Is food life support?

My good friend over at Random brain dribbles wrote something I want to talk about more. He writes:

If she is going to be killed (and let's face it, she's not on a ventilator or a heart/lung machine - she's on a permanent feeding tube. Big difference in degree), then oughtn't we, as a society, do so in a manner known to be quick and painless?

As I said in subsequent comments, I have no problem with the idea of giving morphine to someone whose feeding tube has been removed. In Ms. Schiavo's case, I think that will do more to comfort onlookers than to comfort the patient, but it's worth making sure her death is painless.

The common opinion my friend touches on is this: artificial breathing is life support, but artificial feeding isn't.

What's the difference? It seems to me, the difference in the mind of most is that without breath, people die quickly. Turn off the respirator or the heart machine, and the patient is dead in minutes. Food, on the other hand, we only eat a few times a day. It takes a week to starve to death. Air and food are both basic necessities for life, but food seems less necessary since we can go without it for so long. Calling food "life support" is just a step up from calling television life support. Patients might claim they'll just die if they miss tonight's exciting episode, but it's not true. They also don't die if they miss a meal. Anything you don't really need to live isn't really life support.

This difference is a matter of degree (perhaps a "big difference in degree," as my friend says). "No food" kills as surely as "no air," but more slowly. A patient can go without air for a short time with no ill effects. Likewise food, but the "short time" is longer. I don't think that's enough of a difference to rule food out of the "life support" category. Opinions will differ.