Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

As documented in the book The Case of the Frozen Addicts, a bad batch of so-called synthetic heroin caused, within days, what appeared to be advanced-stage Parkinson’s disease. Thanks to a chemical contaminant called MPTP, young men and women were left trapped inside their bodies, near “complete immobility and rigidity,” in some cases left only “able to move [their] eyes.”

The seminal paper ended with the silver lining that maybe this will help us find the culprit in Parkinson’s. Maybe there’s a similar substance out there killing off our brain cells. “Because of [their] structural similarity to MPTP,” attention turned to a class of chemicals called beta-carboline alkaloids, such as harman, also spelled harmane. And, indeed, higher levels of these toxins are found in the brain fluid of Parkinson’s patients.

These beta-carboline neurotoxins “have been implicated in a number of human diseases” aside from Parkinson’s disease, including “tremor, addiction and cancer.” I’ve already talked about the role of diet in both preventing, and treating Parkinson’s, but the most common movement disorder isn’t Parkinson’s; it’s what’s called “essential tremor,” affecting 1 in 25 adults over 40, and up to 1 in 5 of those in their 90s, making it “one of the most common neurological diseases.” In addition to the potentially debilitating hand tremor, there can be other “neuropsychiatric” manifestations of the diseases, including difficulty walking, “and various levels of cognitive impairment.”

Might those beta-carboline neurotoxins be playing a role? Well, “[h]armane is among the most potent [of these] tremor-producing” neurotoxins. You expose people to these chemicals, and they develop a tremor; you take it away, the tremor disappears. What if we’re exposed long-term?

Well, this recent study found that those with essential tremor have much higher levels of this toxin in their bloodstream compared to those without tremor. The highest levels are found in those who have both essential tremor and cancer—suggesting harmane may be playing a role in both diseases. And the higher the harmane levels, the worse the tremor.

How did they get exposed to these chemicals? Primarily through meat: “beef, chicken, and pork”—and fish, actually.

So, if this potent, tremor-producing neurotoxin is concentrated in “cooked muscle foods,” is meat consumption associated with higher risk of essential tremor? Men who ate the most meat in this study had 21 times the odds of essential tremor.

Just to put that in context, you go back to the original studies on smoking and lung cancer, smoking was only linked to at most like 14 times the odds, not 21.

Yes, “[h]armane…is a potent neurotoxin linked to human diseases, and “cooked meats” are the major source of exposure, but which meat? Like other heterocyclic amines, the levels may be highest in chicken.

Blood levels of this neurotoxin may shoot up within five minutes of eating meat—a slice of turkey, in this case. Five minutes? It’s not even digested by then. “[T]his rapid uptake is indicative of…significant” absorption directly through the mouth, straight into the bloodstream, bypassing the stomach and most importantly, bypassing the detoxifying enzymes of the liver. “This may lead to higher exposure levels in peripheral organs,” like the brain.

“Due to its high [fat] solubility, harmane accumulates in brain tissue.” And, using a fancy brain scan called “proton magnetic resonance spectroscopic imaging,” higher harmane levels are linked to “greater metabolic dysfunction” in the brains of essential tremor sufferers.

Harmane is also found in certain heated plants, like tobacco. A broiled chicken breast has about 13 micrograms, and cigarettes average about 1, so a half-pack of cigarettes would expose us to almost as much of this neurotoxin as a serving of chicken.

Grilled salmon can have as much as chicken, though fried pork appears to be the worst—with fried reindeer not far behind, in the top five. I’d also suggest not eating too many butterflies.

Harmane is created when tobacco is burned, and also when coffee beans are roasted, though coffee intake has not been tied to increased risk (and neither has tobacco for that matter). So, it may be something else in the meat that’s to blame for the 2,000% increase in odds for this disabling brain disease.

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