The grapefruit is actually a hybrid of Barbados origin that was first formed as an accidental cross between sweet orange and pomelo, both of which were introduced from Asia in the 17th century. Grapefruits are yellow-orange in skin color, oblate spheroid in shape with a segmented and acidic flesh, varying in color depending on the cultivars, which include white, pink, and red pulps of varying sweetness. Nutritionally, the gapefruit is a rich source of vitamin C, contains the fiber pectin, and the pink and red hues contain the beneficial antioxidant lycopene. Studies also have shown that this fruit helps lower cholesterol, and there is even evidence that its seeds have antioxidant properties. Additionally, it forms a core part of the "grapefruit diet", the theory being that its low glycemic index is able to help the body's metabolism burn fat.