There has been a hell of a lot of research over the last 150 years which show how dramatically ill you become if those minimum levels are not maintained - scurvy in long sea voyages in the 18th and 19th century are a good example. I think that the reports to which you refer are the taking of massive doses of one or more vitamins. Bodies such as the NIH and equivalent around the world have determined the levels required to avoid deficiency illness.As you say, a deficiency for a few days can easily be made up on return to civilisation. Not true on a long through hike.