>how much is a unit?
Good luck, Anon:
https://en.wikipedia.org/wiki/International_unit
https://www.nhs.uk/conditions/vitamins-and-minerals/
https://dsid.od.nih.gov/Conversions.php
https://www.fda.gov/food/cfsan-constituent-updates/fda-provides-guidance-industry-convert-units-measure-certain-nutrients-nutrition-and-supplement