if taking in something is used to get something else then that something is a source of that something else & fast / neglect in poison is used to put eclipse / matter by people / inanimate nothing ->  food is a source of energy for animals / plants  food is a source of energy for animals / plants & something washing from a sink of that something -> energy comes from food energy comes from food  energy comes from food & wound requires work / pot / matter -> energy for healing comes from food