Delicious, grapefruit is very low in calories, consists of just 42 calories per 100 g. Nonetheless; it is rich in dietary insoluble fiber pectin, which by acting as a bulk laxative helps to protect the colon mucous membrane by decreasing exposure time to toxic substances in the colon as well as binding to cancer-causing chemicals in the colon.
Pectin has also been shown to reduce blood cholesterol levels by decreasing re-absorption of cholesterol binding bile acids in the colon.
The fruit contains very good levels of vitamin-A (provides about 1150 IU per 100g), and flavonoid antioxidants such as naringenin, and naringin. Besides, it is a moderate source of lycopene, beta-carotene, xanthin and lutein. Studies suggest that these compounds have antioxidant properties and are essential for vision. The total antioxidant strength measured in terms of oxygen radical absorbance capacity (ORAC) of grapefruit is 1548 µmol TE/100 g.
Further, vitamin A is also required maintaining healthy mucus membranes and skin. Consumption of natural fruits rich in vitamin-A, and flavonoids helps to protect from lung and oral cavity cancers.
It is an excellent source of antioxidant vitamin-C; providing about 52% of DRI. Vitamin-C is a powerful natural anti-oxidant and helps the body develop resistance against infectious agents and scavenge harmful free radicals. It, furthermore, is required for the maintenance of healthy connective tissue and aids in early wound healing. It also facilitates dietary iron absorption from the intestine.
100 g of fresh fruit contains about 135 mg of potassium electrolyte. Potassium is an important component of cell and body fluids, helps controlling heart rate and blood pressure through countering sodium effects.
Red varieties of grapefruits are especially rich in the most powerful flavonoid antioxidant, lycopene. Studies have shown that lycopene protects skin damage from UV rays, and offers protection against prostate cancer.
Additionally, it contains moderate levels of B-complex group of vitamins such as folates, riboflavin, pyridoxine, and thiamin in addition to some resourceful minerals such as iron, calcium, copper, and phosphorus.