In the last lecture, we talked about water
Afterward, many of the viewers asked,
"Can't I just drink coffee instead?"
or "What about green tea?"
"How about Solomon's seal tea?"
or "Maybe a cassia seed tea?"
Even some elderly viewers asked, "Is roasted barley tea okay?"
and "What about corn tea?"
The variety of questions really took off
So, I'll go over the "water" topic again
Among the drinks we consume, especially in Korea,
and younger women, who may have heard that
it helps with dieting, often ask, "Isn't cornsilk tea okay?"
They ask things like these
Then, health-conscious folks jump in with,
"What about mushroom tea?"
Shiitake, phellinus mushrooms
You name it
I mentioned the conclusion last time
What did I say?
Tea is tea, water is just water
I am not saying you shouldn't drink tea
Go ahead, there's no problem at all
The point is, you can't actually replace water with those teas
Now, what will we talk about today?
Carcinogens in food
It's a pretty serious topic, right?
And look at the examples
Coffee, fries, pepper
We eat these things daily
Practically every day
Even kids love those
The reason I'm bringing this up isn't to scare anyone
It's more like, shouldn't we at least
know what to look out for?
Another big concern I have when I give these talks is
for people who get too concerned about what they eat
Those who are overly sensitive
Like, they even go into whether
they're 'warm-natured' or 'cool natured'
Imagine you're visiting a friend's place, and they serve up some bibimbap
There's all these delicious veggies
and that delicious gochujang sauce
But then you notice there are sliced cucumbers in there and think
"Oh no, I'm cool natured, I shouldn't be eating cucumbers..."
Some people even keep lists
Foods they think they need to avoid
"No cucumbers for me, I'm cool natured"
So, while everyone else is happiliy mixing up and enjoying their bibimbap,
this one is sitting here, stressing over what to do with those cucumber slices
Eventually, they pick them out and push them to the side
Then, have a bite
But even after all that, there's always a chance a tiny piece snuck in, right?
And sure enough, as they're chewing,
they bite in to one
Then they go like this, "Oh no, I ate a cucumber,"
"but I'm cool natured..."
At that point, it's not about being 'cool natured' or whatever
It's more like a mental thing
Honestly, even if you are especially 'coolest natured'
just mixing it up and enjoying it isn't going to hurt you
The real issue is that
it's only a problem if you're eating a ton of foods
that don't suit your body or that you think are 'bad' for you
Having it once or twice?
That's no problem at all
People ask me this question all the time
What question do you think it is?
"Do you eat ramen?"
Well, do I?
Of course! Why wouldn't I?
The problem isn't ramen itself
It's when having it for breakfast because you don't have time
then a cup of noodles for lunch
and ramen again for dinner because you don't feel like cooking
When you're eating it nonstop, it's a real problem
And for the record, I'm not eating it a lot these days
So why do people say ramen's bad?
It's because the noodles are fried in palm oil
which is especially high in saturated fat
Plus, if those go into those packets
and stored in a hot place,
The heat can cause the fat to go rancid, which is where the concern comes from
If you're worried about that, there are non-fried noodles these days
But fried noodles taste great
So, what's the issue? The oil, of course
Here's a little trick, it might take a bit more effort
but you can boil some extra water in an electric kettle
You're boiling water at two places
An electric kettle heats up quickly
Cook the ramen noodles, drain the water
and then pour in the fresh, hot water from the kettle
There are plenty of ways to make it work
Before we dive into today's topic, I just want to say
don't get too stressed about this
I can already picture some of you
waking up tomorrow, holding your morning coffee, trembling
thinking, 'Professor Lee said there's a carcinogen in coffee..'
No, don't worry
It's fine if you drink two or three cups a day
So who should be paying attention?
People who eat a lot of these things, and over a long period of time
And take fries, for example, who eats them the most?
Kids
These days, one of the top kitchen appliances moms buy
for their kids’ health is
the air fryer
Why? Because it can make fries without all the oil
They’ll grab a bag of frozen fries, pop them in the air fryer, and serve them
There's a problem, right?
That’s what I’m talking about
When do we usually use pepper?
When we're grilling meat, right?
