Elderly people with low blood levels of vitamin B-12 and folate may have a higher risk of developing Alzheimer's disease, Swedish researchers reported. The findings suggest that monitoring older people's levels of the vitamins may aid in preventing Alzheimer's, according to a report in the May 8th issue of Neurology, published by the American Academy of Neurology. However, the researchers call their findings "surprising," and emphasize that there is no evidence that deficiencies in vitamin B-12 or folate contribute to the brain abnormalities that are the hallmark of Alzheimer's. Vitamin B-12 plays an important role in maintaining nerve cells, and some research has linked low blood levels of the vitamin to Alzheimer's and mental decline. Few studies have looked at whether there is such a connection between Alzheimer's and folate, a B vitamin key to the production and maintenance of body cells. In a study of 370 men and women aged 75 and older, investigators found that those with low levels of either vitamin were twice as likely as those with normal levels to develop Alzheimer's over a 3-year period. Surprisingly, the link was even stronger among study participants who performed well on mental tests at the start of the study, according to Dr. Hui-Xin Wang and colleagues at the Karolinska Institute in Stockholm, Sweden. The reason for the link is unclear, but low blood levels of B-12 and folate can lead to elevations in the protein homocysteine, which is known to damage nerve cells, the authors note. Previous research has linked this to neurological or psychiatric disorders - but never to Alzheimer's disease. Professor David Smith, of the Alzheimer's Research Trust, said the research confirmed previous studies, which suggested a similar link. "None of the published studies can establish whether or not the low levels of vitamins actually cause some cases of Alzheimer's disease. It will be necessary to carry out further research, including clinical trials of vitamin supplementation, in order to test this hypothesis. There is thus no justification at present to take extra amounts of these vitamins in the hope that they will prevent the development of dementia, unless of course indicated by a doctor," he said. Professor Smith said further research on the question was being undertaken in several countries, including the UK. Most people get enough vitamin B-12 in their diets to maintain healthful levels, but some--including the elderly--stand a greater chance of being deficient. The vitamin is found in animal products, including meat, fish, eggs and milk. Folate occurs naturally in foods such as leafy green vegetables, dried beans and peas, and citrus fruits; many cereals are fortified with folic acid, the synthetic form of folate.