EFFECTS OF 30 DAYS OF UNDERNUTRITION ON PLASMA NEUROTRANSMITTER PRECURSORS, OTHER AMINO-ACIDS, AND BEHAVIOR

As part of a 30-day field exercise, 17 soldiers consumed a calorie-def icient, lightweight ration (1946 kcal/day) while 17 others consumed a calorie-adequate control ration (2782 kcal/day). Mean energy expenditu re for both groups was 3200 to 3300 kcal/day. Plasma amino acid !el ei s Mere assessed at the start, after 14 days, and at the completion of the study. Behavioral resting was conducted at the stars and completio n of the study. Alanine, which is used for gluconeogenesis, fell from 389 to 323 nmol/mL over the trial among those who consumed the calorie -deficient diet, whereas it increased in the control group. Plasma tyr osine also fell significantly, from 70 to 52 nmol/mL, as did tryptopha n (from 62 to 55 nmol/mL) in the calorie deficient group. The ratio of tyrosine to other large neutral amino acids, an indicator of tyrosine transport to the brain, also fell in the deficient group (from 0.104 to 0.084). At the completion of the study, plasma tryptophan ratio was significantly lower in the calorie deficient group (0.091) compared w ith the control group (0.103). Decrements in tryptophan, but not tyros ine, ratio were associated with impairments ill simple and choice visu al reaction time (r = -0.4415, P = 0.009; r = -0.4029, P = 0.018, resp ectively). Therefore, changes in plasma amino acids occurring during a controlled form of undernutrition can be substantial; some of these a lterations may be related to the functional consequences of undernutri tion. (C) Elsevier Science Inc.