An Oxford University study found that a high dosage of the vitamin shortened the rate of brain shrinkage in elderly people with memory problems.
Vitamin B-6 and B-12, as well as folic acid, lower the levels of an amino acid that is linked to the brain-cell damage similar to that seen in Alzheimer's.
Patients with the highest levels of the amino acid in their blood showed the most benefit.
The results conflict with earlier findings that Alzheimer's disease patients did not benefit from vitamin B.
This study is published in the journal of American Medical Association.