Yeah 400-600 is nothing and bare minimum for survival. I take at least 4000 a day on average as here in the winter I get almost no time in the sun since it's dark when I leave for the office and dark when I leave the office, recently my dad's doc recommended that he take 10,000 a day until his next test as he had low levels this winter. Vitamin D3 is used by the body for many things like generating testosterone, if anything there's a reason right there why they keep telling you that you don't need more vitamin D.

Magnesium is another one where the RDA is too low. They say 400mg/day but I was still getting woken up at night by leg cramps. I found a calculator that said for my body weight I should be taking around 700mg/day, that amount fixed my issue.

Yeah 400-600 is nothing and bare minimum for survival. I take at least 4000 a day on average as here in the winter I get almost no time in the sun since it's dark when I leave for the office and dark when I leave the office, recently my dad's doc recommended that he take 10,000 a day until his next test as he had low levels this winter. Vitamin D3 is used by the body for many things like generating testosterone, if anything there's a reason right there why they keep telling you that you don't need more vitamin D.