People taking high levels of the nutrient folate through food and supplements are less likely to develop Alzheimer's disease, researchers have argued.
The study found folate, vitamin B12 and vitamin B6 helped process the amino acid, homocysteine, high levels of which have been linked to heart disease, stroke and dementia.
Scientists from the Columbia University Medical Center in New York tested 965 people without dementia and followed them to see if they developed the disease.
After follow-up, 192 of the participants, who had an average age of 75.8, developed Alzheimer's.
Writing in the Archives of Neurology journal, the authors said those taking more folate had lower homocysteine levels, which could potentially reduce the risk of developing Alzheimer's.
However, they added that it was too early to make definitive judgements about the role of folate in the development of the disease.
"The decision to increase folate intake to prevent Alzheimer's disease should await clinical trials," the report concluded.