To evaluate the effect of daily ingestion of the probiotic Lactobacillus reuteri on the levels of secretory IgA and the cytokines Il1-beta, IL-6, IL-8 and IL-10 in saliva of healthy young adults.

Study design: A randomized, double-blind, cross-over design separated by three weeks run-in and wash-out periods. Each intervention period is three weeks and the participants are allocated to the test and placebo regimes in a randomized order.

Material: 41 healthy adults are enrolled after informed consent from the School of Dentistry, University of Copenhagen.

Methods: Samples of resting, unstimulated whole saliva (UWS) and stimulated whole saliva (SWS) are collected five times during the study period. The samples are immediately frozen in 0.5 ml aliquots.

Intervention: The subjects are instructed to ingest two tablets containing Lactobacillus reuteri or placebo, twice daily for 3 weeks. No probiotic food or health products are allowed during the intervention period. All normal oral hygiene routines should be maintained during the entire study. The compliance is checked through interviews. Any perceived side effects are reported without delay to the research staff.

Endpoints: The concentration of total protein and secretory IgA in saliva are determined with the enzyme-linked immune-sorbent assay (ELISA). The levels of the cytokines IL1-beta, IL-6, IL-8 and IL-10 is determined by Luminex-technology.

Scientific importance: The study may provide evidence that probiotic supplements can influence the innate defense system in the whole saliva which may open up for novel strategies to combat oral diseases.

Inclusion Criteria:

• Healthy individuals with no chronic compromising illnesses
• No medication intake for serious chronic diseases
• No regular intake of probiotic products up till one month before inclusion

Exclusion Criteria:

• Recent antibiotic therapy (within the last six months)
• Pregnant or lactating women
• Active infection that needs treatment with antibiotics