Vitamin B12: benefits, dosage, contraindications
Other name(s)
Cobalamin
Scientific name(s)
Cyanocobalamin, Hydroxocobalamin, Methylcobalamin
Family or group:
Vitamins
Indications
Scoring methodology
EFSA approval.
Vitamin B12 deficiency ✪✪✪✪✪
A vitamin B12 deficiency can take months or even years to become symptomatic because of the body's large stores. Deficiencies can be secondary to inadequate intake in adults, mainly with a vegan diet or a diet very low in dairy products and meats, or secondary to an absorption defect. Vitamin B12 deficiency causes megaloblastic anemia, gastrointestinal lesions and neurological damage that can range from an inability to produce myelin to degeneration of the axon and the nerve cell body. Neurological symptoms caused by vitamin B12 deficiency may include neuropsychiatric disorders such as depression, paresthesias, ataxia, memory loss, weakness, and changes in personality and mood. Treatment of B12 deficiencies is classically based on parenteral administration of this vitamin, in the form of cyanocobalamin and, less often, hydroxocobalamin. The recommended regimen consists of intramuscular injection of 1000 µg of vitamin B12 daily for one week, then 1000 µg weekly for one month, followed by an injection of the same monthly dose; this is usually recommended for life, particularly in Biermer's disease (pernicious anemia due to vitamin B12 malabsorption). Oral administration of cyanocobalamin has also been shown to be effective in the context of the syndrome of failure to dissociate vitamin B12 from its carrier proteins (this syndrome is characterized by an inability to release vitamin B12 from food proteins and/or intestinal transport proteins, notably in the case of hypochlorhydria, while absorption of 'unbound' vitamin B12 is normal) and in Biermer's disease. The loading dose is 500 to 1000 µg/day orally (1000 µg/day in Biermer's disease) for one month. The maintenance dose is 125 to 500 µg/day until the cause is corrected, or 1000 µg/day for life in the case of Biermer's disease.
Posologie
By mouth
4 - 1000 µg
cyanocobalamin
Effective treatment of cobalamin deficiency with oral cobalamin.
Normalization of low serum vitamin B12 levels in older adults by oral treatment.
Oral or parenteral therapy for B12 deficiency
Vitamin B12 deficiency in adults: causes, clinical manifestations and treatment
Emotional balance ✪✪✪✪✪
Vitamin B12 contributes to the normal function of the nervous system and to normal mental functions. rnrnA vitamin B12 deficiency causes psychological disorders: memory problems, irritability, depression, personality disorder, dementia, delirium and psychosis.rnrn
Posologie
By mouth
4 µg
Fatigue ✪✪✪✪✪
Vitamin B12 plays a key role in energy production, DNA synthesis, and nervous system function. Its deficiency can lead to megaloblastic anemia and neurological disorders, contributing to fatigue and cognitive decline. By supporting DNA synthesis for cellular repair and the formation of red blood cells, as well as the metabolism of fats and carbohydrates, B12 is essential for maintaining optimal energy. rnrnIn 2012, European health authorities (EFSA, European Food Safety Authority and the European Commission) concluded that foods and food supplements containing vitamin B12 can claim to contribute to the reduction of fatigue.rnrnClinically, there is evidence that intramuscular injections of vitamin B12 in the form of hydroxocobalamin, at a dose of 5 mg twice weekly, may improve the general well-being of patients complaining of fatigue. rnrn
Posologie
Oral administration
4 - 5000 µg
hydroxocobalamin
Canker sores ✪✪✪✪✪
In cases of oral aphthosis (canker sores), clinical research shows that applying a topical ointment containing 500 µg of vitamin B12 for 2 days reduces pain by 80% compared with a control ointment that does not contain vitamin B12. Other clinical studies show that taking 1000 µg of vitamin B12 sublingually once daily for 6 months significantly reduces the duration of aphthous episodes, the number of ulcers, and the intensity of pain, compared with placebo, in patients with normal vitamin B12 levels.rnrn
Posologie
Topical, oral
500 µg
2 - days
ointment
Hyperhomocysteinemia ✪✪✪✪✪
Hyperhomocysteinemia is known as a risk factor for cardiovascular diseases. Oral vitamin B12 taken in combination with folic acid, and sometimes with pyridoxine (vitamin B6), can reduce serum homocysteine concentrations. Taking folic acid at a dose of 0.5 to 5 mg per day lowers fasting homocysteine levels by an average of 25%. The addition of 0.5 mg of vitamin B12 per day results in a further reduction in homocysteine levels of approximately 7% on average, although this effect is probably only observed in people with vitamin B12 deficiency. Vitamin B12 in combination with folic acid and other vitamins also appears to markedly reduce homocysteine levels in patients with end-stage renal disease. A dose of 400 to 500 mcg of vitamin B12, in combination with 0.4 to 5 mg of folic acid and 16.5 mg of pyridoxine (vitamin B6), has been used.
Posologie
Oral administration
400 - 500 µg
Cyanocobalamin
Synergies
Vitamin supplements and cardiovascular risk: review of the randomized trials of homocysteine-lowering vitamin supplements.
