Cancer patients must pay attention! This fruit is now widely available, but you may not be suitable to eat it!

This starts with grapefruit, especially grapefruit/grapefruit is rich in a substance calledfuranocoumarin, which is a natural substance.44>CYP3A4Enzyme inhibitors.

During the process of drug metabolism in the human body,CYP3A4Enzymesplay a catalytic role in drug metabolism. In clinical practice, over 50% of drugs require CYP3A4 for metabolism and clearance from the body.

When the CYP3A4 enzyme encounters furanocoumarin compounds that inhibit it, this metabolic pathway becomes blocked, leading to two distinct but equally dangerous outcomes:

① Drug accumulation and toxicity

Normally, drugs that should undergo a round of metabolism in the intestine are not metabolized as expected due to the "blocking" effect of furanocoumarin compounds in grapefruit, resulting in an abnormal increase in drug concentration in the blood (plasma drug concentration), equivalent to "overdosing", which may increase the risk of adverse reactions.

② Reduced efficacy

Certain prodrugs, such as irinotecan and cyclophosphamide, requireactivation by CYP3A4enzyme to exert their anticancer effects. The inhibition of furanocoumarin compounds in grapefruit can reduce the production of active metabolites, which is equivalent to"weakening"the drug's efficacy.

What's more troublesome is that the recovery of CYP3A4 in the intestine requires the enzyme to be resynthesized, which takes approximately 24~72hours. In other words, it is best to avoid grapefruit for

Chemotherapy drugs that must be kept away from grapefruit

Targeted drugs that must be kept away from grapefruit^[2] 

Due to space limitations, you may not find the drug you are using in the table. Don't worry, you can take out the drug instruction manual in your hand and look for the section on Contraindications or Precautionsto see if there are any restrictions related to “grapefruit, grapefruit juice, etc.”.

Umbelliferae vegetables, include celery, cilantro, fennel, and carrot, which are all well-known to us. Among them, there are quite a few "hidden champions" of furocoumarin , with some even surpassing grapefruit in content:

① Parsley

contains 35~55 mg of furocoumarin per 100 grams of fresh parsley leaves, which is already comparable to grapefruit , and the 'parsley powder' that people often use for seasoning when cooking, after being dried, increases furocoumarin by 3fold .

② Common celery

Celery leaves contain 8~18 mgof furocoumarin per 100g of fresh leaves, while celery stems contain 1~4 mgper 100g. Eating normally about 100g has little effect, but forPeople who are accustomed to drinking celery juice should be wary of the risks posed by concentrated furanocoumarins. Coriander, also known as cilantro, contains 5 to 12 mg of furanocoumarins per 100 grams of fresh leaves. However, as coriander is typically used as a seasoning and consumed in small amounts, there is no need for strict control. The exception is those who have a strong preference for coriander, known as "coriander heads".

Carrots

The furanocoumarins in carrots are mainly concentrated in the leaves, while the root and stem parts that we commonly eat contain very low levels of furanocoumarins. They can be consumed normally."

In the long-term battle against cancer, every detail can affect the final outcome. Every year when pomeloes are in season, some people fall victim to their toxicity. I hope you, who are reading this article, can share it and help more people avoid this hazard.

Reference source:

[1]Rendic S, Ci Carlo FJ.  Human cytochrome P450 enzymes: a status report summarizing their reactions, substrates, inducers, and inhibitors.   Drug Metab Rev  1997; 29:413-580.

[2]Guiding Principles for the Clinical Application of Novel Antitumor Drugs (2024 Edition)). National Health Commission. January 2025.

Written by: Li Si

Audited by: Lehe New Medical Department
 

Edited/typeset by JOJO  

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