Bowel Wars: Hydrogen Sulfide vs. Butyrate
There's a take-off of the industry slogan "Beef: It's What's For Dinner" ---
"Beef: It's What's Rotting in Your Colon."
I saw this on a shirt once with some friends
and I was such the party pooper -- no pun intended --
explaining to everyone how meat
is fully digested in the small intestine,
and never makes it down into the colon.
No fun hanging out with biology geeks --- but I was wrong!
It's been estimated that with a typical Western diet,
up to 12 grams of protein per day can escape digestion,
and when it reaches the colon
it can be turned into toxic substances like ammonia.
This degradation of undigested protein in the colon is called putrefaction,
so a little meat can actually end up putrefying in our colon.
The problem is that some of the by-products of this putrefaction can be toxic.
It's generally accepted that carbohydrate fermentation
- the fiber and resistant starches that reach our colon -
results in beneficial effects for the host
because of the generation of short chain fatty acids like butyrate,
whereas protein fermentation is considered detrimental for us.
Protein fermentation mainly occurs in the lower end of colon,
when carbohydrates get depleted
and results in the production of potentially toxic metabolites.
Perhaps that's why we see more colorectal cancer
and ulcerative colitis lower down,
because that's where the protein is putrefying.
The most simple strategy to reduce the degree
of potentially harmful compounds by protein fermentation
is probably a reduction in dietary protein intake.
But the accumulation of these harmful by-products of protein metabolism
may be attenuated by the fermentation of undigested plant matter.
This study showed that if you give people foods containing resistant starch
-- that means starch resistant to small intestine digestion
so it can feed our good bacteria down in our colon;
foods such as cooked beans, peas, lentils, raw oatmeal, cold pasta --
you can block the accumulation of these potentially
harmful byproducts of protein metabolism.
The more starch ending up in the stool, the less ammonia, for example.
But there's protein in plants, too.
The difference is that animal proteins tend to have
more sulfur-containing amino acids
like methionine that can be turned into hydrogen sulfide in our colon,
the rotten egg gas that may play a role in the development
of the inflammatory bowel diseases
like ulcerative colitis as I've covered previously.
The toxic effects of hydrogen sulfide appear to be mediated
through blocking the ability of our colon cells to utilize butyrate,
which is what our good bacteria make from the fiber we eat.
So it's like this constant battle in our colon
between the bad metabolites of protein, hydrogen sulfide,
and the good metabolites of carbohydrates, butyrate.
Using human colon samples they were able to show
that the adverse effects of sulfide could be reversed by butyrate.
So we can either cut down on meat, eat more plants, or both.
But there's two ways hydrogen sulfide can be produced.
Though it's mainly present in our large intestine
as a result of the breakdown of these sulfur-containing proteins,
rotten egg gas can also be generated
from inorganic sulfur preservatives like sulfites and sulfur dioxide.
Sulfur dioxide is used as a preservative in dried fruit,
and sulfites are added to wine.
We can avoid sulfur additives by reading labels or by just choosing organic,
since by law they're forbidden from organic fruits and beverages.
Now cabbage family vegetables naturally have some sulfur compounds,
but thankfully, after following more than a 100,000 women for over 25 years,
cruciferous vegetables were NOT associated with elevated colitis risk.
But because of the animal protein and preservative laden processed foods,
the standard American diet may have five or six times more sulfur
than a diet centered around unprocessed plant foods,
which may help explain the rarity of inflammatory bowel disease
among those eating traditional whole food plant-based diets.