The grapefruit (Citrus paradisi) is so named because it grows in clusters in the same way as grapes, However, grapefruit is grouped with other citrus fruit such as the orange, lime and lemon. The grapefruit is thought to be a result of natural breeding between the orange and another citrus fruit called the pomelo, and may have originated in Barbados in the 1700’s. Like all citrus fruits, the grapefruit has some unique nutritional properties amongst other fruits that makes them worthy of discussion. Citrus fruits are generally high in flavonoids of the subclass flavanones. The flavanones in grapefruit include hesperidin and naringin which are the glycosides (bonded to a sugar) of hesperetin and naringenin, respectively. The total flavanone content of grapefruit is around 27 mg per 100 grams of fruit (as aglycones), with naringenin being the dominant flavanone1. The white grapefruit varieties have slightly higher flavanone concentrations that the pink varieties. Flavanones may help protect from cancer and cardiovascular disease because they are antioxidants and may be involved in gene regulation.
Grapefruits like all citrus fruits are also rich in vitamin C, and contain high concentrations of potassium but low concentrations of sodium. Their vitamin C, potassium and flavanone profile makes them cardioprotective as these nutrients show beneficial effects against cardiovascular disease. Further, grapefruits contain pectin, a form of soluble fibre that may also be cardioprotective. The edible part of a grapefruit contains roughly 4 % pectin with the total grapefruit containing around 8 % pectin. A 15 gram portion of grapefruit pectin per day has been shown to be able to lower plasma cholesterol levels by around 10 %, which suggests that eating two grapefruits per day could lower the risk of cardiovascular disease by around 20 %. Pectin is found not just in grapefruits and many other fruits contain sizable amounts of pectin. Naringin may also normalise hematocrit levels through the elimination of red blood cells from the body. However, naringenin does not affect normal hematocrit levels and actually raises low levels. Such balancing effects are common in many herbs but this effect is not understood to science.
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