"Does Heme Iron Cause Cancer?"
In muscle meat there’s a heme protein that contributes
to the meaty taste of meat.
Well, there’s a heme protein in the roots of soybean plants too
that can be churned out to provide a similar flavor and aroma
in plant-based meat, which is used to make
the Impossible Burger possible.
The question is: are there any downsides?
When the European Food Safety Authority was considering
the safety of adding heme iron to foods, their main concern
was a potential increased risk of colon cancer.
We know meat causes cancer.
Processed meat—bacon, ham, hot dogs, lunch meat, and sausage—
is considered a Group 1 carcinogen, meaning we know
it causes cancer in people, with the same level of certainty
that something like smoking causes cancer.
Whereas something like a burger, just probably
causes cancer in people, kind of like DDT.
But what’s the role of heme iron?
I mean, there are all sorts of potential mechanisms
to explain the cancer risk.
Meat’s got the pro-inflammatory long-chain omega-6
arachidonic acid, more of the aging- and cancer-associated
methionine, trans fat, endogenous hormones like IGF-1,
not to mention the ones that are implanted in animals
as hormonal growth-promoters.
Then there are all the toxic pollutants that build up
the food chain, like pesticides—
I didn’t even know about the formaldehyde.
According to the prestigious IARC,
the International Agency for Research on Cancer,
there is strong evidence that heterocyclic aromatic amines
contribute to the cancer-causing mechanism.
These DNA-damaging compounds are formed when muscle tissue
is exposed to high, dry heat – grilling, roasting, baking, broiling_
basically anything above steaming or stewing.
There is also strong evidence that the formation of so-called
N-nitroso compounds contribute to the cancer-causing mechanism.
These are carcinogens that can form inside our gut
when we eat the meat. But there is also strong evidence,
according to the IARC, that heme iron contributes
to the cancer-causing mechanism.
Normally, I might leave it there, but other authoritative bodies
I respect, like the American Institute for Cancer Research
and the World Cancer Research Fund, are more tentative.
While they agree there is some evidence that the consumption
of foods containing heme iron might increase the risk
of colorectal cancer, they consider the evidence
suggesting such a connection to be limited.
Much of the available evidence is based on lab animal data
such as this: in which dietary heme was found
to disrupt the gut flora, aggravate inflammation,
and potentiate the development of intestinal tumors in mice.
But it’s critical to note that in all the laboratory
animal models that have been used,
the rodents ingested meat or heme equivalent
to people eating up to 40,000 pounds of meat a day.
Even the smallest dose would be like
a dozen Impossible Burgers a day.
It’s easy to see how casual readers could get confused, though.
In this study, ascribing a central role for heme iron
in the colon cancer development associated with meat,
the authors claimed they were aimed at determining
at nutritional doses, which was the main factor involved
in cancer promotion. So, doses of heme were chosen
to mimic red meat consumption and… Boom!
Significant increase in tumor load.
The researchers conclude that their findings
strongly “suggest that at concentrations that are in line
with human meat consumption, heme iron is associated
with the promotion of colon [cancer development].”
But if you look at the actual diet they were given
and do the math, that’s 500 times the level of heme
found in people’s diets, in excess of
like 70 pounds of meat a day.
Of course, even if they really did use the right doses
they’re still going to end up with data on the wrong species,
which brings us to clinical studies which we’ll explore next.