A balanced diet is the first key to a strong immune system. Apart from having well-balanced macronutrients (carbs, proteins & fats) in the diet, including the micronutrients (minerals & vitamins) plays a vital role in maintaining immunity to the optimum. The important micro-nutrients include:
Vitamin B6 found in chicken, salmon, tuna, bananas, green vegetables and potatoes (with the skin)
Vitamin C found in citrus fruits like Indian gooseberries, oranges and strawberries, tomatoes, broccoli and spinach.
Vitamin E found in almonds, sunflower oil, sunflower seeds, peanut butter and spinach, nuts etc.
Other food sources like, mushrooms, blue berries, watermelon, wheat germ, yogurt, green tea, ginger, garlic, pomegranate, spinach, broccoli, kale etc also provide a mix of trace vitamins like Vit K, Folate, Magnesium and Zinc
Our body absorbs vitamins more easily from food sources rather than supplements, so include these in the diet instead of oral supplements.