https://www.ncbi.nlm.nih.gov/m/pubmed/22364157/ https://www.ncbi.nlm.nih.gov/m/pubmed/22364157/ Note that 'required' likely means "less than the RDA" and that

https://www.ncbi.nlm.nih.gov/m/pubmed/22364157/ https://www.ncbi.nlm.nih.gov/m/pubmed/22364157/ Note that 'required' likely means "less than the RDA" and that RDAs are often set on the basis of "having less than this much will imminently lead to some sort of dysfunction" as opposed to "the amount that actually makes your body happy".