Cause of Alzheimer’s discovered: where you live and what you eat are crucial

[UK] A POISONOUS algae found in freshwater lakes in the UK is being blamed for an increase in the number of people developing dementia, which is expected to hit one million by 2050.

A toxin produced by the blue-green algae, also being linked to motor neurone disease (MND), has been discovered in plants and seafood and scientists fear it is contaminating the food chain and triggering the devastating brain diseases.

The algae, found in freshwater lakes and reservoirs throughout Britain, produces a toxin called BMAA, often as a by-product of its algal bloom.

The brains of people who have suffered from Alzheimer’s and MND were found to contain high levels of BMAA and monkeys given a diet rich in the toxin developed Alzheimer’s-like symptoms in less than five months.

If the link is confirmed between the toxin and humans, it would be the first major environmental factor linked to the increasing rate of Alzheimer’s.

In the Pacific island of Guam, where there are high levels of BMAA in the diet, researchers found astonishing rates of a neurodegenerative illness, while in the US and France, a rare MND has been observed among people living around lakes and lagoons contaminated with algal BMAA.

Although a link to the food chain has not yet been established, seafood, including French mussels and oysters and Portuguese cockles grown in estuaries, have all been found to contain BMAA.

The toxin appeared to be widespread in British inland waters in a 2008 study, with blue-green algae samples from 12 freshwater lakes and reservoirs across England, Scotland and Wales – some drinking-water reservoirs, others recreational waters, and some used for fishing – all testing positive.

And MND rates are up to 25 times higher than expected in people living by BMAA-contaminated lakes and lagoons.

Professor Paul Cox, a leading researcher in the field, said the poisonous algae toxin could be the “third factor” behind the rapid increase in the amount of people suffering from Alzheimer’s after old age and the fact doctors are better than ever before at diagnosing the disease.

Blue-green algae grows throughout Britain, including in Cornwall, pictured

He said: “We know the single biggest risk factor for Alzheimer’s disease is age, and as our population ages, people will get it more. Secondly, we are getting better at diagnosing and finding Alzheimer’s cases.

“We are adding the possibility of a third factor – which is exposure to an environmental toxin.”

Professor Cox, director of the Institute for Ethnomedicine in the US state of Wyoming, was in charge of the research using vervet monkeys, the findings of which were published in the journal Proceedings of the Royal Society B last week.

The animals were fed bananas laced with BMAA and began to exhibit abnormal brain structures called plaques and tangles, similar to those found in brains of Guam islanders who died of an Alzheimer’s-like illness called ALS/PDC, within 140 days.

Some sufferers of ALS/PDC show signs similar to dementia while in others it appears more like MND or Parkinson’s.

Alzheimer's will affect one million people in Britain by 2050
Alzheimer’s will affect one million people in Britain by 2050

In some villages, where locals eat flour derived from contaminated cycad plants or BMAA-ridden bats, one in four gets the disease.

Professor Cox, famed for discovering an anti-HIV drug made from the bark of a tropical tree, said if BMAA was proven to trigger Alzheimer’s and MND it was “potentially very worrying”.

He said: “The parts of the vervets’ brains we found plaques in, and the density of the tangles, was very similar to early-stage Alzheimer’s disease.”

Given the potential risks, there should be more widespread environmental monitoring of BMAA in the UK.

Professor Geoffrey Codd, macrobiologist

“Something is going on here. BMAA could be a contributory factor in some people.”Although research has been carried out into BMAA in the past, it has usually focussed on the threat to fish and the short-term effects the toxin can have on people who swim in contaminated water, rather than the potential long-term health effects.

Dr James Metcalf, who was involved in the study while at Dundee University and is now a colleague of Professor Cox in Wyoming, said: “BMAA seems to be potentially quite commonly found.”Both scientists stressed it is not yet understood what concentrations of BMAA might be harmful to humans, and said it was likely that only those with certain genes were susceptible to the substance.

Professor Cox said: “We think there is a gene-environment interaction. Perhaps some people are exposed to this toxin and, instead of excreting it, they accumulate it. If the genes are the gun, the toxin is the trigger.”

They agreed more research was needed.

Blue-green algae, like this pictured in Scotland, has been linked to Alzheimer's
Blue-green algae, like this pictured in Scotland, has been linked to Alzheimer’s

Professor Geoffrey Codd, Macrobiologist at Dundee and Stirling Universities, said: “A growing body of research suggests BMAA may contribute to neurodegenerative illnesses.

“But there is a huge amount we simply do not know.

“All we can say is BMAA is a candidate environmental risk factor. We can’t put it any stronger than that.

“Given the potential risks, there should be more widespread environmental monitoring of BMAA in the UK. Furthermore, while BMAA and these other substances can potentially be removed by water treatment, there should be monitoring to ensure that happens.”

Dr Laura Phipps from Alzheimer’s Research UK said the research in vervet monkeys “suggests that BMAA exposure could directly lead to hallmark features of neurodegenerative disease, providing new insight into the likely cause of this condition on Guam”.

She added: “While investigating rare forms of dementia can lead to insights into the more common causes of the condition, further research is needed to understand whether the findings have relevance to diseases like Alzheimer’s or Motor Neurone Disease in other parts of the world.”

The Motor Neurone Disease Association declined to comment.


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