How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Vitamin B12
The only vitamin truly absent from a 100 % plant-based diet. Essential if you eat neither meat, nor fish, nor eggs, nor dairy products.
Benefits
- Improves nerve measurements and diabetic neuropathy pain after one year (1,000 µg per day)
- Enhances the effect of an antidepressant in patients with low B12 levels
- In pregnant women, raises the B12 level of the mother, the infant, and breast milk
- Corrects a low level in elderly people, whose absorption decreases with age
Precautions
An established deficiency damages the nervous system, sometimes irreversibly: it is screened for, it is not waited out. High-dose folic acid can mask a B12 deficiency on a blood test. Also good to know: when the level is already normal, 16 pooled trials find no effect on memory, mood, or fatigue — B12 corrects a deficiency, it does not boost an organism that does not lack it. Furthermore, long-term follow-up has associated prolonged intake of B12 with folic acid with an increased risk of colorectal cancer.
Recommended dosage
50 µg per day were enough to raise a low level in elderly people, 10 µg were not; 500 to 1,000 µg in diabetes trials.
How to take it
- Dose: in elderly people with low levels, 50 µg per day raised vitamin B12 in the blood, 10 µg did not.
- Without a deficiency, expect nothing from it: the meta-analysis of 16 trials finds no effect on memory, mood, or fatigue in people without a deficiency or advanced neurological disorder.
- High doses are medical: 500 to 1,000 µg per day in diabetes and diabetic neuropathy trials, over several months to a year.
- Pregnancy and breastfeeding: 50 to 250 µg per day in trials. At 250 µg, the mother's, baby's, and breast milk's levels improved.
- With long-term folic acid: in 2,524 people, the combination was linked to more cancers, including colorectal ones. The authors suggest reserving it for proven deficiencies.
What the studies say
This systematic review and meta-analysis evaluated the efficacy of vitamin B12 supplementation, alone or in complex with other B vitamins, to improve cognitive functions, depressive symptoms, and fatigue. The analysis of 16 randomized controlled trials found no evidence of a beneficial effect on these parameters in patients without advanced neurological disorders or overt vitamin B12 deficiency. Vitamin B12 supplementation is therefore probably ineffective for these uses in this population.
Markun S, Gravestock I, Jäger L, Rosemann T, Pichierri G, Burgstaller JM. — Nutrients (2021) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more