The Effect of A Whey-Protein and Galacto-Oligosaccharides Based Product on Parameters of Sleep Quality, Stress, and Gut Microbiota in Apparently Healthy Adults with Moderate Sleep Disturbances: A Randomized Controlled Cross-Over Study

Nutrients. 2021 Jun 27;13(7):2204. doi: 10.3390/nu13072204.


People experiencing sleep problems may benefit from nutrients supporting serotonin metabolism and stress reduction. We studied the effect of a dairy-based product (DP) containing protein, galacto-oligosaccharides, vitamins and minerals, on sleep quality, stress, and gut-microbiota. In a cross-over RCT (three weeks intervention; three weeks washout), adults (n = 70; 30-50 y) with sleep disturbances (Pittsburgh Sleep Quality Index (PSQI) ≥ 9) consumed products 1 h before bed-time. Sleep quality (PSQI) was measured weekly, stress at base- and end-line (Depression Anxiety Stress Scale and saliva cortisol). Fecal samples were collected in the 1st intervention period only. Compared to placebo (skimmed milk), PSQI was only lower at day 14 in the 2nd intervention period in intention-to-treat (ITT) (p = 0.017; n = 69) and per-protocol (PP) (p = 0.038; n = 64) analyses. Post-hoc analysis (modified-PP: n=47, with baseline PSQI ≥ 9, and endline day 14), however, showed a decrease in PSQI (-1.60 ± 2.53; p = 0.034). Early morning saliva cortisol decreased versus placebo (p = 0.045). Relative abundance of Bifidobacterium increased (p = 0.02). Redundancy analysis showed an inverse relationship between baseline microbiota composition and baseline PSQI (p = 0.046). Thus, although DP did not improve sleep quality in ITT and PP populations, it did in the modPP. DP reduced salivary cortisol and stimulated Bifidobacterium, which possibly is important for sleep improvement.

Keywords: GOS; galacto-oligosaccharides; microbiota; skimmed milk powder; sleep; stress; tryptophan; whey protein.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Bifidobacterium / metabolism
  • Cross-Over Studies
  • Double-Blind Method
  • Feces / microbiology
  • Female
  • Gastrointestinal Microbiome / physiology*
  • Humans
  • Male
  • Oligosaccharides / therapeutic use*
  • Sleep / drug effects*
  • Sleep Wake Disorders / diet therapy*
  • Tryptophan
  • Whey
  • Whey Proteins / therapeutic use*


  • Oligosaccharides
  • Whey Proteins
  • Tryptophan