A new study shows that vitamin B12 may protect against Alzheimer's disease, adding more evidence to the scientific debate about whether the vitamin is effective in reducing the risk of memory loss.

The research will be published in the October 19, 2010, issue of Neurology®, the medical journal of the American Academy of Neurology.

"Our findings show the need for further research on the role of vitamin B12 as a marker for identifying people who are at increased risk of Alzheimer's disease," said study author Babak Hooshmand, MD, MSc, with Karolinska Institutet in Stockholm, Sweden. "Low levels of vitamin B12 are surprisingly common in the elderly. However, the few studies that have investigated the usefulness of vitamin B12 supplements to reduce the risk of memory loss have had mixed results."

For the seven-year study, researchers took blood samples from 271 Finnish people age 65 to 79 who did not have dementia at the start of the study. During that time, 17 people developed Alzheimer's disease. Blood samples were tested for levels for homocysteine, an amino acid associated with vitamin B12, and for levels of the active portion of the vitamin, called holotranscobalamin. Too much homocysteine in the blood has been linked to negative effects on the brain, such as stroke. However, higher levels of vitamin B12 can lower homocysteine.

The study found that for each micromolar increase in the concentration of homocysteine, the risk of Alzheimer's disease increased by 16 percent, whereas each picomolar increase in concentration of the active form of vitamin B12 reduced risk by two percent. The results stayed the same after taking into account other factors, such as age, gender, education, smoking status, blood pressure and body mass index. The addition of folate did not appear to raise or lower the risk of Alzheimer's disease.

"More research is needed to confirm these findings before vitamin B12 should be used solely as a supplement to help protect memory," said Hooshmand.

Vitamin B12 can be found in fish, poultry and other meat products.

The study was supported by the Karolinska Institutet, the Swedish Research Council for Medical Research, the European Commission Seventh Framework Programme, the Academy of Finland, the Ragnhild and Einar Lundströms Minne Lindhés Foundation, the Stohnes Foundation, the Gamla Tjanarinnor Foundation and the Dementia Foundation of Sweden.