Increase in stage 4 sleep after ingestion of a tryptophan-free diet in humans.

The polygraphic sleep pattern following the ingestion of an aminoacid mixture containing all essential aminoacids was compared with that following the same mixture lacking tryptophan in 12 healthy volunteers. The tryptophan-free mixture caused a decrease in stage 4 sleep latency and an increase (from 14.9% to 28.3%) in stage 4 sleep during the first 3 hours of sleep. A not significant decrease in light sleep and REM sleep was observed during the same period. During the second part of the night no significant differences were found between the two treatments.