Coumadin (Warfarin) is an anti clotting drug shown to have significant benefit in protecting people with atrial fibrillation from having a stroke. Can patients on Coumadin eat all the green leafy vegetables with vitamin K, which may shorten their clotting time? The answer most emphatically is YES! Inform the physician who is monitoring the Coumadin and clotting time that you are regularly going to be eating copious amounts of healthy green leafy vegetables. He/she will appropriately adjust the Coumadin dose.