Effect of i.v. amino acids on satiety in humans

Parenteral nutrients suppress oral food intake. Separate i.v. infusion of amino acids (IVAA) at high doses affects gastrointestinal motility and secretion. However, little is known on the effects of separate i.v. infusion of amino acids at these high doses on satiety. Therefore, we have studied the effect of two different doses of a commercially available mixed amino acids solution on satiety and food intake.

Six healthy volunteers (ages 20 to 34 years) were studied on three separate occasions in random order during (a) i.v. saline (control), (b) low-dose IVAA ([LDA] 125 mg protein/kg/h, Vamin 18EF; Kabi Pharmacia BV, Woerden, The Netherlands), or (c) high-dose IVAA ([HDA] 250 mg protein/kg/h) for 360 minutes. Subjective criteria such as wish to eat, prospective feeding intentions, and feelings of hunger and fullness were scored on 100-mm visual analog scales at 30-minute intervals. Food preference also was measured every 60 minutes with food selection lists. At the end of the experiment a meal was presented.

Feelings of fullness were significantly (p < .05) increased during both LDA and HDA. The wish to eat was significantly (p < .05) decreased during HDA compared with control and LDA. Prospective feeding intentions also tended to be reduced during HDA (not significant). Feelings of hunger were not significantly different between the three experiments. Total food selection was significantly (p < .05) decreased during LDA and HDA, mainly because of a significantly (p < .05) decreased preference for fat-rich items. However, the total amount of food consumed at the end of the experiment was not significantly different between the three experiments.

The present study shows that in healthy volunteers, IVAA (1) increase satiety ratings, (2) increase feelings of fullness, (3) decrease preprandial food selection, and (4) have no effect on subsequent oral food intake.