Yogurt
As you know, the gut contains both bad and good bacteria and is responsible for more than just digestion—it accounts for 50 percent of your body’s immune response. Also, the good bacteria decreases cold duration and boosts immunity, maintaining you healthier. You should start eating plain yogurt for a better result.
Sunflower seeds
These seeds are packed with vitamin E and zinc. Vitamin E fights free radicals that could weaken your immune system. Zinc can function as an antioxidant and also prevents free radicals from injuring your cells. Researchers found that zinc prevents the immune system from excess inflammation.