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evans s, daly a, chahal s, macdonald J, macdonald a
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dietetic department birmingham children’s hospital, steelhouse Lane, birmingham
the primary treatment of phenylketonuria (pKu) is a restrictive lowphenylalanine diet with a limited range of natural foods allowed. within the confines of the dietary restriction, it is important to encourage a wide range of flavour preferences to maximize food choice. Basic taste perceptions of bitterness and sweetness are largely innate and evident at birth (1).
The early introduction of bitter-tast- the confines of their dietary restricing phenylalanine (phe)-free L-amino tion (7). However, it is unknown if acid supplements from diagnosis (<14 ‘flavour imprinting’ occurs due to the days of age), may be an important in- early introduction of L-amino acids fluence on food preferences in PKU. and, if so, how long this effect may
There is a sensitive learning pe- last. The aim of this controlled proriod in the first few months of life, spective study was to determine the during which unpalatable flavours flavour preferences of children with can be rendered palatable (2). Hydro- PKU and to compare these with a lysed formulas designed for cows’ group of healthy age matched control milk protein intol- children. erance contain free There is a sensitive learning amino acids, di- methods and tripeptides and period in the first few Thirty-five children have similar bitter with PKU aged flavour notes (e.g. months of life, during which four to 13 years of sulphur volatiles) age following a low to vegetables like unpalatable flavours can be phenylalanine diet broccoli (3). There providing ≤10g/ is considerable evi- rendered palatable. day of natural prodence to demon- tein, were comstrate that children pared with 35 age/ given these formu- gender-matched las during infancy are more likely to controls on a normal diet. Children prefer broccoli and other bitter and tasted 10 blinded puree foods (apsour-tasting foods than children who ple, banana, strawberry, low protein received sweeter milk-based formula custard, broccoli, cauliflower, carand the effects of this on flavour pref- rot, sweet potato, lemon, coffee) in erences can continue for several years random order and rated them using after the initial exposure (4-6). So it a seven-point pictorial hedonic scale might be expected that introduction (8) (super yummy to super yucky) of L-amino acid supplements in PKU and then ranked them in preferential may have a similar impact. order. Caregivers completed a neo-
Parental likes and dislikes and phobia questionnaire to measure their food neophobia may also affect chil- child’s variety-seeking tendency with dren’s food choices. There is evidence respect to food (9). Caregivers also that young children with PKU eat a completed a food frequency questionlimited range of foods even within naire indicating the number of times/
week children consumed each of 60 commonly eaten food items and how often children consumed each of the 10 test foods.
ResuLts Rating of Foods (1 = super yucky and 7 = super yummy) Both groups of children preferred sweet foods to savoury, sour and bitter. The three most liked foods by PKU children, irrespective of age, were custard, banana and apple, and for control children the same, but in reverse order. On average, PKU children rated most foods higher than controls, particularly custard (5.8 vs 4.8; p=0.001), sweet potato (4.6 vs 3.4; p=0.009) and carrot (4.6 vs 3.5; p=0.009).
Food Ranking (1 = most liked, 10 = least liked) The three most highly ranked foods by PKU children were custard, banana and strawberry and for controls, banana, apple and custard. PKU children liked sweet potato significantly more than control children (PKU 5.3 vs 6.5; p=0.03), whilst control children preferred apple (PKU 5.0 vs 3.5; p=0.02). When considered in food groups, control children ranked fruits higher than PKU children (PKU 4.6 vs 3.7; p=0.03) whilst PKU children ranked vegetables higher than controls (PKU 5.6 vs 6.3; p=0.05).
In the PKU group caregivers significantly underestimated their children’s liking for custard (child 3.4 vs parent 6.0; p<0.0001) and coffee (7.6 vs 8.2; p=0.02) and overestimated their liking for strawberry (4.8 vs 2.6; p=0.0005). Control group caregivers also overestimated liking for strawberry (4.4 vs 2.1; p<0.0001) and carrot (6.3 vs 5.2; p=0.03), but underestimated liking for cauliflower (6.5 vs 7.5; p=0.05) and coffee (7.7 vs 9.4; p=0.0002).
Food Frequency Questionnaire Per week, children with PKU consumed 50 to 100 percent more than control children of high energy, sugar containing drinks (9.4/week vs 2.9/week; p<0.0001), sweets (6.3 vs 2.8; p=0.001), chips/fries (3.2 vs 1.5; p=0.002), sweet biscuits (6.0 vs 3.4; p=0.01), crisps (4.1 vs 2.6; p=0.01) and pasta/low protein pasta (5.2 vs 2.5; p=0.006).
