The influence of nutrition on IGF-1 in tube-fed profoundly retarded adults

Objective: This study was conducted to determine whether IGF-1 concentratio ns are low in nonambulant profoundly retarded adults and to identify associ ated nutritional factors. Methods: Serum IGF-1, albumin, pre-albumin, creatinine, zinc (Zn) and plasm a amino acids were measured before and after a four-week 25% increase in fo rmula in 25 individuals, divided into those fed by day (Group A) or by nigh t (Group B). Results: Circulating IGF-1 was low in nine of the 22 subjects (40.9%) inclu ded in the analysis. Mean IGF-1 increased 10.4% (p=0.004). Despite high int akes of essential amino acids and Zn, initial mean plasma tryptophan and ph enylalanine were low, and serum Zn was low in 40.9% of subjects. Plasma try ptophan was low at both samplings and correlated with circulating IGF-I con centrations (p=0.02) at the beginning of the study. Serum IGF-1 and Zn also correlated (p=0.02) initially. Conclusions: IGF-1 is commonly low in this population and is associated wit h low plasma amino acid and Zn concentrations, despite high intakes of thes e nutrients. The causes and clinical implications of these abnormalities ne ed further study.