synthetic tetrahydrobiopterin (BH4), an enzyme cofactor, allows a patient subgroup to relax their diet. However, dietary protocols guiding the adjustments of protein equivalent [...] Read more.
The traditional treatment for phenylketonuria (PKU) is a phenylalanine (Phe)-restricted diet, supplemented with a Phe-free/low-Phe protein substitute. Pharmaceutical treatment with synthetic tetrahydrobiopterin (BH4), an enzyme cofactor, allows a patient subgroup to relax their diet. However, dietary protocols guiding the adjustments of protein equivalent intake from protein substitute with BH4 treatment are lacking. We systematically reviewed protein substitute usage with long-term BH4 therapy. Electronic databases were searched for articles published between January 2000 and March 2020. Eighteen studies (306 PKU patients) were eligible. Meta-analyses demonstrated a significant increase in Phe and natural protein intakes and a significant decrease in protein equivalent intake from protein substitute with cofactor therapy. Protein substitute could be discontinued in 51% of responsive patients, but was still required in 49%, despite improvement in Phe tolerance. Normal growth was maintained, but micronutrient deficiency was observed with BH4 treatment. A systematic protocol to increase natural protein intake while reducing protein substitute dose should be followed to ensure protein and micronutrient requirements are met and sustained. We propose recommendations to guide healthcare professionals when adjusting dietary prescriptions of PKU patients on BH4. Studies investigating new therapeutic options in PKU should systematically collect data on protein substitute and natural protein intakes, as well as other nutritional factors. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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15 pages, 311 KiB  
Review
Protein Substitutes in PKU; Their Historical Evolution
by Anne Daly, Sharon Evans, Alex Pinto, Catherine Ashmore and Anita MacDonald
Nutrients 2021, 13(2), 484; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13020484 - 02 Feb 2021
Cited by 26 | Viewed by 5680
Abstract
Protein substitutes developed for phenylketonuria (PKU) are a synthetic source of protein commonly based on L-amino acids. They are essential in the treatment of phenylketonuria (PKU) and other amino acid disorders, allowing the antagonistic amino acid to be removed but with the safe [...] Read more.
Protein substitutes developed for phenylketonuria (PKU) are a synthetic source of protein commonly based on L-amino acids. They are essential in the treatment of phenylketonuria (PKU) and other amino acid disorders, allowing the antagonistic amino acid to be removed but with the safe provision of all other amino acids necessary for maintaining normal physiological function. They were first formulated by a chemist and used experimentally on a 2-year-old girl with PKU and their nutritional formulations and design have improved over time. Since 2008, a bioactive macropeptide has been used as a base for protein substitutes in PKU, with potential benefits of improved bone and gut health, nitrogen retention, and blood phenylalanine control. In 2018, animal studies showed that physiomimic technology coating the amino acids with a polymer allows a slow release of amino acids with an improved physiological profile. History has shown that in PKU, the protein substitute’s efficacy is determined by its nutritional profile, amino acid composition, dose, timing, distribution, and an adequate energy intake. Protein substitutes are often given little importance, yet their pharmacological actions and clinical benefit are pivotal when managing PKU. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)

Other

Jump to: Research, Review

19 pages, 2379 KiB  
Systematic Review
Is the Phenylalanine-Restricted Diet a Risk Factor for Overweight or Obesity in Patients with Phenylketonuria (PKU)? A Systematic Review and Meta-Analysis
by Catarina Rodrigues, Alex Pinto, Ana Faria, Diana Teixeira, Annemiek M. J. van Wegberg, Kirsten Ahring, François Feillet, Conceição Calhau, Anita MacDonald, André Moreira-Rosário and Júlio César Rocha
Nutrients 2021, 13(10), 3443; https://0-doi-org.brum.beds.ac.uk/10.3390/nu13103443 - 28 Sep 2021
Cited by 28 | Viewed by 4220
Abstract
Although there is a general assumption that a phenylalanine (Phe)-restricted diet promotes overweight in patients with phenylketonuria (PKU), it is unclear if this presumption is supported by scientific evidence. This systematic review aimed to determine if patients with PKU are at a higher [...] Read more.
Although there is a general assumption that a phenylalanine (Phe)-restricted diet promotes overweight in patients with phenylketonuria (PKU), it is unclear if this presumption is supported by scientific evidence. This systematic review aimed to determine if patients with PKU are at a higher risk of overweight compared to healthy individuals. A literature search was carried out on PubMed, Cochrane Library, and Embase databases. Risk of bias of individual studies was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies, and the quality of the evidence for each outcome was assessed using the NutriGrade scoring system. From 829 articles identified, 15 were included in the systematic review and 12 in the meta-analysis. Body mass index (BMI) was similar between patients with PKU and healthy controls, providing no evidence to support the idea that a Phe-restricted diet is a risk factor for the development of overweight. However, a subgroup of patients with classical PKU had a significantly higher BMI than healthy controls. Given the increasing prevalence of overweight in the general population, patients with PKU require lifelong follow-up, receiving personalised nutritional counselling, with methodical nutritional status monitoring from a multidisciplinary team in inherited metabolic disorders. Full article
(This article belongs to the Special Issue Diet Therapy and Nutritional Management of Phenylketonuria)
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