The difference between a nutritious compound and a deadly one can be tiny. The difference between cis and trans fats, for example, is a mere bend in the molecule. Removing an oxygen from the link between the “components” of a disacharide could easily turn it or its metabolites into a carcinogen. Remember that DNA has a ribose structure in it — a sugar. Mess with sugar molecules and you could create a sugar derivative that confuses a genetic enzyme — viola, cancer.
The only safe chemicals are chemicals we have evolved with.
If “evolution” is looked to as the architect of mankind, it would be expected to do a spectacularly poor job with the needs of the aged. After all, once you’re past child rearing age, if not child bearing age (and in past times, it was normal for people to begin bearing children while still in their teens), you are no longer Darwin fodder. Culture and spirituality and reverence for the aged are all luxury in a world where one is for oneself and survival is for the fittest.