"The Role Milk May Play in Triggering Parkinson's Disease"
Parkinson's disease is a neurodegenerative brain disorder
that affects millions of people. What causes it?
Well, if you look at lifestyle factors associated with Parkinson's disease,
the strongest dietary association
with increased risk of Parkinson's disease is dairy consumption.
In fact, dairy products are the only food group that has been
consistently associated with a high risk of developing Parkinson's.
Five large prospective studies have confirmed the link — including the two
Harvard cohorts, the Harvard Nurses' Health Study and
other Health Professionals —
which followed more than a hundred thousand people for decades,
in the largest analysis of dairy and Parkinson's disease to date,
analyzing more than a thousand newly diagnosed cases.
And all the studies found a link between dairy and Parkinson's,
most finding a significant link: about a 50% increased risk overall
in those drinking the most milk, compared to those drinking the least
at a p value of less than 0.00001, meaning less than 1 in 100,000
you'd only get a finding that extreme by chance.
Okay, but why is there a link at all? Despite clear-cut associations
between milk intake and Parkinson's disease incidence,
there is no rational explanation, concluded one review.
A year later though, we got a clue: "Midlife milk consumption
and substantia nigra neuron density at death."
What does that mean? Parkinson's is caused when most of the nerve cells
in a critical part of the brain are killed off.
So if you go back and see how much milk people were drinking
in their 40s, 50s, and 60s, and then look at their brains on autopsy
and count how many of these critical neurons they had left,
in every single quadrant neuron density was maximized
in those who consumed no milk
and lowest in those who consumed the most milk.
Even after removing the Parkinson's cases, those drinking two cups of milk
a day had up to 40% fewer nerve cells in that critical brain region.
What's in milk that could be wiping out brain cells?
Among those who drank the most milk, residues
of the pesticide heptachlor epoxide were found in 9 out of 10 brains.
A-ha, so maybe the finding of pesticide residues more commonly in the brains
of those who drank the most milk could explain how milk could be
cause-and-effect related to Parkinson's disease risk.
Now that's not the only potential explanation.
Remember my video on how meat contains that clumpy
neurotoxic protein alpha-synuclein? Well, dairy products may contain
trace amounts as well, but we don't have confirmation of that.
Could the milk sugar galactose be the missing link?
That's what lactose in milk breaks down into in the body, and galactose
is what's used to induce aging, to experimentally cause aging in the brain.
When you drink it, the galactose is picked up by your brain
within a few hours, and for doses above 100 mg/kg,
it appears that galactose can cause pathological
alterations in brain cells, similar to those observed in Parkinson's disease.
And these quantities can be reached and surpassed
with the simple daily consumption of two glasses of milk,
the main dietary source of galactose in humans.
And of all your brain cells, those dopaminergic neurons,
the ones that you need to retain to prevent Parkinson's,
may be more vulnerable to galactose-induced damage,
galactose-induced oxidative stress. Galactose may also explain
the findings that link milk drinking with higher death rates.
Now you may be thinking, well, duh, the saturated butterfat
is just cutting people's life short, but higher mortality with higher milk
consumption is observed, irrespective of the milk fat content.
Skim milk might be fat free, but it's not lactose free.
Can't you just use lactose-free milk?
What about Lactaid? That has the lactase enzyme added
to make lactose-free milk, but it just breaks down the lactose into galactose
in the carton rather than in your gut,
so you're still ingesting the same amount of galactose.
Perhaps no wonder then that greater milk intake at midlife
may be associated with greater rate of cognitive decline.
I mean, researchers use galactose to create brain aging in the laboratory.
Administration of D-galactose, a metabolic derivative of lactose,
has been extensively used to mimic cognitive aging
through oxidative stress in animal models.
Compared to those who said they "almost never" drink milk,
those drinking more than a glass a day appear more likely
to suffer a global decline in their cognitive function.