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"Is Liquid Smoke Flavoring Carcinogenic?"

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We know smoke inhalation 
isn't good for us,

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what about smoke 
ingestion?

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Decades ago, smoke 
flavorings were tested

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to see if they caused DNA 
mutations in bacteria,

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and the test 
was negative.

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Even as more and more 
smoke flavoring was added,

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the DNA mutation rate 
remained about the same.

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But the fact that something 
is not mutagenic in bacteria

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has little predictive value 
for its effect on human cells,

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so a group at MIT tested 
a hickory smoke flavoring

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

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Unlike the bacteria, 
the mutation rate shot up

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as more and more liquid 
smoke was added.

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But there is little evidence 
that mutagenic activity

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in a particular human cell 
line is more closely related

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to human health risk than is 
mutagenic activity in bacteria.

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In other words, just 
because liquid smoke

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causes DNA mutations to human 
cells in a petri dish,

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

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

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A decade later researchers 
tested to see what effect

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liquid smoke had on 
overall cell viability.

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If you drip water on 
cells, nothing happens,

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they keep powering away 
at around 100% survival.

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But drip on more and 
more wood fire smoke

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and you can start killing 
some of the cells off.

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Cigarette smoke 
is more toxic,

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

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at the supermarket killed 
off even more cells,

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leading them to conclude that 
the cytotoxic potential

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of some commercial smoke 
flavorings is greater

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than that of liquid 
cigarette smoke–

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a finding they no doubt celebrated 
given that the researchers

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

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

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

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

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

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

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that binds to our 
DNA, shown in blue.

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It activates our 
DNA repair enzymes.

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

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and a few of the liquid smoke 
flavorings activated P53

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almost as much as a chemotherapy 
drug like Etoposide

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whose whole purpose is 
to break DNA strands.

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Other flavorings 
didn't seem as bad,

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

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

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The p53-activating property 
in liquid smoke was eliminated

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

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so if we bake something with 
liquid smoke for long enough

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it should eliminate 
this effect,

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

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didn't appear to work.

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

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

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

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Why do they say IF thought 
to be deleterious?

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

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Remember, they're measuring 
P53 activation,

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and that's not 
necessarily a bad thing.

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

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It's considered a 
tumor suppressor gene,

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because it helps 
repair our DNA.

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

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It's like the 
broccoli story.

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Cruciferous vegetables dramatically 
boost our liver's detoxifying enzymes.

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Is this because our body 
sees broccoli as toxic

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and is trying to get 
rid of it quicker?

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

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It's maybe a biological 
phenomenon known as hormesis,

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

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Like exercise is a 
stress on the body,

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

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

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but their consumption is associated 
with lower cancer risk.

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

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Due to the limitations 
of the available tests

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

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or any other food 
for that matter.

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

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chemicals that we 
know cause cancer.

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This was first attempted 
back in 1971.

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One of the seven liquid 
smoke flavors they tested

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contained a polycyclic 
aromatic hydrocarbon

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known to be 
cancer-causing,

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

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A later study, tested 
across the board,

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looking specifically at 
5 different carcinogens

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in retail liquid 
smoke seasonings.

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

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Hickory smoke flavoring 
only has 0.8 per teaspoon,

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

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And mesquite liquid 
smoke, only 1.1.

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

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

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you capture the smoke 
flavor compounds

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without capturing most of 
the smoke cancer compounds.

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

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foods directly exposed 
to actual smoke.

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For example, smoked 
ham comes up to here,

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and smoked turkey 
breast up to here.

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

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But one serving of 
barbecued chicken takes us...

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over the top.

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Less than a single drumstick 
and we may nearly

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double our daily allotment 
of these carcinogens.

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Nothing, however, 
is as bad as fish.

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Smoked herring? 140.

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

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smoked salmon.

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