And depending on how we sprinkle that pepper,
we could end up with a lot of carcinogens in what we’re eating
Let's talk about this
First, let's talk about coffee
As you know, coffee is only grown in certain areas known as the coffee belt
It grows only in this area
And as today’s topic is coffee,
we can se that coffee consumption has been steadily increasing
Especially in Korea, where coffee holds some serious records
One of the biggest coffee franchises here made over 2 trillion won in annual sales
And which age group makes up the biggest chunk of those sales?
Women in their 20s and 30s
Women in their 20s to 30s
These days, they even buy 1L size coffee
It's almost like people think drinking two or three of those a day makes you trendy
Young women in their 20s and 30s are a highly important group in our society
Why?
They’re the ones who will bring in the next generation
Just think, when a baby is born, it's a big celebration, right?
It is, right?
These days people struggle with pregnancy, obstructed labour, and even infertility
I’m not saying coffee is the only cause,
but it could be a factor, why?
The amount has gone way up
Korea’s per capita coffee consumption ranks right at the top globally
At the top
These days, if you don’t have coffee after a meal,
People consider you strange, right?
"Let's grab a coffee" because automatic
after having a meal
It has become a part of the culture, which is why I'm talking about this topic today
Now, I bring this up because I never used to drink coffee myself
I studied abroad in the U.S. and lived there for about nine years,
but it wasn’t about disliking coffee I just couldn’t handle it
Recently, I worked on a government study analyzing the coffee Koreans drink
For three years, I had the chance to analyze all kinds of commercial coffee,
and I was surprised by what I found
I kept wondering, why don’t people seem more concerned about the issues?
People just care about taste and aroma
They think it's a preference thing
Just like how people smoke
despite all the carcinogens in cigarettes
So, they don't consider the health impact
They've completely
overlooked it, thinking
"It's just a preference"
But here's the thing, while cigarettes might be a preference
coffee is not a preference, but a food
People consume them that much
It’s not just a preference anymore, right?
Almost everyone drinks it,
and globally, the consumption levels are massive
According to statistics,
the average person consumes 360 cups of coffee per year
50 million people drink that much coffee
Now, here’s where it got interesting
On March 30, 2018, the California Superior Court
made a ruling about coffee
You can find this online
Basically, they decided that
every coffee shop in California, including Starbucks and 90 other chains,
had to put up a warning sign
The sign had to say something like, the coffee we serve contains carcinogens
Drinking this coffee while pregnant may lead to miscarriage
This ruling caused a massive stir
Not just in California,
but worldwide
People in the coffee industry,
coffee lovers, and even environmental groups all got involved
Now, it’s been a while
It's been three years since then,
and while the judge who made the ruling
can’t really comment on it anymore,
if you look up articles, you’ll see a lot pushing back against that decision
So, what about coffee?
The argument is that the amount of carcinogens in coffee is so small
that it’s not a real concern
That carcinogen is called acrylamide
This acrylamide carciinogen
isn’t naturally found in coffee beans
Not in coffee beans
When does it form?
During the roasting process
This carcinogen forms during the roasting process
But up until now, what’s been the main focus during roasting?
Just the taste and aroma
Why?
Because it sells well
But here’s my point
With coffee consumption going up,
if we start paying more attention to the roasting process,
we could have coffee that’s tasty and aromatic without the carcinogens
So, I kind of feel burdened
If I talk about the topic of coffee
there are many people who show interest
But this is all based on articles online
The debate around carcinogens in coffee will keep coming up
Alright, let us go into further detail
When we get coffee beans, they start out as green beans
They’re literally green in color,
which is why they’re called green beans
Then what do we do with them?
We roast them
Once they’re roasted,
they turn into the coffee beans
Now, we brew those beans
in all kinds of ways to make coffee
When does acrylamide form?
Only during roasting
It only form when heat is applied
It didn't exist at first
So, when did this become an issue?
Back in 2002, a research team in Sweden reported that
french fries had a problem
This kicked off the whole discussion,
eventually bringing coffee into the mix
Now, when coffee is roasted,
it can be done lightly
or strongly
When you roast stronger, it makes the coffee darker
If lightly roasted, the color is lighter
When you roast coffee beans
even when you roast grains, it turns brown, right?
