eli5: why can’t human body produce Vitamin C?


The other day I learn that the only thing that the human body can’t produce is Vitamin C; that’s why we have to take it in external way.

If our body can produce other vitamins, why not Vitamin C? What do human not have to produce Vitamin C?

In: 366

Well, it’s kind of tricky to produce. Fruit trees spend a lot of energy creating it and we avoid that effort by eating fruit. Fruit trees produce it as a side effect of protecting themselves from their own predators.

At some point in the human evolution we had the ability to produce it, but lost it as we started eating foods rich in vitamin C, if i remember correctly.
And if i remember correctly, once the gene for it got turned off, evolution doesn’t try it again(not a gene expert)

Most mammals can produce it, but we had lost the gene which is necessary for this very long ago. Why? Our ancestors didn’t need it, they ate enough fruits to cover the demand for vitamin C, so producing it wasn’t advantageous anymore.

One more thing – vitamin C is not the only thing humans can’t produce, we can’t create some aminoacids for example.

Humans can’t produce any of the vitamins without help, and many not at all, that’s why they’re called vitamins (“vital” because they’re essential to life + “amine” because they were originally thought to be proteins).

We also don’t produce B12, nor do other animals. It’s made by bacteria but we need B12 otherwise some serious issues can occur over time – nerve and brain problems and even heart failure in the most extreme cases.

Take yo vitamins people!