If you take the blood thinner warfarin (Coumadin, Jantoven) to ward off clots, you’ll need to watch what you eat. Vitamin K can affect how the drug works. So you have to be careful about the amounts of kale, spinach, Brussels sprouts, chard, or collard or mustard greens you eat. Green tea, cranberry juice, and alcohol can affect blood thinners, too. So ask your doctor about them.