Sir Karl Popper suggested reality is objective, our description of reality (conjectures) only provisionally true and subject to further inquiry (refutations). I can see that as truth being local in time, true for now. Most or all conjectures will be refuted over time, at minimum by being added to and clarified.

I think some of what we know about nutrition will endure (humans prosper when we drink clean water in some amount and with some regularity) but much of it seems in great flux. What constitutes nutrition in different nations today differs, whatever the objective truth might be. And nutrition within a single nation isn't for all (what an infant needs versus an adult, for example).