Nature's Harbor Citrus Bioflavonoid Complex offers the highest concentration of bioflavonoids derived from lemons, oranges, and grapefruit. Citrus Bioflavonoids aid in the absorption and retention of Vitamin C. Vitamin C (ascorbic acid) is one of the most important nutrients and an essential antioxidant for the human body. The antioxidant properties of Vitamin C support the immune system and help to protect the body from the damaging effects of free radicals. The body requires Vitamin C to help build collagen, which is necessary for healthy bones, teeth, cartilage, skin, and blood vessels. Vitamin C also aids in the absorption of iron.