Unless we manage to survive on supplements and eat only portion of plants that can grow back, eating more often than not involves us taking a life to stay alive.

That's one way of looking at it.

In the food chain, plants make food and animals eat plants, sometimes plants digest or make use of animals - but whatever is at the top of the food chain finally dies and its body decomposes, giving itself back to the soil. Plants then absorb the nutrients from the soil. At each state of the process, different life-forms act as stewards of the "material" on which life runs. What we call "life" could be just a perceived manifestation of the continuous cycle than runs through the whole food chain. Just like a jar of soil and water when shaken settles into layers - neither the soil nor the water need to "think" about what to do; it happens because the soil, the water, the jar and the Earth all agree that that is the way of things that rises out of natural ease.

That is, until the modern man comes into the picture. The modern eats everything, but in the end when he dies, his body is burnt up and put into a container, so that nothing returns to the soil. "Natural" is hardly an apt description for the modern man.

[fork 1]
Some decide that they should not eat at the expense of another life. Some define for themselves whatever they think is "natural". For me, I think the only things that are "natural" are natural selection and random mutation. In the modern context, this natural selection and random mutation is best seen in the way language evolves. Maybe that could imply that one single person can never be "natural". "Natural" is whatever that happens to happen, when viewed from the collective consciousness of the entire species, food chain, or ecosystem. Man's "un-natural-ness" becomes "natural" when taken into the context of the Earth's history.

[fork 2]
"Natural" and "artificial" in this case could be an analogy for "analogue" and "digital", for "being" and "doing", for "feeling(receptive)" and "thinking(creative)". Modern man prefers "digital", "doing" and "thinking". I would like to think that sufficiently advanced "digital" technology approaches the analogue, an identity based solely on "doing" is also a way of "being", that there is a way of thinking that is indifferentiable from feeling, and that the artificial when taken far enough, approaches the natural.

[fork 3]
Now say, is it possible to create a machine, that can absorb minerals and synthesize sugars, amino acids then proteins, and go all the way until it becomes flesh-like substance that can form a diet that sustains human life, all through made-created autonomous processes? Would the medium of such processes be subject to man's own discourses and receive objections because it could be called "life"?

[wait]

Which is why when I eat, I give thanks, eat my meat, and shut up.