Protein is such an important nutrient. It's one of the basic building blocks of the human body. According to About.com, next to water, protein is the most plentiful substance in the body. It builds and repairs body tissues, produces enzymes, hormones, and other substances the body uses. With so many options available, why not choose a greener protein source? Next time you're grocery shopping, try one of these green protein option.

Top five green protein sources: