SAN DIEGO (Reuters Health) - Adding support to a controversial theory linking aluminum with Alzheimer's disease, new research indicates the disease is more common in regions of northwest Italy where levels of aluminum in drinking water are highest.

And when the investigators studied the effects of one form of the metal on two types of human cells in the lab, they found it hastened cell death.

"We were absolutely surprised by these results," said study author Dr. Paolo Prolo, a researcher at the University of California at Los Angeles. "I did not expect any effect from aluminum."

In findings released here Monday at the annual Experimental Biology meeting, Prolo and colleagues focused on monomeric -- single molecule -- aluminum. This is the type that can be most easily absorbed by human cells, he said.

While there have been suggestions that aluminum cookware might pose a risk for Alzheimer's, the type of aluminum used in pots and pans consists of multiple molecules and does not appear to affect human cells, according to Prolo. "There is almost no evidence that the cookware is dangerous," he said.

When the researchers tested water in regions of northwest Italy in 1998, they found that total aluminum levels -- including monomeric and other types of aluminum -- ranged from 5 to 1,220 micrograms per liter, while monomeric aluminum levels alone ranged from 5 to 300 micrograms per liter.

Environmental officials generally recommended that total aluminum levels be below 200 micrograms per liter, Prolo noted.

After comparing this data to death rates from Alzheimer's in those regions, the researchers found that the disease was more common in areas with the highest levels of monomeric aluminum.

Back in the lab, Prolo and colleagues then tested the effects of monomeric aluminum on human immune-system cells and bone cancer cells. Ideally, human brain cells would be tested but these are not readily available because a biopsy of a patient's brain is necessary to acquire them, he said.

"We found that a very low quantity of aluminum added to our cell cultures was modifying cellular processes" like normal cell death, Prolo told Reuters Health.

When the aluminum was paired with beta-amyloid, a protein found in the brains of Alzheimer's patients, the combination killed off even more cells.

Because aluminum could kill both types of human cells, these findings raise the question of whether aluminum is potentially involved in other diseases, Prolo said.

But much more research is needed to understand how the metal does or does not affect people, he added.

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