American Journal of Clinical Nutrition, Vol 27, 572-579, Copyright © 1974 by The American Society for Clinical Nutrition, Inc.

Relationship of dietary tryptophan and niacin to tryptophan metabolism in alcoholics and nonalcoholics

¹ From the Food and Nutrition Department, Southern Illinois University, Carbondale, Illinois 62901

Calculated daily dietary intakes of tryptophan and niacin were analyzed by statistical correlation with 24-hr urinary excretions of nine metabolites of tryptophan. The metabolites were: 5-hydroxyindoleacetic acid (5-HIAA) and indoleacetic acid derived through the "indole pathway:" anthranilic acid, o-aminohippuric acid, acetylkynurenine, kynurenine, xanthurenic acid (XA). and kynurenic acid (KA) derived through the "kynurenine pathway;" and indican, formed in the intestine. Correlations between 5-HIAA and all other urinary metabolites were also calculated. The data for a group of alcoholics, all of whom had shown mental derangements, were compared with those of nonalcoholics. Results revealed tryptophan in the diet was significantly positively correlated with XA and KA in nonalcoholics and with 5-HIAA in alcoholics. The increase in dietary niacin significantly correlated with increases in XA, KA, and 5-HIAA in nonalcoholics, but only with an increase in 5-HIAA in alcoholics. The differences in significant correlations between alcoholics and nonalcoholics were interpreted as indicative of abnormal tryptophan metabolism in alcoholics. Discussion suggested genetic, adaptive, and dietary bases for this abnormality. The statistical treatment and the parameters incorporated into the study appear to hold good potential for strictly controlled future experiments. The question of whether the phenomena observed are a result of alcoholic addiction or a cause of addiction may be answered by applying these techniques over a long enough period of controlled dietary intakes to eliminate adaptive enzyme mechanisms.