{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T09:03:58Z","timestamp":1784624638309,"version":"3.55.0"},"reference-count":57,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T00:00:00Z","timestamp":1784592000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Galen Ltd."}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nutrients"],"abstract":"<jats:p>Background\/Objectives: In phenylketonuria (PKU), adherence to protein substitute (PS) is frequently suboptimal due to poor palatability, high volume, and sensory fatigue. A novel phenylalanine (Phe)-free L-amino acid microtablet PS has been developed to address these barriers. The microtablets incorporate a cellulose-based taste-masking coating and a sodium-alginate inner matrix intended to enable controlled amino acid release over approximately three hours. This study evaluated their short-term tolerability, acceptability, and adherence in children with PKU, with extended follow-up in a subgroup. Methods: A 7-day observational study was conducted in participants with PKU aged \u22653 years on a low-Phe diet in a single centre. The test product provided protein equivalent (PE) 54 g\/100 g. Participants replaced at least one daily dose of their usual PS with the test product, providing 10 g or 20 g\/day PE, with one child receiving 80 g\/day. Daily gastrointestinal (GI) symptoms, PS intake, and adherence were recorded. Acceptability was assessed using structured ratings of palatability, ease of use, and overall preference. Longer-term tolerability and acceptability were then assessed in four adolescents who elected to continue the test product for an additional 28 days. Results: Ten participants completed the 7-day study. Adherence to the test product was high (80%), exceeding adherence to participants\u2019 usual PS (70%). At baseline, nine participants reported none\/mild GI symptoms, most commonly flatulence. One participant reported moderate\/severe symptoms including constipation, flatulence, diarrhoea, bloating, burping, and abdominal discomfort. By day 7, all participants reported no or mild symptoms, with complete resolution in the child with moderate\/severe baseline symptoms. Acceptability ratings were comparable between the test product and usual PS, and nine children (90%) reported no difficulty taking the test product. During the 28-day extension, adherence remained high, GI tolerance was maintained, and improved preference was noted, particularly due to reduced aftertaste. Conclusions: This novel slow-release PS microtablet was well tolerated, acceptable, and associated with high adherence. Its taste-masked, low-volume format offered practical advantages that may support sustained dietary adherence. Longer-term controlled studies are necessary to confirm these findings.<\/jats:p>","DOI":"10.3390\/nu18142375","type":"journal-article","created":{"date-parts":[[2026,7,21]],"date-time":"2026-07-21T08:14:27Z","timestamp":1784621667000},"page":"2375","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Use of a Slow-Release Phenylalanine-Free Microtablet Protein Substitute in Children and Adolescents with Phenylketonuria: An Observational Pilot Study"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4859-5288","authenticated-orcid":false,"given":"Martina","family":"Tosi","sequence":"first","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2579-8699","authenticated-orcid":false,"given":"Anne","family":"Daly","sequence":"additional","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Catherine","family":"Ashmore","sequence":"additional","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2941-9505","authenticated-orcid":false,"given":"Ozlem","family":"Yilmaz Nas","sequence":"additional","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8206-0829","authenticated-orcid":false,"given":"Alex","family":"Pinto","sequence":"additional","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7654-3621","authenticated-orcid":false,"given":"Sharon","family":"Evans","sequence":"additional","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2896-3509","authenticated-orcid":false,"given":"Anita","family":"MacDonald","sequence":"additional","affiliation":[{"name":"Department of Dietetics, Birmingham Women\u2019s and Children\u2019s Hospital, Birmingham B4 6NH, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,7,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"109125","DOI":"10.1016\/j.ymgme.2025.109125","article-title":"European Guidelines on Diagnosis and Treatment of Phenylketonuria: First Revision","volume":"145","author":"MacDonald","year":"2025","journal-title":"Mol. 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