Summary
This study is designed to evaluate the effect of a probiotic dietary supplement containing Streptococcus salivarius on serum PFAS levels in male firefighters with documented occupational PFAS exposure, following twice-daily use over a 12-week period.
Detailed Description
This randomized, placebo-controlled, double-blind, crossover pilot study will use serum PFAS measurements, questionnaires and stool sample analyses to evaluate changes in PFAS levels, gastrointestinal symptoms and fatigue with a probiotic dietary supplement compared to a placebo. Each crossover period will last 12 weeks, separated by a four-week washout period. The study will consist of eight study visits: Screening Visit, Period 1 Baseline Visit (Day 0), Day 42 Call, Period 1 Day 84 Visit, Day 98 Call, Period 2 Baseline Visit (Day 112), Day 156 Call, and Period 2 Day 196 Visit.
Eligibility Criteria
Age Range: 18 years to No maximum
Inclusion Criteria:
* Able to give written informed consent
* Male firefighter with previous career exposure to PFAS
* BMI between 18.5 and 35 kg/m²
* Serum PFOS level ≥5 ng/mL at screening
* Willing to consume the study product daily for the duration of the study
Exclusion Criteria:
* History of drug and/or alcohol abuse (\>15 standard drinks per week)
* Food allergy, intolerance or dietary restriction that, in the opinion of the investigator, would preclude consumption of the study product
* Blood donation within the past 3 months
* Current smoker of \>20 cigarettes per day, or former smoker with a history of ≥20 cigarettes per day who quit within 6 months prior to Visit 1
* Any significant acute or chronic health condition that would prevent participation, pose a risk, or confound interpretation of results, including: diagnosed gastrointestinal disorders (irritable bowel syndrome, inflammatory bowel disease, Crohn's disease, ulcerative colitis, coeliac disease, or other chronic diarrhoeal disorders); uncontrolled medical conditions; history of chronic kidney or liver disease; chronic inflammatory or autoimmune disease; history of gastrointestinal surgery; hospitalisation within the past 3 months
* Current or recent (past 12 weeks) use of medications affecting bile acid metabolism (e.g. bile acid sequestrants, fibrates) or antibiotics
* Current or recent (past 4 weeks) use of supplements affecting gut microbiota (prebiotics, probiotics, postbiotics, fibres, synbiotics), detoxification pathways (milk thistle, N-acetylcysteine, glutathione) or bile acid metabolism (e.g. psyllium husk)
* Current or recent (past 2 weeks) consumption of prohibited foods, including probiotic yoghurts
* Considered by the investigator unlikely to comply with study requirements
* Current participation in another clinical study, or insufficient time elapsed since a previous experimental study