Since modern medical technology can support the non-intelligent functions of a human body virtually indefinitely (subject to natural aging), the issue has arisen as to whether people in irreversible coma and on life-support systems should be maintained in a vegetative state or allowed to die.
A brain dead survivor of a UK soccer riot in 1989, who had his chest crushed and brain deprived of oxygen, had his feeding bottle discontinued in 1993 following a court order which ruled he had no hope of recovery. The Law Lords called on Parliament to draw up guidelines for future cases, saying the courts were the wrong bodies to decide such controversial ethical and moral issues.
If the reflex and metabolic functions of the human body are normal, it is not appropriate to withdraw nourishment, by way of feeding tubes, in order to "let nature run its course". This would be death by starvation, in a similar way to refusing to spoon-feeding an old person with senile dementia. A death with dignity would mean to continue with supporting the natural functions of the body, but when it starts to fail or an infection strike, as will happen, there should be no interventions (antibiotics etc) to stave off the inevitable.