That browning reaction is called the Maillard reaction
Named after a French scientist, it’s pronounced a few ways
Anyway, the French scientist said, it produces carcinogens when turns brown
and aroma also
When you bake bread, it turns brown and releases that delicious smell
That's all because of
the Maillard reaction
While it creates flavor, it also produces carcinogens
It can't be avoided
It’s a trade-off
This browning reaction, or Maillard reaction,
usually happens between 150 and 180 degrees Celsius
when amino acids meet reducing sugars
Now, there are different amino acids
For instance, in baked bread, the amino acid lysine reacts with glucose
to give that fresh-bread smell
The maple syrup aroma comes from serine
When it comes to grilled meat,
the browning releases that amazing roasted aroma
That's also because of an amino acid called cystine
that reacts with heat, creating the smell of cooked meat
The problem with coffee and potatoes is they contain asparagine
When asparagine meets glucose and hits that browning temperature,
it creates acrylamide, a carcinogen
When I talk about this, people ask, "What about scorched rice?"
"Isn’t that browned, too?"
Is that fine?
Yes, but it’s fine, why?
Because rice has very little asparagine
The problem only arises when asparagine is there
What contains asparagine a lot, did I say?
In coffee and potatoes
Do you understand now?
So, no need to worry about scorched rice
I’m sure people will still ask,
“But I eat scorched rice every day, is it safe?”
Yes, absolutely
Please enjoy
Our ancestors weren't ordinary people
They wisely told us to enjoy scorched rice
So go ahead and enjoy it
Now, here’s where people often get it wrong with coffee
Like I mentioned, the carcinogen acrylamide is
currently classified as Group 2A by the WHO
What does 2A mean?
It’s been proven to cause cancer in animals,
but studies on humans are still ongoing
Group 1 substances are confirmed carcinogens for both animals and humans
So, while acrylamide is proven to be a carcinogen in animals,
it’s still being studied in humans
So, some people think it's okay to consume since it's only Group 2A
But that’s not true
If science has shown cancer risk in animals
that’s a warning sign
That means,
it’s best to eat less
And speaking of roasting,
coffee shops often go for dark roasts,
where beans are roasted longer
Have you ever heard that
sesame oil and perilla oil can contain carcinogens?
Haven't you heard about this?
Sesame oil and perilla oil both can contain carcinogens
when they are roasted
Traditionally, how did we roast sesame and perilla seeds?
We roasted them strongly
Why? Because that's how you get a richer aroma and more oil out of them
Grandmas would take their homegrown seeds
to the local oil mill in plastic bags
The owners knew the more you roast,
the better the smell and the more oil you get
So, oil mills everywhere
roast them like that
for more flavor and a stronger aroma
Let’s say an oil shop owner tries to give healthier one
by roasting sesame seeds lightly, which means less aroma and less oil
Then customers start complaining,
"Where’s the rest of the oil?"
"Other places give me a full bottle, "
"why do I only get half here?"
But here’s the deal
The more you roast sesame or perilla seeds, the more carcinogens,
specifically benzopyrene, are produced This is a Group 1 carcinogen
It is a powerful one
It's a strong carcinogen
That’s why worldwide, all sesame oil, perilla oil,
soybean oil, olive oil, every type of oil is tested
If two micrograms of benzopyrene per kg is found, it's immediately discarded,
banned for sale
Strict regulations are in place
because benzopyrene is
a Group 1 carcinogen,
meaning it’s a confirmed cancer risk
So, it's strictly regulated
Why do people say to not eat burnt meat?
That’s because of benzopyrene
That black color on charred meat is full of it
So, eating blackened meat isn’t good
Now, you might be thinking,
“But I’ve eaten a lot of burnt meat, and I’m fine!”