Intake of fruit and vegetables and most other foods was similar across PKU and control groups, with daily servings of about three fruit, three vegetables, one to two milk/milk replacements, two bread/low protein bread and two to three water; and weekly servings of three to four sugar-free drinks and five to six natural fruit juices.
The four most frequently eaten study foods per week for both groups were: strawberry (PKU 4.2 vs 2.8; p=0.01), banana (PKU 3.6 vs 3.4), apple (PKU 3.4 vs 3.5) and carrot (PKU 3.3 vs 3.3). Sweet potato was eaten more frequently by children with PKU (1.5 vs 0.5; p=0.004).
neophobia scale (1 = always, 7 = never) Children with PKU were consistently reported by caregivers to be more food neophobic than control children, being more particular about what foods they eat (mean: PKU 2.7 vs 4.2; p=0.001), less trusting (mean: PKU 3.4 vs 4.5; p=0.002) and more fearful of new foods (mean: PKU 3.4 vs 4.6; p=0.003). However, whilst children with PKU were more uncomfortable in new and different situations, their
neophobia did not make them less social, as both groups were equally comfortable talking with, or sitting next to a stranger.
discussion Despite anecdotal evidence and studies in children taking protein hydrolysate formula, children with PKU aged ≥ four years did not prefer bittertasting foods associated with the taste of L-amino acids, nor did they prefer savoury foods in preference to sweet foods. In fact, children with PKU demonstrated a significant preference for sweet foods. This suggests that the taste imprinting seen in previous studies (4, 10, 11) may be limited to infancy and pre-school age, decreasing with continuing exposure to a wider range of foods.
Food neophobia is a protective trait designed to prevent humans from ingesting potentially harmful foods (12), so it is not surprising that children with PKU are particularly food neophobic as they are educated from an early age that high protein foods are potentially harmful. Whilst children with PKU may generally be more reluctant to try new foods, in this study they appeared to be less fussy, consistently rating most foods higher than control children. Therefore, whilst neophobia may inhibit children with PKU from trying a wider variety of foods, it is not necessarily because they are averse to the flavour.
This study suggests that any taste imprinting that may exist in PKU does not extend beyond the pre-school years. Consistent and frequent intake of sweetened phe-free L-amino acid supplements from the age of three years may well mask the bitter flavours of some L-amino acids. The increase in the proportion of energy from food and the reduction in energy from L-amino acid supplements with increasing age may also act to normalise taste preferences. However, children with PKU are significantly more fearful of new and unfamiliar foods and attention to caregiver influences and food neophobia requires further study.
references 1 anliker Ja, bartoshuk L, Ferris aM et al. Children’s food preferences and genetic sensitivity to the bitter taste of 6-n-propylthioruracil (PrOP). am J Clin Nutr 1991; 54: 316-320 2 beauchamp GK, Mennella Ja. Flavour perception in human infants: development and functional significance. Digestion 2011; 83 (suppl 1): 1-6 3 Menella Ja, Kennedy JM, beauchamp GK. Vegetable acceptance by infants: effects of formula flavours. Early Hum Dev 2006; 82(7): 463-68 4 Mennella Ja, beauchamp GK. Flavour experiences during formula feeding are related to preferences during childhood. Early Hum Dev 2002; 68(2): 71-82 5 beauchamp GK, Mennella Ja. Early flavour learning and its impact on later feeding behaviour. J Pediatr Gastroenterol Nutr 2009; 48 (Suppl 1): S25-30 6 beauchamp GK, Mennella Ja. Flavour perception in human infants: development and functional significance. Digestion 2011; 83 (Suppl 1): 1-6 7 MacDonald a, rylance G, asplin D et al. abnormal feeding behaviours in phenylketonuria. J Hum Nut Diet 1997; 10: 163-70 8 Chen aw, resurreccion aVa, Paguio LP. age appropriate hedonic scales to measure food preferences of young children. J Sensory Stud 1996; 11: 141-63 9 Pliner P, Hobden K. Development of a scale to measure the trait of food neophobia in humans. appetite 1992: 19: 105-20 10 Owada M, aoki K, Kitagawa t. taste preferences and feeding behaviour in children with phenylketonuria on a semisynthetic diet. Eur J Pediatr 2000; 159(11): 846-50 11 Sullivan Sa, birch LL. Pass the sugar, pass the salt: experience dictates preference. Developmental Psychology 1990; 26: 546-51 12 Knaapila a, tuorila H, Silventoinen K et al. Food neophobia shows heritable variation in humans. Physiol behav 2007; 91: 573-78
