We often start taking vitamin C once we're sick, and it surely helps (try 800mg every 20 minutes when you've already got a cold or flu), but citrus fruit and juice, a great source of vitamin C, can actually help prevent illness by creating stronger cells that deflect virus and germs.
Sweet potatoes are abundant during cold and flu season and it's a good thing because they're loaded with a healthy dose of beta-carotene, which creates vitamin A in the body. This crucial nutrient boosts immune function by lowering the amount of free radicals, helping to eliminate the cause of sickness.
While you probably won't put them on your pizza, super mushrooms such as cordyceps and reishi have well documented antioxidant and immune boosting benefits. Reishi is actually considered the king of herbs out of thousands in Chinese medicine. You can find them dried or in tinctures.
Boosting your intake of whole grains such as brown rice increases vitamin E, known to enhance production of B cells, which destroy illness-causing bacteria. And pinto beans are a rich source of zinc. You need zinc to fight off the infection before you even know you have it. Who's savoring every bite of a tasty rice and bean burrito now?
Flax oil is loaded with healthy omega-3 fatty acids. This important oil boosts production of phagocytes, which like to eat foreign bacteria. Flax oil is also great in easing the effects of infection on the body. It also boosts brain function so you'll remember that the number one way to avoid colds and flus in the first place is by regularly washing your hands, especially if you have any plans of putting them anywhere near your eyes, nose or mouth.