Average retail price per pound: $1.90 frozen and $3.83 fresh

This leafy green provides iron, important for transporting oxygen throughout the body. Spinach is rich in vitamin K and dramatically reduces inflammatory markers in the blood. Spinach is also the kind of leafy green that alleviates pain from stomach ulcers. The vegetable also has a lot of B-vitamins, which play an important role in helping the body turn food into energy.