This post looks for reliable studies and reliable sources to figure out if there is a link to aluminum exposure and intake, and Alzheimer's disease.
- From Medscape, updated Apr 15, 2015:
- Dietary aluminum is ubiquitous but in such small quantities that it is not a significant source of concern in persons with normal elimination capacity.
- Approximately 95% of an aluminum load becomes bound to transferrin and albumin intravascularly and is then eliminated renally.
- Toxic effects are dependent upon the amount of metal ingested, entry rate, tissue distribution, concentration achieved, and excretion rate.
- At physiological pH, aluminum forms a barely soluble Al(OH)3 that can be easily dissolved by minor changes in the acidity of the media.
- In healthy subjects, only 0.3% of orally administered aluminum is absorbed via the gastrointestinal (GI) tract, and the kidneys effectively eliminate aluminum from the human body.
- If a significant aluminum load exceeds the body's excretory capacity, the excess is deposited in various tissues, including bone, brain, liver, heart, spleen, and muscle. This accumulation causes morbidity and mortality through various mechanisms.
- Aluminum brain concentrations should be lower than 2 μg/g. (2 micrograms of aluminum per gram of brain tissue.)
- Aluminum causes an oxidative stress within brain tissue. Since the elimination half-life of aluminum from the human brain is 7 years, this can result in cumulative damage via the element's interference with neurofilament axonal transport and neurofilament assembly.
- A possible etiologic link between aluminum exposure and Alzheimer disease emerged from a 1965 study showing that aluminum causes neurofibrillary tangles in the brains of rabbits (this was not a human study). Subsequent research has largely failed to support this hypothesis, however. For example, the clinical manifestations and underlying neuropathology of aluminum-induced encephalopathy in dialysis patients bear no resemblance to those of Alzheimer disease.
- Excess aluminum has caused anemia, which looks similar to lead poisoning.
- Aluminum toxicity is usually found in patients with renal impairment.
- From "Aluminum and silica in drinking water and the risk of Alzheimer's disease or cognitive decline: findings from 15-year follow-up of the PAQUID cohort". NIH. Dec 8, 2008. (This was a study done in France.)
- Using a Cox model, a high daily intake of aluminum was significantly associated with increased risk of dementia. Conversely, an increase of 10 mg/day in silica intake was associated with a reduced risk of dementia. However, the geographical exposure to aluminum or silica from tap water was not associated with dementia.
- Although knowledge of the pathophysiology of AD has greatly progressed over the past decades, its causal mechanisms are far from clear.
- Cognitive decline was greater in subjects with a high daily Al intake (greater than 0.1 mg/day or an increase of 0.1 mg/day). However, Al had no significant association with the values of the MMSE scores (a measure of global mental status) at inception in the cohort. (NOTE: "cognitive decline" is not Alzheimer's.)
- Among the 20 most influential subjects (about 1% of the sample) 7 had a high consumption of aluminum (> 0.100 mg/day).
- World Health Organization paper from 2010. PDF here, about 23 pages.
- Airborne aluminium levels range from 0.0005 μg/m over Antarctica to more than 1 μg/min industrialized areas (WHO, 1997).
- In drinking water systems in Canada that have surface water sources and use aluminium salts, the mean total aluminium concentration was estimated to be 101 μg/l.
- In a survey of 186 community water supplies in the United States of America (USA), median aluminium concentrations for all finished drinking-water samples ranged from 0.03 to 0.1 mg/l (30ug to 100ug); for facilities using aluminium sulfate coagulation, the median level was 0.1mg/l, with a maximum of 2.7 mg/l (2700 ug/l) (Miller et al., 1984). (Using the 2700 ug/l, and 0.3% is absorbed into the body, the body would be absorbing 8.1 ug/l of water of aluminum. Then 95% of that is eliminated through the kidneys so the body is left with .405 ug/l of aluminum.)
- In a study of 10 Sprague-Dawley rats, Aluminium did not accumulate in a dose-dependent manner in the organs and tissues examined.
- No adverse effects on body weight or longevity were observed in Charles River mice (54 males and 54 females per group) receiving 0 or 5 mg of aluminium (as potassium aluminium sulfate) per kilogram of diet during their lifetime (Schroeder & Mitchener, 1975a; WHO, 1989)
- Two groups of Long-Evans rats (52 of each sex) received 0 or 5 mg of aluminium (as potassium aluminium sulfate) per litre of drinking-water during their lifetime. No effects were found on body weight; average heart weight; glucose, cholesterol and uric acid levels in serum; and protein and glucose content and pH of urine. The lifespan was not affected (Schroeder & Mitchener, 1975b; WHO, 1989).
- Behavioural impairment has been reported in laboratory animals exposed to soluble aluminium salts (e.g. lactate, chloride) in the diet or drinking-water in the absence of overt encephalopathy or neurohistopathology. Both rats (Commissaris et al., 1982; Thorne et al., 1987; Connor, Jope & Harrell, 1988) and mice (Yen-Koo, 1992) have demonstrated such impairments at doses exceeding 200 mg of aluminium per kilogram of body weight per day. (This is far more than a person would get from city water treated from aluminum sulfate.)
- There is little indication that aluminium is acutely toxic by oral exposure despite its widespread occurrence in foods, drinking-water and many antacid preparations (WHO, 1997).
On the whole, the positive relationship between aluminium in drinking-water and AD [Alzheimer disease], which was demonstrated in several epidemiological studies, cannot be totally dismissed. However, strong reservations about inferring a causal relationship are warranted in view of the failure of these studies to account for demonstrated confounding factors and for total aluminium intake from all sources.
It's still not clear if Aluminum is corellated with dementia (or Alzheimer's, which is a different diagnosis) or if there is causation.
If you have any studies you would like me to add, put a link in the comments to this post and what you thought was interesting to add.