American Journal of Clinical Nutrition, Vol 25, 976-979, Copyright © 1972 by The American Society for Clinical Nutrition, Inc.

Plasma tryptophan response curve and tryptophan requirements of children with Down's syndrome

Five children with Down's syndrome, aged 6 to 13 years old, were given a diet based on a synthetic amino acid mixture, patterned as in egg protein, and supplying graded levels of tryptophan. Pre- and postprandial plasma free tryptophan levels were measured. The plasma tryptophan level was low and constant at and below a tryptophan intake of 4 mg/kg body wt, increased linearly between this intake level and 7 mg/kg body wt, at which point it reached an upper plateau. From the plasma tryptophan response curve, the minimum tryptophan requirement in these children is estimated to be approximately 4 mg/kg body wt per day.