In your book The Straight Dope you wrote about a possible link between aluminum and Alzheimer’s disease. You waffled on the question of whether aluminum actually caused Alzheimer’s and gave your stock response that research was continuing (equivalent to Ann Landers kissing off a question by telling the writer to seek professional advice). Well, here it is 13 years later, during which research presumably has continued. I have read at least two articles in the past few years saying aluminum has been pretty much ruled out as a factor in Alzheimer’s. Isn’t it about time to get your dope straight? –Jerry C., Chicago

What’s the matter, Jer, wake up on the wrong side of the Dumpster? Much as I’d like to report snappier results, here it is 13 years later, during which time a huge amount of research has been done, and scientists still don’t know for certain what role if any aluminum plays in Alzheimer’s disease. The aluminum industry argues that, given the murky state of current knowledge, there’s no point in trying to avoid the various forms of the metal, and I’d venture to say the typical doctor’s advice is not to worry about it. But that doesn’t mean aluminum is harmless. It just shows the difficulty of doing research on a disease so poorly understood.

As with a lot of things involving the brain, our understanding of Alzheimer’s remains sketchy. Only in the last few decades has the condition we used to call senile dementia been recognized as a disease (and therefore potentially treatable) rather than an inevitable consequence of old age. No one knows exactly what causes Alzheimer’s. (Want to hear the theories about peptides or the microtubule-associated protein tau? Didn’t think so.) There’s no satisfactory animal model that experimenters can use to investigate the effects of Alzheimer’s on humans. To this day a postmortem examination of the brain is the only way to positively distinguish Alzheimer’s from other forms of mental impairment. (Little Ed, for example, doesn’t have Alzheimer’s; he’s just confused.)

As for aluminum, we’re not even sure whether the brains of Alzheimer’s patients contain elevated levels of the stuff. Research findings have been contradictory. Some skeptics have argued that the aluminum seen in early research was the result of contamination during the test.

Several teams have tried to determine whether aluminum in drinking water is related to the number of Alzheimer’s cases. (Aluminum is often added to water supplies as a clarifying agent.) The results have been all over the place, for obvious reasons: Alzheimer’s cases aren’t always reported, people move around a lot, they may be exposed to aluminum from other sources, drinking water accounts for only a small portion of total aluminum exposure, and so on.

Even some early animal experiments have been called into question. In the 1960s and ’70s researchers found that rabbits exposed to aluminum salts suffered severe neurological damage similar in some ways to Alzheimer’s. But close examination of the nerve tissue revealed significant differences, and many researchers now think aluminum poisoning and Alzheimer’s are two completely different ailments.

Aluminum hasn’t been ruled out as a contributor to Alzheimer’s. But it’s safe to say that what once seemed like a promising avenue of research doesn’t seem so promising now. If, despite the foregoing, you still want to limit your aluminum exposure, you want to use deodorant rather than antiperspirant. The latter generally contains aluminum; the former generally doesn’t.

Art accompanying story in printed newspaper (not available in this archive): illustration by Slug Signorino.

Cecil Adams is the world’s most intelligent human being. We know this because: (1) he knows everything, and (2) he is never wrong. For more, see The Straight Dope website and FAQ.