Fermented Milk Drink With Lacticaseibacillus Paracasei Strain Shirota Helps Triathletes With Cold-Like Symptoms Before and After a Race

Federal University of São Paulo80 enrolled

Overview

This study aims to evaluate whether a fermented milk drink containing the probiotic strain Lacticaseibacillus paracasei strain Shirota (LCS), commonly found in Yakult®, can help reduce upper respiratory symptoms in triathletes before and after competition. Athletes often experience cold-like symptoms due to physical stress, intense training, and immune system challenges. The study investigates whether daily consumption of this probiotic drink can help improve immune response and reduce the incidence or severity of symptoms such as sore throat, nasal congestion, or coughing. This is a randomized, double-blind, placebo-controlled, parallel-group study involving healthy adult triathletes. Participants will be randomly assigned to receive either the probiotic drink or a placebo for a specific period before and after a triathlon event. Symptoms and health markers will be tracked through questionnaires and biological samples. The goal is to explore whether probiotic supplementation can provide practical, non-pharmacological support for athletes' immune health and well-being during intense physical activity.

Background: Endurance athletes are frequently exposed to high physical stress, which may lead to temporary immune suppression and increased susceptibility to upper respiratory tract infections (URTIs). Previous studies suggest that probiotics may play a role in supporting the immune system. Objective: To assess the efficacy of a fermented milk drink containing Lacticaseibacillus paracasei strain Shirota (LCS) in reducing upper airway symptoms in triathletes before and after a competitive event. Study Design: This is a multi-center, double-blind, randomized, placebo-controlled, parallel-group study. Eligible participants will be healthy adult triathletes preparing for a scheduled race. They will be randomized to consume either the probiotic drink or a placebo daily, starting several weeks before the race and continuing for a defined recovery period afterward. Primary Outcome: -Salivary IgA Concentration The primary outcome is the change in salivary immunoglobulin A (IgA) concentration before and after the competition, assessed at five time points. This measure will reflect mucosal immune function and the potential modulatory effect of daily intake of fermented milk containing Lacticaseibacillus paracasei strain Shirota. Secondary Outcomes: * Systemic Immune and Inflammatory Response Blood samples will be analyzed for markers of systemic immune activation and inflammation (e.g., cytokines), collected at five time points to evaluate the broader immunomodulatory effects of the probiotic intervention. * Upper Airway Symptoms Incidence, severity, and duration of upper airway symptoms (e.g., sore throat, cough, nasal congestion) will be assessed using the Wisconsin Upper Respiratory Symptom Survey-21 (WURSS-21). Higher scores indicate more severe symptoms and a greater impact on daily functioning. * Mood State Mood state changes will be evaluated using the Brunel Mood Scale (BRUMS) across six subscales. Total Mood Disturbance (TMD) scores will reflect the psychological response to training and competition. Higher scores indicate worse mood states.

Interventions

Intervention Name: Fermented milk containing Lacticaseibacillus paracasei strain Shirota. Intervention Name: Non-fermented milk (placebo)DIETARY_SUPPLEMENT

Participants will ingest 80 mL per day of fermented milk containing 40 billion colony-forming units (CFU) of Lacticaseibacillus paracasei strain Shirota (LcS), starting 30 days before a triathlon competition and continuing until 14 days post-race. The fermented milk is stored refrigerated and consumed once daily.

Non-fermented milk (placebo)DIETARY_SUPPLEMENT

Participants will ingest 80 mL per day of non-fermented milk identical in taste, appearance, and packaging to the probiotic drink, but without Lacticaseibacillus paracasei strain Shirota. Administration follows the same schedule as the probiotic group.

Eligibility

Sex: ALLMin age: 25 YearsMax age: 45 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Aged between 25 and 45 years. * Amateur triathletes with regular endurance training and prior competition experience. * In good general health, with no history of chronic diseases or conditions affecting immune or inflammatory responses. * Willing and able to comply with all study procedures, including sample collections and completion of validated questionnaires at five time points. * Agree to consume a daily dose of fermented milk containing Lacticaseibacillus paracasei strain Shirota (LcS) or placebo from 30 days before until 14 days after the competition. * No use of probiotics, antibiotics, or immunomodulatory supplements in the 30 days prior to enrollment Exclusion Criteria: * Known allergy or intolerance to dairy products, including lactose. * Use of probiotics or antibiotics within 30 days prior to enrollment. * Current use of any pharmacological treatment. * History of chronic rhinopathy. * Diagnosis of autoimmune disease. * History of recurrent infections not involving the upper airway. * Presence of major medical conditions or chronic diseases, including but not limited to respiratory or gastrointestinal disorders. * Incomplete or missing data necessary for determining eligibility or for study outcomes.

Outcomes

Primary Outcomes

Salivary IgA Concentration

The primary outcome measure is the change in salivary immunoglobulin A (IgA) concentration after daily intake of fermented milk containing Lacticaseibacillus paracasei strain Shirota. Saliva samples will be collected from participants at five time points: 30 days before the competition, 24 hours before, immediately after, 72 hours after, and 14 days post-competition. The concentration of salivary IgA will be measured to assess the impact of probiotic supplementation on immune function.

Time frame: Pre-study: 30 days before the competition (baseline) During study: 24 hours before the competition Post-study: Immediately after the competition, 72 hours post-competition, and 14 days after the competition

Secondary Outcomes

Immune/Inflammatory Response

The secondary outcome measure is the assessment of systemic immune and inflammatory responses. Blood samples will be collected at five time points: 30 days before the competition, 24 hours before, immediately after, 72 hours after, and 14 days post-competition. These samples will be analyzed for markers of immune activation and inflammation to assess the effects of probiotic supplementation.