If an effect refers to a Food, it means any Food artifact, not just a Food token. For example, when you activate the second ability of Ragost, Deft Gastronaut (which says “{1}, {T}, Sacrifice a Food: Ragost deals 3 damage to each opponent”), you can sacrifice Nutrient Block to pay its cost.

You can’t sacrifice a Food to pay multiple costs. For example, you can’t sacrifice a Nutrient Block to activate its own last ability and also to pay the cost of Ragost, Deft Gastronaut’s second ability.