A broken final step in vitamin production
In animals that can make vitamin C, the body builds it through a chain of chemical reactions. In humans, the gene for an enzyme called gulonolactone oxidase no longer provides working instructions. That enzyme normally carries out the final step, converting a compound made by the body into vitamin C. The rest of the pathway cannot make up for its absence, so eating vitamin C is the way to complete what our cells cannot.
This is not a matter of willpower or diet preference: the missing enzyme is part of human biology. Vitamin C is therefore an essential nutrient for us, meaning we must obtain it from outside the body.
Why the missing ingredient matters
Vitamin C helps the body make collagen, a structural protein that strengthens connective tissues. Collagen supports skin, blood vessels, gums, and the framework that helps wounds hold together as they heal. When vitamin C intake stays too low, collagen production falters; severe deficiency can lead to scurvy, with symptoms such as bleeding gums, easy bruising, and wounds that heal poorly.
The practical consequence is simple but important: foods supply a molecule that many animals can manufacture internally. Fruits and vegetables are familiar sources, but the key point is not a particular “superfood.” It is that regular access to vitamin-C-containing food keeps a missing step in human metabolism from becoming a weak link in the body’s connective tissues.
