Why Vitamin B12 matters

It is needed in vanishingly small amounts, yet without it, blood, nerves, and DNA itself cannot be properly made.

Few nutrients do so much with so little. Vitamin B12 is required in only microgram quantities, yet it sits at the centre of some of the body's most essential machinery.

What it does

B12, or cobalamin, acts as a cofactor for enzymes involved in making red blood cells, building and maintaining the myelin sheath that insulates our nerves, and synthesising DNA and neurotransmitters.¹ It is, in short, essential to the blood, the nervous system, and the very copying of our genetic code.

When it runs low

Deficiency is not subtle in its consequences. It can cause megaloblastic anaemia and a range of neurological and neuropsychiatric problems, from nerve damage and numbness to depression and, in severe cases, confusion and memory loss.¹² Because some of the nervous-system damage can become irreversible, catching it early matters.

A nutrient needed in traces, and indispensable in every one of them.

Who is at risk

Two groups warrant particular attention. Older adults often absorb B12 poorly, owing to common conditions such as autoimmune gastritis and to medications like antacids that interfere with uptake.² And because B12 is found almost exclusively in animal foods, people following vegan or vegetarian diets generally need reliable supplementation.³

Why it matters

B12 is a reminder that “small” and “trivial” are not the same. A nutrient measured in millionths of a gram can decide the health of the blood and the integrity of the nervous system, and, when it is so easy to supply, there is little reason to go without.