 Lou Gehrig's disease, known as amyotrophic lateral sclerosis, or ALS, strikes healthy middle-aged people seemingly at random. And 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. So ALS is more common than generally recognized, an incidence rate now close to that of multiple sclerosis. What causes it? Well, 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. Cicad 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, it was calculated that people would have to eat like 1,000 kilograms a day to get a toxic dose. That's like a ton of seeds daily. So the whole Cicad theory was thrown out, and the trail went cold. But then famed neurologist Oliver Sacks and colleague had an idea. Cicad seeds were not all the natives ate. They also ate fruit bats, stewed in coconut milk, and guess what these so-called flying foxes ate? Cicad tree seeds. So maybe this is a case of biomagnification up the food chain. Remember how you'd have to eat like a ton of seeds worth of BMAA to run into problems? Well guess how much builds up in the flesh of flying foxes? A ton worth of BMAA. And the natives also ate other animals that foraged on the seeds. The final nail in the coffin was the detection of high levels of BMAA in the brains of 6 out of 6 native victims of the disease on autopsy, but not in control brains of healthy people that died. So with a final puzzle piece apparently in place, the solution 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 for the hack of it, when the researchers were choosing a comparison group of control brains, they threw in two cases of Alzheimer's disease, and they had BMAA in their brains too. But these were Alzheimer's victims in Canada, on the opposite side of the globe, so they ran more autopsies. No BMAA in the control brains, but BMAA was detected in all of the Canadian Alzheimer's victims tested. Wait a second. Canadians don't eat fruit bats? Well, the neurotoxin isn't made by the bat. Yeah, it's made by the trees, but Canadians don't eat cycad trees either. Their flag doesn't look like this. Turns out that cycad trees don't make the neurotoxin either. A blue-green algae that grows in the roots of cycad trees makes the BMAA that gets into the seeds, that gets into the bats, that gets into the people. And it's not just this type of blue-green algae, but nearly all types of blue-green algae found all over the world produce this neurotoxin. 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 US, Australia, the Middle East, everywhere. So 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. Maybe the Canadians were a fluke? No. The researchers found BMAA in the brains of Floridians, who died from sporadic Alzheimer's disease and ALS. But not in the brains of those died from a different neurodegenerative disease called Huntington's, which we know is caused by genetic mutation, not some neurotoxin. Significant levels of BMAA in 49 out of 50 samples from 12 Alzheimer's patients and 13 ALS patients. The results for American Alzheimer's and ALS patients from the Atlantic Southeast compared to Canadian Alzheimer's patients from the Pacific Northwest suggest that exposure to BMAA may be widespread. The same thing was then found in the brains of those dying from Parkinson's disease. You can even pick up more BMAA in the hair of live ALS patients compared to controls. So, is BMAA this neurotoxin found in Florida seafood? All over the place, in freshwater fish and shellfish, like oysters and bass, and out in the bay. In fact, some of the fish, shrimp, and crabs had levels of BMAA comparable to those found in the fruit bats in Guam. In the U.S., the fish may be the fruit bats.