Vitamin B12
Vitamin B12 is a water-soluble vitamin needed for the nervous system, the making of blood cells and DNA synthesis. It occurs naturally only in animal sources.
| Type | Water-soluble vitamin |
|---|---|
| Main roles |
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| Sources |
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| Deficiency note | A shortfall is associated with anaemia and with nervous system symptoms; because those symptoms can have other causes, a blood test and a doctor's assessment are needed. |
| Caution | Supplements often come up for people eating plant-based diets; the need, the form and the duration should be settled together with a doctor. |
Why is it a special vitamin?
Two things set B12 apart from other vitamins. First, it occurs naturally only in animal foods: meat, fish, eggs, milk and dairy products are the main sources. Second, its absorption depends on a particular protein secreted by the stomach (intrinsic factor), so absorption can falter in some digestive conditions even when intake is adequate.
What does it do in the body?
B12 takes part in maintaining the protective sheath around nerve cells (myelin), in making red blood cells and in DNA synthesis. It works together with folate, and the balance between the two matters for the formation of blood. Daily requirements vary with age and physiological state; needs can differ during periods such as pregnancy and breastfeeding.
Who should pay attention?
Vegans and people eating a largely plant-based diet, people whose stomach acid declines with age, those who have had certain stomach or bowel operations and people taking some medicines over long periods are among the groups advised to be more careful about B12. Symptoms such as fatigue, a burning tongue or numbness in the hands can stem from many different causes, so a blood test and a doctor's assessment are the right route rather than self-diagnosis. Supplements often come up for people eating plant-based diets; the form and the need should be planned with a doctor.
Related terms: Folate, Iron, Salmon, Egg