I came to read this post after reading other relevant article and find the wiki explanation the most neutral among everything I red.
Here below is a copy of the article:
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Metals have been implicated in neurodegenerative diseases, although it is unlikely that they are the sole cause for any of them. Interest in a possible connection between aluminum and Alzheimer’s disease arose when autopsies of the brains of Alzheimer’s patients revealed higher than normal concentrations of aluminum. The toxicity of aluminum has been the subject of much controversy in the past few decades. Although it is generally believed that the metal is harmless to human health, a role for aluminum in Alzheimer’s disease has been suggested. The exact mechanism of aluminum toxicity is not known and a direct causal role has not been determined. Many scientists believe that the buildup of aluminum in the brain of Alzheimer’s patients is the result of damage to nerve cells, rather than the cause of this damage. Some studies have even suggested that the processing of the brain tissue at autopsy may artificially raise aluminum levels. However, there is some evidence showing that aluminum compounds may increase the formation of agents called reactive oxygen species. These substances, which are constantly formed in the human body, have been shown to damage proteins and play a role in various diseases. In relation to Alzheimer’s disease, these compounds may play an important role in nerve cell damage. Aluminum is also known to alter the activity of several key enzymes in the central nervous system. Further, there are also some studies showing elevated risk of Alzheimer’s disease in areas where there is high concentration of aluminum in drinking water. This is in contrast to many studies examining antacid exposure and Alzheimer’s disease that have been largely negative (antacids contain thousands of times more aluminum than the amounts taken in through drinking water). Exposure to aluminum from cooking utensils, baking powder, deodorants, or antacids is not sufficient to cause the disease. In total, these studies provide some evidence that potential links between aluminum and Alzheimer’s disease exist, but this area requires continued research efforts.

Hope this clear some clouds..

Roberto