I’m often asked what my opinion
about a diet or disease is.
Who cares what my or anyone else’s opinion is.
All we should care about is what the science says.
What does the best available balance of evidence
Published in the peer- reviewed medical literature
have to say right now?
Welcome to the Nutrition Facts Podcast,
I’m your host, Dr. Michael Greger.
I know so many people
who have been diagnosed with Alzheimer’s disease,
the most common cause of dementia.
And I bet you do too.
In fact, more than six million people in the US have it.
So how do we avoid becoming one of those statistics?
That's a main thrust of my forthcoming book,
How Not to Age.
But in the meanwhile,
here's a discussion of some little-known risk factors in this,
our 300th podcast episode.
In our first story, we explore the effect of pesticides on Alzheimer’s disease.
Although there is a growing list of Alzheimer's disease
susceptibility genes, even if you put them all altogether,
they account for less than half of all Alzheimer's cases.
The single most compelling piece of data on the potential control
we have over the disease is the fact that if you have
identical twins, with the exact same genes, even if one gets
Alzheimer's the other usually does not.
So, we have to think about all the other
contributing factors beyond just genetics.
In my video on pesticides and cancer, I talked about this study.
There’s a list of chlorinated pesticides, including DDE
(a metabolite of DDT) that are classified by the EPA
as probable human carcinogens.
But in the study, blood levels of DDE and others were
associated not with increased cancer mortality,
but increased risk of other-cause mortality.
This led researchers to speculate it may be due to
an associated increased risk of diabetes or dementia.
I’ve talked previously about the diabetes link.
What about dementia?
“Elevated Serum Pesticide Levels and Risk for Alzheimer Disease.”
A research team at Rutgers found significantly higher blood
levels of DDE in Alzheimer’s disease patients compared to controls,
and autopsy studies show blood levels
are a good proxy for brain levels.
Those with the highest levels were at about four times
the odds of being demented with Alzheimer's.
And in a petri dish, DDE increases amyloid precursor protein levels
in human brain cells, providing a potential mechanism.
Put all these studies together, and there does indeed seem
to be a link, consistent with data showing about a doubling
of risk for developing dementia among
those acutely pesticide poisoned.
Among U.S. elders, DDT and its breakdown product DDE are also
associated with increased risk of cognitive decline in general.
DDT was extensively used in the United States
from the 1940s through the 1960s.
At its peak, we were churning out 180 million pounds a year.
And it’s still in our bodies to this day,
contaminating the bloodstreams of more than 90 percent of Americans,
and DDE, the pesticide linked to quadrupling the odds
of Alzheimer’s, were at the highest levels.
It’s still in our bodies because it’s still in the food supply.
In my last video on the topic, I noted that the levels of
DDT, DDE, and other banned pesticides and pollutants
were much lower in the breast milk from a vegetarian mother
compared to breast milk of her non-vegetarian sister.
And the largest difference was noted for DDE,
which was four times lower in the vegetarian sister.
These toxins build up the food chain; so, it makes sense that
the most contaminated foods are meat, fish, and dairy products.
5 to 10 times higher levels in meat, eggs,
fish, and dairy than what they found in plant foods.
And unfortunately, cooking doesn’t destroy pollutants like DDE—
in fact it may make them even more concentrated.
And this is for a pesticide that may increase the risk
of Alzheimer’s disease as much as if you carried
the so-called Alzheimer’s gene APOE 4.
In our next story, we look at the role of meat
on Alzheimer’s disease.
What is behind the dramatic increase in dementia
in Japan over recent decades?
Maybe it’s rising obesity rates
or the increases in cholesterol, saturated fat, and iron,
or increases in animal products and meat.
Overall, calories just went up about 10% in Japan,
whereas animal fat and meat consumption rose 500%,
about 10 times the rise in sugary junk.
Now, during this timespan, rice consumption went down,
but the thinking is that
rather than white rice somehow being protective,
maybe they were just eating something worse instead.
It’s like when you find fish consumption
is correlated with less disease,
you wonder if it’s because they’re eating that
rather than some worse meat.
If you look across multiple countries,
you see a similar pattern,
with the most important dietary link to Alzheimer’s
appearing to be meat consumption,
with eggs and high-fat dairy also maybe contributing.
There appears to be a really tight correlation
between Alzheimer’s and per capita meat supply.
And, then, studies within countries uncover similar findings,
with Alzheimer’s and cognitive decline
associated with meaty, sweety, fatty diets,
whereas most plant foods were associated
with risk reduction.
This could be for a variety of reasons.
Animal products tend to have
more copper, mercury, lead, and cadmium,
and no folate,
but contain saturated fat and cholesterol,
and pro-inflammatory advanced glycation end products;
so many mechanisms that dietary modification
may be our best bet
for reducing risk of Alzheimer’s disease.
But, how do we know it’s cause-and-effect –
the evidence that meat consumption
is causally linked to Alzheimer’s disease?
Well, there’s the strength of the association,
the consistency across different types of studies,
the fact that the dietary changes
preceded the risk of dementia,
the dose response—
more meat linked to more risk—
a bunch of plausible mechanisms.
We know that meat is a risk factor
for other chronic diseases,
but there’s never been randomized controlled trial
to put it to the test.
