Aluminium and Alzheimer’s: An unproven link

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By Alice Newman-Sanders | Wednesday 24 January 2024

On International Day of Education, we’re sharing information we hope answers a common question we get about dementia risk, to raise awareness of factors that do and don’t contribute to our likelihood of developing diseases like Alzheimer’s.

Many people worry about developing a disease like Alzheimer’s and want to know what things can increase their risk. There has always been scepticism around whether exposure to metals from various environmental sources causes Alzheimer’s disease.

Currently, no research proves that day-to-day exposure to environmental metals causes Alzheimer’s, but it’s a question we’re often asked. Here we break down the evidence behind aluminium, which has been a long-term culprit of this scepticism.

How are we exposed to aluminium?

You might be thinking of tin foil or saucepans, but smaller traces of aluminium are all around us and our bodies are exposed to it every day.

Aluminium is the most abundant metal, making up 8% of the earth’s crust. Because of this, soil contains aluminium, and it also enters water sources through natural processes like rocks wearing away. This means many foods, particularly fruit, vegetables and seafood, contain aluminium due to it being in the soil and water where food is grown or lives. The air we breathe also contains natural traces of aluminium, from the eruption of volcanoes and weathering processes.

Human activities such as mining, industrial processes and waste water treatment can also release aluminium into our environment. Acid rain, caused by industrial pollutants dissolving in rain water, has worsened this effect as aluminium can dissolve more easily in acidic conditions and enter water sources.

Some food additives contain aluminium and cooking with certain aluminium utensils may further increase the levels found in our food. Emissions from various human activities like burning coal, car exhaust fumes and mining has also contributed to higher levels of aluminium in the air.

Other sources of aluminium include anti-perspirants, cosmetics and vaccines. Some vaccines contain small, safe amounts of aluminium, as it helps trigger the immune system’s response to the vaccine, which in turn boosts the level of immunity the person has.

This may sound like a lot but even though it’s everywhere, the levels of aluminium most of us are exposed to everyday are considered safe. A healthy individual normally carries between 30-50 mg of aluminium in their body.

What do our bodies normally do with aluminium?

Aluminium has no biological function in our bodies and since it is everywhere, and very high levels of it can also be harmful, our bodies have evolved efficient ways to get rid of it and keep us safe. Only a very tiny 0.1% of aluminium from our food and drink is absorbed by the gut and enters the bloodstream. In healthy individuals, this is swiftly and efficiently removed by the kidneys and leaves the body in urine, as shown in the diagram below.

But what about the brain? Our brains are protected from harmful substances by something called the blood-brain barrier. This is made up of very tightly packed cells, which only let certain things like oxygen and nutrients through it to reach our brain cells. Therefore, in a healthy individual, aluminium isn’t thought to build-up in the brain, and is only present at extremely low levels.

Where does the idea of a link between aluminium and Alzheimer’s originate from?

The idea that aluminium exposure is involved in the development of Alzheimer’s originates from 1965 and there have been several layers added to this story since.

By chance in 1965 it was discovered that an aluminium-containing injection, administered into the brains of rabbits, caused tangles and fibres of misfolded proteins to build-up – and these initially appeared similar to those seen in Alzheimer’s. A different study involving post-mortem examinations then reported higher than normal levels of aluminium in the brains of people who had died with Alzheimer’s disease.

A few years later, it was also proposed – but not proven – that aluminium in the liquid used to treat people with kidney failure, might be the cause of specific dementia symptoms in these individuals. This was proposed because higher levels of aluminium were found in the brains of patients affected by these neurological symptoms. All of this early research, led to suspicion that aluminium from various sources, such as cookware, foods, vaccines and even water, could be linked to Alzheimer’s.

However, through continued investigation, research has disproved this early evidence, and aluminium hasn’t since been found to be a direct cause of Alzheimer’s disease. It was later revealed that the tangles and fibres of misfolded protein found in rabbits’ brains in 1965, were very biologically different to the tangles and fibres found in the brains of people with Alzheimer’s disease. The symptoms and underlying brain changes in the kidney failure patients were also later found to be very different to the changes seen in Alzheimer’s disease.

What does recent research show?

Despite most of the initial evidence being undermined, the study that found high levels of aluminium in the brains of people who had died with Alzheimer’s has been reinforced by more recent research. This research has shown higher aluminium levels in the brain and the fluids that bathe the brain in people with Alzheimer’s when compared to healthy individuals.

But just spotting higher levels doesn’t mean they are a cause of the disease.

When someone has Alzheimer’s disease, their brain cells become damaged and don’t function normally. This loss of function affects how many biological systems work, including the blood-brain barrier. A damaged blood brain barrier allows things to enter our brain tissue that wouldn’t normally get through, like aluminium particles. Research also shows that our brain’s waste disposal system doesn’t function properly in Alzheimer’s disease, which means that if aluminium does get through, it might not be removed as efficiently. This is why most scientists think that aluminium build-up in the brain is more likely to be a consequence of Alzheimer’s disease rather than a cause.

Scientists have also found aluminium in the same areas of the brain where amyloid plaques, a hallmark feature of Alzheimer’s disease, are found. This is illustrated in the diagram below. This, and research showing a high concentration of aluminium in these plaques, has led some to suggest that it could have a role to play in the formation of these plaques in the first place. This is just a theory, and studies to date have failed to confirm it.

Because the kidneys remove aluminium, people with low kidney function can have a higher level of aluminium in their body. Studying these patients has given researchers an opportunity to see if these higher levels of aluminium affect their brain health. Research into these patients with kidney failure and others that have a higher exposure to aluminium than the normal population, has found no link between this higher aluminium exposure and an increased risk of Alzheimer’s disease.

So, what can we conclude?

Looking at all the evidence in this field of Alzheimer’s research, there is not enough high-quality evidence to conclude that everyday aluminium exposure in a healthy individual causes Alzheimer’s disease. It is possible that larger, more sophisticated studies may one day find a link, but for now we can be reasonably confident that exposure to aluminium doesn’t seem to be an important risk factor for the disease.

Less harmful common metals, such as copper, zinc and iron, are important for our health – including for normal brain cell functioning, but research is ongoing to see if they contribute to dementia risk in higher levels. Alzheimer’s Research UK is currently funding research investigating the relationship between iron and dementia risk. You can read more about this here.

Other rarer, but more toxic metals, such as mercury and lead, have been shown to have negative effects on the brain which may lead to Alzheimer’s. This has particularly raised concerns over links between air pollution and dementia, as pollution from some sources can contain elevated levels of these metals – you can read more about air pollution and dementia here. However most people aren’t exposed to high amounts of these metals on a daily basis in the same way we’re all exposed to aluminium.

It is important to note though, that most cases of dementia are caused by a complex mix of factors that interact together to make a disease like Alzheimer’s more likely to develop, not by one thing alone like aluminium. These factors include our age, genetics, lifestyle and environment. You can find out more about risk factors you can change and ways to protect your brain health by taking the Think Brain Health Check-in.

If you have any more questions about metal exposure and dementia risk, contact the Alzheimer’s Research UK Infoline Team on 0300 111 5111 or infoline@alzheimersresearchuk.org

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About the author

Alice Newman-Sanders

Information Officer

Team: Information services