In addition to the effects of drugs, many foods and nutrients can also affect the anticoagulant effect of warfarin. When patients take oral warfarin for anticoagulation therapy, they should try to maintain a balanced dietary structure, not to add nutrients blindly, and to monitor prothrombin time (PT) and international normalized ratio (INR) regularly. Grapefruit contains ingredients that inhibit hepatic cytochrome P450 (CYP) 3A4 activity, which reduces the metabolism of warfarin and makes the anticoagulant effect stronger. Fish oil enhances the anticoagulant effect of warfarin by inhibiting platelet aggregation and reducing the levels of thromboxane A2 and vitamin K-dependent coagulation factor VII. The anticoagulant effect of warfarin is also enhanced by the combination of mango and warfarin, but the mechanism of action is not known. Foods rich in vitamin K, such as many green leafy vegetables, egg yolks, pork liver, and green tea, may reduce the anticoagulant effect of warfarin. Avocados, soy milk, and seaweed can weaken the anticoagulant effect of warfarin by altering its metabolism or affecting its absorption.