From kombucha to cold water swims, sleep to supplements, so many things are claimed to help enhance your immune system. We investigate the evidence, and ask if it's possible to avoid catching a virus this winter (and still leave the house). Plus, James braves 3.9 degree water to see for himself if cold water swimming has any affect on our immune systems.Guests: Margaret McCartney - Resident GP and expert in evidence-based medicine John Tregoning - Professor in Vaccine Immunology at Imperial College London Eleanor Riley - Professor of Immunology and Infectious Disease at University of EdinburghPresenter: James Gallagher Producer: Hannah Robins Content Editor: Holly Squire The programme was produced in partnership with the Open University.