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It's too early, however, to recommend bottled water to everyone, says study co-author D. Larry Sparks, a senior scientist at Arizona's Sunhealth Research Institute. "It could help, but we don't know. What we're able to induce in the rabbits and what shows up in Alzheimer's disease (in humans) are strikingly similar, but we don't know if there's a direct correlation between the two."

Alzheimer's strikes an estimated one in 10 people over the age of 65 and nearly half of those older than 85, but its cause remains a mystery. Doctors suspect blockages within the brain known as "senile plaques" contribute to the illness. Research suggests that cholesterol contributes to these blockages, just as it clogs arteries.

During previous research on rabbits fed cholesterol to cause the plaques to form, Sparks and colleagues noticed their brains did a better job of clearing away the blockages when they drank distilled water instead of tap water.

In the new study, researchers added tiny amounts of copper to the distilled water given to a group of rabbits and compared them to other rabbits that drank ordinary distilled water. Previous research has shown those with Alzheimer's disease tend to have higher levels of copper in their bloodstream.

The findings appear in this week's online issue of the Proceedings of the National Academy of Sciences.

After 10 weeks, the rabbits who drank the copper water developed more plaques. The rabbits also showed signs of brain damage when they took a test in which a puff of air is blown into their eyes right after they hear a tone. Normal rabbits learn to close their eyelids when they hear the tone, Sparks says. But the rabbits with brain damage failed to remember what to do.

Copper is one of several metals in tap water that may be culprits in the development of Alzheimer's disease, explains Dr. Paul Tuite, an assistant professor of neurology at the University of Minnesota. Aluminum, copper and zinc all may play a role "by possibly increasing the risk of the condition," he explains.

One study even suggested that drugs that suck copper out of the brain helped reduce the formation of plaques in mice, says Dr. James Grisolia, a neurologist at Scripps Mercy Hospital in San Diego.

Copper may be needed to help protein bunch up and form an "insoluble glob that becomes the start of a senile plaque," he explains.

The new research is "promising and interesting," says Dr. Irene Litvan, director of the Movement Disorder Program at the University of Louisville. "In lieu of complex and risky therapies, simple measures such as using distilled water rather than tap water when one is exposed to a high cholesterol diet may have some 'protective effect,'" Litvan says. "It's an interesting issue for prevention."

Sparks, who found varying levels of copper in samples of municipal tap water, says there's certainly no harm in drinking purer forms of water. But more research is needed into tap water's effects on humans. His own new study "needs to be replicated, and we need to find out the exact mechanism of how this happens," he says. "We've got a lot of work to do."

For more information about Alzheimer's Disease research and treatment, please visit www.AlzheimerSupport.com.