celiac disease, is credited with having discovered this
important mediator of gut permeability.) This
“hyperpermeability” can occur in anyone but is exaggerated
in those with celiac disease. For this population, gluten
evokes an overt autoimmune response, causing the lining of
the small intestine to become damaged over time.
One of the dangers of a more permeable gut is that it
allows bacterial endotoxin (also known as
lipopolysaccharide, or LPS) to cross over into circulation.
As I’ve mentioned in previous chapters, LPS is a molecule
that makes up part of the membrane of certain bacteria that
normally live within the safe harbor of our large intestine.
When leaked into circulation, endotoxin sets off an acute
pro-inflammatory response, signaling a systemic bacterial
invasion. LPS exposure is directly related to pro-
inflammatory cytokine production and an increase in
oxidative stress, wreaking havoc on a wide range of bodily
systems—including your brain.
When animals are inflamed, usually from infection, they
exhibit strange behavioral changes, displaying symptoms of
lethargy, depression, anxiety, and reduced grooming. They
retract from the herd and become more sedentary, a means
of reserving the body’s energy for healing and isolating
them from the healthy. This is not a phenomenon exclusive
to farm animals—humans react similarly. They become
irritable, lose interest in food and socializing, and have
trouble focusing and even remembering recent events.^22
These are called sickness behaviors, and it’s a phenomenon
well known to farmers, zookeepers, and scientists.
Psychologists believe this to be a motivational state—an