Grapefruit and medicines: why it matters so much
The interaction between grapefruit and medicines is one of the best-studied food-drug interactions. Section “Food and medicines: with what, and when” covered the general rules; this section looks in detail at grapefruit and related citrus fruits.
01Short answer
02Simple explanation
No grapefruit or pomelo.
No bitter orange.
The effect lasts days.
Sweet oranges: usually fine.
03Scientific explanation
FDA: furanocoumarins in grapefruit juice irreversibly block gut CYP3A4; the effect lasts until new enzyme is made.
WHO: foodborne illness is more severe in people with weakened immunity; the five keys are keep clean, separate, cook thoroughly, keep food at safe temperatures, and use safe water and raw materials.
04What happens in the body?
Hidden sources
Some fruit blends, juices and cocktails contain grapefruit; read the label.
Earlier intake
If you were eating grapefruit before treatment began, tell your team.
Neutropenia
When neutrophils are low, even ordinary germs can cause serious infection, which is why the rules are stricter.
General rules
This section is part of the general food-safety rules in “Handwashing: the simplest protection” and “Eggs and dairy: safe choices” and “Food safety: four simple rules”.
05Safety: four steps
Check, swap the risky, prepare properly, use in time.
06Key points at a glance
| Topic | In brief |
|---|---|
 Hidden sources | Some fruit blends, juices and cocktails contain grapefruit; read the label. |
 Earlier intake | If you were eating grapefruit before treatment began, tell your team. |
 Neutropenia | When neutrophils are low, even ordinary germs can cause serious infection, which is why the rules are stricter. |
 General rules | This section is part of the general food-safety rules in “Handwashing: the simplest protection” and “Eggs and dairy: safe choices” and “Food safety: four simple rules”. |
07Key terms
- Furanocoumarin
- A grapefruit substance that blocks the enzyme.
- Venetoclax
- A targeted medicine used in some leukemias.
- Foodborne infection
- An infection spread through food or water.
- Neutropenia
- Low neutrophils.
08Key points
- Avoid grapefruit.
- Read labels.
- Ask your pharmacist.
- When in doubt, throw it out.
- Call if you have a fever.
09Frequently asked questions
Is even a slice harmful?
For some medicines even a small amount has an effect; avoid it.
Is lemon OK?
Lemon is usually safe.
Are these rules for ever?
No. They are usually relaxed as blood counts recover; your team will say.
10Questions for your doctor
Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.
Is even a slice harmful?
Is lemon OK?
Are these rules for ever?
12Sources
- U.S. Food and Drug Administration. Grapefruit Juice and Some Drugs Don't Mix
- World Health Organization. Five Keys to Safer Food manual
- World Health Organization. Food safety fact sheet
- U.S. Food and Drug Administration. Safe Food Handling
- National Cancer Institute. Eating Hints: Before, During, and After Cancer Treatment
- Annals of Oncology, 2020. Cancer-related fatigue: ESMO Clinical Practice Guidelines for diagnosis and treatment
- Sleep Medicine Reviews, 2016. A systematic review and meta-analysis of randomized controlled trials of cognitive behavior therapy for insomnia (CBT-I) in cancer survivors
- CDC. Preventing Food Poisoning
- American Cancer Society. Food Safety During Cancer Treatment
- Leukemia & Lymphoma Society. Diet Guidelines for Immunosuppressed Patients