Aluminium sulphate
An aluminium salt used as a firming agent in a handful of specialist foods. Aluminium accumulates in the body and neurotoxicity is the regulatory benchmark concern.
Aluminium builds up in the body over time. Regulators have set a weekly limit for total dietary aluminium intake because of neurotoxicity signals in animal studies, and high-end population estimates can exceed that limit when all food sources are combined.
What is it?
Aluminium sulphate is an inorganic salt formed from aluminium and sulphuric acid. It dissolves readily in water and carries the metallic element aluminium into foods that contain it.
What does it do?
Acts as a firming agent, keeping food tissue crisp and structurally intact during processing. It can also buffer acidity and, in liquid egg white, stabilises foam by interacting with proteins to produce a stiffer, more durable structure.
Where you will see it
Permitted in only two food categories in the UK and EU: candied cherries (where it keeps the flesh firm through the sugar-soaking process) and liquid egg white used to make egg foams (such as commercial meringue bases). It appears on labels as 'aluminium sulphate' or 'E520'.
What the science says
Neurotoxicity: the benchmark concern
Regulatory agencies set the tolerable weekly intake for aluminium based on neurotoxicity observed in animal experiments. In rats and mice, sustained aluminium exposure at high doses impaired brain development and nervous-system function. Although these doses are far above what the food additive contributes in practice, neurotoxicity is established as the critical endpoint that limits how much aluminium regulators consider acceptable across all dietary sources combined.
EFSA identified neurotoxicity as the critical endpoint for aluminium, establishing a tolerable weekly intake of 1 mg aluminium per kilogram of body weight per week across all dietary sources.
Animal studies reported no-observed-adverse-effect levels for neurotoxicity in the range of 10 to 42 mg aluminium per kilogram of body weight per day in rats and mice, with developing nervous systems showing the greatest sensitivity.
Exposure from food additives versus total dietary aluminium
Most aluminium in the diet comes from naturally occurring levels in cereals, vegetables and drinking water, not from food additives. At the narrow uses currently permitted for E520, the contribution to total aluminium intake is close to zero. At the 95th percentile of exposure estimates for all aluminium sources combined, some population groups can exceed the tolerable weekly intake, but EFSA noted those estimates are highly conservative and the additive contribution is minimal.
EFSA concluded that aluminium sulphates (E520-523) at authorised uses and levels were not a safety concern in their own right, but noted that 95th-percentile dietary aluminium exposure from all sources could exceed the TWI for some population groups, with estimates considered very conservative.
Aluminium accumulation in the body
Aluminium is not an essential nutrient. The body absorbs a small fraction of ingested aluminium and excretes most of it via the kidneys, but some accumulates in bone and brain tissue over years. People with impaired kidney function clear aluminium less efficiently, raising their body burden more quickly with the same dietary intake.
Aluminium is absorbed in small amounts from the gastrointestinal tract and accumulates primarily in bone and brain; renal clearance is the main elimination route, and impaired kidney function increases retention.
Where it stands with the regulators
Who should be careful
People with reduced kidney function should be aware that aluminium clears more slowly from their bodies, raising their total body burden over time. E520 appears only in very specific products (candied cherries and commercial egg-white products) so incidental exposure from everyday shopping is rare. Look for 'aluminium sulphate' or 'E520' on the label.
The honest read
The science on aluminium and health is genuinely complicated by the fact that aluminium is everywhere in the environment and diet, making it hard to isolate the contribution of any single additive. The neurotoxicity signal comes from animal experiments at doses far above what food additives supply. Human epidemiological data on dietary aluminium and brain health remain limited and contested. Regulators have set a tolerable weekly intake as a precautionary ceiling and have narrowed the permitted uses for aluminium additives over time. Whether the current ceiling is conservative enough for sensitive groups, including developing brains and people with kidney disease, is a question the science has not fully resolved.
Related additives
Common questions
Is E520 banned in the UK?
No. E520 is permitted in the UK under retained EU food additive law, but only in two specific foods: candied cherries and liquid egg white used for egg foams. It is not a general-purpose additive.
Does aluminium from E520 build up in the body?
A small proportion of ingested aluminium is absorbed and can accumulate in bone and brain tissue over years. The kidneys excrete most of it, but people with impaired kidney function retain more. The regulatory weekly intake limit covers all dietary aluminium sources combined, not just food additives.
What foods contain E520?
In practice, candied cherries and some commercial liquid egg-white products. It is not found in everyday grocery items such as bread, dairy, snacks or soft drinks. Its use is very narrow.
Is E520 vegan?
E520 itself is a synthetic inorganic salt with no animal origin. However, one of its two permitted food uses is liquid egg white, which is not vegan. In candied cherries it would be vegan.
Sources
- EFSA ANS Panel: Re-evaluation of aluminium sulphates (E 520-523) and sodium aluminium phosphate (E 541) as food additives, EFSA Journal 2018
- EFSA AFC Panel: Safety of aluminium from dietary intake, EFSA Journal 2008
- UK FSA Approved Additives and E Numbers
- EU Regulation 1333/2008 on food additives (UK legislation.gov.uk)
- The Food Additives and Novel Foods (Authorisations and Miscellaneous Amendments) and Food Flavourings (Removal of Authorisations) (England) Regulations 2024
- FSA Authorised Regulated Food and Feed Products for Great Britain
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