The key secret to cold and flu prevention starts with your diet, says Dr. Allana Polo, ND, a certified naturopathic physician and owner of Polo Health + Longevity Centre. Your first step: Avoid sugar and processed foods, especially anything that's "white." "These foods weaken or suppress our immune system by putting extra stress on the body," she says. If you're in need of a sugar fix, put on a pot of herbal chocolate tea. The cacao can satisfy your sweet tooth while supplying antioxidants and zinc to bolster immunity.