Alzheimer’s disease: is it aluminum? – aluminum in the body may play a role
Lisa Poniatowski Easley
ALZHEIMER’S DISEASE Is It Aluminum?
Should you throw away your aluminum pots and pans, stop using antiperspirants and antacids, and drink aluminum-free water? Reports about the effect of aluminum on the body, and the implication that it plays a role in Alzheimer’s disease, have prompted many people to worry.
“You can’t believe the number of these calls that I get,” says Dr. Daniel Perl, a neuropathologist at Mount Sinai Medical Center in New York and a proponent of the aluminum theory. “I get hundreds of them.”
Theories aboud concerning the cause of Alzheimer’s, a progressive debilitating disease characterized by dementia, which affects more than one-tenth of Americans over the age of 65 and nearly half of those over 85. Scientists are currently pursuing several possibilities, including genetic factors, the effect of aging on the immune system, and the role of environmental toxins such as aluminum.
Why has aluminum been linked to Alzheimer’s disease? The circumstantial evidence that aluminum can be associated with – or sometimes cause – damage in the nervous system is compelling:
* Aluminum accumulates in lesions in the brains of Alzheimer’s patients. It builds up in degenerating nerve fibers (neuritic plaques) and shriveled filaments inside the cells (neurofibrillary tangles), as shown in the illustration on the next page.
* Before the cause was recognized, people receiving dialysis for chronic renal failure would sometimes develop “dialysis dementia.” Accumulation of aluminum in their bodies led to brain damage resembling that of Alzheimer’s disease, although the tangles have proved to be different in structure from those in Alzheimer’s. (Eliminating aluminum from dialysis fluid and equipment has subsequently made dementia an exceedingly rare complication of the procedure.)
* Studies on the island of Guam, where the water has a high level of aluminum, show that the natives suffer from an increased frequency of neurological diseases characterized by aluminum-containing tangles similar to those in Alzheimer’s. Aluminum is not believed to be the primary cause of these diseases, but a contributory role has not been ruled out.
* Several epidemiological studies have linked the risk of developing Alzheimer’s disease to the level of aluminum in drinking water. The methods used in these surveys have, however, been challenged.
* When aluminum is injected directly into the fluid bathing the brain of a rabbit, the animal develops neurofibrillary tangles similar, but not identical, to those characteristic of Alzheimer’s disease. Obviously, people aren’t injected in this way. But aluminum solutions placed in the nasal cavity of a rabbit also cause neurological damage, suggesting that the nose can serve as a route to conduct aluminum to the brain.
* People with Down’s syndrome who live past the age of 40 almost always develop Alzheimer’s disease. At autopsy their brains have been found to contain plaques, tangles, and high levels of aluminum.
“Mounting evidence gives cause for concern,” according to Dr. Donald R. McLachlan, a researcher at the University of Toronto. In the early 1970s he conducted the first research that found high levels of aluminum accumulated in brain tissue from patients with Alzheimer’s. “I think it would be irresponsible of us to say that we can be cavalier about the use of aluminum.”
All the studies have their critics, though, and despite the growing body of evidence, the Environmental Protection Agency, the Food and Drug Administration, the National Institute on Aging, and the Alzheimer’s Disease and Related Disorders Association (ADRDA) agree that none of these observations is sufficient to establish a causal relationship between aluminum and Alzheimer’s disease. Dr. Creighton Phelps, vice president of medical and scientific affairs at ARDRA in Chicago, says, “Until there is more conclusive scientific evidence that aluminum plays a causal role in the disease, we are not recommending that the public take any extraordinary steps to avoid it.”
Dr. Zaven Khachaturian, associate director of the Neuroscience and Neuropsychology of Aging program at the National Institute on Aging in Washington, D.C., says, “At this stage, there isn’t solid evidence to indicate whether the aluminum itself actually causes the lesions or whether the lesions get there because there is a defect in the cells, thus allowing the aluminum to accumulate in those structures. Whether it’s cause or effect is not known; that’s what needs to be determined.”
Even the proponents of the aluminum theory do not argue that aluminum is the sole cause of the disease – just that it may play a role. “We don’t argue that aluminum causes the disease by any means,” says Dr. McLachlan, one of the most vocal supporters of the aluminum theory. “Alzheimer’s disease is multifactorial, like every other major disease, and aluminum is just one of the factors.”
