Alzheimer's disease is a progressive and fatal disorder that affects an estimated 5.3 million Americans. It is the most common form of dementia, accounting for 50% to 80% of all cases. One of the symptoms of dementia is brain shrinkage, which can lead to cognitive impairment and is an early warning sign for Alzheimer's.

Now, researchers have found that high doses of vitamin B may reduce brain shrinkage in older people by as much as one half, thus potentially delaying the onset of Alzheimer's disease.

To learn more about this effect, scientists followed 168 seniors who were experiencing some form of cognitive decline, usually marked by lapses in memory and language problems. These issues were regarded as above and beyond the usual level that arise normally from aging, therefore making them possible precursors to dementia.

The subjects were divided in two groups, one of which was given high levels of the B vitamins (folate, B6, and B12) which were well above the daily recommended dose. The other group received a placebo (control group).

After two years, the seniors were brought in and the degree to which their brains had shrunk was measured. Normally, after the age of 60, the brain shrinks on average at the rate of 0.5% every year. In people who are experiencing mild cognitive impairment, the rate of shrinkage can occur at twice that rate, and people who are suffering from Alzheimer's disease experience shrinkage at a rate of 2.5% a year.

However, when high doses of vitamin B were taken, shrinkage of the brain slowed by as much as 30%, and in certain instances, by as much as 50%, which is comparable to a person with no cognitive impairment.

The reason that researchers looked at B vitamins is because they are involved in the control of the substance homocysteine. High levels of homocysteine are associated with faster rates of brain shrinkage and Alzheimer's disease.

In the study in question, researchers believe that it was in fact vitamin B's effect on homocysteine levels that slowed the rate of brain shrinkage and thereby helped to protect the brain.

While the authors of the study indicate that more work needs to be done, the initial results are promising and suggest an important link between diet and mental health, particularly how B vitamins may offer protection against Alzheimer's disease.

B vitamins are found naturally in a meat, fish, eggs, and green vegetables. Before going out and taking large quantities of B vitamins, however, speak with your doctor or a nutritional expert.

For more information about Alzheimer's disease, visit the website for the Alzheimer's Association and the National Institute of Aging, a division of the National Institutes of Health (NIH).