Withdrawal of support (feeding tube, respirator, stabilizing medication, etc) is the only legal option for allowing someone to die now. All but the feeding tube will typically result in death in minutes.

Starvation will take days. That sucks.

Why can't we use the same lethal injection protocol used for capitol punishment? Its specifically designed to be humane (unlike starvation) and I see no difference between this and "putting down" a terminally ill animal.