Dr. McLachlan believes that the controversy over aluminum derives in part from the inability of one laboratory to reproduce the results found in another. Some of this he attributes to the difficulty of the analytic methods needed to detect aluminum accurately. “I suspect this will be a raging controversy for some time,” he says.
The ubiquitous element
This debate among scientists is particularly alarming to the general public because aluminum is everywhere. Aluminum is the third most common element in the earth’s crust, after oxygen and silicon, so everyone is exposed to it. Although it is ubiquitous in the environment, aluminum serves no known purpose in the human body. In healthy bodies very little ingested aluminum is absorbed; most is excreted by the kidneys. According to the Aluminum Association, adult humans consume an average of 10-15 milligrams of aluminum a day from food, water, and food additives. Yet only trace amounts accumulate in the body: a normal person has no more than 30-45 milligrams.
Aluminum compounds in soil and water are taken up by plants, especially those grown in acidic soil. Naturally abundant in tea leaves, berries, spinach, and some herbs and spices, such compounds are also absorbed by foods cooked in aluminum pans. Acidic foods such as tomatoes, rhubarb, cabbage, apricots, cranberry sauce, and sauerkraut take up the most. (The amount depends on the type of cookware used, the length of cooking time, and the acidity of the water.)
Aluminum compounds are used in many health products, including antiperspirants, antacids, buffered aspirin, cosmetics, and ointments, as well as in such processes as water purification, gas absorption, food preservation, and paper making.
Not all aluminum compounds are easily absorbed by the human body. Thus, while some may be harmless, others could be more of a problem. For example, aluminum hydroxide, which is commonly used in antacids, is not readily dissolved, whereas a much higher proportion of the more soluble compound aluminum citrate is absorbed. “Naive statements have been made about how people who take a lot of antacids do not get Alzheimer’s disease, and therefore aluminum is unimportant,” says Dr. Perl. “You have to look at the form in which the aluminum is being delivered.”
Does this mean that some aluminum compounds are dangerous and others are not? “We know very little about that,” says Dr. Perl, who points out that the hazard presented by mercury depends very much on the form it is in when encountered by the body. “Inorganic mercury is only somewhat toxic. For hundreds of years people took mercury-containing diuretics and other drugs. But a very small amount of methylmercury, an organic compound, is devastating. It is a severe neurotoxin – a thousand times more toxic than inorganic mercury – yet it’s still mercury.”
Are precautions necessary?
“At this stage, I don’t think anyone has a definitive answer for those who ask whether they should throw away their aluminum pots or stop using aluminum products,” says Dr. Khachaturian. “If somebody is really concerned, the conservative thing would be not to use them. But there’s no evidence that avoiding them is going to prevent Alzheimer’s disease.”
Even the staunchest supporters of the aluminum theory, including Drs. Perl and McLachlan, are cautious about recommending products to avoid. Neither has made major lifestyle changes concerning aluminum products, although Dr. McLachlan carefully reads product labels and Dr. Perl doesn’t use aerosol antiperspirants because the aluminum released is airborne and more easily inhaled. “However,” he says, “my hand doesn’t shake when I reach for an aluminum pan.”
“Doing Alzheimer’s research is like doing a puzzle with a thousand pieces,” says Dr. Perl. “Aluminum is one of those pieces – it’s on the table. But we don’t know whether it’s in the center of the picture or out on the periphery and just another piece.”
PHOTO : Above: Alzheimer’s disease preferentially affects nerve cells clustered in certain regions of the brain (shown in red). Damage to the areas known as the amygdala and the hippocampus causes the memory defect. Damage to the cortex probably impairs intellectual function more generally.
PHOTO : Left: A nerve cell (neuron) damaged by Alzheimer’s disease is shown adjacent to a normal cell. Outside the damaged cell there is a neuritic plaque – an accumulation of abnormal protein (called amyloid) and degenerating nerve endings. Within the cell a buildup of dense material is organized into tangled fibers. At higher magnification, these neurofibrillary tangles are seen to consist of paired filaments wound around each other. Aluminum atoms (red dots) are associated with both the plaques and the tangles; they are also found attached to DNA in the nucleus of the cell.
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