Low protein staple foods, nutritional status and disease management in children and adults with phenylketonuria

Cochrane, Barbara Karen (2014) Low protein staple foods, nutritional status and disease management in children and adults with phenylketonuria. MSc(R) thesis, University of Glasgow.

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Introduction: Phenylketonuria (PKU) is an autosomal, recessive inborn error of metabolism caused by a deficiency of the enzyme Phenylalanine Hydroxylase (PAH). Reduced activity or absence of PAH results in increased concentrations of phenylalanine in plasma and brain, which if not addressed will result in severe disability and reduced quality of life.
The accepted management of PKU is to restrict intake of dietary phenylalanine and to adhere to a semi-artificial diet which consists of: a phenylalanine free protein substitute; measured amounts of phenylalanine containing foods; specially manufactured low protein staple foods (LPSF) and vir-tually unrestricted use of phenylalanine free natural foods. Dietary restriction of phenylalanine was first reported in the early 1950’s and although the use, format and efficacy of the protein substitute has been well researched, evidence for the use of the LPSF is scarce.
Anecdotally the LPSF are believed to play a substantial role in PKU management and con-tribute to the nutritional requirements of patients. However, how patients and their carers perceive their usefulness and the role they play in the overall management of the disease has not been evaluat-ed. Recommendations exist for the amount of LPSF required by patients has been produced by the NSPKU society, but are not evidence based.

Aim: To evaluate the contribution LPSF make to the typical diet of children with PKU. To explore any association between LPSF and nutritional status, quality of life, diet variety and any issues pa-tients and carers may face when obtaining supplies.

Method: The use of LPSF in PKU management was evaluated in two ways: a) by a survey of adult patients and carers of children from metabolic centres throughout Scotland, to explore perception of the need for LPSF and any issues faced when obtaining supplies, b) a cross-sectional study using pa-tients from one of the metabolic centres to determine the contribution these foods make to the nutri-tional status and quality of life. This was achieved by allocating patients into user groups dependent on daily use of LPSF using food diaries and and Food Frequency Questionnaire (FFQ).

Study 1: 178 questionnaires were sent to patients with PKU in Scotland returning a response rate of 46%. 97% of patients and carers who responded understood the need for LPSF in managing their condition, with 96% using the LPSF to control phenylalanine levels; 80% used the foods to provide diet variety and satisfy appetite. The most common foods requested were core LPSF of pasta and pasta products (77% of monthly prescriptions); flour mix (61%). Greater than 40% of respondents reported that the sensory properties of LPSF were good. However, 49% of respondents experienced comments from primary health care providers when requesting prescriptions, with 59% of these hav-ing a comment of a negative nature which affected the number of prescription requests made. Of the respondents 50% ordered less than the amount of LPSF recommended by the NSPKU society. When questioned about use of a home delivery service, 51% used this service for ordering LPSF and 68% had attended cookery workshops arranged by their dietitian. No information regarding disease se-verity was requested for this survey.

Study 2: 40 patients (children aged between 2-17 years: 56% (n=23) male) were recruited of whom 30 (75%) completed the seven-day food diary and FFQ. 67% (n=27) had classical PKU; 7.5% mod-erate (n=3) and 25% (n=10) having mild PKU (exchanges / day: 2-6 ; 7-8; 9-13). Of the children, 67% (n=27) had a SDS BMI within the normal range; 22% (n=9) were overweight; 7% (n=3) obese. Those of secondary school age (27%; n=11) took significantly less energy (%EAR) from the protein substitute than the younger children (p=0.007). When the subjects were allocated into LPSF user groups, no difference between SIMD score, quality of life domains, metabolic control or height was observed between the groups. However, the low users of the LPSF had a significantly higher SDS weight (p=0.047) and SDS BMI ((p=0.036). Children from the mildest disease category recorded the lowest amount of energy from the LPSF (p=0.012), and ingested significantly more energy from snack foods (which included both LPSF and regular snack foods) [high vs. medium vs. low: median (IQR): 12% (11); 14% (13); 36% (26) (p=0.010)]. All patients from the three LPSF user groups took less than 50% of non-protein energy (%EAR) from LPSF (0-49%). Low users in particular only took between 0-17% of the recommended number of units suggested by the NSPKU society. The use of food from groups as outlined in the NDNS survey was similar for children with PKU as with the general population however intake of all food groups was lower, especially in the potatoes and cereal (including LPSF) groups.

Conclusion: Patients and their carers have a positive attitude and perception on the use and need for LPSF in the management of their diet for PKU, but have issues in obtaining supplies. Low users of LPSF were in the milder disease category and had a greater intake of energy from snack foods, also a higher SDS weight and SDS BMI.
Low users of LPSF who have milder mutations of PKU should be encouraged by their meta-bolic specialists in the use of use some protein dense foods to provide their phenylalanine require-ments. This would allow the use of a greater amount of LPSF to ensure that energy needs are met by the staple LPSF rather than regular high energy snack type foods. Support by specialists in the meta-bolic centres to aid parents and carers obtain sufficient supplies of LPSF in a timely manner is essen-tial to promote use of product.
Further studies are needed to determine the perception of the usefulness of LPSF in the man-agement of PKU by patients with mild disease and by low users of LPSF. In addition there is a need to explore whether it is low LPSF users who find it most difficult to obtain supplies. Studies with the adult PKU population exploring any association between obesity and use of LPSF are also necessary given the lack of information in this group of patients.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Phenylketonuria, low protein staple foods, nutritional status, disease management
Subjects: R Medicine > RJ Pediatrics
R Medicine > RJ Pediatrics > RJ101 Child Health. Child health services
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Life Sciences
Supervisor's Name: Gerasimidis, Dr . Konstantinous
Date of Award: 2014
Depositing User: Mrs Barbara K Cochrane
Unique ID: glathesis:2014-5724
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jan 2015 10:56
Last Modified: 14 Jan 2015 14:40
URI: https://theses.gla.ac.uk/id/eprint/5724

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