That’s because, thankfully, God designed our immune system
to handle a certain amount of carcinogens
But if someone’s lifestyle
or diet weakens their immune system,
the day their immunity dips
and they eat a piece of burnt meat,
that’s when it can become a problem
Similarly, when coffee beans are roasted too dark,
the beans get a shiny, oily surface
Leave them like that for too long,
and that same benzopyrene carcinogen can start forming
That’s why nowadays, there’s a lot of testing
on dark roast coffee for benzopyrene
But still, there’s no official standard
for coffee yet,
they’re using standards from sesame and perilla oils to test it
Some coffees pass with no issues, while others show concerning levels
So, during the last 5-6 years,
people have been wanting light-roasted coffee
People are saying coffee should be light,
have a fruity or floral taste
That’s where the whole specialty coffee thing comes in,
with a shift from dark to light roast
But here’s the catch, that carcinogen, acrylamide,
actually shows up more in light roasts
Yes, it’s mostly in light-roasted coffee
They are wrong about coffee
If you go dark roast, there’s a risk of getting benzopyrene
but if you go light roast to get
that fruity, floral flavor,
you’re getting more acrylamide
Basically, Koreans are drinking coffee at both extremes
I'm telling you this again
Don’t let this make you freak out in the morning over your cup of coffee
A cup or two isn’t an issue
This is more of a heads-up for people who drink a lot of coffee long-term
It's just good to know
And now, things have moved a step further
With concerns growing, Korea’s MFDS couldn’t ignore this anymore
So, on October 15, 2020, they announced that,
starting January 1, 2021, new limits would be set
0.3 mg/kg for infant cereals,
0.8 mg/kg for coffee,
and 1.0 mg/kg for fried potato products
Now, of course,
with COVID, many cafes have been struggling to stay open, right?
But the MFDS had no choice but to announce these rules
because of the rising consumption levels
Especially for kids who eat
a lot of cereal and fries
So, even though the MFDS understands the hardships of cafes and restaurants
they still made the announcement
And actually,
these limits are set pretty high
compared to Europe, about double, in fact
So, they tried to be lenient,
but something had to be done
My lectures aren’t about scaring you
I only give talks
when there are actual solutions
If I didn’t have any alternatives for things like
coffee, pepper, or fries,
it would just be a scare session, right?
So now, let’s dive into a lecture where we talk about real options
But here’s the tricky part
When I give a lecture about coffee,
it’s a bit sensitive because the coffee industry here is huge
They’ve built their own niche,
their own storytelling for customers,
mostly focused on taste and aroma
So, when we start talking about health, it makes them a bit uncomfortable
They wonder how customers will react
But change needs to happen
If there’s a way to adjust things
so customers can enjoy coffee that’s flavorful
and healthier, that’s the way to go
It’s not like we can just say, “Oh, we didn’t know before,"
"so let's ignore it"
"and keep going." We are past that point
So, how do we reduce them?
This isn’t just my own idea,
you can find tons of research online
about acrylamide reduction methods
Globally,
not only in Korea,
there has been massive investment and effort
put into finding ways to lower acrylamide levels
and everyone is trying to make a change
But here in Korea, we’ve been
a bit slow to catch up
I’ve mentioned this a few times on public broadcasts,
but moving forward,
I’ll keep pushing to shift toward healthier food options that fit our times
Alright, so let’s talk about solutions
First up, coffee
When does coffee produce carcinogens?
During roasting
So, is there a way to roast coffee without creating carcinogens?
From my research, the answer is yes
There is a way
I shared this with lots of coffee experts, but no one really followed through
So, I spent
millions of won to buy a roaster myself
I tested different roasting methods
and analyzed the results in my lab,
and it turns out
it’s entirely possible to make coffee with almost no carcinogens
I’ve even filed a patent for this method
If any businesses
are interested
in making healthier coffee for consumers,
I’m open to collaborating
without pushing hard on patent rights
This is something experts can absolutely solve
But now,
they just do not want to
Why?
They feel uneasy about how coffee drinkers will think about this
It’s natural to wonder, "Was the coffee I drank yesterday okay?"
There’s no easy answer to that,
and that’s what makes this a bit tricky
But even so, this is something we need to keep working on and improving
Now, let’s talk about French fries
Which country do you think
has done the most research on fries?
The United States
Why?