When you read reviews of the damaging effects
of high-fat diets to the brain and cognition,
a number of factors are proposed
to account for the high-fat diet-induced
damage to the brain.
Oxidative stress, insulin resistance, inflammation,
and changes to blood vessels
and the integrity of the blood brain barrier.
But, these are based mostly on studies of rodents.
Yes, high fat diets can cause
energy dysfunction in the brain,
based on fancy MRI techniques.
With CT scans, you can follow this
intracranial artery stenosis,
this brain artery clogging, over time,
and follow the progression from mild cognitive impairment
to Alzheimer’s disease.
Those who only had low-grade stenosis
were pretty stable over time
in terms of their cognitive function
and ability to dress themselves,
and other activities of daily living,
whereas those with more clogging
started slipping over the years.
And those who started out with the most
brain atherosclerosis rapidly went downhill,
and twice as likely to progress
to full-blown Alzheimer’s.
Chronic consumption of standard Western diets,
and rich in saturated fat and cholesterol,
may compromise our cerebrovascular integrity
compromise the blood vessels in our brain.
So, of course, drugs are recommended,
“pharmacological modulation” of diet-induced dysfunction.
But why not just try to eat healthier in the first place?
Finally today, we look at reducing glycotoxin intake
to ward off Alzheimers.
Each of us has about 6 billion miles of DNA.
How does our body keep it from getting all tangled up?
There are special proteins called histones,
which act like spools with DNA as the thread.
Enzymes called sirtuins wrap the DNA
around the histones spools
and in doing so silence whatever genes
were in that stretch of DNA,
hence their name sirtuins,
which stands for silencing information regulator.
Although they were discovered only about a decade ago,
the study of sirtuins has become one
of the most promising areas of biomedicine,
since they appear to be involved
in promoting healthy aging and longevity.
Suppression of this key host defense
is considered a central feature of Alzheimer’s disease.
Autopsies of Alzheimer’s victims reveal that loss of sirtuin enzyme activity
is closely associated with the accumulation
of the plaques and tangles in the brain
that’s characteristic of Alzheimer’s disease.
Sirtuins appear to activate pathways
that steer the brain away from the formation
of plaque and tangle proteins.
Because a decrease in sirtuin activity
can clearly have deleterious effects on nerve health,
they’re trying to come up with drugs
to increase sirtuin activity,
but why not just prevent its suppression in the first place?
Glycotoxins in food suppress sirtuin activity-
these so-called advanced glycation end products, or AGE’s.
Our modern diet includes excessive AGE’s,
which can be neurotoxic.
High levels in the blood
may predict cognitive decline over time.
If you measure the urine levels of glycotoxins
flowing through the bodies of older adults,
those with the highest levels
went on to suffer the greatest cognitive decline
over the subsequent nine years.
As we age, our brain literally shrinks.
In our 60's and 70's we lose an average of five cubic centimeters
of total brain tissue volume every year,
but some lose more than others.
Brain atrophy may be reduced in very healthy individuals,
and a few people don’t lose any brain at all.
Normally we lose about 2% of brain volume every year,
but that’s just the average.
Although the average brain loss for folks
in their 70's and 80's was 2.1%,
some lost more, some lost less,
and some men and women lost none at all
over a period of four years.
Researchers in Australia provided the first evidence
linking AGEs with this kind of cerebral brain loss.
So limiting one’s consumption of these compounds
may end up having significant public health benefits.
Because sirtuin deficiency is both preventable
and reversible by dietary AGE reduction,
a therapeutic strategy that includes eating less AGE's
may offer a new strategy to combat the epidemic of Alzheimer’s.
Some of these glycotoxins are produced internally,
particularly in diabetics,
but anyone can get them from smoking and eating,
particularly foods high in fat and protein.
In a previous video I listed the 15 foods most contaminated with glycotoxins,
mostly chicken, but also pork, beef, and fish,
which may help explain why those that eat the most meat
may have triple the risk of getting dementia
compared to long-time vegetarians.
We would love it if you could share with us your stories
about reinventing your health through evidence-based nutrition.
Go to nutritionfacts.org/testimonials.
We may share it on our social media to help inspire others.
To see any graphs, charts, graphics, images, or studies mentioned here,
please go to the Nutrition Facts Podcast landing page.
There you’ll find all the detailed information you need –
plus, links to all of the sources we cite to each of these topics.
For a timely text on the pathogens that cause pandemics,
order the e-book, audiobook, or hard copy
of my last book, “How to Survive a Pandemic”.
For recipes, check out my second-to-last book,
my “How Not to Diet Cookbook”.
It’s beautifully designed with more than 100 recipes
for delicious and nutritious meals.
And all the proceeds I receive from the sales
of all my books goes to charity.
NutritionFacts.org is a nonprofit, science-based public service,
where you can sign up for free daily updates
on the latest in nutrition research via bite-sized videos and articles.
Everything on the website is free.
There’s no ads, no corporate sponsorship.
It’s strictly non-commercial. I’m not selling anything.
I just put it up as a public service, as a labor of love,
as a tribute to my grandmother,
whose own life was saved with evidence-based nutrition.