"Is Liquid Smoke Flavoring Carcinogenic?"

We know smoke inhalation 
isn't good for us,

what about smoke 
ingestion?

Decades ago, smoke 
flavorings were tested

to see if they caused DNA 
mutations in bacteria,

and the test 
was negative.

Even as more and more 
smoke flavoring was added,

the DNA mutation rate 
remained about the same.

But the fact that something 
is not mutagenic in bacteria

has little predictive value 
for its effect on human cells,

so a group at MIT tested 
a hickory smoke flavoring

they just bought at the store against 
two types of human white blood cells.

Unlike the bacteria, 
the mutation rate shot up

as more and more liquid 
smoke was added.

But there is little evidence 
that mutagenic activity

in a particular human cell 
line is more closely related

to human health risk than is 
mutagenic activity in bacteria.

In other words, just 
because liquid smoke

causes DNA mutations to human 
cells in a petri dish,

doesn't mean that it does the 
same thing within the human body.

Damaging DNA is just one of many 
ways chemicals can be toxic to cells.

A decade later researchers 
tested to see what effect

liquid smoke had on 
overall cell viability.

If you drip water on 
cells, nothing happens,

they keep powering away 
at around 100% survival.

But drip on more and 
more wood fire smoke

and you can start killing 
some of the cells off.

Cigarette smoke 
is more toxic,

but 3 out of 4 of the brands 
of liquid smoke they bought

at the supermarket killed 
off even more cells,

leading them to conclude that 
the cytotoxic potential

of some commercial smoke 
flavorings is greater

than that of liquid 
cigarette smoke–

a finding they no doubt celebrated 
given that the researchers

were paid employees of the 
R.J. Reynolds Tobacco Company.

Unfortunately, they didn't name 
names of the offending brands.

That's one of the reasons I was 
so excited about this new study,

where they tested—and named 15 
different brands of liquid smoke.

This maximum "response" they were measuring 
was what was called p53 activation.

P53 is a protein we make, 
illustrated here in pink and red,

that binds to our 
DNA, shown in blue.

It activates our 
DNA repair enzymes.

So a big P53 response might be 
indicative of a lot of DNA damage,

and a few of the liquid smoke 
flavorings activated P53

almost as much as a chemotherapy 
drug like Etoposide

whose whole purpose is 
to break DNA strands.

Other flavorings 
didn't seem as bad,

though there was a hickory smoke 
powder that ranked pretty high,

as did the fish sauce, though smoked 
paprika didn't register at all.

The p53-activating property 
in liquid smoke was eliminated

by standard baking 
conditions (350°F for 1h),

so if we bake something with 
liquid smoke for long enough

it should eliminate 
this effect,

though just boiling, even for 
an hour, or slow cooking

didn't appear to work.

They conclude, "If the DNA-damaging 
activities of liquid smoke"

"were thought to be deleterious, 
it might be possible to replace"

"liquid smoke with other, 
safer, smoky substances."

Why do they say IF thought 
to be deleterious?

That's because they're not 
directly measuring DNA damage.

Remember, they're measuring 
P53 activation,

and that's not 
necessarily a bad thing.

P53 is considered "Guardian of 
our Genome," guardian of our DNA.

It's considered a 
tumor suppressor gene,

because it helps 
repair our DNA.

So if something boosts the activity 
of P53, is that good or bad?

It's like the 
broccoli story.

Cruciferous vegetables dramatically 
boost our liver's detoxifying enzymes.

Is this because our body 
sees broccoli as toxic

and is trying to get 
rid of it quicker?

Either way, the end result from 
broccoli is good, lower cancer risk.

It's maybe a biological 
phenomenon known as hormesis,

that which doesn't kill 
us may make us stronger.

Like exercise is a 
stress on the body,

but in the right amount can make 
us healthier in the long run.

So, for example, teas and coffees 
caused P53 activation as well,

but their consumption is associated 
with lower cancer risk.

So it's hard to know what to make 
of that smoke flavoring P53 data.

Due to the limitations 
of the available tests

it's hard to calculate the genotoxic 
potential of liquid smoke,

or any other food 
for that matter.

A better approach may be to just analyze 
liquid smoke for known carcinogens,

chemicals that we 
know cause cancer.

This was first attempted 
back in 1971.

One of the seven liquid 
smoke flavors they tested

contained a polycyclic 
aromatic hydrocarbon

known to be 
cancer-causing,

but there's a bunch of similar 
carcinogens that they didn't test for.

A later study, tested 
across the board,

looking specifically at 
5 different carcinogens

in retail liquid 
smoke seasonings.

The recommended daily upper safety 
limit for these carcinogens is 47.

Hickory smoke flavoring 
only has 0.8 per teaspoon,

so you'd have to drink three bottles 
a day to bump up against the limit.

And mesquite liquid 
smoke, only 1.1.

It turns out that most of these 
carcinogens in smoke are fat soluble,

and so when you make a water-based 
solution, like liquid smoke,

you capture the smoke 
flavor compounds

without capturing most of 
the smoke cancer compounds.

The only time you need to really 
worry is eating smoked foods,

foods directly exposed 
to actual smoke.

For example, smoked 
ham comes up to here,

and smoked turkey 
breast up to here.

So one sandwich and we may 
be half way to the limit.

But one serving of 
barbecued chicken takes us...

over the top.

Less than a single drumstick 
and we may nearly

double our daily allotment 
of these carcinogens.

Nothing, however, 
is as bad as fish.

Smoked herring? 140.

And we have to shrink down the graph 
to fit the worst of the worst...

smoked salmon.

One bagel with lox could take 
us 10 times over the limit.