Also look at Liebig's barrel (https://en.wikipedia.org/wiki/Liebig%27s_law_of_the_minimum#Liebig's_barrel) https://en.wikipedia.org/wiki/Liebig%27s_law_of_the_m

Also look at Liebig's barrel (https://en.wikipedia.org/wiki/Liebig%27s_law_of_the_minimum#Liebig's_barrel) https://en.wikipedia.org/wiki/Liebig%27s_law_of_the_minimum#.... It was originally applied to plant growth, but it is a helpful metaphor for vitamin substitution.