Vitamin B12 (cobalamin) B
Critical in a vegan diet; in athletes with adequate intake there is no effect
Citable fact
«Vitamin B12 (cobalamin)» — evidence level B. Dosage: The adult requirement is 2.4 µg per day. With a vegan diet and malabsorption — 25–100 µg per day orally or 1000 µg 1–2 times a week. No safe upper level has been established: excess is excreted. Injectable forms — only as prescribed by a doctor for confirmed deficiency. Source: PMID 16573356, permanent link to the source in the list below.
How it works
A coenzyme of methylmalonyl-CoA mutase and methionine synthase: myelin synthesis, erythropoiesis, fatty acid metabolism. Deficiency leads to megaloblastic anemia and neuropathy.
Dosage and intake
The adult requirement is 2.4 µg per day. With a vegan diet and malabsorption — 25–100 µg per day orally or 1000 µg 1–2 times a week. No safe upper level has been established: excess is excreted. Injectable forms — only as prescribed by a doctor for confirmed deficiency.
Orally on an empty stomach or with food; large doses are taken in divided amounts, since only a fraction is absorbed.
Forms
Cyanocobalamin and methylcobalamin with hydroxocobalamin have been studied; there are no proven differences in effectiveness in humans. Sublingual forms are an alternative in malabsorption; injections — only as prescribed by a doctor.
What is confirmed
- Prevents and corrects megaloblastic anemia
- Needed for normal nervous system function
- Essential on a vegan and strict vegetarian diet
Adverse effects and limitations
- Deficiency may be masked by folic acid intake
- Blood B12 level does not always reflect tissue status — methylmalonic acid and homocysteine are more reliable
- Injectable forms - only as prescribed by a physician
Interactions
- Metformin and proton pump inhibitors reduce absorption
- High doses of vitamin C can destroy B12 in the intestine
Who must not use it
- Under 18 years: Prevention of deficiency in children is carried out by age and as prescribed by a doctor.
- Pregnancy and lactation: The requirement increases; vegetarian women are advised to take supplements under medical supervision.
- vegan diet
- long-term use of metformin or proton pump inhibitors
- bariatric surgery
- atrophic gastritis
Sources
- Vegetarian diets : nutritional considerations for athletes · Venderley AM, Campbell WW · Sports medicine (Auckland, N.Z.), 2006 · PMID 16573356
- Considerations for the Consumption of Vitamin and Mineral Supplements in Athlete Populations · Peeling P, Sim M, McKay AKA · Sports medicine (Auckland, N.Z.), 2023 · PMID 37358750
See also
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