What Vitamin C does in the body

Collagen formation

This is the one that explains most of the others. Vitamin C is a required cofactor for the enzymes that hydroxylate collagen — the step that lets collagen strands form a stable triple helix. Without it, the body builds collagen that does not hold.

Collagen is the structural protein of skin, gums, blood vessels, cartilage, bone and scar tissue. Its role in wound healing, in gum health and in skin structure all follow from this single biochemical fact.

Antioxidant activity

Vitamin C donates electrons readily, which makes it an effective biological antioxidant: it contributes to the protection of cells from oxidative stress. It also regenerates other antioxidants — vitamin E among them — after they have been used, so its effect extends past what it neutralises directly.

Carnitine, and energy

Vitamin C is required to build L-carnitine, the molecule that carries fatty acids into the mitochondria — where they are burned for energy. Two of the enzymes in that pathway do not function without it.

This is the role most often missing from popular accounts of Vitamin C, and it is arguably the most useful one to know. It is why fatigue tends to appear among the first things people notice, well before anything shows up in skin or gums.

It is also the reason a list of deficiency signs that is otherwise all collagen — gums, skin, wound healing — still has tiredness at the top of it.

Neurotransmitters and hormones

The enzyme that converts dopamine into norepinephrine requires Vitamin C. So does the amidation step that completes several peptide hormones, and parts of amino acid metabolism.

Ascorbic acid is not purely structural. It sits inside the chemistry of signalling, which is a different kind of role from holding tissue together.

Iron absorption

Vitamin C converts dietary iron into a form the gut absorbs far more readily. This matters disproportionately in India, where a large share of dietary iron comes from plant sources that are poorly absorbed on their own.

It is also the most actionable thing on this page: taking iron-rich food with a Vitamin C source in the same meal measurably changes how much iron you actually get from it.

Immune function

Vitamin C accumulates in white blood cells at concentrations many times higher than in plasma and is consumed as those cells work. It contributes to the normal function of the immune system.

What it does not do is prevent, treat or shorten any illness. The evidence on colds specifically is far weaker than folk belief suggests, and no claim to the contrary is made anywhere on this site.