"Is Heme Iron the Reason Meat Is Carcinogenic?"
US Patent No. 9,700,067 was Impossible Food’s dream
of improving plant-based meat substitutes to better replicate
the aromas and flavors of meat by using plant-based heme.
OK, but what about the heme-induced formation of nitroso compounds.
When we eat lots of meat, you can pick up more and more
nitroso compounds in people’s poop, a small fraction of which
may be due directly to the heme.
The toxicological significance of this remains to be established,
since only some nitroso compounds are of concern.
But should the nitroso compounds formed in the intestine
as a result of heme consumption be shown to be mutagenic
or carcinogenic, this might help explain the association
between red meat consumption and colorectal cancer.
But you don’t know, until... you put it to the test.
“DNA damage is considered an essential component
in the [development] of colonic cancer”;
so, researchers looked at “fecal water genotoxicity.”
You’ve heard of green tea, black tea?
This is more like brown tea, basically a filtered fecal smoothie.
That’s definitely one where you want to double-check
the blender lid is on tight.
But what they found was that the DNA-damaging effects
of the fecal water was independent of the amount
of nitroso compounds they found.
Now the lack of correlation between the apparent
total nitroso compound concentrations and DNA damage
could be due to much lower levels of nitroso compounds
found in fecal water compared to the feces themselves.
I mean, just looking at the fecal water, the nitroso compounds
are the same across meat groups, but the real poop had the real scoop.
Ideally, though, we’d like to know what’s happening in the human colon.
So, researchers took biopsies before and after a week
that included a few daily servings of beef and veal.
Not only did they see more than a “twofold increase
in fecal water genotoxicity” that correlated with
pro-carcinogenic gene expression changes in the
before-and-after biopsy specimens, after just one week.
Still, there has only been “circumstantial evidence
that the [N-nitroso compounds] formed in the large bowel
after eating [meat]….may be important genotoxins”until ...now,
or at least until this study.
A significant increase in nitroso compounds,
significantly correlated with a significant increase
in DNA damage characteristic of N-nitroso genotoxicity.
You can visualize the DNA damage in rectal biopsies—
the brown staining on the right—after a month
of three beef and lamb servings a day.
The researchers suggest dietary heme as a reasonable explanation,
but the lowest dose of heme showing evidence of direct DNA-damage,
in this case from freshly resected colon tissue, was 10 micromoles.
I contacted Impossible and they said that’s equivalent
to three times the concentration of heme found in their burgers.
After completing this deep dive, therefore, it’s not clear to me
that heme at typical dietary doses causes harm,
and even less clear that heme is a culprit
in the meat and cancer connection.
If it’s not the heme, though, what is it?
Well, there are “reasons to suspect involvement
of bovine infectious factors in colorectal cancer.”
There are heat-resistant tumor-causing viruses
that could survive meat cooked medium or rare.
A specific class of infectious agents that have been isolated
from both cows and around human colon cancer tissue,
not to mention the brains of MS victims.
“What do breast and colorectal cancers
and multiple sclerosis all have in common?”
Several potentially infectious factors from cattle blood and milk,
but that’s a whole video topic in and of itself.
Less speculatively, it could just be the saturated and trans fats,
or sulfur-containing amino acids concentrated in the meat
interacting with our gut microbes, resulting in oxidative stress
and inflammation that drives the cancer.
If you compare the gut bacteria in stools from cancer patients
to healthy subjects, a high meat-to-fruit-and-veggie ratio
“appears to associate with outgrowth of bacteria
that might contribute to a more hostile gut environment.”
A hunt for “global microbial signatures that are specific
for colorectal cancer” suggested a “metabolic link
between cancer-associated gut microbes and a fat- and meat-rich diet.”
Maybe it’s from the meat putrefying in your colon.
Putrefaction inside the human gastrointestinal tract
pertains to decomposition of undigested proteins in the gut.
Some of the products of this putrefaction process, like ammonia,
putrescine, and uremic toxins like cresol, indole, and phenol
have been implicated in the development of colorectal cancer.
But cut out the meat, and levels of some of these compounds
may fall by more than half, perhaps because
they cultivated fewer putrefying bacteria.
Bad bacteria also produce secondary bile acids,
which are associated with both cancer risk and cancer progression
as a potential promoter of colorectal tumor enlargement,
in part by damaging the intestinal lining, causing a leaky gut.
Put people on a diet packed with animal foods, and you get
a massive increase in the bacterial production within days;
whereas if you cut meat, you can go the other way.
Even just eating more plant-based, swapping out the standard
American diet for healthier fare remarkably reduced
secondary bile acids by 70% within just two weeks.
There also may be a “strong link between colorectal cancer
and trimethylamine N-oxide (TMAO), a gut microbial metabolite
of dietary meat and fat.” Maybe that’s the link
between what our gut bugs are doing with meat
and risk of colorectal cancer.
Maybe because of the inflammation caused by TMAO,
but if could also be the oxidative stress,
or DNA damage, or protein disruption.
Or what about the nonhuman sialic acid known as Neu5Gc
that is incorporated into the tissues of meat consumers
and elicits an inflammatory immune reaction?
And antibody levels against this foreign compound found in meat
are associated with colorectal cancer risk.
One could go on and on.
The bottom line health-wise is that while nutrition experts
are understandably concerned you’re going to be ordering
that Impossible Whopper with fries and a Coke,
hey—it’s better than getting fries and a Coke with a regular Whopper.