What’s the best way to stay healthy
in the face of so much conflicting nutrition information?
Well, ideally, you would go to the source.
The gold standard;
the peer-reviewed medical literature.
Read through stacks of the latest medical journals.
But who’s got time for that?
I do!
Welcome to the Nutrition Facts Podcast.
I’m your host, Dr. Michael Greger.
Today we look at the pros and cons of coffee
for the liver, mind and brain.
And we start by asking
which coffee is healthier: light roast or dark roast?
For those drinking non-paper- filtered coffee, like boiled,
French press, or Turkish coffee,
the amount of cholesterol- raising compounds
in the lightest roast coffee may be twice as high
compared to using very dark roast beans.
So, it appears some of the cholesterol- raising compounds are destroyed by roasting;
so, in this case darker would be better, or…
you can just use a paper filter and eliminate 95 percent
of the cholesterol-raising activity of coffee regardless
of the roast as I’ve described before.
But I did another video showing dark roasting may also destroy
up to nearly 90 percent of the chlorogenic acids,
which are the antioxidant, anti-inflammatory phytonutrients
purported to account for many of coffee’s benefits.
So, in that case, light roast would be better.
On the other hand, dark roasting can wipeout up to 99.8 percent
of pesticides in conventionally grown coffee,
and more than 90 percent of a fungal contaminant
called ochratoxin, which is a potent kidney toxin found
in a wide range of food ingredients that can get moldy.
But then, what about the polycyclic aromatic hydrocarbon products
of combustion that are suspected to be carcinogenic and DNA damaging?
Darker roasts may have up to four times more than light roasts.
Thus, they advocate controlling roasting conditions
to cut down on these combustion compounds.
Just to put things in perspective, even the darkest roast coffee
might only max out at a fraction of a nanogram of benzopyrene per cup—
considered to be the most toxic of these compounds—
whereas a single medium portion of grilled chicken
could have over 1,000 times more.
Overall, you don’t know if light versus dark roast
is better until you… put it to the test.
This study found that dark roast coffee is more effective than light roast coffee
in reducing body weight.
Folks were randomized to a month of drinking two cups a day
of light roast coffee or dark roast coffee,
roasted from the same batch of green coffee beans.
And in normal weight subjects it didn’t seem to matter—
no significant weight changes either month—
but in overweight study subjects, they ended up about six pounds lighter
drinking dark roast coffee compared to light roast coffee;
more than a pound a week lost just drinking a different type of coffee.
What about light versus dark in relation to blood sugars?
We've known since 2015 that even a single cup of coffee
can affect the blood sugar response.
What is not known is whether this increase in blood sugars
is actually clinically meaningful.
After all, coffee consumption does not seem to increase the risk of diabetes,
and if you compare light roast coffee to dark roast coffee
right before chugging down about 20 teaspoons of sugar,
there didn’t appear to be any difference.
Perhaps the take home message is: light or dark,
maybe we shouldn’t be adding 20 spoonfuls of sugar.
And finally, what about the effect of different roasts
on heartburn and stomach upset?
We know that “coffee consumption is sometimes associated
with symptoms of stomach discomfort;”
and so, researchers stuck pH probes down into people’s stomachs
to measure the amount of stomach acid generated by different types of coffee.
The way you chart stomach acid secretion in the stomach
is called a “gastrogram.”
You basically give people some baking soda,
which starts out alkaline, and measure the pH in the stomach
to see how long it takes the body to restore the stomach
back down into an acid bath: about 15, 20 minutes.
But if you mix that same amount of baking soda with dark roast coffee,
it takes longer, meaning the dark roast coffee
is suppressing stomach acid secretion,
since it takes longer to normalize the pH.
Give people more of a medium roast coffee, though,
and we see a dramatically different effect—
an acceleration of stomach acid secretion,
returning the stomach to acidic conditions three times faster
than drinking dark roast coffee, hence the title:
“..[dark roast coffee] is less effective at stimulating [stomach] acid secretion…
compared to a medium roast [coffee]”, but you don’t know if that translates
into symptoms—clinical effects— until you put it to the test.
“The most commonly used coffee bean roasting process
is referred to as convection or ‘flash’ roasting,” which just takes a few minutes.
“An alternative method is conduction roasting,”
which roasts at a lower temperature for a longer time—hours—
and this results in so-called low acid coffee.
And, supposedly, there are anecdotes from coffee-sensitive individuals
suggesting that this low-acid coffee
“does not precipitate or aggravate heartburn.”
