BIOAVAILABILITY OF ALUMINIUM IN ALUM-TREATED DRINKING WATER AND FOOD

Report No WSAA 203

November 1998

 

EXECUTIVE SUMMARY

 

Background

 

The role of dietary aluminium in the aetiology of Alzheimer’s disease remains controversial. Several epidemiological studies have associated the presence of aluminium in drinking water with the incidence of Alzheimer’s disease, despite the fact that water provides a relatively minor proportion of intake compared with other dietary sources. If aluminium in alum-treated drinking water does contribute significantly to blood aluminium, it would have to be much more bioavailable than aluminium from food.

 

Objectives

 

The aim of this study was to determine the relative bioavailabilities of aluminium naturally present in food and in alum-treated drinking water (ATW) from a town water supply, with and without the addition of citrate, using 29 volunteers ranging in age from 36-76 years.

 

Conclusions

 

Concentrations of aluminium in the urine of 29 healthy volunteers on a controlled diet ranged from 0.68-6.02 µg A1/L or 1.76-9.34 µg Al/24 h (mean of 4.1+1.6 µg Al/24 h). 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 of previously reported values for aluminium in plasma.

 

There was no significant increase (p>0.05) in plasma aluminium following ingestion of ATW or food (with or without citrate). There was, however, a statistically significant increase (p<0.01) of 9% in mean daily aluminium excretion in urine following ingestion of ATW. The presence of citrate in the ATW did not increase the uptake or excretion of aluminium. Males had significantly higher (50% increase, p<0.01) aluminium urinary excretion rates than females. There was no significant difference (p>0.05) in the urinary excretion rates of aluminium with the age of the volunteers.

 

The bioavailability of aluminium from ATW, calculated from the urinary excretion data, was 0.37% of the total aluminium in ATW or 0.56% of the chemically labile fraction of aluminium in ATW. The bioavailability of aluminium from food plus tea ranged from 0.28-0.64%, depending upon the assumed bioavailability of aluminium in tea. This suggests that the bioavailabilities of aluminium from food and ATW were similar. It was estimated that drinking 1.6 L of ATW containing 140 µg Al/L would contribute only 0.4-1.1% of the lifetime body burden of aluminium when 3mg Al/day is consumed in the diet. This is a minor proportion considering the relatively large and variable intake of aluminium from food by humans.

 

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