While there is no doubt that excess vitamin intakes are useless or even harmful, the problem is that for most vitamins there is a great uncertainty about which are the optimum daily doses, because the controlled experiments that would be needed to determine those doses would be rightly deemed as unethical.

Therefore, since we only have some weak circumstantial evidence, debates about how much vitamin D is good, and the same about other vitamins, will continue. As long as the uncertainty persists, it is safer to ingest somewhat higher doses of vitamins than those recommended, but not many times higher.

The conclusions of the article were that high amounts of vitamin D have been shown to be correlated with good health outcomes, but the supplementation studies could not reproduce the same outcomes, so it remains mysterious what factor was associated with vitamin D in the studies with positive effects and whether vitamin D itself had any role or its presence was just a coincidence.