What Is the Cause of ALS?

Image Credit: GraphicStock. This image has been modified.

Lou Gehrig’s disease, known as amyotrophic lateral sclerosis or ALS, strikes healthy, middle-aged people seemingly at random. Of the major neurodegenerative diseases, it has the least hope for treatment and survival. Although mental capabilities stay intact, ALS paralyzes people, often from the outside in, and most patients die within three years when they can no longer breathe or swallow. At any given time, an estimated 30,000 are fighting for their life with it in this country. We each have about a 1 in 400 chance of developing this dreaded disease.

ALS is more common than generally recognized, with an incidence rate now close to that of multiple sclerosis. What causes it? 50 years ago scientists found that the rate of ALS among the indigenous peoples on the island of Guam was 100 times that found in the rest of the world, potentially offering a clue into the cause of the disease. So, instead of 1 in 400, in some villages in Guam, 1 in 3 adults died of the disease!

Cycad trees were suspected, since the powdered seeds were a dietary staple of the natives, and there were reports of livestock showing neurological disease after eating from it. And indeed, a new neurotoxin was found in the seeds, called BMAA. Maybe that’s what was causing such high levels of ALS? But the amount of BMAA in the seeds people ate was so small that it was calculated that people would have to eat a thousand kilograms a day to get a toxic dose—that’s around a ton of seeds daily. So, the whole cycad theory was thrown out and the trail went cold.

But then, famed neurologist Oliver Sachs and colleagues had an idea. Cycad seeds were not all the natives ate. They also ate fruit bats (also known as flying foxes) who ate cycad tree seeds. So, maybe this is a case of biomagnification up the food chain, as about a “ton’s” worth of BMAA does accumulate in the flesh of flying foxes.

The final nail in the coffin was the detection of high levels of BMAA in the brains of six out of six native victims of the disease on autopsy, but not in control brains of healthy people that died. So, with the final puzzle piece apparently in place, the solution was found to this mysterious cluster on some exotic tropical isle of ALS/PDC, so-called because the form of ALS attacking people in Guam also had signs of Parkinson’s disease and dementia; so, they called it ALS parkinsonism dementia complex. So, when the researchers were choosing a comparison group of control brains, they also included two cases of Alzheimer’s disease. But these brains had BMAA in their brains too. And not only that, but these were Alzheimer’s victims in Canada, on the opposite side of the globe. So, the researchers ran more autopsies and found no BMAA in the control brains, but BMAA detected in all the Canadian Alzheimer’s victims tested.

Canadians don’t eat fruit bats. What was going on? Well, the neurotoxin isn’t made by the bats, it’s made by the trees, although Canadians don’t eat cycad trees either. It turns out that cycad trees don’t make the neurotoxin either; it’s actually a blue-green algae that grows in the roots of the cycad trees which makes the BMAA that gets in the seeds, which gets in the bats, that finally gets into the people. And it’s not just this specific type of blue-green algae, but nearly all types of blue-green algae found all over the world produce BMAA. Up until only about a decade ago, we thought this neurotoxin was confined to this one weird tropical tree, but now we know the neurotoxin is created by algae throughout the world: from Europe to the U.S., Australia, the Middle East, and elsewhere.

If these neurotoxin-producing blue-green algae are ubiquitous throughout the world, maybe BMAA is a cause of progressive neurodegenerative diseases including ALS worldwide. Researchers in Miami put it to the test and found BMAA in the brains of Floridians who died from sporadic Alzheimer’s disease and ALS, but not in the brains of those that died of a different neurodegenerative disease called Huntington’s, which we know is caused by a genetic mutation, not some neurotoxin. They found significant levels of BMAA in 49 out of 50 samples from 12 Alzheimer’s patients and 13 ALS patients. The results (shown in the my video ALS: Fishing for Answers) for American Alzheimer’s and ALS patients from the Atlantic southeast and from Canadian Alzheimer’s patients from the Pacific Northwest suggested that exposure to BMAA was widespread. The same thing was then found in the brains of those dying from Parkinson’s disease. You can apparently even pick up more BMAA in the hair of live ALS patients compared to controls.

So, is BMAA present in Florida seafood? Yes, in freshwater fishes and shellfish, like oysters and bass, and out in the ocean as well. Some of the fishes, shrimps, and crabs had levels of BMAA comparable to those found in the fruit bats of Guam.

In the U.S., fish may be the fruit bats.

Maybe the ice bucket challenge should be to not serve seafood in them. See my video Diet and Amyotrophic Lateral Sclerosis (ALS) for more.

Diet may also play a role in other neurodegenerative disorders:

In health,
Michael Greger, M.D.

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