Gilhelmi said:
He doesn't need nutrition per se. The OP is an English speaking teenager on a videogame forum, you can be almost sure him and his brother are not in need of food and if they are malnourished it's a culturally issue, not an economic one. Having something in the stomach however will trick the brain into eating the sense of appetite.
Herbicides and the possible bacteria or parasites are the drawback, easing a very slight hunger risking getting sick seems quite the dumb choice, I guess he can take the risk safely in this case but wouldn't bet on him on the Hunger Games.