This is the argument against pharmaceuticals, and I think it is a strong one: If defeating your body's natural systems via interfering with a single biochemical pathway makes you healthier, then your ancestors would have easily evolved such a thing. Every biochemical pathway has regulators, and natural selection can adjust them. Exogenous substances adjusting these pathways is directly in contradiction to what your body is trying to do (for example, anti-inflammatories defeat your body's natural inflammation; anti-pyretics defeat your body's natural fever; pain relievers defeating our body's natural way of avoiding further tissue damage). And clearly your body is trying to be healthy.

There are exceptions, however; pharmaceutical interventions that don't fall into that category. But businesses want to sell more things to make more money, and so they will expand into drug targets that wise people would best avoid.