Imagine your most cherished memories fading away as your mental powers decline, stolen by dementia. It's a distressingly common scenario, given that dementia affects about 5% to 8% of Americans over age 65...and as many as half of those over age 85.

There are many different types of dementia, the most common of which is Alzheimer's disease. Scientists are still struggling to figure out what sets off the degenerative process of Alzheimer's, but they do know that once it has begun, deterioration increases as plaque is deposited in the brain...neurons lose their ability to function and eventually die...and the brain shrinks considerably, actually losing volume.

It would be ideal if we could figure out a way to prevent dementia from ever getting started, but learning how to slow down its progress would also be good news. In that regard, we've just taken a big step forward--because even though seemingly promising drugs have failed in clinical trials, researchers have discovered that a common vitamin could hold the key to slowing down dementia's progress.

Delving Deeper

The study participants included 156 seniors age 70 and up who had mild cognitive impairment (MCI). More than just the typical age-related memory problems, such as forgetting where you left the car keys, MCI is characterized by trouble recalling information that previously would have been easily remembered, such as appointments or conversations.. and/or difficulty making sound decisions or completing complex tasks. People with MCI are at increased risk for eventually developing Alzheimer's disease or some other type of dementia.

Researchers measured the size of each participant's brain using MRI images. They also measured blood levels of a protein called homocysteine, elevated levels of which have been linked to increased dementia risk in many earlier studies. Then half the participants were given a daily high-dose vitamin-B supplement-consisting of 0.5 milligrams (mg) of vitamin B-12...20 mg of vitamin B-6...and 0.8 mg of folic acid (vitamin B-9—while the other half received a placebo.

After two years, the MRIs and blood tests were repeated.

Results: People in the vitamin-B group had homocysteine levels that were 29.4% lower than those in the placebo group and they showed less loss of brain volume (atrophy). By further analyzing the MRI images using 3D reconstruc tions, the researchers determined that the vitamin B group had significantly less atrophy than the placebo group in key parts of the brain related to memory and cognitive decline-parts that are most affected by MCI and Alzheimer's. What's more, an important type of brain tissue called gray matter (which contains nerve cell bodies) shrank in these brain regions by just 0.5% in the vitamin-B group, compared with a 3.7% loss in the placebo group. This was a very significant difference!

For their next analysis, the researchers divided the study participants into two groups ac cording to their homocysteine levels at the start of the study, comparing those whose measurements were below the median against those whose measurements were above the median.

What they found: Among people who had high homocysteine levels, those taking the placebo lost 5.2% of their gray matter...while those taking vitamin B lost just 0.6% of their gray matter in the brain regions that showed significant benefit from vitamin-B supplementation. For those who already had low homocysteine levels, there was no difference in gray matter loss among placebo users versus vitamin-Busers-meaning that taking vitamin B was beneficial only for people with high homocysteine. The researchers concluded that taking vitamin B (particularly vitamin B-12) was as protective as having low homocysteine levels.

In addition, the researchers conducted tests of memory and cognitive function and they found, as expected, that people who lost less gray matter did significantly better than those whose brains had suffered more atrophy. For example, among the high-homocysteine group, people who received the vitamin-B treatment were 69% more likely than placebo users to be able to correctly remember a list of 12 words.

To B or not to B: It's too early to suggest that everyone should be supplementing with B vitamins, the researchers noted. For one thing, in this study the vitamin-B combination was protective only for people who had high homocysteine levels. For another thing, consuming too much of the B vitamins could create problems-for instance, excess folic acid has been linked to cancer cell stimulation, while excess vitamin B-6 has been linked to nerve damage. Finally (and unfortunately), an earlier study found that people who already had moderate-to-severe Alzheimer's disease did not benefit from taking vitamin-B supplements.

Still, it's worth talking with a doctor who is knowledgeable about nutrition to see whether vitamin-B supplementation might be appropriate for you, particularly if blood tests show that you are deficient in B vitamins or have a high level of homocysteine and/or if you already have signs of mild cognitive impairment. And there's certainly no harm in increasing your consumption of vitamin-B-rich foods, such as clams, fish, liver, milk and spinach.

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