{"id":{"repo_id":"plymouth","oai_identifier":"oai:pearl.plymouth.ac.uk:hp-theses-1031"},"canonical_url":"https://search.dev.ndltd.org/etd/plymouth/oai:pearl.plymouth.ac.uk:hp-theses-1031","repository":{"repo_id":"plymouth","name":"University of Plymouth","base_url":"https://pearl.plymouth.ac.uk/do/oai"},"display":{"title":"Factors affecting metabolism and metabolic control in phenylketonuria","abstract":"Phenylketonuria (PKU) is an inherited metabolic disorder treated by a phenylalanine restricted diet in order to avoid neurocognitive impairment. Blood phenylalanine is the main outcome marker which is modulated by many dietary factors. Traditionally, L-amino acid-based protein substitutes are the main nitrogen source but more recently glycomacropeptide-based protein substitutes (GMP) have been introduced and are associated with several health benefits. The following aspects were studied in this thesis: 1) metabolic control achieved in patients with PKU compared with the European PKU guidelines; 2) life-long change in natural protein tolerance; 3) impact on metabolic control of different natural protein sources (animal vs. plant); 4) effect of unmeasured amounts of fruit and vegetables containing phenylalanine 76-100mg/100g on metabolic control; and 5) health benefits of GMP.<br/>The results of these studies showed that blood phenylalanine increased with age especially in patients with classical PKU (cPKU) and a higher frequency of blood phenylalanine monitoring was associated with better metabolic control. Natural protein (NP) intake was at its highest in patients aged 19-30y and patients with cPKU tolerated less than 50% of NP compared with patients with mild PKU (mPKU). Over restriction of NP was observed in mPKU patients. Sixty five percent (n=26/40) were able to increase NP by a median of 12g/day without loss of metabolic control. Animal protein sources had a higher impact on blood phenylalanine control compared with plant sources. However, some patients were unable to tolerate fruit and vegetables containing phenylalanine 76-100 mg/100g when given in uncontrolled amounts. Furthermore, exchange-free foods in the current dietary system added an extra 40% NP to the prescribed amount without any negative impact on blood phenylalanine control. Although GMP improved<br/>gastrointestinal symptoms, it had a negative impact on blood phenylalanine control when providing 100% of the protein equivalent requirements from protein substitute.<br/>Overall, this research program described novel data that will impact future PKU guidelines and will help influence and improve the daily care of patients with PKU.","abstract_html":"Phenylketonuria (PKU) is an inherited metabolic disorder treated by a phenylalanine restricted diet in order to avoid neurocognitive impairment. Blood phenylalanine is the main outcome marker which is modulated by many dietary factors. Traditionally, L-amino acid-based protein substitutes are the main nitrogen source but more recently glycomacropeptide-based protein substitutes (GMP) have been introduced and are associated with several health benefits. The following aspects were studied in this thesis: 1) metabolic control achieved in patients with PKU compared with the European PKU guidelines; 2) life-long change in natural protein tolerance; 3) impact on metabolic control of different natural protein sources (animal vs. plant); 4) effect of unmeasured amounts of fruit and vegetables containing phenylalanine 76-100mg/100g on metabolic control; and 5) health benefits of GMP.&lt;br/&gt;The results of these studies showed that blood phenylalanine increased with age especially in patients with classical PKU (cPKU) and a higher frequency of blood phenylalanine monitoring was associated with better metabolic control. Natural protein (NP) intake was at its highest in patients aged 19-30y and patients with cPKU tolerated less than 50% of NP compared with patients with mild PKU (mPKU). Over restriction of NP was observed in mPKU patients. Sixty five percent (n=26/40) were able to increase NP by a median of 12g/day without loss of metabolic control. Animal protein sources had a higher impact on blood phenylalanine control compared with plant sources. However, some patients were unable to tolerate fruit and vegetables containing phenylalanine 76-100 mg/100g when given in uncontrolled amounts. Furthermore, exchange-free foods in the current dietary system added an extra 40% NP to the prescribed amount without any negative impact on blood phenylalanine control. Although GMP improved&lt;br/&gt;gastrointestinal symptoms, it had a negative impact on blood phenylalanine control when providing 100% of the protein equivalent requirements from protein substitute.