There are 9 Amino Acids body can’t produce by itself from de novo and must be taken in as food, they are Phenylalanine, Valine, Threonine, Tryptophan, Methionine, Leucine, Isoleucine, Lysine, and Histidine, another amino acid Arginine is essential in children but adults can produce enough
This chart shows the complete synthetic pathway — so, the synthesis of all 20 amino acids. Humans have lost the ability to make histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine — which essentially means that we lost an enzyme that processes pyruvate into leucine and valine (yellow box, bottom left), a single enzyme required to turn aspartate into precursors for four others (green box, left), an enzyme that converts glutamine into histidine (red box, right), and the enzymes that make tryptophan and phenylalanine (blue box, top right).
So, we can’t produce these 9 essential amino acids because the body doesn’t have these 5 enzymes above, and why we don’t have them? I care about this question because if we have these 9 essential amino acids, is that means we don’t have to eat so many kinds of food?
An answer from Quora about Why can’t the body make essential amino acids?
I’m sorry this answer is going to be rather light on detail, but a biochemist or an evolutionary biologist will be able to fill in the historical details for you. Essentially at some juncture in our (that is higher mammals) evolutionary history the biological facilities to create from scratch essential amino acids became obsolete as organisms that ate other organisms who did have these biological facilities, were able to salvage these amino acids from digestion.
So as is often the case with evolution, it all boils down to efficiency. At the point when essential amino acids could be obtained through diet, the mechanism to create them internally was no longer needed, and the energy spent maintaining the various pathways and their equipment would be better spent elsewhere. So it was an evolutionary trade off, as soon as there existed sufficient population of essential amino acid producing organisms, mutations concerning other areas of survival were favourable over genes coding for the mechanism of amino acid creation.
I can’t find the specifical answer fit my need, thereby mark two disciplines, biochemist and evolutionary biologist, to study later
