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What Causes What
MECHANISM0 NULL

Vitamin / mineral supplementation → Cognitive performance

A rise in Vitamin / mineral supplementation does not identify a change in Cognitive performance.

Chen 2021 found that six months of folic acid plus vitamin B12 moved MoCA total by about one point versus placebo in 120 people with Alzheimer's in Tianjin, while a 2003 Cochrane review of B12 in dementia with low serum B12 found no cognitive effect.

Randomized trial · Contested · N=120

Supported by an experiment or a tightly identified design. Read the caveats.

Mechanism

B vitamins are cofactors in the one-carbon cycle. Folate and B12 help remethylate homocysteine to methionine. The folk story is that a high homocysteine number damages the brain, so a B-vitamin pill that lowers it should protect memory. Chen, Liu, Ge, and colleagues (2021) tested that in 120 people with probable Alzheimer's in Tianjin. China does not fortify flour with folic acid. Everyone stayed on a cholinesterase inhibitor or memantine. Half took folic acid 1.2 mg plus B12 50 µg a day for six months. Half took matching starch tablets. Participants did not know which. The trial was single-blind. Mean MoCA at baseline was about 12. The interaction on MoCA total was 1.03 points (95% CI 0.11 to 1.96, P=0.029). Naming and orientation moved. The ADAS-Cog total, the usual Alzheimer's severity scale, did not (P=0.123), and only 39 people sat that battery. Malouf and Areosa Sastre (Cochrane, 2003) reviewed randomized double-blind trials of vitamin B12 versus placebo. They included two trials in people who already had dementia and low serum B12. That is the named-deficit test. There was no statistically significant treatment effect. The reviewers wrote that evidence of efficacy was insufficient. Wang, Zhu, Xing, Jia, and Tang (2022) pooled 25 trials, 20 cohorts, and 50 cross-sectional studies. The trial MMSE difference was 0.14 points (95% CI 0.04 to 0.23) in 6,155 people. The difference appeared in trials longer than a year and in people without dementia. The dementia stratum crossed zero. Higher dietary folate and later dementia is an observational diet finding, not a pill trial. More papers of the same design do not settle the claim.

Caveats

Chen enrolled people with Alzheimer's, not people picked for low B12 or low folate. Baseline B12 was about 280 pmol/L. Baseline folate was about 15 nmol/L. Homocysteine was about 14 µmol/L. This is not a deficiency-correction trial. The trial was single-blind and six months. Nineteen people did not finish. ADAS-Cog was missing for most of the sample. Everyone was already on dementia medication. The Cochrane file is two small trials in dementia with low B12. It is available here only as an abstract. The reviewers could not show a cognitive benefit from treating that deficit. Wang mixes trial MMSE scores with observational diet and blood-level papers. The 0.14 MMSE point is not a named task leaving a named deficit. The dementia-stratum trials were null. Smith 2011 (VITACOG) is already on file here. That paper's primary result is whole-brain atrophy rate. The authors say the trial was not powered for cognition and that cognitive scores would be reported separately. A post-hoc line ties faster atrophy to a lower final MMSE. That is not a treatment contrast on a cognitive test. This page does not include it. Srinivasan 2017 gave B12 to pregnant women and scored infants at nine months on the Bayley. That is prenatal maternal supplementation and infant neurodevelopment, not adult pills and adult cognition. van der Zwaluw 2017 measured brain volumes after B-PROOF. There is no cognitive test on that page. This page is B vitamins and folate, not iron stores. Ferritin sits on another edge. This page does not speak to jobs. It is not medical advice and not a recommendation to take B vitamins, to skip them, or to treat a homocysteine number.

Effect

qualitative. Chen 2021: MoCA total interaction β 1.033 (0.105-1.961), P=0.029, N=120 AD. ADAS-Cog total not different. Cochrane 2003: two B12 RCTs in dementia with low B12, no effect. Wang 2022 MMSE MD 0.14 (0.04-0.23).

Nodes

Lifestyle & environmentVitamin / mineral supplementationPsychology & behaviorCognitive performance

Named confounders

Cite this page

What Causes What. “Vitamin / mineral supplementation → Cognitive performance.” https://whatcauseswhat.org/edges/e-vitamins-cognition (atlas updated 2026-09-02).

https://whatcauseswhat.org/edges/e-vitamins-cognition

Papers