The blood-thinning medication, warfarin decreases the chance of harmful blood clots by blocking the effects of vitamin K which helps blood-clotting proteins form in the liver. Your warfarin dose is determined by your PT or INR measurements that show how long it takes for your blood to form clots.
A document published by ImpactTeam looks at how your diet affects warfarin and how the amount of vitamin K in your diet will determine the warfarin dose needed to prevent bleeding. Warfarin may have possible interaction with cranberry juice, mango juice, grapefruit juice, caffeine, charbroiled foods, alcohol, garlic, soy, ginger, and green tea. In addition, there is potential interaction of dietary supplements with warfarin.
Source: Warfarin and your Diet