Aluminium is the third most common element found in the earth’s crust, after oxygen and silicon. It has been estimated that the average human body contains, at most, 35 mg of aluminium, of which approximately 50% is in the lungs, and most of the remainder is in the skeleton.

There is no known biological role for aluminium - it does not appear to be an essential trace element for humans - and the body has highly effective barriers to exclude aluminium and similar metals. Only a very small fraction of aluminium in the diet is taken up from the gut and in healthy individuals the kidneys quickly excrete most of this absorbed aluminium.

The brain is vulnerable to many substances, including aluminium, but there is a "blood-brain barrier" which prevents the aluminium in blood from readily entering this organ. When aluminium blood levels are high, bones appear to act as a "sink", taking up aluminium and releasing it slowly over a long period of time.

Aluminium in the diet of an adult usually ranges from about 2.5 to 13mg per day, although people on special medication may receive more than 1000 mg per day, usually as aluminium hydroxide. Recent studies have shown that the absorption of aluminium from the digestive tracts is often as low as 0.001%, although up to about 0.1 % - 1.0% can be absorbed when it is in the form of citrate.

When the natural barriers that limit the absorption of aluminium are bypassed via intravenous administration, or when the ability of the kidneys to excrete aluminium is impaired, accumulation of aluminium compounds in the body may occur. Under normal circumstances the body does not accumulate significant aluminium.

Patients with severe kidney failure, including those on dialysis treatment face a multitude of problems, including the inability to excrete absorbed aluminium. The use of modern aluminium free dialysate solutions or new techniques (such as reverse osmosis) now prevents dialysis dementia. The acute "dialysis dementia" described in the early days of renal dialysis has no connection with Alzheimer's disease, in dialysis dementia there are neither neurofibrillary tangles nor senile plaques and the dementia can be reversed by treatment with drugs to remove aluminium.

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