Vitamin B12 (Cobalamin)

Vitamin B12

Snapshot

Vitamin B12 is a water‑soluble essential nutrient that supports red blood cell formation, neurological function, DNA synthesis, and energy metabolism.

 

---

What is Vitamin B12 (Cobalamin)?

Vitamin B12 refers to a family of corrinoid compounds—including methylcobalamin and adenosylcobalamin—that act as cofactors for methionine synthase and methylmalonyl‑CoA mutase, critical enzymes in one‑carbon metabolism and fatty acid catabolism.

---

Where It Comes From

Vitamin B12 is synthesized by certain bacteria and archaea. Dietary sources include animal products such as meat, fish, dairy, and eggs. Vegans and vegetarians may obtain B12 from fortified foods or supplements. Absorption requires gastric acid, intrinsic factor, and an intact ileum.

---

Key Nutrients & Compounds

Provides methylcobalamin (active in the cytosol) and adenosylcobalamin (active in mitochondria), along with cyanocobalamin and hydroxocobalamin forms used in supplements.

---

Health Benefits

Vitamin B12 supports erythropoiesis by enabling DNA synthesis in bone marrow; maintains myelin integrity and neurological function; facilitates homocysteine remethylation to methionine, reducing cardiovascular risk; and contributes to energy production through propionate metabolism.

---

Recommended Dosage

The adult Recommended Dietary Allowance is 2.4 µg per day. Higher doses (500–1,000 µg daily) are used in supplements to ensure adequate absorption in individuals with malabsorption or atrophic gastritis.

---

How to Use It

Take oral B12 supplements (methylcobalamin or cyanocobalamin) with or without food. Sublingual or intramuscular routes may be employed for those with absorption issues. Consistent daily or weekly dosing ensures sufficient stores.

---

Who Should Use It?

Individuals over age 50, those with pernicious anemia, gastrointestinal disorders (e.g., celiac, Crohn’s), vegans, and people on long‑term metformin or proton pump inhibitors may require supplementation.

---

Possible Interactions or Cautions

High‑dose vitamin C taken simultaneously may degrade B12 in the gut; space doses by at least two hours. Certain antibiotics and anticonvulsants can interfere with B12 metabolism. Monitor levels in patients receiving nitrous oxide anesthesia.

---

Final Thoughts

Vitamin B12 is indispensable for hematologic, neurologic, and metabolic health. Routine dietary intake from animal sources or fortified products usually suffices, with supplements tailored to individual absorption and dietary patterns.

---

Scientific Studies

Allen LH. Causes of vitamin B12 and folate deficiency. Nutr Rev. 2008;66(12 Suppl 2):S2–S17. https://doi.org/10.1111/j.1753-4887.2008.00140.x

Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149–160. https://doi.org/10.1056/NEJMcp1113996

O’Leary F, Samman S. Vitamin B12 in health and disease. Nutrients. 2010;2(3):299–316. https://doi.org/10.3390/nu2030299