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Steven R. Gundry, MD

Updated: 02/02/2022

Inflammation may start in the gut, but it can spread to the brain. Luckily, diet tweaks can help heal them both.

Have you ever taken a few long, deep breaths in a moment of stress and noticed how much better you feel? Anytime you consciously use your breath to calm yourself down, you’re accessing your vagusnerve — a nerve that starts at your brain stem and winds its way through your body, coiling itself around your heart and your gut. The vagus nerve plays a critical role in the microbiota-­gut­-brain axis — it is a key communication channel used for the cross talk between the brain and the microbiome.

Vagus Nerve: A Landline

The vagus nerve is involved in an incredible amount of regu­latory activity — it helps to modulate inflammation, regulate your hunger and satiety levels and monitor your energy needs. Think of it as a landline for microbe­-gut­-brain chatter; it physically con­nects one part to the other in communication. The vagus nerve doesn’t only send signals downward from the brain; it’s a bidirec­tional nerve pathway that also picks up signals from your gut and broadcasts them upstairs, likely via newly discovered cells called neuropods that project off your gut lining. If these cells detect a leaky gut, the signal is sent to your brain — “It’s chaos down here!” — and the brain responds by signaling for your immune system to investigate. And just like that, inflammation is ignited in the gut while simultaneously started in the brain.

Cytokines: A Wireless Network

While the vagus nerve is the landline of the microbiota­-gut-­brain axis (an actual cord connecting the two), there is a second, “wireless” kind of network that facilitates communication as well: free-­floating inflammatory cytokines that have launched into your bloodstream as a result of leaky gut. These cytokines can cause real trouble when they make their way past another important barrierin your body — the one that protects your brain, also known as the blood­-brain barrier. This critical border is made of cells that allow in needed materials — such as glucose, oxygen, amino acids and hormones, as well as protective gasotransmitters — while keeping unwanted or hazardous matter out. In between the cells of this border are — you guessed it — tight junctions that ensure nothing sneaks through, just like in your intestine. The barrier also has controllable pores called aquaporins that move water in and out.

The walls in your intestine and your brain are similar enough that they are susceptible to the same type of breaching from di­etary and environmental assaults — and suffer from the same re­sulting inflammation. For example, it's known that the Western diet (high in sugar and saturated fat and low in microbe­-feeding fiber) impairs the integrity of the blood­-brain barrier and weak­ens cognition and memory by causing dysfunction in the part of the brain assigned memory duties, the hippocampus. Alarm­ingly, glyphosate — the leaky­-gut-­inducing ingredient in Roundup and similar herbicides — also has been shown to weaken the blood­-brain barrier.

"A diet that is high in sugar and saturated fat and low in microbe­-feeding fiber impairs the integrity of the blood­-brain barrier and weak­ens memory."

Lectins: A Cause of Inflammation

Now for the lectins (a kind of plant protein that protects plants from being eaten). It has been proved that the loss of brain­-barrier integ­rity may also be caused by P­-glycoprotein dysfunction. What are P-glycoproteins, you ask? A class of lectins called aquaporins — yes, that’s right, the same type of compounds that populate your blood­-brain barrier and your gut wall! In nature, aquaporins are found in a variety of plants, including spinach, corn, potatoes, soybeans, green bell peppers and tobacco.

In certain people, a leaky gut and a tendency toward sensitivity to these lectins can cause the immune system to develop antibodies to the lectin aquaporins in food... which can then lead it to mistakenly attack the aquaporins in the gut wall and brain. Now before you panic about eating spinach, take note: Most of us don’t react to the aquaporins in spinach. But in some tricky cases, the sophisticated testing I use in my clinic has re­vealed that these aquaporin­-containing foods are a hidden cause of a patient’s leaky gut and brain, and removing them makes a sur­prisingly big difference.

It is important to recognize that disruptions in the blood­-brain barrier and resulting brain inflammation are also related to the epidemic of neurological issues affecting all ages today, from dementia and Alzheimer's to autism, depression, and schizo­phrenia, as well as some neurological diseasesthat have an im­munologic component like multiple sclerosis. Thus, removing inflammatory chemicals and cleaning up your diet can heal and seal your blood­-brain barrier, so it certainly seems worth the effort. Because whether the signals to your brain to “launch the inflammatory defenses!” have come via the landline (your vagus nerve) or wirelessly (cytokines slipping through the blood­-brain barrier), the resulting response in our brain can be devastating in both the short­ and long­term.

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