Title: Dietary Aluminium

Key words: aluminium toxicity, cooking utensils, case history

Date: July 2000

Category: Nutrition & the Environment

Type: Article

Author: Dr van Rhijn

Dietary Aluminium

Absorption, Storage & Excretion

 

Introduction

Reports associating aluminium (Al) with skeletal and neurological disorders suggest that Al exposure pose a toxic hazard. Aluminium intake from foods, cooking utensils and food containers may provide a basis for increased Al concentrations in body fluids and tissues.

Absorption, Storage & Excretion

Intestinal absorption of Al from food contributes significantly to systemic exposure despite apparent protection from low absorption (95% excreted in stool) and high kidney excretion. Bioavailability depends on dietary composition, intraluminal pH, speciation & quantity, presence of competing (iron, calcium) or complexing (enhanced by citrate1) substances, gut mucosal effects and systemic factors2. Various absorption sites and transcellular & paracellular passage routs have been reported, each related to a different Al species (hydrated ionic, citrate complex)3. Al is stored mainly in bone (one cause of hip fractures), arteries and soft tissues (liver, lungs, thyroid, brain) and accumulation occurs in patients with chronic renal failure4. Total Al content of the adult body is estimated at 50 - 150 mg.

Aluminium in Food and Utensils

Aluminium containers are widely used to cook, to freeze or wrap foods despite evidence that Al can migrate from containers (data is scarce). The highest release, albeit low, is into acidic and salty foods. The daily intake of Al, even if all foods were prepared and stored in Al containers, added up to approximately 6mg/day5. This is a very low value compared with the Provisional Tolerable Weekly Intake of 7 mg/kg body weight (60 mg/day for adult) established by the Joint FAO/WHO Expert Committee on Food Additives. Other sources estimate the mean dietary exposure of Al at 3200 m g/day, and the provisional tolerable daily intake (PTDI) for a 60 Kg adult at 6mg/day6, or the average daily amount of Al ingested to range from 10 - 100 mg7.

Typical Case History

The Regular Telly Dinner Scenario

Fred and Joe’s favourite and regular telly dinner, conveniently heated in an aluminium container, was a take-away of curried textured soy mince and rice followed by rhubarb crumble with custard. Fred drank beer with his meal, but Joe’s mildly impaired renal function caused him to drink orange juice at meals. The relative changes in aluminium concentration expected in their body fluids and tissues are discussed below.

This dinner provides a rich supply of Al from:

Other contaminants9 include aluminium packaging (cans are lacquered to prevent absorption) and cooking utensils. Rhubarb cooked in aluminium provides 8500 m g/100gr. The mean value for Al in beer ranges from 36.5 to 795.2 m g/L10, but another study estimates levels at 57 m g per pint and 111 – 280 m g /L11 if contaminated from Al containers. Orange juice (citric acid) may enhance absorption. Excretion of aluminium is facilitated through reduced absorption, by fluoride, silicon (rice), amino acids (taurine, methionine, cystine, glutathione), milk (custard), vegetables & garlic and via chelation from body tissues, by citric acid (citrus fruit), malic acid (rhubarb) and succinic acid (artificial flavour).

Conclusion

Numerous factors regarding Al analysis (low levels, contamination risk, unhomogenous samples, complexity of matrices.) make interpretation of tissue levels difficult. This was recently confirmed by a study which showed a ten to fifteen-fold variation of Al levels in liver and bone12. Taking all the interactions into consideration, it appears that Joe runs the highest risk of Al accumulation in his body fluids and tissues over time with this habitual diet.

 

References

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