Why you need it: Vitamin K is a crucial ingredient in coagulation, or blood clotting. Without it, your body would not be able to stop bleeding when you bruise or cut yourself. Where to get it: Green, leafy vegetables are the best source of this vitamin, also known as phylloquinone. Kale leads the pack with 1.1 mg per cup, followed by collard greens and spinach (about 1 mg per cup), and more exotic varieties like turnip, mustard, and beet greens.