&lt;br/&gt;Overall, this research program described novel data that will impact future PKU guidelines and will help influence and improve the daily care of patients with PKU.","abstract_has_math":false,"creators":["Amorim Pinto, Alex"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Anita MacDonald, Júlio César Rocha, Anne Payne, Mary Hickson"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-01-01T08:00:00Z","date_published":"2025-01-01T08:00:00Z","updated_at":"2026-07-24T03:49:35Z","subjects":["Phenylketonuria","Phenylalanine","Metabolic control"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://pearl.plymouth.ac.uk/hp-theses/29","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Anita MacDonald, Júlio César Rocha, Anne Payne, Mary Hickson"]},{"key":"dc:creator","label":"Author","values":["Amorim Pinto, Alex"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2025-06-16T07:00:00Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-01-01T08:00:00Z"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Phenylketonuria","Phenylalanine","Metabolic control"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://pearl.plymouth.ac.uk/hp-theses/29"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Phenylketonuria (PKU) is an inherited metabolic disorder treated by a phenylalanine restricted diet in order to avoid neurocognitive impairment. Blood phenylalanine is the main outcome marker which is modulated by many dietary factors. Traditionally, L-amino acid-based protein substitutes are the main nitrogen source but more recently glycomacropeptide-based protein substitutes (GMP) have been introduced and are associated with several health benefits. The following aspects were studied in this thesis: 1) metabolic control achieved in patients with PKU compared with the European PKU guidelines; 2) life-long change in natural protein tolerance; 3) impact on metabolic control of different natural protein sources (animal vs. plant); 4) effect of unmeasured amounts of fruit and vegetables containing phenylalanine 76-100mg/100g on metabolic control; and 5) health benefits of GMP.<br/>The results of these studies showed that blood phenylalanine increased with age especially in patients with classical PKU (cPKU) and a higher frequency of blood phenylalanine monitoring was associated with better metabolic control. Natural protein (NP) intake was at its highest in patients aged 19-30y and patients with cPKU tolerated less than 50% of NP compared with patients with mild PKU (mPKU). Over restriction of NP was observed in mPKU patients. Sixty five percent (n=26/40) were able to increase NP by a median of 12g/day without loss of metabolic control. Animal protein sources had a higher impact on blood phenylalanine control compared with plant sources. However, some patients were unable to tolerate fruit and vegetables containing phenylalanine 76-100 mg/100g when given in uncontrolled amounts. Furthermore, exchange-free foods in the current dietary system added an extra 40% NP to the prescribed amount without any negative impact on blood phenylalanine control. Although GMP improved<br/>gastrointestinal symptoms, it had a negative impact on blood phenylalanine control when providing 100% of the protein equivalent requirements from protein substitute.<br/>Overall, this research program described novel data that will impact future PKU guidelines and will help influence and improve the daily care of patients with PKU."]},{"key":"dc:title","label":"Title","values":["Factors affecting metabolism and metabolic control in phenylketonuria"]}]}],"canonical_facts":{"dc:contributor":["Anita MacDonald, Júlio César Rocha, Anne Payne, Mary Hickson"],"dc:creator":["Amorim Pinto, Alex"],"dc:date.available":["2025-06-16T07:00:00Z"],"dc:date.issued":["2025-01-01T08:00:00Z"],"dc:description.abstract":["Phenylketonuria (PKU) is an inherited metabolic disorder treated by a phenylalanine restricted diet in order to avoid neurocognitive impairment. Blood phenylalanine is the main outcome marker which is modulated by many dietary factors. Traditionally, L-amino acid-based protein substitutes are the main nitrogen source but more recently glycomacropeptide-based protein substitutes (GMP) have been introduced and are associated with several health benefits. The following aspects were studied in this thesis: 1) metabolic control achieved in patients with PKU compared with the European PKU guidelines; 2) life-long change in natural protein tolerance; 3) impact on metabolic control of different natural protein sources (animal vs. plant); 4) effect of unmeasured amounts of fruit and vegetables containing phenylalanine 76-100mg/100g on metabolic control; and 5) health benefits of GMP.<br/>The results of these studies showed that blood phenylalanine increased with age especially in patients with classical PKU (cPKU) and a higher frequency of blood phenylalanine monitoring was associated with better metabolic control. Natural protein (NP) intake was at its highest in patients aged 19-30y and patients with cPKU tolerated less than 50% of NP compared with patients with mild PKU (mPKU). Over restriction of NP was observed in mPKU patients. Sixty five percent (n=26/40) were able to increase NP by a median of 12g/day without loss of metabolic control. Animal protein sources had a higher impact on blood phenylalanine control compared with plant sources. However, some patients were unable to tolerate fruit and vegetables containing phenylalanine 76-100 mg/100g when given in uncontrolled amounts. Furthermore, exchange-free foods in the current dietary system added an extra 40% NP to the prescribed amount without any negative impact on blood phenylalanine control. Although GMP improved<br/>gastrointestinal symptoms, it had a negative impact on blood phenylalanine control when providing 100% of the protein equivalent requirements from protein substitute.<br/>Overall, this research program described novel data that will impact future PKU guidelines and will help influence and improve the daily care of patients with PKU."],"dc:identifier":["https://pearl.plymouth.ac.uk/hp-theses/29"],"dc:language":["eng"],"dc:subject":["Phenylketonuria","Phenylalanine","Metabolic control"],"dc:title":["Factors affecting metabolism and metabolic control in phenylketonuria"],"dc:type":["Thesis"]},"updated_at":"2026-07-24T03:49:35Z"}