The natural orange colour found in the flesh of sweet potatoes is due to the rich content of beta carotene, a natural antioxidant that is converted to vitamin A in the body. Since low levels of vitamin A are linked to a compromised immune system, keeping intake adequate is key during the fall. Tip: bake a few sweet potatoes at once, and use the flesh in recipes like pancakes and smoothies for a supplement-free and naturally sweet boost of nutrition.