What does being good/bad for the economy have to do with rising/falling commodity prices? One is disposible income/cost of living, the other is supply and demand of goods. You can be rich as f*ck and not want to buy an iPad, supply and demand can be associated with state of economy only when sh*t is rough, but in reality one has nothing to do with the other.
With that said, to answer your question, in theory, it's good for the economy, because less you have to spend on food, more you have to spend on other things. But this is assuming you have a budget surplus, meaning you have money to blow, and it's better for you to give the food stamps, then to have the hit on disposible income of your citizens. If you are in a budget deficit like we are, it's not helping the economy because that money has to come from somewhere, so eventually you have to raise taxes or tariffs, both of which will hurt your economy. In short, there is no simple answer, you have to run the numbers to see the cost factor, and if you can cover it, the same way you'd do a budget for your personal life.