Vitamin B12

Cognitive Benefits

By Charles Li, MD

TL;DR: Vitamin B12 & Brain Health

Vitamin B12 has long been suspected of helping to maintain healthy brains because of its role in metabolizing potentially toxic chemicals.
Chemistry of B12
B Vitamins, including Vitamin B12, remove homocysteine, which has been linked to a higher risk of Alzheimer's Disease and dementia in general.
More Study Needed
However, at the moment, studies on Vitamin B12 and cognitive function have remained inconclusive on whether consuming more Vitamin B12 causes improved brain health. Some evidence exists of a correlation.


Does nutrition help with brain health?

Vitamin B12 plays important roles in metabolism. It helps your enzymes perform complex chemistry as they break down what we eat.

One reaction that's of particular interest for doctors is the breakdown of a molecule we call homocysteine.

Vitamin B12 Facts
Vitamin B12 is a water soluble vitamin, otherwise known as cobalamin, that you obtain from your diet. It plays key roles in metabolism, nerve health, and red blood cell generation.

Homocysteine & Dementia

We get homocysteine from the foods that we eat, particularly from meat. When we don’t get enough Vitamin B12, homocysteine can build up in our bodies. 

One of the effects of having too much homocysteine is a higher risk of Alzheimer’s Disease and dementia. 

In one study, researchers found that individuals with the highest levels of homocysteine had a 2.2 times higher risk of developing Alzheimer’s disease.

Does homocysteine correlate with dementia risk?

A cross-sectional study on homocysteine and dementia found that high homocysteine levels correlates with a 2.2x increase in dementia risk. Researchers studied 1092 subjects with an average age of 76. 

Study Source
From the abstract:

"Over a median follow-up period of eight years, dementia developed in 111 subjects, including 83 given a diagnosis of Alzheimer's disease...An increased plasma homocysteine level is a strong, independent risk factor for the development of dementia and Alzheimer's disease."

Seshadri, 2002, NEJM

Vitamin B12 & Alzheimer's Disease

Theoretically, having enough Vitamin B12 should help reduce our levels of homocysteine.

However, the question remains, does providing Vitamin B12 as a supplement help prevent Alzheimer’s disease?

The answer still not entirely clear, partly because of the difficulty of running a good clinical trial.

One very small study has found some evidence that providing Vitamin B12 supplements to those who lack Vitamin B12 may help improve key brain functions, in particular verbal skills.

However, the study was small, and not particularly well-designed for this purpose. We still do not know have a clear answer one way or the other.

Vitamin B12 & Cognition

A study on 125 subjects found that Vitamin B12 may improve cognitive function among those who have low B12 levels. Researchers found that those who received Vitamin B12 treatment had significantly improved verbal skills.

Study Source
From the abstract:

"All patients with cognitive impairment should be investigated for B12 deficiency. Vitamin B12 treatment may improve frontal lobe and language function in patients with cognitive impairment, but rarely reverses dementia."

Vitamin B12 deficiency in dementia and cognitive impairment: the effects of treatment on neuropsychological function


We know that Vitamin B12, on a biochemical level, plays a key role in brain health.  Due to a lack of good direct clinical data, experts do not yet recommend going to your store and buying Vitamin B12 supplements. However, it adds more evidence for the benefits of a healthy balanced diet for the brain.