Abstract: Background & aims: Treating phenylketonuria based upon strict vegetarian diets has occasionally been
found to hamper physical development, some patients presenting with growth retardation and
malnutrition. In addition, some researchers have reported an association between higher protein intakes
and attaining better developmental outcomes, although it remains unclear which protein fraction
(natural or synthetic) has the greatest influence on growth. The present study aimed to evaluate
anthropometric characteristics and nutrition in a cohort of patients with phenylketonuria and mildhyperphenylalaninaemia from birth to adulthood.
Methods: We conducted a retrospective longitudinal study comparing anthropometric characteristics
(weight, height, body mass index, and growth rate) in our patients and healthy subjects, with the
measurements expressed as z-scores. Nutritional issues were also considered. Data were collected every
6 months from birth to 18 years of age.
Results: Growth impairment was observed in phenylketonuric patients. Specifically, there were two
well-differentiated periods throughout which height fell well below z-score ¼ 0: from birth to two years
of age, and on reaching adulthood. We also found height and weight to be positively correlated
with phenylalanine intake. No growth retardation was seen in the patients with mildhyperphenylalaninaemia.
Conclusions: Phenylketonuric patients showed growth impairment in the early stages, with higher
phenylalanine intakes being associated with attaining better developmental outcomes in this period. Therefore, prescribing very stringent diets in the early years might predispose phenylketonuric patients
to retarded growth later in life, with growth outcomes in adulthood being well below the 50th percentile
for healthy subjects.
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