Probiotics Mitigate Stress and Inflammation in Malnourished Adults via Gut Microbiota Modulation: A Randomized Controlled Trial

Maryam Ahmadi-Khorram^1,2Alireza Hatami^1,2Parastoo Asghari^1,2Ali Jafarzadeh Esfehani³Asma Afshari¹Fateme Javdan¹Mohsen Nematy^3*

• ¹Department of Nutrition, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
• ²Student Research Committee, Mashhad University of Medical Sciences, Mashhad, Iran, Mashhad, Iran
• ³Metabolic Syndrome Research Center, Mashhad University of Medical Sciences, Mashhad, Iran

Objective: Malnutrition negatively affects mental health by altering neurotransmitter function and increasing stress responses. The gut-brain axis is pivotal in this process, and probiotics may mitigate stress. The current study examined the effects of multi-strain probiotic supplementation on stress levels in underweight individuals using the Perceived Stress Scale (PSS).Methods: A double-blind, randomized, placebo-controlled trial involved 100 underweight participants were randomized to receive either a probiotic supplement (Lactobacillus acidophilus, L. casei, L. rhamnosus; 3 × 10⁹ CFU) or placebo for eight weeks. Stress levels, anthropometric measures, and inflammatory markers (ESR, CRP) evaluated at baseline and post-intervention.Results: Ninety participants (mean age: 26.22 ± 7.42 years) completed the study (probiotic: n=47; placebo: n=43). Baseline age (p=0.051) and gender (p=0.1010.010) showed no significant differences. Post-intervention, the probiotic group exhibited significant weight increases (p=0.005), waist circumference (p=0.038), and hip circumference (p=0.008), and a significant reduction in Perceived Stress Scale (PSS) scores (p<0.001) in comparison to the placebo.Inflammatory markers (ESR, CRP) also decreased significantly in the probiotic group (p<0.001).Within-group analysis revealed improvements in anthropometric measures and inflammatory markers in both groups (p<0.05), but stress reduction was more pronounced in the probiotic group (34% vs. 9.3%, p=0.017). A significant time-group interaction was observed for stress scores (p<0.001).The findings suggest that probiotic supplementation reduces stress levels in underweight individuals, possibly through gut microbiota modulation and inflammation reduction.Further research with larger samples and microbiome analysis is warranted.In conclusion, administering probiotics to underweight patients positively impacts their mental health and exhibits anti-inflammatory effects.