Effect of acute tryptophan depletion on mood and appetite in healthy female volunteers

Twelve healthy female subjects received the following three drinks in a double-blind, semi-balanced, cross over design: (a) 50 g of amino acids without L-tryptophan (LTP); (b) 50 g of amino acid with LTP (balanced); (c) plain water. Compared to both the balanced amino acid mixture and plain water, the LTP drink significantly lowered plasma total and free tryptophan at 4.5 h. However, compared to the two control conditions, there was no effect of the LTP drink on subjective ratings of mood or hunger. Similarly, the LTP drink did not alter significantly either total calorie intake or the macronutrient content of a test meal 5 h after drink ingestion.