When you look up that citation, though, they just cite data
from the Puroast Coffee company, makers of low acid coffee.
It should therefore come to no surprise
that it was the same company that funded the study.
If you go their website, they claim that “the health benefits associated with drinking
Puroast Low Acid coffee will become almost immediately obvious
to those who suffer from acid reflux, heartburn, or indigestion”,
with over 90 percent of customers surveyed receiving symptom relief;
and so, they decided to put their money where mouth was.
But before I get to the results, it’s important to realize that
when they say low acid, they’re not talking about stomach acid;
they’re talking about roasting so long that they destroy
more of the chlorogenic acid within the coffee bean.
You know the antioxidant, polyphenol, phytonutrient chlorogenic acid...
You know the anti-diabetic, anti-cancer,
anti-inflammatory, anti-obesity antioxidant...
But hey, if it causes less stomach discomfort maybe it’s worth it?
Thirty coffee-sensitive individuals completed
a randomized, double-blind, crossover study in which the symptoms
of heartburn, regurgitation, and stomach upset were assessed
following the consumption of the Puroast brand low acid coffee
versus conventionally roasted regular Starbucks coffee,
and to the funder’s chagrin, no benefit whatsoever was found
with the low acid coffee.
Consumption of both coffees resulted in heartburn, regurgitation,
and stomach upset in most individuals.
So much for that ridiculous 90 percent-of-customers claim.
No significant differences in the frequency or severity
of heartburn, regurgitation, or dyspepsia were demonstrated
between the two coffees, either in a fasting state or after a test meal.
They couldn’t find any way to make the low acid coffee look better.
So, they had this initial thought that a difference in coffee acidity
may explain the company’s claims; however, when put to the test
in a randomized, controlled study, they found no difference in symptoms,
suggesting the whole coffee acidity thing doesn’t explain
the sensitivity some people have, and I think further,
acts as a reminder that we should never believe claims
made by anyone trying to sell us something.
In our next story, we discover new data
that suggests even paper-filtered coffee
may raise LDL cholesterol.
In a video I did a decade ago—
I explained that the cholesterol-raising
factor in coffee does not pass through
a drip coffee paper filter.
Give people French press coffee,
which is filtered, but without paper,
and their cholesterol swells up
over time starting within just two weeks,
but switch them to paper-filtered coffee,
and their cholesterol comes
right back down.
Same amount of coffee,
but just prepared differently.
The cholesterol-raising factor from
coffee beans has since been identified—
it’s the fatty substances in the oil
within coffee beans.
One reason it took us so long
to figure that out is that it didn’t
raise cholesterol in rats or hamsters,
or even monkeys, but it did
in human beings.
But, it apparently gets stuck
in the paper filter.
This explains why filtered coffee
doesn’t affect cholesterol,
whereas boiled, French press,
or Turkish coffees do.
Espresso as well, which has 20 times
more of the cholesterol-raising
substance cafestol than
paper-filtered drip coffee,
with Turkish and boiled coffee
being the worst,
though instant and percolator coffee
are pretty low, even without
the paper filter.
Note, if you make drip coffee
with one of those metal mesh filters
without the paper, it would presumably
be just as bad as like the French press.
So, the studies in general appeared
to consistently find that it was
this fatty component that was then
filtered out by paper,
but a small number of studies suggested
that filtered coffee may also increase
cholesterol levels, and began to cast
some doubt onto what appeared
to be a fairly clear picture.
So, yeah, the cholesterol-raising
effects brought about by the consumption
of filtered coffee may not be as strong
as those of the boiled coffee,
but maybe we shouldn’t discard
the possibility that filtered coffee
may also play a small, but important,
role in raising cholesterol.
I knew about this study,
where three cups a day of filtered coffee
raised total cholesterol,
but the rise in LDL “bad” cholesterol
was not statistically significant.
Same with this study, where stopping
filtered coffee reduced total cholesterol,
suggesting perhaps only partial removal,
but no one had ever just measured
the levels of the cholesterol-raising
compounds in the paper filters…
until now.
The results showed that most of the
cholesterol-raising cafestol was retained
by the coffee grounds, rather than
actually getting stuck in the filter itself.
In other words, the principal function
of the paper filter is to not
necessarily to block the compound
itself, but to block any fine particles
that are carrying the compound.
Like, when you make French press coffee,
there’s that fine mesh screen,
but you still notice a little sludge
at the bottom of the cup;
that’s the tiny particles that pass through
and can carry some of the risk.
