“That really changed the whole complexion of the thing,” recalls Perl, now a professor of pathology in the Uniformed Services University of the Health Sciences in Bethesda. “I was getting called all the time, because there was so much public interest.”
Despite the rise in interest, no one could figure out what this meant for human health. Part of the problem was that scientific techniques were — and still are — too imperfect to provide an answer. Whether they were studying brain cells or conducting population-wide epidemiological studies that tracked aluminum exposure and Alzheimer’s risk, researchers lacked the tools to get very precise or conclusive results.
“Aluminum is so common, so prevalent in the environment, that studying it is a hard task,” says John Savory, a professor emeritus of pathology at the University of Virginia who helped discover that aluminum exposure can cause neurological and dementia-like symptoms in dialysis patients. “Just a speck of dust can contaminate your sample, because it’s everywhere.”
It’s found in nature
Naturally occurring aluminum is the third-most-abundant element on Earth, so it really is everywhere. Because it’s present in the soil, it can be found in certain foods, such as spinach and tea. It’s also used in a number of industrial processes that bring it into close contact with humans. Although many studies of aluminum exposure have focused on drinking water — utilities often use aluminum salts to clarify and purify their water — it is also found in cookware and food packaging, in antacids, antiperspirants and a handful of medications, and in some processed foods. That makes teasing out people’s exposures to aluminum over a lifetime, and the effect of those exposures, “very hard to do,” Perl says.
It’s no surprise, then, that 30 years of studies on the aluminum-Alzheimer’s link have yielded conflicting results.
For example, a 1997 study of nearly 1,000 men from England and Wales found little association between their Alzheimer’s disease incidence and their estimated exposure to aluminum through drinking water, but a 15-year study that followed 1,925 French men and women concluded that high aluminum consumption from drinking water might be a risk factor for Alzheimer’s disease. In a 2003 World Health Organization survey of six high-quality epidemiological studies of aluminum in drinking water as a risk factor for Alzheimer’s disease, three found a positive association, while three did not.