When I was a schoolkid, a teacher taught me a little trick to correctly associate the juice from citrus trees with vitamin c and scurvy. (Think of their common link : "C".)
I have found it useful to do much the same with the juice from penicillium molds, penicillin and pneumonia. (Think of their common link : "P".)
Today we realize that a food consists mostly of water (needed for digestion itself as well as for the rest of our bodily activities) and non-toxic materials we can not digest ( bone and fibre) also needed for digestion.
Each food also tends to be valued for the large amount of a single essential food type it produces .
( Think fat for butter, milk for the mineral calcium , meat for protein, potato for starch carbohydrates, oranges for vitamin c) but each of course also produces some of most of the other food types.
We need great varieties of unpurified foods because we need trace (or bigger) amounts of not just vitamins and minerals but also of different types ( in chemical terms , different shapes) of the basic sugars, fats and proteins to survive and grow healthy.
Variety even trumps sheer volume.
Finally a food tends to produce small amounts of substances that while perhaps not originally designed by the plant or animal to be a poison, are toxic to humans.
We manage these poison issues by avoiding plants or animals filled with them, by avoiding plant parts filled with them, only picking plants at certain times of their growing cycle, or by treating the food before cooking - or by expecting cooking to de-nature the poison.
Finally we manage them by eating them quite deliberately but hopefully in small amounts : coffee or alcohol for example.
If we accept this new science, we can see why it is better to eat "impure" (so called - inaccurately) oranges than it is to take daily semi-synthetic vitamin c pills described (inaccurately) as pure.
Ditto, we could take our penicillin not in pure pills ( inaccurately so called) but as penicillium juice and done with care - the same sort of care we need to take while eating potatoes - it will not harm us and is certainly better than fighting a severe infection without any antibiotic.
This is one of the basic thesis of my book : wartime penicillin thought of a sort of vitamin ...