Can silica in tap water prevent Alzheimer's?

According to a Reuters report, high silica levels in tap water may prevent or reduce the occurrence of Alzheimer’s disease in a population.

In a study conducted over a period of more than ten years, researchers followed the health of over 7,000 French women from five different cities. The findings suggest that a high level of silica contained in tap water seems to dramatically reduce the occurrence of Alzheimer’s disease:

Women with normal or higher mental function at the outset had a higher daily silica intake, the investigators report in the American Journal of Clinical Nutrition. The relationship remained statistically significant after taking account of age, location, income, educational level and history of stroke.

In a second phase of the study, women living in Toulouse who had normal or higher cognitive scores were followed for up to seven years. During that time, 60 women developed Alzheimer's disease while 323 maintained normal cognitive function

The women with Alzheimer's disease were 2.7 times more likely to have daily silica intake considerably lower than those without Alzheimer's disease, the researchers found.

Previous research has linked aluminum with the formation of “senile plaque”, believed to be a contributing cause in the development of Alzheimer’s, and the researchers have suggested that perhaps silica counteracts the effect of aluminum. The French study did not find a correlation between aluminum levels cognitive functions, but the researchers explained that this may be because aluminum levels among the subjects were very low overall.