You go to a salad bar. Everything looks so colorful, crispy, and tasty. You don’t know it and can’t see it, but there may be some fungus lurking or even a parasite right inside that healthy-looking lettuce or shredded carrots or in that pile of garbanzo beans. It may have come from the hands of a food handler back in the kitchen who wasn’t wearing gloves. They may not know they are contaminated. Or they may not have washed their hands adequately. Or it may have come in from the water the veggies were washed with.

You swallow, and these pathogens first enter your stomach. Ideally, your parietal cells make sufficient stomach acid. This means there is an adequately healthy, harsh, acidic gastric environment that will do these bugs in. Remember, a critical job of hydrochloric acid is to eradicate pathogens that gain entry into us through food or water.

Let’s say that you’re on acid blockers, or you’re in your mid-60s, or going through a divorce with huge stress and mounting bills—all conditions that can be linked to insufficient stomach acid production. Sadly, some pathogens make it on through from your stomach into your upper intestines and your duodenum.

Infection by giardia parasites (giardiasis) is a common problem in the U.S. because these parasites can be found in municipal water supplies, whirlpool spas, swimming pools, and streams and lakes. The giardia first bumps into your intestinal mucosa, which is mucus merged with epithelium cells that make up your gut wall. Together, their job is to fight off microbial invasion, like this giardia.

Digestion is a two-part job—absorption and protection. The mucosa fiercely defends your wellness. It’s where your body’s largest population of immune cells live. The mucosa is lined with finger-like villi and microvilli for absorption of nutrients. But these villous projections and their underlying tissues also protect.

Scattered along the mucosa are Peyer’s patches—clumps of lymphoid tissue imbedded with a mixture of protective immune cells (T and B lymphocytes, macrophages and dendritic cells). One of the key functions of the Peyer’s patch is to “sample” whatever has gotten into your gut to discern if it’s a “friend” or “foe.” For the Peyer’s patch to accomplish this tasting maneuver, it has a much thinner layer of mucus than its adjacent tissues. This allows the “tongues” from the dendritic cells, which live in the patches, easier access to taste what’s going on between epithelial cells.

Let’s say they start tasting that giardia. Dendrites from the dendritic cells inside the lymph tissue “lick” some of the giardia cells and, if they do their job right, they find these foreign cells to be dangerous. The dendritic sampling then sends out warning signals to other specialized cells of your immune system. For example, particular phagocytic cells (called M cells) now rally to help. Your gut can also up-regulate (promote the production) of other protective cells called T regulatory cells (Treg for short).

Treg cells are immune system ZEN cells. They are very good at telling good from bad and keeping balance and calm, all the while avoiding nasty inflammation in your immune system. Tregs enter like the proverbial cavalry, coming to save the pro-inflammatory day. Thus, lymphoid tissue is set up to defend us from pathogens. But it also wears several hats. Lymphoid gut tissue can also help the body create healthy tolerance to harmless microbes and to essential foods that we require daily to stay alive.

Once informed of the giardia, appropriately responsive Treg cells migrate over to the lamina propria inside the villi. There they promote the secretion of anti-inflammatory and immune supportive cytokines, molecules made by the immune system. The most protective anti-inflammatory cytokine boosted by healthy Tregs is named interleukin 10, better known as IL-10. It protects the epithelium against damaging inflammation from giardia. It also protects against potential inflammatory cytokines produced by the skirmish as phagocytes rush in to engulf and kill the invading giardia.

Treg cells triggering high levels of IL-10 are critical to protect the gut from the inflammatory processes that could be set into motion by giardia entering its terrain. But you can have faulty Treg cells. Oy. Defects in Tregs can lead to insufficient levels of protective anti-inflammatory IL-10. Your gut is then exposed to an excess of pro-inflammatory cytokines (Il-6, IL-12, and IL-23). These hit the gut wall like a jackhammer. Damage, damage, damage.

That salad bar lunch you thought was such a healthy choice is now causing you to have loose stools, perhaps even bloody stools, bloat, cramping, and pain. Maybe even brain fog and aching joints. Possibly more issues in your tissues. Yet you have no idea that all these symptoms link back to that bug your gut just can’t fight off in its deepest recesses.

Research is suggesting this is how diverse cases of inflammatory bowel disease or other serious gut disorders get started. A pathogen gets in “too deep” inside the intestinal terrain. Maybe it gets in from a salad bar or swimming in contaminated water or even from kissing a stranger who has severe gum disease, and an unhealthy oral biome, and if you also have a Treg glitch, or excessive exposure . . . boom! A dangerous process silently starts.

Continual exposure to unhealthy bugs that aren’t identified or treated effectively, insufficient stomach acid, lengthy protocols of acid blockers, too many rounds of antibiotics (though not all antibiotics are culprits), other gut damaging medications, genetic glitches, and nutraceutical insufficiencies can ALL promote out of balance inflammation. This may stealthily set the scene for serious bowel disorders or even systemic diseases that don’t seem to go away no matter what you do or what experts you work with..

The best defense against parasitic infection? Make sure your gut is working as it should!