Vitamin supplementation reduces blood homocysteine levels: a controlled trial in patients with venous thrombosis and healthy volunteers.
Preventive health care, 2000 update: screening and management of hyperhomocysteinemia for the prevention of coronary artery disease events. The Canadian Task Force on Preventive Health Care.
Dose-dependent effects of folic acid on blood concentrations of homocysteine: a meta-analysis of the randomized trials.
Treatment of hyperhomocysteinemia in hemodialysis patients and renal transplant recipients.
Diagnosis and treatment of hyperhomocysteinemia.
Homocysteine lowering effect of different multivitamin preparations in patients with end-stage renal disease.
Treatment of mild hyperhomocysteinemia in renal transplant recipients versus hemodialysis patients.
Lowering blood homocysteine with folic acid-based supplements: meta-analysis of randomized trials. Homocysteine Lowering Trialists' Collaboration.
AMD ✪✪✪✪✪
A large-scale clinical study shows that taking 50 mg of pyridoxine per day in combination with 1 mg of cyanocobalamin and 2.5 mg of folic acid, for an average of 7.3 years, significantly reduced, compared with placebo, the risk of developing AMD (age-related macular degeneration) in women aged 40 years with a history of cardiovascular disease or with cardiovascular disease risk factors.
Posologie
Orally
1000 µg
7 - years
cyanocobalamin
Synergies
Diabetic neuropathy ✪✪✪✪✪
Clinical evidence shows that taking vitamin B12 in the form of methylcobalamin or cyanocobalamin, in combination with benfotiamine (the natural form of vitamin B1) and pyridoxine (vitamin B6), for 9 to 12 weeks may improve some symptoms of diabetic neuropathy. In addition, taking oral methylcobalamin for up to 4 months appears to improve pain associated with diabetic peripheral neuropathy, but may not improve nerve conduction. rnrnThe daily dose was 1500 mcg of methylcobalamin for 3 to 4 months.rnrn
Posologie
Oral
1500 µg
4 - months
methylcobalamin
Synergies
The effect of prostaglandin E1.alpha CD on vibratory threshold determined with the SMV-5 vibrometer in patients with diabetic neuropathy.
Effect of mecobalamin on diabetic neuropathies. Beijing Methycobal Clinical Trial Collaborative Group
A benfotiamine-vitamin B combination in treatment of diabetic polyneuropathy.
Therapeutic efficacy of "Milgamma" in patients with painful diabetic neuropathy.
Alzheimer's disease ✪✪✪✪✪
Research shows that a high intake of vitamin B12 is not associated with a reduced risk of developing Alzheimer's disease. However, clinical research shows that taking 0.5 mg of vitamin B12, 20 mg of vitamin B6 and 0.8 mg of folic acid per day for 24 months slows brain atrophy in patients with Alzheimer's disease.rnrn
Posologie
Oral
500 µg
24 - months
cyanocobalamin
Synergies
Depression ✪✪✪✪✪
Elevated homocysteine and low levels of vitamin B12 and folate are frequently observed in depression. Observational studies have shown that 30% of patients hospitalized for depression suffered from a vitamin B12 deficiency. rnrnAn epidemiological study found that a daily dietary intake of at least 4.79 mcg of vitamin B12 was associated with a 58% lower risk of depression compared with a daily intake below 3.16 mcg in older men. rnrnrnrnrnrn
Posologie
Oral
4 µg
Risk of depression in pregnant women with low-normal serum Vitamin B12
Treatment of depression: time to consider folic acid and vitamin B12
Vitamin B(12) deficiency and depression in physically disabled older women: epidemiologic evidence from the Women's Health and Aging Study
Hepatitis ✪✪✪✪✪
Preliminary clinical research conducted in patients with chronic hepatitis C virus infection shows that administration of vitamin B12 in the form of cyanocobalamin at a dose of 5000 mcg intramuscularly every 4 weeks, in combination with standard treatment, significantly improves the viral response compared with standard treatment alone. rnrn
Posologie
Oral
5000 µg
cyanocobalamin
Properties
Essential
Vitamin B12 is involved in DNA synthesis, as well as in the development, myelination, and function of the nervous system. Within the cell, vitamin B12 is involved in two essential metabolic functions: - In the mitochondrion, adenosylcobalamin serves as a cofactor for methylmalonyl-CoA mutase, enabling the production of succinyl-CoA from methylmalonyl-CoA. Succinyl-CoA plays a key role in fatty acid oxidation and ketogenesis. - In the cytoplasm, methyl-B12 serves as a cofactor for methionine synthase, which produces methionine from homocysteine. This provides a means to metabolize homocysteine, which is potentially toxic, to produce the methionine essential for protein synthesis, and to supply the cell with methyl group donors. European health authorities (EFSA, the European Food Safety Authority, and the European Commission) have concluded that food supplements containing vitamin B12 (cobalamin) contribute to normal energy-yielding metabolism, the normal functioning of the nervous system, normal homocysteine metabolism, normal mental function, red blood cell formation, the reduction of tiredness and fatigue, the normal functioning of the immune system, and cell division.
