"Are Pre-Cut Vegetables Just as Healthy?"
Seven years ago I introduced the endotoxin theory literature,
which sought to explain how a single meal of sausage and egg McMuffins
could cripple artery function within hours of consumption.
Maybe because such a meal causes inflammation by inducing a low-grade
endotoxemia, endotoxins in the bloodstream within hours of consumption.
Endotoxins are structural components of gram-negative bacteria like E. coli,
and certain foods have such high bacterial loads, like ground meat,
the thought was that it was the endotoxins in the food
that was triggering the inflammation.
Critics of the theory argue that because we have so many bacteria
already living in our colon, so many endotoxins just sitting down there
in our large intestine, a few more endotoxins in our food
wouldn't matter much in terms of causing systemic inflammation.
After all, we have like two pounds of pure bacteria down there
where the sun don't shine, so there could be like a whole ounce of endotoxin.
And the lethal dose of intravenously injected endotoxin could be
just like a few millionths of a gram, so we could have like a million lethal doses
down there, but the apparent paradox is explained by compartmentalization.
It's location, location, location.
Poop is harmless in your colon, but shouldn't be injected
into your bloodstream, or eaten for that matter, particularly with fat,
as that can promote the absorption of endotoxins up in the small intestine—
even well-cooked poop.
You can boil endotoxins for two hours straight
with no detriment in their ability to induce inflammation.
You could easily kill off any bacteria if you boiled your poop soup long enough,
but you can't kill off the endotoxins they make,
just like you can't cook the crap out of the meat.
The consumption of meat contaminated with feces
doesn't just cause food poisoning.
It can spill out during during the evisceration process,
when the digestive tract is ruptured.
Even when slaughterhouse workers trim off the visible fecal contamination,
the trimming itself can, ironically, sometimes lead
to an increase in certain fecal bacteria, thought to be caused
by cross-contamination from one carcass to the next.
Then, even when properly stored in the fridge,
endotoxins start accumulating along with the bacterial growth.
What about other foods?
The highest levels of endotoxins were found in meat and dairy,
and the lowest levels in fresh fruits and vegetables.
But that was testing whole fruits and vegetables.
Most spoilage organisms can't penetrate
the plant's surface barrier and spoil the inner tissues.
That's why fruits and veggies
can just sit out there all day in the sun out in the fields.
But once you cut them open, though, and bacteria can gain access
to the inner tissues, within a matter of days your veggies can start to spoil.
So what does that mean for all those convenient
prechopped veggies these days?
While endotoxins were not detectable in the majority of unprocessed vegetables,
once you damage the protective outer layers of vegetables,
you diminish their resistance to microbial growth. So while
freshly chopped carrots and onions start out with undetectable levels,
day after day, even kept chilled in the fridge, you start to get
the growth of bacteria, and along with them endotoxin buildup.
Not as much as meat, but not insignificant.
Enough to make a difference, though?
You don't know, until you put it to the test.
What would happen if you switched people between a diet
expected to have a lower endotoxin load to foods containing more endotoxins,
like going from intact meat like steaks and whole fruits and vegetables,
to more like ground beef and prechopped veggies and more ready-made meals?
After just one week on the lower endotoxin diet,
people's white blood cell count,
which is an indicator of total-body inflammation dropped 12%,
but then bumped 14% up after just four days on the higher endotoxin diet.
And they actually lost a pound and a half on the lower endotoxin diet
and slimmed their waist a bit.
But they weren't really eating otherwise identical diets.
Looked like they were eating more meat and cheese overall
on the higher endotoxin diet,
and maybe getting more food additives in the ready-made meals,
so how do we know endotoxins had anything to do with it?
That's where the onion study comes in.
A new study was designed based on two meals that differed in their content
of bacterial products, but which were otherwise nutritionally identical.
So they compared freshly chopped onion to prechopped onion
that had been refrigerated for a few days.
It wasn't spoiled; it was still before the "best before" date.
So would it make any difference?
Within three hours of consumption, the fresh onion meal caused
significant reductions in several markers of inflammation.
That's what fruits and vegetables do; they reduce inflammation.
But these effects were not observed after eating the prechopped onions.
For example, here's one inflammatory marker.
Three hours after eating fresh-chopped onions,
a significant drop in inflammatory status. But three hours after eating
the exact same amount of prechopped onions, no significant change.
So it's not like the prechopped onions caused more inflammation,
like in the meat, eggs, and dairy studies,
but they did appear to extinguish
some of the anti-inflammatory effects of the onion.
In conclusion, the modern trend towards eating the prechopped vegetables
rather than whole intact foods is likely to be associated
with increased oral endotoxin exposure.
It's definitely still better to eat
prechopped vegetables than no vegetables,
but chopping your own might be the healthiest.