Aluminium. It’s everywhere, but is it safe or a Toxin?

Aluminium. It’s everywhere, but is it safe or a Toxin?

InterClinical eNews April 2018, Issue 79

Aluminium is ubiquitous in the environment. In recent years, it’s been increasingly incorporated in consumer products, foodstuffs, and drinking water with a presumption of safety. This presumption is based on the belief that as it is not overtly toxic in acute low-dose ingestion, cumulative consumption must also be benign. This month, we review the research to shed light on this assumption. 

Aluminium Background

Aluminium (Al) is the most abundant metal in the earth’s crust, and it is widely distributed. It is a very reactive element and is never found as a free metal in nature, it is found combined with other elements, most commonly with oxygen, silicon, and fluorine. These chemical compounds are commonly found in soil, minerals (e.g., sapphires, rubies, turquoise), rocks (especially igneous rocks), and clays. Al, as the metal, is obtained from aluminium-containing minerals, primarily bauxite; it is light in weight and silvery-white in appearance.

A Toxin?

No known physiologic need exists for aluminium; however, because of its atomic size and electric charge (0.051 nm and 3⁺, respectively), it is sometimes a competitive inhibitor of several essential elements with similar characteristics, such as magnesium (0.066 nm, 2⁺), calcium (0.099 nm, 2⁺), and iron (0.064 nm, 3⁺). At physiologic pH, aluminium forms a barely soluble Al(OH)₃ that can be easily dissolved by minor changes in the acidity of the media.(4)

Approximately 95% of an aluminium load becomes bound to transferrin and albumin intravascularly and is then eliminated. In healthy subjects, only 0.3% of orally administered Al is absorbed via the gastrointestinal (GI) tract, and the kidneys effectively eliminate al from the human body.  Only when the GI barrier is bypassed, such as by intravenous infusion or in the presence of advanced renal dysfunction, does Al have the potential to accumulate. As an example, with intravenously infused aluminium, 40% is retained in adults and up to 75% is retained in neonates.(6) 

^{Mayor et al. suggested that the parathyroid hormone may increase intestinal absorption of aluminium. (6)}

Aluminium in Water

No physiological requirement for aluminium in human health has been found yet. (1)  Contrary to the popular assumption of safety, chronic low-level ingestion exceeding 1 g per day has been implicated in several conditions, including hypophosphataemia (caused by Al forming insoluble compounds with phosphate), hypercalcaemia, bone resorption, osteomalacia and Alzheimer’s disease. Embryotoxic effects have also been shown in preclinical trials.(1,2)  Along with the total limit for ingestion, a ‘safe’ drinking water limit of 0.6 mg/ L or 600 ppm per day has been proposed based on a 40-day aluminium balance study.(1)

Aluminium in Food

Aluminium is used in cookware, as takeaway containers and as a food foil for baking and food storage. Research has confirmed that it is more likely to leach into acidic foods such as lemons and oranges and some salty proteinaceous foods such as salmon and ham. (2) The leaching effect increases up to 18-fold when food is cooked and/or stored in aluminium foil on a tray made of an alloy with a higher electrical potential than aluminium, for example, stainless steel. (2)

In Personal Care Products

However, the most common route of aluminium exposure is through the use of antiperspirants, which contribute approximately 2 g of aluminium per day to the skin. This is absorbable, not directly via the skin epidermis but rather via the hair follicles, apocrine and eccrine sweat ducts.(1)  Additionally, certain sunscreens can contribute up to 5 g per day.(1)

Al is also commonly found in consumer and personal care products; pharmaceutical products such as antacids, adjuvants and prescription medications and is used to remove sediment from drinking water. The residual aluminium left in the water can range from 1.17 mg/L to 5.35 mg/L.(3)

Comparative Absorption Rates

Absorption from the intestinal tract is calculated at about 1% of ingested aluminium suggesting those who drink unfiltered water may be absorbing somewhere between 0.07 mg/L and 0.018 mg a day if they ingest around 1.5 litres of water daily. Absorption estimates from cosmetics, sunscreens and environmental exposure are harder to predict. It is unknown how much is absorbed via the skin sweat glands and whether it accumulates in the lymphatics, as not all of it is thought to be excreted via the urinary system. (1)

Pharmacy antacids contribute approximately 138 mg aluminium per dose and with an upper limit of 8 per tablets per day, providing a possible daily dose of 1.104 g per day – above the recommended daily limit.

The unwitting body burden can vary significantly from one person to another depending on food and water sources and consumer products used. Caution needs to be exercised to keep exposure to a minimum to avoid negative cumulative exposure effects.

Aluminium Sources

Aluminum is found in consumer products, including:

• antacids
• astringents
• buffered aspirin
• food additives
• antiperspirants 
• cosmetics
• nutraceutical – Some Australian Professional-only formulations utilise Al as an excipient – ALWAYS CHECK!
• Added during the processing of foods, such as:
  • flour
  • baking powder
  • colouring agents
  • anticaking agents

HTMA & Aluminium  

Aluminium has become a common mineral in the environment and is often considered an environmental toxin. It enters the human body through many pathways. Hair tissue mineral analysis is one of the best ways to test for aluminium in your patients easily. Chronic low-level, cumulative aluminium ingestion is not necessarily safe.

Individual body burden varies from person to person depending on the level of ingestion of the local water supply, the extent of personal product, pharmaceutical, sunscreen, and antacid use, and the methods of food preparation employed. Silica may be used as an antagonist of Aluminum to displace it in the body.

REFERENCES

1. Exley C.
   Human exposure to aluminium. Environmental Science: Processes &
   Impacts. 2013;15(10):1807-16. 
2. Ertl K,
   Goessler W. Aluminium in foodstuff and the influence of aluminium foil
   used for food preparation or short time storage. Food Additives &
   Contaminants: Part B. 2018 Feb 19.
3. Alexeeff,
   George V. Public health goal for aluminium In drinking water. 2001

4. Yokel RA, McNamara PJ. Aluminium toxicokinetics: an updated minireview. Pharmacol Toxicol. 2001 Apr. 88(4):159-67. 

5. Brown RO, Morgan LM, Bhattacharya SK, Johnson PL, Minard G, Dickerson RN. Potential aluminum exposure from parenteral nutrition in patients with acute kidney injury. Ann Pharmacother. 2008 Oct. 42(10):1410-5.

6. Trapp GA. Interactions of aluminum with cofactors, enzymes, and other proteins. Kidney Int Suppl. 1986 Feb. 18:S12-6.

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