# Exploratory Study on Microbiota and Immune Responses to Short-Term L. paracasei CNCM I-1518 Consumption in Healthy Adults

## TL;DR

This study shows that short-term consumption of L. paracasei CNCM I-1518 can improve immune function and gut microbiota balance in healthy adults.

## Contribution

The novel contribution is demonstrating the dual immunomodulatory and microbiota-balancing effects of L. paracasei CNCM I-1518 in a 15-day intervention.

## Key findings

- L. paracasei CNCM I-1518 increased B lymphocytes, monocytes, and leukocytes while reducing eosinophils.
- Serum IgG and complement proteins C3 and C4 levels were elevated, indicating enhanced humoral immunity.
- The probiotic reduced Clostridium and increased Lactobacillus, improving gut microbiota balance.

## Abstract

Background/Objectives: The gut microbiota and immune system are interconnected, with targeted nutritional interventions offering potential to modulate immune function. This study aimed to evaluate the short-term immunomodulatory effects of Lacticaseibacillus paracasei subspecies paracasei CNCM I-1518 (L. paracasei CNCM I-1518) in healthy adults. Methods: A 15-day dietary intervention was conducted involving healthy adults. Nutritional status, dietary habits, and systemic immune biomarkers were assessed, alongside changes in gut microbiota composition. Results: The results revealed significant effects on both cellular and humoral immunity. Cellular immunity was enhanced through increased circulating B lymphocytes, absolute monocyte counts, and leukocyte numbers, alongside reduced eosinophil levels, potentially mitigating allergic responses. Humoral immunity was improved by elevated serum IgG1, IgG2, and IgG4 levels, enhancing defenses against pathogenic antigens, and increased serum complement proteins C3 and C4, supporting innate immunity. Microbiota analysis showed a reduction in Clostridium and the Clostridium/Escherichia coli ratio, with a notable increase in the Lactobacillus/Clostridium ratio, highlighting the strain’s ability to reshape intestinal bacterial balance. Conclusions: A short-term intake of L. paracasei CNCM I-1518 can simultaneously modulate immune function and gut microbiota composition, supporting its potential as a targeted dietary intervention to promote immune health.