Scientists from Northwest A&F University (China) have found that a combination of walnut peptides and the amino acid theanine can improve sleep quality in people experiencing chronic stress. The results of this multi-stage study were published in the journal Food & Function.

The research was conducted across several models, ranging from zebrafish and laboratory mice to humans. In animal experiments, the walnut-based supplement restored sleep architecture, increased the proportion of deep slow-wave sleep, and reduced corticosterone levels—a stress hormone associated with overactivation of the hypothalamic–pituitary–adrenal (HPA) axis.

The researchers also observed increased levels of GABA and tryptophan—substances involved in nervous system relaxation and melatonin synthesis. This suggests that the combination affects not only hormonal but also neurochemical mechanisms of sleep regulation.

The effect was confirmed in the clinical part of the study as well. In an eight-week placebo-controlled trial involving adults with sleep disturbances, supplementation with walnut peptides and theanine led to longer nighttime sleep duration and improved subjective sleep quality as measured by the PSQI scale.

The authors note that these findings make the combination a promising approach for supporting sleep under chronic stress, although larger clinical studies are needed to draw definitive conclusions.