Mat, the Fitness Director at the Northwest CT YMCA, chose another food that I eat nearly everyday as the next superfood. Spinach is awesome and should be incorporated in everyone's diet.
So why is spinach important? Just look at Popeye! It does build strength as it's 30% protein. If you combine spinach with sunflower seeds or beans, you'll have a complete protein, all of the necessary amino acids required to build muscle.