Tryptophan levels, excessive exercise, and nutritional status in anorexia nervosa

Objective: It has been hypothesized that reduced dietary availability of tr yptophan may be the cause of impaired serotonin activity in underweight ano rexics. The study reported here evaluated the relationship between tryptoph an availability in the blood and nutritional status in anorexia nervosa. Me thods: The total amount of tryptophan and the ratio between tryptophan and other large neutral amino acids (TRP/LNAA) were assessed in a sample of 16 starving anorexic patients. Body weight and composition and energy intake w ere evaluated in all. patients. All subjects also completed self-reported q uestionnaires such as the Hopkins Symptom Checklist and Eating Disorders In ventory (EDI). Results: The TRP/LNAA ratio seems to be higher in patients w ith a more severe catabolic status. It is, in fact, significantly inversely correlated with body mass index, body fat, muscle mass, daily energy intak e, and daily tryptophan intake. The TRP/LNAA ratio also correlates with gro wth hormone and the EDI drive for thinness. Patients who exercise excessive ly had significantly higher TRP/LNAA ratios. Conclusions: in starving anore xic patients, the TRP/LNAA ratio does not seem to be determined by the cont ent of tryptophan in the diet, but it correlates with measures of catabolis m. The relationship of the TRP/LNAA ratio to excessive exercise and starvat ion indicates the importance of further investigations exploring the role o f tryptophan availability in maintaining anorexia nervosa.