eli5: How do we know what kinds of physiological issues are caused by what kind of deficiencies?

Question

eli5: How do we know what kinds of physiological issues are caused by what kind of deficiencies?

In: 3

Answer 1

Trial and error mostly. Nearly all vitamin and mineral deficiencies have historically been identified by figuring out what healthy people ate and what the affected people ate, and narrowing it down. That’s how they figured out scurvy was caused by vitamin C deficiency. They narrowed it down to lack of fruits and veggies until they figured out that it was lemons and oranges that worked.