In fact, grapefruit is very rich in nutritional value, it contains a large number of nutritional elements, including protein and organic acids required by the body, it also contains a variety of vitamins and calcium, phosphorus, magnesium and sodium and other essential trace elements of the body. Grapefruit is the best therapeutic fruit for patients suffering from cardiovascular disease and kidney disease. It is an auxiliary treatment for diabetes, vascular sclerosis and other diseases, and has a body-building function for obese people. Why can’t cancer patients eat grapefruit while they are taking targeted drugs? It is because the furanocoumarins and their compounds in grapefruit have a strong inhibitory effect on CYP3A4 activity, interfering with the metabolism of anti-cancer drugs and thus affecting their efficacy in the body. cyp3a4, named cytochrome P4503A4 enzyme, is an important enzyme in the body, mainly found in the liver and small intestine, which can oxidize exogenous organic small molecules, such as toxins or drugs, so that they can be excreted from the body. The cyp3a4 enzyme inactivates many drugs, but at the same time it increases the activity of some drugs, such as grapefruit juice and certain drugs, which can be disturbed by the action of cyp3a4, and these substances will increase or diminish the effect of the drug. There is also a claim that a drug taken with grapefruit is equivalent to taking 20 pills in a row. Researchers found that the potential for CYP3A4 activity inhibition in various juices was grapefruit > blackberry > wild grape > pomegranate > blackberry, in that order. Therefore, patients are advised to avoid grapefruit and beverages and foods containing grapefruit ingredients during the use of targeted drugs.