Vitamin B12 and Alzheimer's disease: mechanisms and clinical studies
What it found
Vitamin B12 is involved in many processes linked to Alzheimer's disease, and some trials in people found benefits for thinking and brain shrinkage, especially in those with high homocysteine or omega-3.
But other trials found no effect on thinking in people with Alzheimer's.
What they found
Studies in people
Brain shrinkage in people
In a two-year trial of people with mild cognitive impairment, those taking high-dose B vitamins had less brain shrinkage per year (0.76% vs. 1.08%) than those on placebo.
Thinking in Alzheimer's patients
Several trials in people with Alzheimer's disease found that B vitamins lowered homocysteine but did not improve thinking scores.
B12 levels in Alzheimer's
A meta-analysis found that people with Alzheimer's disease had lower vitamin B12 levels in their blood than healthy people.
Animal and lab studies
Amyloid plaques in mice
Mice with Alzheimer's-like mutations fed a diet lacking folate, vitamin B6 and vitamin B12 for 7 months had more amyloid-beta peptides and plaques in the hippocampus and cortex than mice on a control diet.
Tau and memory in rats
Rats with high homocysteine had more tau phosphorylation and memory deficits, which were reduced by giving folate and vitamin B12.
Amyloid clumping in lab tests
In test-tube experiments, vitamin B12 slowed the clumping of amyloid-beta into fibrils and broke up existing fibrils.
What the authors conclude
“In conclusion, our review emphasizes the important role of vitamin B12 in AD, which is particularly important, as even in industrialized countries a large proportion of the population might not be sufficiently supplied with vitamin B12.”
Also in their conclusions
- They emphasise the important role of vitamin B12 in Alzheimer's disease.
- They note that even in industrialised countries a large proportion of the population might not be sufficiently supplied with vitamin B12.
- They suggest that vitamin B supplements might be considered as a preventive measure for people with mild cognitive impairment.
How it was done
The authors wanted to summarise the biochemical pathways linking vitamin B12 to Alzheimer's disease and to review clinical studies of vitamin B supplementation, because B12 deficiency is common and may be relevant to the disease.
They reviewed laboratory, animal and human studies on vitamin B12 and Alzheimer's disease, including randomised controlled trials of B vitamin supplements in people with mild cognitive impairment or Alzheimer's disease.
What it can’t tell you
- Animal and lab studies cannot show what happens in people.
- The clinical trials tested B vitamin supplements, often in combination, so the specific effect of vitamin B12 alone is unclear.
- Many trials were short or in people with advanced Alzheimer's, so they may not show whether B12 helps prevent the disease.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Saarland University, Germany; SRH University of Applied Health Sciences, Germany
The paper
- Title
- Mechanistic Link between Vitamin B12 and Alzheimer's Disease
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Lauer AA, Grimm HS, Apel B, et al (2022). Mechanistic Link between Vitamin B12 and Alzheimer's Disease. Biomolecules. doi:10.3390/biom12010129Free full textPubMed 35053277DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error