STOCKHOLM, SWEDEN. Some studies have found a correlation between low vitamin B12 levels and the development of Alzheimer's disease (AD) and dementia; other studies have found no such correlation. Researchers at the Karolinska Institute now provide convincing evidence that a deficiency of either vitamin B12 or folic acid (folate) is associated with an increased risk of AD and dementia.
Their study involved 370 non-demented people aged 75 years and older who were not supplementing with vitamin B12 or folate. The participants were tested at baseline to determine mental status and had blood samples drawn for analysis of vitamin-B12 and folate levels. Only subjects who showed no signs of dementia were included in the follow-up group. Three years later 77 of the participants had developed dementia; of these 59 were diagnosed with AD. Compared with participants with normal levels of vitamin B12 and folate the participants with low levels of at least one of the vitamins had a 2.3 times higher risk of AD and a 1.7 times risk of any kind of dementia. These risk estimates were obtained after adjusting for other risk factors such as age, sex, and educational attainment.
The researchers speculate that homocysteine, a known neurotoxin, may be involved in the development of
AD and that vitamin B12 and folic acid help prevent this effect by reducing homocysteine levels in the