Grapefruit is harvested from the homonymous plant, the evergreen Citrus paradisi native to the Caribbean and then spread to many countries with a temperate climate.

The main producers are the United States (Florida), California and Israel.

White varieties: Marsh, Oroblanco, Duncan,  Golden, Wheeney, Melogold, Sweetie. 

Pink varieties: Marsh Pink, Ray Ruby, Redblush, Shambar, Foster, Henderson.

Red varieties: Star Ruby, Flame, Rio Red

It has a good content of citric acid, potassium, magnesium, vitamin C (1).

Grapefruit juice is one of the relatively low-calorie fruit juices, only 39 calories.

Grapefruit has a high content of polyphenols among which the class of flavonoids counts for 80% (1). Grapefruit seed extract has demonstrated antibacterial efficacy in disinfecting denture surfaces and removing biofilms without causing deterioration on the surface of the resins (2).

Grapefruit studies

Contraindications: If grapefruit is taken in combination with certain drugs (statins, calcium blockers and others) it may cause interactions (3). Consult your doctor.

References_______________________________________________

(1) Ivanova NN, Khomich LM, Perova IB, Eller KI. Grapefruit juice nutritional profile. Vopr Pitan. 2018;87(5):85-94. doi: 10.24411/0042-8833-2018-10057. Epub 2018 Sep 13. PMID: 30592894.

(2) Tsutsumi-Arai C, Takakusaki K, Arai Y, Terada-Ito C, Takebe Y, Imamura T, Ide S, Tatehara S, Tokuyama-Toda R, Wakabayashi N, Satomura K.   Grapefruit seed extract effectively inhibits the Candida albicans biofilms development on polymethyl methacrylate denture-base resin.  PLoS One. 2019 May 28;14(5):e0217496. doi: 10.1371/journal.pone.0217496.

Abstract. This study aimed to investigate the cleansing effects of grapefruit seed extract (GSE) on biofilms of Candida albicans (C. albicans) formed on denture-base resin and the influence of GSE on the mechanical and surface characteristics of the resin. GSE solution diluted with distilled water to 0.1% (0.1% GSE) and 1% (1% GSE) and solutions with Polident® denture cleansing tablet dissolved in distilled water (Polident) or in 0.1% GSE solution (0.1% G+P) were prepared as cleansing solutions. Discs of acrylic resin were prepared, and the biofilm of C. albicans was formed on the discs. The discs with the biofilm were treated with each solution for 5 min at 25°C. After the treatment, the biofilm on the discs was analyzed using a colony forming unit (CFU) assay, fluorescence microscopy, and scanning electron microscopy (SEM). In order to assess the persistent cleansing effect, the discs treated with each solution for 5 min were aerobically incubated in Yeast Nitrogen Base medium for another 24 h. After incubation, the persistent effect was assessed by CFU assay. Some specimens of acrylic resin were immersed in each solution for 7 days, and changes in surface roughness (Ra), Vickers hardness (VH), flexural strength (FS), and flexural modulus (FM) were evaluated. As a result, the treatment with 1% GSE for 5 min almost completely eliminated the biofilm formed on the resin; whereas, the treatment with 0.1% GSE, Polident, and 0.1% G+P for 5 min showed a statistically significant inhibitory effect on biofilms. In addition, 0.1% GSE and 0.1% G+P exerted a persistent inhibitory effect on biofilms. Fluorescence microscopy indicated that Polident mainly induced the death of yeast, while the cleansing solutions containing at least 0.1% GSE induced the death of hyphae as well as yeast. SEM also revealed that Polident caused wrinkles, shrinkage, and some deep craters predominantly on the cell surfaces of yeast, while the solutions containing at least 0.1% GSE induced wrinkles, shrinkage, and some damage on cell surfaces of not only yeasts but also hyphae. No significant changes in Ra, VH, FS, or FM were observed after immersion in any of the solutions. Taken together, GSE solution is capable of cleansing C. albicans biofilms on denture-base resin and has a persistent inhibitory effect on biofilm development, without any deteriorations of resin surface.

(3) Dahan A, Altman H. Food-drug interaction: grapefruit juice augments drug bioavailability--mechanism, extent and relevance. Eur J Clin Nutr. 2004 Jan;58(1):1-9. doi: 10.1038/sj.ejcn.1601736. 

Abstract. More than a decade has passed since it was unintentionally discovered that grapefruit juice interacts with certain drugs. The coadministration of these drugs with grapefruit juice can markedly elevate drug bioavailability, and can alter pharmacokinetic and pharmacodynamic parameters of the drug. The predominant mechanism for this interaction is the inhibition of cytochrome P-450 3A4 in the small intestine, resulting in a significant reduction of drug presystemic metabolism. An additional mechanism is, presumably, the inhibition of P-glycoprotein, a transporter that carries drug from the enterocyte back to the gut lumen, resulting in a further increase in the fraction of drug absorbed. Some calcium channel antagonists, benzodiazepines, HMG-CoA reductase inhibitors and cyclosporine are the most affected drugs. A single exposure to one glass of the juice can usually produce the maximal magnitude of the interaction. The data available so far, concerning this interaction and its clinical implications, are reviewed in this article. It is likely that more information regarding this interaction will accumulate in the future, and awareness of such is necessary for achieving optimal drug therapy.

Lama T A. Grapefruit juice interaction with drugs. Rev Med Chil. 2006 May;134(5):665-6. Spanish. doi: 10.4067/s0034-98872006000500017. Epub 2006 Jun 19. PMID: 16802061.

Palumbo G, Bacchi S, Palumbo P, Primavera LG, Sponta AM. II succo di pompelmo: una potenziale interazione con i farmaci [Grapefruit juice: potential drug interaction]. Clin Ter. 2005 May-Jun;156(3):97-103.

Abstract. More than a decade has passed since it was unintentionally discovered that grapefruit juice interacts with certain drugs. The coadministration of these drugs with grapefruit juice can markedly elevate drug bioavailability, and can alter pharmacokinetic and pharmacodynamic parameters of the drug. The predominant mechanism for this interaction is the inhibition of cytochrome P-450 3A4 in the small intestine, resulting in a significant reduction of drug presystemic metabolism. An additional mechanism is the inhibition of P-glycoprotein, a transporter that carries drug from the enterocyte back to the gut lumen, resulting in a further increase in the fraction of drug absorbed. Some calcium channel antagonists, benzodiazepines, HMG-CoA reductase inhibitors and cyclosporine are the most affected drugs. A single exposure to one glass of the grapefruit juice can usually produce the maximal magnitude of the interaction. The data available so far, concerning this interaction and its clinical implications, are reviewed in this article. It is likely that more information regarding this interaction will accumulate in the future, and awareness of such is necessary for achieving optimal drug therapy.