Bioavailabilityof Aluminium from Drinking Water: Co-exposure with Foods and Beverages
ReportNo WSAA 83
Alum (aluminiumsulphate) is used in the clarification process of raw water for drinking. Arecent study using Sydney drinking water has shown that after alum treatment itcontained a higher proportion of soluble to insoluble aluminium species.Soluble forms of aluminium are bioavailable and toxic. They are readilyabsorbed from the digestive tract into the bloodstream and taken up by bone,brain and other soft tissues.
At high bloodlevels, aluminium causes acute dementia (dialysis dementia) in some renalfailure patients. Epidemiological studies have linked aluminium content indrinking water to the incidence of Alzheimer’s disease, a dementia whichusually develops over a longer time course.
The maininformation known about aluminium bioavailability is that citric acid fromlemon juice combines with aqueous aluminium to form aluminium citrate. This ismuch more readily absorbed than aqueous aluminium alone. The present researchstudied whether other nutrients affect aluminium bioavailability from drinkingwater. Laboratory rats were used to establish a “relative aluminiumbioavailability” database for each test diet. Changes in serum and urinaryaluminium concentrations were measured as an index of aluminiumabsorption/bioavailability.
This researchshowed that diet is a prominent determinant of aluminium bioavailability fromdrinking water. Orange juice, coffee and wine significantly increase the amountof aluminium absorbed from water. Tea, beer, butter, and apple have no effectwhile beef and Vita Wheat biscuits tend to decrease aluminium absorption. Foreach test diet a subpopulation of rats had higher aluminium bioavailabilitythan others and were more at risk. This finding is consistent with previousresearch on humans (Taylor et al., 1992; Harrington et al., 1994).
From this studyand other available data, it becomes clear that aluminium is absorbed throughthe intestine from alum-treated drinking water. However, almost all the knownfacts relate to rats. Further research is urgently required to ascertain ifabsorption occurs to the same degree in humans. If this proves to be the case,then the small daily amount of aluminium that gains access to the body must becritically analysed to find if it produces accumulated damage to brain tissues,particularly in the elderly.
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