PKU watch
by Dr Anita MacDonald Consultant Dietitian in IMD Birmingham Children’s Hospital
One of the UK's top paediatric dietitians, Anita’s specialism lies with inherited metabolic disorders. She spends 50 percent of her professional time in clinical work with children and 50 percent researching and teaching.
Feeding problems in young children with PKU
Feeding problems are common in young children with PKU. A study conducted in the 1990s indicated that 47 percent of caregivers perceived their children to have at least three feeding problems. This is more common than in the general population, where they are estimat- ed to occur in up to 35 percent of young children. Principal problems observed in children with PKU were slowness to feed, a poor appetite, and a limited variety of foods consumed (4). Some difficulties were mild and transient; others more chronic and severe. Reasons for the feeding difficulties were multi-faceted. Some originated as a consequence of the treatment and issues surrounding the disorders; others had similar aetiology to feeding prob- lems seen in the general population.
Development of feeding behaviour Feeding behaviour is learnt through early experiences with food and feeding. Children’s eating patterns are gradually established in the first three years of life. The development of feeding abilities is a dynamic process, as children mature their motor, cognitive and social skills. Between the ages of six to 36 months is particularly chal- lenging. Children develop a sense of their own autonomy, making use of their new skills to control their caregivers and establish independent feeding. Early childhood eating behaviours are heavily influenced by caregivers. Mothers are important in the development of feeding behaviour, particularly as they usually spend more time than fathers in mealtime interactions. During feeding, a reciprocal relationship between the child and main caregiver is required (3), with each recog- nising and interpreting the others verbal and non-verbal communication signals. In PKU, the unprecedented focus on feeding, with every aspect being prescribed, controlled and monitored by professionals, generates additional caregiver anxiety, uncertainty and possibly a feeling of inadequacy, leading to maladjusted mealtime interaction between child and caregiver. This is likely to lead to be- havioural mismanagement, characterised by inconsistent and over-controlling interactions, leading to unproductive, unpleasant and stressful feeding experiences. As well as the familiarity with, and repeated exposure to, a food, its appearance, taste, texture, smell and tempera- ture (3) will all affect its acceptance. In addition, participa- tion in family meals permits the social aspects of feeding to develop. The child will start to begin to imitate the food choices and feeding behaviours of the family members, thereby shaping their own feeding behaviour and food preferences. Also the setting and atmosphere of meal time, as well as the anticipated consequences of eating or not eating all affect a child’s reaction to food.
Types of feeding problems In the study on feeding problems in children with PKU, although poor appetite was one of the main problems
NHDmag.com Aug/Sept '10 - issue 57
associated with mealtimes, it led to other problematic feeding behaviours. Video analysis of mealtime revealed increased frequency of turning head away, closing mouth and becoming distracted when offered food. Children were slower to feed and less likely to eat their meal without prompting. They ate a limited range of foods and were less willing to try new foods, even within the confines of their dietary restrictions. Negative feeding behaviour, such as crying, screaming and gagging was particularly common when taking the protein substitute.
Causes of feeding problems in PKU Feeding problems are caused by a number of interact- ing biological, psychological, physiological, social and environmental factors (8) and it is sometimes hard to define underlying reasons for the difficulties. Biological factors include the protein substitute. Protein substitute is administered to children at least three times daily, usually pre-meals, and contributes approximately 30 percent of the energy intake. This is likely to inhibit appetite for food. In addition, protein substitute has an important role in suppressing blood phenylalanine concentrations and it is generally still administered during illness, but, as a consequence, may cause nausea, gagging, vomiting and abdominal pain. Children may continue to associ- ate this experience with protein substitute post-illness and consequently may be less co-operative in its adherence. In addition, protein substitute is seen as a medicine by some children and this may lead to further conflict. Psychological factors include maternal depression,
depressive symptoms, anxiety and poor general health (5). These are more common among mothers of children with feeding problems, although it is unclear if maternal depres- sion and anxiety may be the cause or result of the feeding problem. The impact of being given a diagnosis of PKU may heighten depression and anxiety, leading to some of the feeding difficulties. Constant battles with protein substi- tute administration may also enhance caregiver anxiety. Caregivers, who eat unhealthily, have an irregular meal plan, or who are inexperienced at parenting, may be more likely to have toddlers with feeding difficulties. Additionally, if family functioning is unhealthy (associated with argu- ments and confrontation), or there are maternal difficulties in trying to readjust to the pressures of becoming a parent it may lead to inappropriate mealtime conditions. Many young children with PKU appear particularly food neophobic (7) and commonly reject new and novel foods in favour of familiar ones. This may be due to lack of exposure to a wide variety of foods in the weaning period, fear of eating unsuitable foods or unpleasant association with trying new protein substitutes or other dietary products. Generally, children with PKU who present with feeding problems as young as six months appear to persist with these for some time. There is also much misunderstanding of the energy
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