But, a little cafestol does
get through the filter.
So, yeah, you can cut out more than
90% – switching from French press,
or one of the metal mesh filters,
by using a paper filter.
If you use coffee that starts out
with a high level of
the cafestol compound,
you’re still clearing out about 95%
with the paper, but there may be
enough left to still bump your LDL,
but you don't know until you...
put it to the test.
They started out with a high cafestol coffee.
After a month of drinking
two cups a day,
their LDL cholesterol
went up significantly,
even though it was paper-filtered.
So, if you have high cholesterol despite
eating a healthy diet, you may want
to try cutting out coffee
and getting retested.
Or, you can try switching to a
lower cafestol coffee.
There’s all sorts of variables,
such as roasting degree or grind size
that may affect cafestol levels.
One can imagine a smaller particle size
would allow for greater extraction.
Roasting appears to destroy some of it;
so, a really dark roast should have less.
But, there’s not much difference between
just light and medium roast.
Indeed, in this study, there was no
significant difference between the
rise in cholesterol after a medium
light roast versus a medium roast.
They both raised bad cholesterol.
Finally today,
we look at the effects of tea and coffee for artery function.
There are dietary guidelines for food, but what about for beverages?
A Beverage Guidance Panel was assembled to provide guidance
on the relative health and nutritional benefits and risks of various beverage categories.
They ranked them from 1 to 6, and water ranked #1.
Soda ranked last at #6.
Whole milk was grouped with beer, with a recommendation for zero ounces a day,
in part out of concern for links between milk and prostate cancer,
as well as aggressive ovarian cancer thanks to IGF-1.
#2 on the list, though, after water, was tea and coffee,
preferably without creamer or sweetener.
Even without creamer, though, lots of unfiltered coffee can raise cholesterol levels,
but the cholesterol-raising compounds are trapped by the paper filter in brewed coffee,
so filtered coffee is probably better.
About 10 years ago a study was published on the effects of coffee
on endothelial function - the function of our arteries.
Within 30 minutes of drinking a cup of coffee
there is a significant drop in the ability of our arteries to dilate,
whereas decaf did not seem to have a significant effect.
This was the first study to demonstrate an acute unfavorable effect
on arterial function for caffeinated coffee,
but one cup of decaf didn’t seem to affect performance.
And two cups of decaf appeared to have a beneficial effect.
So maybe it’s a battle between caffeine and antioxidants.
Something in caffeinated coffee appears to be hurting arterial function,
whereas something in decaf appears to be helping—maybe the antioxidants.
It’s like the story with red wine.
De-alcoholized red wine significantly improves arterial function,
so there’s grape components trying to help,
but the presence of alcohol counteracts and erases the benefit.
Drinking really high antioxidant coffee, by preparing it Greek style, for example,
where you actually drink some of the grounds,
may actually offer an advantage.
That something in caffeinated coffee that appears to hurt, though,
may NOT be the caffeine.
In a randomized, double-blind, placebo-controlled, cross-over study,
researchers found that caffeine alone—about 2 1/2 cups of coffee worth—
—significantly IMPROVED arterial function in both people without and with heart disease.
See coffee contains more than a thousand different components other than caffeine,
many of which are also removed by the decaffeination process,
so there must be something else in the coffee bean that’s causing the problem.
In fact, caffeine may even enhance the repair of the fragile inner lining of our arteries,
by enhancing the migration of our endothelial progenitor cells,
the stem cells that patch up potholes in our artery walls, one could say.
But how might we get the potential benefit of caffeine
without the risky compounds in caffeinated coffee?
Tea.
Tea consumption enhances artery function.
Substantial beneficial effects from both green tea and black tea.
Instead of other components in tea leaves undermining caffeine’s potential benefits,
they appear to boost the benefit in healthy individuals,
as well as heart disease patients,
reversing some of their arterial dysfunction,
both immediately and in the long term.
Now all the measurements in this and the other studies
were done on the brachial artery, the main artery in the arm,
just because it’s easier to get to.
What we care about, though, is blood flow to the heart.
And caffeine appears to impair blood flow to our heart muscle
during exercise even in healthy folks,
but especially those with heart disease.
Thankfully caffeine in tea form appears to have the opposite effect,
significantly improving coronary blood flow,
suggesting that tea consumption has a beneficial effect on coronary circulation,
though the addition of milk may undermine the protective effects.
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