In principle, people can eat grass; it is non-toxic and edible. As a practical food source, however, your lawn leaves a lot to be desired.
There are two main problems with a grass diet. The first is that human stomachs have difficulty digesting raw leaves and grasses. Animals such as cows, on the other hand, have a specialized stomach with four chambers to aid in the digestion of grass (a process called rumination).
Aside from the digestion issues, a second problem with grass as a food source is the mastication. Your dentist would not be pleased; grass contains a lot of silica, an abrasive which quickly wears down teeth. Grazing animals have teeth that are adapted to continually grow, replacing the worn tooth surfaces quickly.
Originally published on Live Science.