Nutrition, physical growth, and bone density in treated phenylketonuria

Dietary treatment of phenylketonuria is well established to be safe and to prevent developmental and mental impairment in patients with low or absent phenylalanine hydroxylase activity. The use of semi-synthetic diets necessitates careful and longitudinal control not only of physical and intellectual development, which are both near normal in well treated patients, but also of potential diet inherent insufficiencies of essential nutrients. Concern has been raised by some reports on growth retardation in young patients on strict diets and on decreased bone density in older phenylketonuric children. The clinical significance of these findings is not known.

Changes have been found, although inconsistently, in connection with selenium, zinc, iron, retinol and polyunsaturated fatty acid status in dietetically treated patients with phenylketonuria. Both the mechanism and significance of these changes is doubtful at present.