Educational information, not medical advice — ask your doctor or midwife.
Grapefruit is the fruit of Citrus paradisi, a citrus tree grown across the Caribbean and other warm regions. In Haiti it is called chadèk or pamplemous. In Cuba it is toronja.
The most important thing about grapefruit is not a health benefit. It changes how your body handles many prescription drugs. That effect is proven in people, and with some drugs it can be dangerous.
Caribbean home practice used the fruit, the juice and the peel for digestion, for colds and fevers, and to "cool" the body. Traditional use tells you a remedy is old and valued. It does not tell you that it works, or that it is safe.
As food, grapefruit is a good source of vitamin C and fibre. As a treatment for any named illness, the human evidence is thin. The clearest, best-proven thing it does is interfere with medicines.
Grapefruit blocks an enzyme in your gut wall called CYP3A4. This enzyme breaks down many drugs before they reach your blood. When it is blocked, more of the drug gets through than the dose intended.
This is not a theory. It has been shown many times in people, and drug makers print warnings about it.
A single glass of juice can be enough. The effect can last 24 hours or more. So spacing the fruit away from your pill does not fix it.
The chemicals behind this are furanocoumarins, mainly bergamottin and a related compound. Grapefruit can also slow a transporter called OATP, which moves some drugs into the body. That can push the level of a few drugs down instead of up.
The traditional claims work differently, and the evidence is weaker. Naringin, the bitter flavonoid in grapefruit, has shown anti-inflammatory and blood-sugar effects in cell and animal studies. Whether that happens in people eating fruit is not established.
Pectin, the soluble fibre in the pulp, may modestly help cholesterol as part of a diet. Vitamin C in the fruit prevents and treats scurvy, which is a real and settled effect. Beyond that, do not expect grapefruit to treat a disease.
Fresh fruit and fresh juice are the common forms, and both carry the drug interaction.
Bottled and frozen juice also carry it. So does white grapefruit, pink grapefruit, and juice mixed into other drinks.
Other forms you may meet:
Peel tea, made from dried or fresh rind, a Caribbean home preparation.
Grapefruit essential oil, used in scent and skin products. It is not for swallowing.
Grapefruit seed extract, sold in drops and capsules as a supplement.
Naringin or bioflavonoid capsules, sold as supplements.
Supplement forms are not standardised. One brand may differ a lot from the next.
Grapefruit arose in Barbados in the 1700s, as a cross between pomelo and sweet orange. It spread through the Caribbean and then to Florida and beyond.
In Haitian and Cuban home practice the fruit became a household remedy. Peel and leaf teas were drunk for colds, fevers and upset stomach. The juice was taken as a tonic and as a "cooling" drink in hot weather.
In parts of the region the bitter peel was also given for poor appetite and sluggish digestion. These were household customs passed down in families, not tested treatments.
The drug interaction was found by accident in the late 1980s. Researchers used grapefruit juice to hide the taste of alcohol in a blood pressure drug study. The drug levels came out far higher than expected, and the grapefruit was the reason.
When to see a doctor: stop grapefruit and get medical advice if you notice new symptoms after eating it while on medicine.
See a doctor the same day for:
Muscle pain, tenderness or weakness, especially on a statin.
Dark or tea-coloured urine.
Dizziness, fainting or a pounding, racing or very slow pulse.
New or unusual bruising or bleeding.
Severe drowsiness or confusion.
Call emergency services for chest pain, collapse, or bleeding you cannot stop.
Do not stop a prescribed medicine on your own. Change the fruit, not the drug, unless your doctor tells you otherwise.
Grapefruit is an ordinary food in the UK, the EU, the US and across the Caribbean, with no restriction on sale. Medicine regulators require grapefruit warnings on the labels of many affected drugs. Grapefruit seed extract and flavonoid capsules are sold as food supplements and are not approved to treat any illness.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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