Vitamin B12 Simply Explained

1. What Is Vitamin B12?

Vitamin B12, also called cobalamin, is a vitamin that dissolves in water. At its center sits a cobalt atom. The body needs it for blood formation, for the nerves and for the breakdown of homocysteine. So that it can be absorbed in the small intestine, the body additionally needs intrinsic factor from the stomach.

2. Where Is It Found, and What Is It Made From?

Only microorganisms can form vitamin B12. In significant amounts it is found in animal foods such as meat, liver, fish, eggs and dairy products. Plant foods provide hardly any usable vitamin B12. For preparations it is produced with bacteria, which is called fermentation.

3. What Does Vitamin B12 Do? What Research Shows

Status in Vegan Diets, Older Age and with Medication

In a vegan diet without additional vitamin B12, the blood values were worse 252632. Also after long-term intake of omeprazole, the values were lower than under other acid inhibitors 35. In people with type 2 diabetes and vitamin B12 deficiency under metformin, two preparations raised the values again 3034.

Nerves and Nerve Damage

In type 2 diabetes with nerve damage, nerve conduction, vibration sensation and pain improved under methylcobalamin 30. In nerve symptoms due to vitamin B12 deficiency, several studies showed improvements 121827. A review links a deficiency of vitamin B12 and other nutrients in a plant-based diet with a higher risk for mental decline 20. However, many of these studies tested only a specific form, and the best form and the best route are still open.

Homocysteine, Heart and Blood Vessels

In adults with vitamin B12 deficiency, the administration of vitamin B12 lowered the blood homocysteine value 518. Intake by mouth was not worse than an injection 518. Also together with folic acid, partly additionally with vitamin B6, homocysteine fell 131617192223. However, many studies tested only this blood value, not heart attacks or strokes.

Memory and Mood

A review reports that hallucinations in vitamin B12 deficiency improved with vitamin B12 alone 12. A good vitamin B12 status in pregnant women was associated with better language and better thinking in the children 14. In mild mental impairment, however, vitamin B12 brought no advantage for memory and mood 24. Also in children under twelve years, no difference in thinking performance appeared 7.

Blood Formation and Anaemia

In blood formation, the picture is mixed. For hemoglobin, tablet, lozenge and injection did not differ 6. Also in children, administration under the tongue and injection into the muscle yielded the same values 31. Before heart operations, a mixture of iron, erythropoietin, vitamin B12 and folic acid reduced the number of blood transfusions 29.

Pregnancy and Children

In pregnancy, the picture is mixed. Observational studies from India link low vitamin B12 values in the mother with more malformations and lower birth weight 28. In other studies, vitamin B12 promoted the mental development of the children; the effect on birth weight remained open 28. A review found lower vitamin B12 values in mothers with malformations of the spinal cord 21.

Other Outcomes

In type 2 diabetes with long-term metformin intake and nerve damage, methylcobalamin improved quality of life 30. For linear growth in children, a review found no difference from placebo (sham treatment) 7. For quality of life under cyanocobalamin, a study found no difference 33. Most of these studies tested methylcobalamin; whether other forms act the same is open.

4. How Was Vitamin B12 Taken in the Studies?

Cyanocobalamin, methylcobalamin, adenosylcobalamin and hydroxocobalamin were used. Methylcobalamin, also called mecobalamin, was mostly used as a tablet, partly also as a gel for application. Often vitamin B12 was tested only together with other nutrients, for example with folic acid and vitamin B6 or with iron and folic acid.

5. Is Vitamin B12 Safe? Side Effects in the Studies

Vitamin B12 was predominantly well tolerated in the forms and routes examined. A review on strongly elevated vitamin B12 values describes antibodies against a transport protein called transcobalamin II after intake 15. Many studies were short or examined different forms and routes. In memory, mood, blood formation and in pregnancy, improvements and results without difference stand side by side.

All details with tables and sources: full expert page on Vitamin B12