Like other citrus fruits, grapefruit contain antioxidants, free radical scavengers, and the fiber pectin. Eating grapefruit not only helps with weight loss but can also help prevent diabetes mellitus. Please note the drug interactions described below.
From Wikipedia: “The grapefruit (Citrus × paradisi) is a subtropical citrus tree known for its sour to semi-sweet somewhat bitter fruit. Grapefruit is a hybrid originating in Barbados as an accidental cross between two introduced species, sweet orange (C. sinensis) and pomelo or shaddock (C. maxima), both of which were introduced from Asia in the seventeenth century. When found, it was named the “forbidden fruit”; and it has also been misidentified with the pomelo.
The grapefruit's name alludes to clusters of the fruit on the tree, which often appear similar to grapes.”
Colors and flavors:
“Grapefruit comes in many varieties. One way to differentiate between varieties is by the flesh color of fruit they produce. The most popular varieties cultivated today are red, white, and pink hues, referring to the internal pulp color of the fruit. The family of flavors range from highly acidic and somewhat sour to sweet and tart. Grapefruit mercaptan, a sulfur-containing terpene, is one of the substances which has a strong influence on the taste and odor of grapefruit, compared with other citrus fruits.”
“Grapefruit and grapefruit juice have been found to interact with numerous drugs and in many cases result in adverse direct and/or side effects (if dosage is not carefully adjusted.)
This happens in two very different ways. In the first it is postulated that the bioactivation effect is from bergamottin, a natural furanocoumarin in both grapefruit flesh and peel that ""inhibits"" the CYP3A4 enzyme, (among others from the P450 enzyme family responsible for metabolizing 90% of drugs). The action of this CYP3A4 enzyme itself ""inhibits"" the metabolism of many medications with the double negative inhibition actually increasing the drug's effects and side-effects. If the drug's breakdown for removal is lessened, then the level of the drug in the blood can become too high or stay too long, leading to adverse effects.
The other effect is that grapefruit can block the absorption of drugs in the intestine. If the drug is not absorbed, then not enough of it is in the blood to have a therapeutic effect. Each affected drug has either a specific increase of effect or decrease.
One whole grapefruit, or a glass of 200 mL (6.8 US fl oz) of grapefruit juice can cause drug overdose toxicity. Drugs which are incompatible with grapefruit are typically labeled on the container or package insert. People taking drugs can ask their health care provider or pharmacist questions about grapefruit / drug interactions.”
“Grapefruit is a rich source (>20% of the Daily Value, DV in a 100 gram serving) of vitamin C, contains the fiber pectin, and the pink and red hues contain the beneficial antioxidant lycopene. Studies have shown grapefruit helps lower cholesterol, and there is evidence that the seeds have antioxidant properties. Grapefruit forms a core part of the "grapefruit diet", the theory being that the fruit's low glycemic index is able to help the body's metabolism burn fat.
Although grapefruit seed extract (GSE) is promoted as a plant-based preservative by some natural personal care manufacturers, studies have shown that the apparent antimicrobial activity associated with GSE preparations is merely due to contamination with synthetic preservatives such as parabens.
There is a popular myth that grapefruits contain high amounts of spermidine, a simple polyamine that may be related to aging. The myth probably relies on the confusion between spermidine and putrescine. While citrus fruits show high amounts of putrescine, they contain very little spermidine.”
“Grapefruit has also been investigated in cancer medicine pharmacodynamics. Its inhibiting effect on the metabolism of some drugs may allow smaller doses to be used, which can help to reduce costs.”