According to animal studies, taurine produces anxiolytic effect and may act as a modulator or antianxiety agent in the central nervous system by activating the glycine receptor.[45][46][47]
Lysine has a known anxiolytic action through its effects on serotonin receptors in the intestinal tract. One study on rats[32] showed that overstimulation of the 5-HT4 receptors in the gut are associated with anxiety-induced intestinal pathology. Lysine, acting as a serotonin antagonist and therefore reducing the overactivity of these receptors, reduced signs of anxiety and anxiety-induced diarrhea in the sample population. Another study showed that lysine deficiency leads to a pathological increase in serotonin in the amygdala, a brain structure that is involved in emotional regulation and the stress response.[33]
Human studies have also shown negative correlations between reduced lysine intake and anxiety. A population-based study in Syria included 93 families whose diet is primarily grain-based and therefore likely to be deficient in lysine. Fortification of grains with lysine was shown to reduce markers of anxiety, including cortisol levels, and also led to potentiation of benzodiazepine receptors (common targets of anxiolytic drugs such as Xanax and Ativan).[34]