Effects of kiwifruit on innate and adaptive immunity and symptoms of upper respiratory tract infections.

Maintenance of an adequate and properly regulated immune system is essential for health and well-being. Components in food may modulate immune responses in a positive way (immunonutrition), and some of these components are present in kiwifruit. Kiwifruit contains vitamin C, carotenoids, polyphenols, and dietary fiber, and these are all potentially beneficial to the immune system. Research that has contributed to our understanding of the beneficial effects that kiwifruit may have on immune responses spans from in vitro studies using cell lines and human blood cells, to using animal models targeting both mucosal and systemic immunity. Some limited human intervention trials have been undertaken and are described, in which kiwifruit has been shown to influence a number of biomarkers of oxidative stress and beneficial immune responses, to reduce the incidence and severity of symptoms of upper respiratory tract infections and potentially be more beneficial than supplementation with vitamin C alone.