Inclusion Criteria:  Planning to run one of the long-distance races included.  Exclusion Criteria:  Not having run at least 21 km previously, smoking, living too far away from the study area, unwilling to abstain from probiotic supplementation during treatment period, unwilling to abstain from NSAIDs or gut-permeability lowering supplements before the run, regular use of prescribed drugs (including hormonal contraceptives).