Besides extensive studies, there is little reason to be sure any particular intake of a particular nutrient or medicine is optimal. What is considered "natural", "normal" or "sufficient" is not necessarily the best in terms of the results you are going get.

Theoretically it is well possible (unless real studies indicate it's not) unnaturally huge dose of a particular nutrient may happen to be very beneficial. It is also possible deficiency in particular nutrients may happen to be beneficial too.

Although I'm not actually one of vitamin mega-dosing maniacs, I actually believe the chances the official RDAs (let alone ordinary rations) are optimal are fairly low.