The biological behaviour and bioavailability of aluminium in man, with special reference to studies employing aluminium-26 as a tracer: review and study update

Abstract

Until 1990 biokinetic studies of aluminium metabolism and biokinetics in man and other animals had been substantially inhibited by analytical and practical difficulties. Of these, the most important are the difficulties in differentiating between administered aluminium and endogenous aluminium-especially in body fluids and excreta and the problems associated with the contamination of samples with environmental aluminium. As a consequence of these it was not possible to detect small, residual body burdens of the metal following experimental administrations. Consequently, many believed aluminium to be quantitatively excreted within a short time of uptake in all, but renal-failure patients. Nevertheless, residual aluminium deposits in a number of different organs and tissues had been detected in normal subjects using a variety of techniques, including histochemical staining methods. In order to understand the origins and kinetics of such residual aluminium deposits new approaches were required. One approach taken was to employ the radioisotope (67)Ga as a surrogate, but this approach has been shown to be flawed-a consequence of the different biological behaviours of aluminium and gallium. A second arose from the availability, in about 1990, of both (26)Al-a rare and expensive isotope of aluminium-and accelerator mass spectrometry for the ultra-trace detection of this isotope. Using these techniques the basic features of aluminium biokinetics and bioavailability have been unravelled. It is now clear that some aluminium is retained in the body-most probably within the skeleton, and that some deposits in the brain. However, most aluminium that enters the blood is excreted in urine within a few days or weeks and the gastrointestinal tract provides an effective barrier to aluminium uptake. Aspects of the biokinetics and bioavailability of aluminium are described below.

Plasma and Urinary Aluminum Concentrations in Severely Anemic Geophagous Pregnant Women in the Bas Maroni Region of French Guiana: A Case-Control Study

“…This absorption is greatly increased by the concomitant intake of citrate, which is present in citrus juices, soda, and some beers that are often taken with pemba. 27,28 No significant difference was found between our anemic patients and controls in terms of easily identifiable sources of aluminum, such as drinking water (the aluminum content of drinking water in West French Guiana regularly exceeds recommended limits) and the consumption of drinks from metal cans. If we also consider plasma folate and vitamin B12 concentrations, we can assume that the women in the two groups had largely similar dietary habits.…”

“…It is found in kitchen utensils, packaging, tap water flocculants, food additives, antiperspirants, and antacid medication, for example. 26 In a report on the studies of the United States Food and Drug Administration, Priest 27 estimated that daily aluminum intake is of the order of 10 mg in populations with a Western-style diet. Antiacid drugs, produced from clays very similar to those preferred by geophagous individuals, may supply up to 1 g of aluminum per day, about ten times as much as a normal diet.…”

“…Antiacid drugs, produced from clays very similar to those preferred by geophagous individuals, may supply up to 1 g of aluminum per day, about ten times as much as a normal diet. 27 Aluminum ingestion, whether dietary or medical, is followed by very low levels of absorption in the digestive tract of the order of 1%. This absorption is greatly increased by the concomitant intake of citrate, which is present in citrus juices, soda, and some beers that are often taken with pemba.…”

The meaning of aluminium exposure on human health and aluminium-related diseases

“…Skeletal deposits represent the reservoir for the longterm retention of aluminium within the human body, with half-times being typically 10 -20 years (59) . The cycle of aluminium in bones starts with the transfer of metal ions from transferrin and citrate in the blood stream to bone surfaces, where aluminium becomes attached.…”

“…Many divalent and trivalent metal ions, including aluminium, mainly deposit in the skeleton, and for this reason, these metals are often referred to as bone-seekers (59) . Skeletal deposits represent the reservoir for the longterm retention of aluminium within the human body, with half-times being typically 10 -20 years (59) .…”