BIOAVAILABILITYOF ALUMINIUM IN ALUM-TREATED DRINKING WATER AND FOOD

ReportNo WSAA 203

November 1998

EXECUTIVESUMMARY

Background

Therole of dietary aluminium in the aetiology of Alzheimer’s disease remainscontroversial. Several epidemiological studies have associated the presence ofaluminium in drinking water with the incidence of Alzheimer’s disease, despitethe fact that water provides a relatively minor proportion of intake comparedwith other dietary sources. If aluminium in alum-treated drinking water doescontribute significantly to blood aluminium, it would have to be much morebioavailable than aluminium from food.

Objectives

Theaim of this study was to determine the relative bioavailabilities of aluminiumnaturally present in food and in alum-treated drinking water (ATW) from a townwater supply, with and without the addition of citrate, using 29 volunteersranging in age from 36-76 years.

Conclusions

Concentrationsof aluminium in the urine of 29 healthy volunteers on a controlled diet rangedfrom 0.68-6.02 µg A1/L or 1.76-9.34 µg Al/24 h (mean of 4.1+1.6 µg Al/24h). Concentrations of aluminium in blood plasma ranged from 0.24-1.25 µg Al/L(mean of 0.47+0.12 µg Al/L) which are towards the lower end ofpreviously reported values for aluminium in plasma.

Therewas no significant increase (p>0.05) in plasma aluminium following ingestionof ATW or food (with or without citrate). There was, however, a statisticallysignificant increase (p<0.01) of 9% in mean daily aluminium excretion inurine following ingestion of ATW. The presence of citrate in the ATW did notincrease the uptake or excretion of aluminium. Males had significantly higher(50% increase, p<0.01) aluminium urinary excretion rates than females. Therewas no significant difference (p>0.05) in the urinary excretion rates ofaluminium with the age of the volunteers.

Thebioavailability of aluminium from ATW, calculated from the urinary excretiondata, was 0.37% of the total aluminium in ATW or 0.56% of the chemically labilefraction of aluminium in ATW. The bioavailability of aluminium from food plustea ranged from 0.28-0.64%, depending upon the assumed bioavailability ofaluminium in tea. This suggests that the bioavailabilities of aluminium fromfood and ATW were similar. It was estimated that drinking 1.6 L of ATWcontaining 140 µg Al/L would contribute only 0.4-1.1% of the lifetime bodyburden of aluminium when 3mg Al/day is consumed in the diet. This is a minorproportion considering the relatively large and variable intake of aluminiumfrom food by humans.

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