What is vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin from the B-complex that plays an exceptionally important role in energy metabolism, blood formation, nerve function, and DNA synthesis. It is the only vitamin that contains a metal ion (cobalt) - hence the name - and is produced exclusively by microorganisms (bacteria).

Since vitamin B12 is found in significant amounts only in animal-based foods (e.g., meat, fish, eggs, and dairy products), vegetarians and vegans in particular are at risk of developing a deficiency. Adequate intake is essential for the health of the brain, nerves, and blood cells.

In the body, vitamin B12 is stored in the liver - in some cases for several years - and is therefore available as a reserve. However, a special transport protein, known as intrinsic factor, is required for absorption in the intestine. It is produced in the stomach lining.

How does vitamin B12 work?

Vitamin B12 is involved in numerous vital processes and acts as a coenzyme in several central metabolic pathways.

Energy and cell metabolism:
Cobalamin is essential for converting nutrients into energy. It supports the breakdown of fatty acids and amino acids and contributes to the production of ATP - the most important energy source for cells. A deficiency can lead to fatigue, lack of energy, and muscle weakness.

Blood formation:
Vitamin B12 is necessary for the formation and maturation of red blood cells in the bone marrow. Together with folate, it supports healthy cell division. A deficiency leads to megaloblastic anemia, which manifests as paleness, shortness of breath, dizziness, and weakness.

Nervous system and brain function:
B12 is indispensable for the formation of the myelin sheath - the protective covering surrounding nerve fibers and enabling rapid signal transmission. A deficiency can cause tingling, numbness, concentration problems, mood swings, or even permanent nerve damage. It also plays a role in the synthesis of neurotransmitters that influence mood and mental clarity.

Homocysteine breakdown and heart health:
Together with vitamin B6 and folate, vitamin B12 helps break down homocysteine, an amino acid that, at elevated concentrations, can promote inflammation and vascular damage. In this way, it actively contributes to protecting the cardiovascular system.

DNA synthesis and cell regeneration:
Cobalamin is essential for DNA replication and repair. Particularly rapidly dividing cells - such as those in the bone marrow, mucous membranes, and skin - depend on an adequate supply.

Benefits of vitamin B12

  • Supports energy production and reduces fatigue

  • Promotes the formation of red blood cells and helps prevent anemia

  • Protects the nervous system and improves concentration and memory

  • Supports DNA synthesis and cell regeneration

  • Regulates homocysteine levels and strengthens the heart and blood vessels

  • Promotes mood and may alleviate depressive symptoms

  • Supports the immune system and brain function

  • Important for a healthy pregnancy and child development

Possible side effects and interactions

Vitamin B12 is very well tolerated because excess amounts are excreted in the urine. Even high doses in the form of dietary supplements are considered safe, as the body absorbs only as much as it needs.

A deficiency commonly occurs in older people, vegans, vegetarians, and individuals with absorption disorders (e.g., gastritis, celiac disease, chronic intestinal disease, or after stomach surgery). Symptoms often develop gradually and may be neurological or hematological.

Certain medications, such as metformin (for diabetes), proton pump inhibitors (e.g., omeprazole), or birth control pills, may impair the absorption of vitamin B12.

Conclusion

Vitamin B12 is an essential multitasker for energy, nerves, blood, and the brain. It supports the body and mind in many ways - from cell renewal and nerve transmission to protecting the cardiovascular system. Since it is found almost exclusively in animal products, vegans, older people, and individuals with digestive problems in particular should ensure targeted intake. High-quality supplements containing methylcobalamin or hydroxocobalamin offer particularly good bioavailability and effectively help maintain performance, mental clarity, and overall well-being.

Sources

  1. O’Leary F, Samman S. (2010): Vitamin B12 in health and disease. Nutrients, 2(3), 299–316.

  2. Allen LH. (2009): Causes of vitamin B12 and folate deficiency. Food Nutr Bull, 29(2 Suppl), S20–S34.

  3. Green R, et al. (2017): Vitamin B12 deficiency. Nat Rev Dis Primers, 3, 17040.

  4. Hunt A, Harrington D, Robinson S. (2014): Vitamin B12 deficiency. BMJ, 349, g5226.