"The Role Meat May Play in Triggering Parkinson's Disease"
Parkinson's disease is an ever-worsening neurodegenerative disorder that results
in death and affects about 1 in 50 of us when we get older.
A small minority of cases are genetic and run in families,
but 85 to 90% of cases are sporadic, meaning they just seemingly pop up
out of nowhere.
It's caused by the death of a certain kind of nerve cell in the brain.
Once about 70% of them are gone, the symptoms start.
Okay, so what kills off those cells? It's still not completely clear,
but the abnormal clumping of a protein called alpha-synuclein (α-synuclein)
is thought to be involved. Why? Because if you inject blended
Parkinson's brains into the heads of rats or monkeys, you can induce
Parkinson's pathology and symptoms,
or even just injecting the pure clumped α-synuclein strands themselves.
Okay, but how do these clumps naturally end up in the brain?
It all seems to start in the gut.
The part of the brain where the pathology often first shows up is directly connected
to the gut, and we have direct evidence of the spread
of Parkinson's pathology from the gastrointestinal tract to the brain.
Alpha-synuclein from brains of Parkinson's patients
is taken up in the gut wall,
and creeping up the vagal nerves from the gut into the brain.
But this was in rats. If only we had a way to go back
and look at people's colons before they got Parkinson's.
And indeed, we can. Old colon biopsies were dredged up
from people who had later developed Parkinson's,
and years before symptoms arose, you could see the α-synuclein in their gut.
Research supported by the Michael J. Fox Foundation has found
you can reliably distinguish the colons of patients from controls
by the presence of the Parkinson's protein lodged in the gut wall.
But how did it get there in the first place?
Perhaps vertebrate food products
as a potential source of prion-like α-synuclein.
See, nearly all of the animals with back bones that we eat--
cows, chickens, pigs, and fish-- express the protein α-synuclein.
And so when we eat common meat products, when we eat
skeletal muscle, we're eating nerves, blood cells,
and the muscle cells themselves.
Every pound of meat has like a teaspoon to a tablespoon of blood in it,
and that alone could be an α-synuclein source
to potentially trigger a clumping cascade
of our own α-synuclein in the gut. Though it may seem intuitive
that dietary α-synuclein could seed this kind of buildup in our gut,
what evidence do we have that it's actually happening?
These are pretty interesting data.
There's a surgical procedure called a vagotomy
in which the big nerve that goes from your gut to your brain is cut
as an old-timey treatment for stomach ulcers.
Would cutting communication between the gut and the brain reduce Parkinson's risk?
Apparently so, suggesting that the gut to brain vagal nerve
may be critically involved in the development of Parkinson's disease.
Now, of course, many people regularly consume meat and dairy products,
but only a small fraction of the general population will develop Parkinson's.
So there must be other factors at play that may somehow provide
an opportunity for unwanted dietary α-synuclein
to enter the host and initiate disease.
For example, your gut becomes leakier as you age so might that play a role?
Well, what else makes your gut leaky?
Dietary fiber deprivation has also been shown to degrade the intestinal barrier
and enhance pathogen entry.
So this all raises possibilities for food-based therapy.
Parkinson's patients have significantly less Prevotella in their gut, a friendly
fiber-eating flora that bolsters your intestinal barrier function.
So low levels of Prevotella are linked to a leaky gut,
which has been linked to intestinal α-synuclein deposition.
But fiber-rich foods may bring Prevotella levels back up.
Therefore, by adopting a plant-based diet,
in addition to getting the beneficial effects of phytonutrients,
it's possible that increasing overall fiber intake may modify
the gut microbiome and gut leakiness in beneficial ways.
So, does a vegan diet, one with lots of fiber and no meat,
reduce risk for Parkinson's disease?
Parkinson's does appear to be rare in quasi-vegan cultures.
Rates are about five times lower in rural sub-Saharan Africa for instance.
Now all this time we were thinking the benefits seen for Parkinson's
from plant-based diets was due to the antioxidants
and anti-inflammatory nature of the animal-free diets,
but maybe it's also due to the increased intestinal exposure to fiber and
decreased intestinal exposure to ingested nerves, muscles, and blood.