I think the statement “the human digestive system is very efficient at squeezing everything it can out of any food?" refers to the way the stomach is good at absorbing the wanted nutrients and keeping them in the body, while disposing of the unwanted waste and toxins. The biomolecules are broken down to preserve only certain nutrients within the molecules.
All of these are not part of the life cycle. It's man-made. Think of it in biology terms - something that's created genetically.
Natural Selection, Charles Darwin coined the term “survival of the fittest”