Usages associés
Neurological
Methylcobalamin, a form of vitamin B12, appears to improve alertness and reduce sleep duration in subjects with normal sleep, possibly by acting on melatonin. On the other hand, some research shows that high serum homocysteine levels and low folate and vitamin B12 levels may be associated with cognitive decline and dementia. Some researchers believe that vitamin B12 supplementation may improve symptoms of chronic fatigue syndrome by correcting red blood cell abnormalities and improving oxygen delivery to tissues.
Usages associés
Cardiovascular
Vitamin B12 is required for one of the pathways of homocysteine metabolism. The remethylation of homocysteine to methionine requires the use of folate and vitamin B12 in the form of methylcobalamin as a cofactor. Therefore, oral intake of vitamin B12 in combination with folic acid and sometimes with pyridoxine (vitamin B6) can reduce serum homocysteine concentrations. Some studies suggest that elevated homocysteine levels may cause damage to vascular endothelial cells, impair endothelium-dependent vasodilation, increase oxidation and arterial deposition of low-density lipoproteins (LDL), increase platelet adhesion, and activate the coagulation cascade.
Usages associés
Anticancer
It is thought that vitamin B12 has anticancer properties, and that vitamin B12 supplementation may play a role in the prevention of cervical cancer. However, high serum vitamin B12 levels have been associated with an increased risk of prostate cancer. Moreover, research in subjects with hepatocellular carcinoma suggests that the presence of tumor markers in association with a high serum vitamin B12 level is a poor prognostic indicator. rnrn
Hepatoprotective
A vitamin B12 deficiency leads to a decrease in the activity of serine dehydratase (SDH) (an enzyme involved in hepatic gluconeogenesis) and of tyrosine aminotransferase in the rat liver. rnrnFurthermore, vitamin B12 decreased blood levels of aspartate aminotransferase and alanine aminotransferase in mice with liver lesions induced by dimethylnitrosamine, which suggests a possible hepatoprotective effect. rnrnrnrn
Usages associés
Antioxidant
Recent studies have shown that vitamin B12 and its cobalamin-based derivatives have an antioxidant effect at pharmacological concentrations. rnrn
Safe dosage
Pregnant women aged 18 years and older: 4.5 µg
Breastfeeding women aged 18 years and older: 5 µg
Infants 7 to 11 months old: 1.5 µg
Adults aged 18 years and older: 4 µg
Children 1 to 6 years old: 1.5 µg
Children 7 to 10 years old: 2.5 µg
Children 11 to 14 years old: 3.5 µg
Children 15 to 17 years old: 4 µg
Interactions
Médicaments
Chloramphenicol: strong interaction
In some patients, chloramphenicol (an antibiotic) may inhibit or delay the reticulocyte response to vitamin B12 supplementation. If co-administration is unavoidable, reticulocyte counts should be monitored closely.
Colchicine: moderate interaction
Colchicine, at doses of 1.9 to 3.9 mg per day, can disrupt normal intestinal mucosal function, leading to malabsorption of several nutrients, including vitamin B12.
H2 antihistamines: moderate interaction
Reduced gastric acid and pepsin secretion caused by H2 antihistamines can reduce the absorption of vitamin B12 from ingested foods. As a result, the likelihood of developing a vitamin B12 deficiency is increased by 25% in individuals taking H2 blockers for 2 years or more. H2 antihistamines include cimetidine (Tagamet), ranitidine (Zantac), nizatidine (Axid), and famotidine (Pepcid).
Metformin: moderate interaction
Metformin, an oral antidiabetic, can reduce serum levels of vitamin B12 and folic acid. This effect can lead to hyperhomocysteinemia, which may increase the risk of cardiovascular disease in diabetic individuals.
Aspirin: moderate interaction
Clinical research suggests that acetylsalicylic acid (aspirin) increases the risk of vitamin B12 deficiency.
Nitrous oxide: moderate interaction
Nitrous oxide (also called nitrous oxide) inactivates the cobalamin form of vitamin B12 by oxidation. Symptoms due to nitrous oxide are not apparent in individuals with normal vitamin B12 levels (unless exposure is repeated and prolonged). However, symptoms such as sensory neuropathy, myelopathy, and encephalopathy can be seen in people with vitamin B12 deficiency.
Anticonvulsants: moderate interaction
Phenytoin, phenobarbital, and primidone are anticonvulsants that reduce the absorption of vitamin B12 when administered in combination with it.
Plantes ou autres actifs
Vitamin B12: moderate interaction
High doses of folic acid can mask a vitamin B12 deficiency. Indeed, folic acid can improve the symptoms of megaloblastic anemia.
Contraindications
Angioplasty: contraindicated
The intravenous combination of vitamin B12, vitamin B6, and folic acid is not recommended in a patient who has had a coronary stent placed during angioplasty. Indeed, the combination of these vitamins may increase the risk of restenosis.
Leber's disease: contraindicated
Vitamin B12 is contraindicated in the early stages of Leber's disease (a hereditary atrophy of the optic nerve). Vitamin B12 can cause severe and rapid optic atrophy.