Because fries always come with hamburgers
You know, the french fries
The one which is chopped
and curved potato chips
are products of America
But eating french fries with a hamburger
is normal in the U.S. and Europe
But back in 2002, Sweden found that fries contain high levels of carcinogens
Since then, hundreds of studies from chemists and food scientists
have been published
on ways to minimize carcinogens
when frying potatoes,
whether with an air fryer or in oil
Here's three key methods to reduce those carcinogens
First, don’t use frozen potatoes
Freezing increases the concentration of reducing sugars,
which leads to higher acrylamide levels when frying
Not using frozen potatoes
can be done at home
So, instead of grabbing a bag of frozen fries for convenience,
try cutting fresh potatoes at home
If you can’t get that fry shape, round slices work just fine
Remember, do not use frozen potatoes
Second, after slicing the potatoes, wash them
but not just with water
Use water with a bit of diluted vinegar
This lower pH helps reduce acrylamide formation
You can also add a pinch of salt to the vinegar water
Potatoes washed in
this vinegar-salt solution
tend to have much lower acrylamide levels
Alos, a lower temperatue
I know it’s tempting to increase
the heat to fry them faster,
but cooking at high temperature to get that deep brown color isn’t necessary
Aim for a lighter golden brown
Even if it is not super crispy, it's enough for the kids to enjoy
By frying at a lower temperature for a bit longer,
you can really cut down on carcinogens in French fries
This is backed by significant research
Dozens of studies published in high-impact journals like SCI
Pepper
Koreans usually add pepper in two ways
First, when they marinate meat
They marinate meat with pepper and onions
Second, they sprinkle pepper when grilling meat
This is how they usually have pepper
But how do people abroad typically add pepper to meat?
They wait until the meat is fully cooked
and add freshly ground pepper at the table
Right?
Here’s why this matters
The pepper we buy has already been roasted
When pepper is exposed to high heat,
carcinogens can form
So, the rule of thumb is
to add pepper at the table
When?
Right before you eat
Always season with pepper at the table, not while cooking
We ran these experiments ourselves with the Ministry of Food and Drug Safety
When we tested pepper
that was added before
or during cooking,
we found a significant increase
in carcinogens
So, how should you use pepper?
Add it at the table after the meat is cooked, and enjoy it safely
Got it?
That’s the solution here
Here's a question
I usually skip breakfast but need my coffee
to wake up and start the day
I also have 2-3 more cups in the afternoon,
but I'm worried about too much caffeine, so I’m thinking of switching to decaf
Wouldn’t it be fine to drink a lot of decaf?
You might already sense the answer, it’s not ideal.
Decaf still has some caffeine,
and caffeine itself is a stimulant
The main issue?
When you’re tired,
caffeine doesn’t actually relieve your fatigue
instead, it tricks your brain into thinking
you're not tired
So if you keep drinking coffee while exhausted,
it catches up with you physically
Right?
That fatigue and body aches?
That’s your body telling you to rest,
but we keep reaching for coffee
to push through
So, caffeine is a stimulant,
but it doesn’t actually relieve fatigue, it just makes you forget you’re tired
Over time, that hidden fatigue builds up and can lead to health issues
Generally, it’s recommended to keep caffeine intake around 400 mg per day,
with a typical coffee cup containing about 100–150 mg
This means that 2-3 cups a day is the max
if you're looking to stay within the recommended caffeine levels
Going beyond that can lead to issues like
having trouble sleeping,
and others
And caffeine is also addictive
So, it's not good to drink too much coffee
So people wanted to take the caffeine out of coffee
which is how decaffeine was made
In the past, caffeine was removed using harsh chemical methods,
which caused other health concerns
Now, caffeine is extracted more safely
but it’s still not 100% caffeine-free
Decaffeine doesn't mean it has all of the caffeine extracted
It just means it has less caffeine
so it’s best not to overconsume it
I usually drink green or black tea instead of coffee
I’ve heard that tea is a better option even though it also includes caffeine
Is there a difference between the caffeine in tea and coffee?
Caffeine is caffeine
It’s the same in both coffee and tea
But tea has
additional beneficial compounds, like catechins,
So, while tea does have caffeine,
those extra compounds make it a bit gentler on the system
But at the end of the day, caffeine is still caffeine
So enjoy tea as you would coffee
Given the nature of my job, I often have to work late into the night
My colleague has energy drinks, saying they help him stay awake
I’ve heard students rely on these, too
What effect do they have on health?
I actually answered this earlier
What's the best thing to do when your job requires night shifts?
Rest should be the top priority
Those drinks don’t actually restore energy
They just create the illusion of recovery, letting fatigue pile up over time
With that, I’ll wrap up my lecture
I hope you stay healthy