Technically, people vary so much we can't even tell you your needs. E.g. the RDA is sth like a 2 sigma excess. It's not enough for 4% or so of ppl. And even

Technically, people vary so much we can't even tell you your needs. E.g. the RDA is sth like a 2 sigma excess. It's not enough for 4% or so of ppl. And even if we could know out needs from day to day, the food varies quite a bit, by varietal, location and season. There's still more wiggle room, bc if we get excesses or shortages, our responses may vary unpredictably. With extra calories, we might suddenly decide to clean the garage. We are not precise machines in a precise environment. Our sexual reproduction and mutations -and that of our food- constantly reshuffle the deck, guaranteeing we can only make broad predictions. The best we can do is accumulate knowledge, observe and create feedback.