[boyband6666]

The interesting analogy Ross Tucker (https://sportsscientists.com/who-are-we/) uses is adding vitamins and mineral is like adding a wheel to a car. If you onyl have 3, then adding the 4th is really going to make a massive difference. If you already have enough however, it's like adding a 5th wheel, which will essentially do nothing, and could be harmful.

It works well as an explanation, as people do seem to try and reduce complex functions to simple rules, and extrapolate from specific populatiosn to create general rules (not helped by studies that are minimally generalisable)

[ozay]

Also look at 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.