Large number of randomized-controlled trials shows that Vitamin C and Zinc ameliorate symptoms and shorten the duration of respiratory tract infections
The concentration of vitamin C rapidly declines in the plasma and leukocytes during infection or stress according to Swiss researchers. Supplementing with Vitamin C improves components of immune function in humans such as the ability to fight bacteria and Natural Killer Cell activity, and also improves the proliferation of lymphocytes and the actual immune punch these cells have against rampaging infections. Vitamin C also protects our cells from the very activity of our own immune system. Likewise low levels of Zinc or Zinc deficiency impair cellular immunity (for instance decreased phagocytosis and decreased Natural Killer Cell activity, with a weakened ability by immune cells to fight an infection). Therefore both play a part in resisting an infection; decreasing the risk of developing the infection, decreasing the severity and the duration. A large number of randomized-controlled, intervention trials with intakes of up to 1,000mg of Vitamin C and 30mg of Zinc are available. These trials document that adequate intakes of Vitamin C and Zinc ameliorates symptoms and shorten the duration of respiratory tract infections including the common cold. Furthermore, Vitamin C and Zinc reduce the incidence and improve the outcome of pneumonia and diarrhea infections even in children. The research is published in the February 2006 issue of Annals of Nutrition and Metabolism.