Have you ever found yourself thinking, \u201cI don\u2019t feel sick, exactly. I just don\u2019t feel \u2026\u00a0right?\u201d<\/p>\n
If so, odds are that you\u2019re correct \u2014 and it may have something to do with the gut-brain axis. This connection between your digestive tract and central nervous system allows your brain and gut to communicate with and influence each other constantly.<\/p>\n
But how does it work? How would you know if yours is not functioning well? And, is there anything you can do to support the gut-brain axis?<\/p>\n
We went to Xiling Shen, Ph.D.<\/a>, a gastrointestinal medical oncology researcher at UT MD Anderson<\/a> who is studying the gut-brain axis<\/a>. Here\u2019s what he shared.\u00a0<\/p>\n What\u00a0is\u00a0the\u00a0gut-brain axis?<\/p>\n The gut-brain axis is how the brain monitors what\u2019s happening in the digestive tract.<\/p>\n The brain and spinal cord make up the central nervous system. The nerves that stretch down into the gut and other areas of the body make up the peripheral \u2014 or outlying \u2014 nervous system.<\/p>\n \u201cBut the gut-brain axis involves more than just the gut (the tube that stretches from the mouth to the anus),\u201d Shen explains. \u201cThe peripheral nervous system reaches into every organ that\u2019s involved with digestion, including the liver, gallbladder and pancreas.\u201d\u00a0\u00a0<\/p>\n What is the significance of the gut-brain axis?<\/p>\n Historically, it\u2019s been easy for doctors to dismiss vague concerns like, \u201cI\u2019m not really sure what\u2019s wrong. I just know I don\u2019t feel well,\u201d as imaginary. Now, scientists understand a bit more about how the brain and body interact, so they can recognize that some of these complaints are valid.<\/p>\n \u201cThe connection between the gut and the brain is considered so significant today that the gut is sometimes referred to as \u2018the second brain,\u2019\u201d says Shen. \u201cIt might be more accurate to call it \u2018the first brain,\u2019 though, since even the simplest organisms have to eat and process their food. The gut had to evolve first, before the brain.\u201d<\/p>\n So, can your gut\u00a0status\u00a0affect your mental health?<\/p>\n Absolutely. \u201cThe neurons in your gut actually make up the largest portion of the peripheral nervous system,\u201d says Shen. \u201cAnd, most of the serotonin your body makes is produced in the gut.\u201d<\/p>\n Serotonin is a chemical that acts as a neurotransmitter in the brain and a hormone in the body. It carries messages between nerve cells and helps regulate our moods.<\/p>\n \u201cWhat we are finding is that many people who\u2019ve been diagnosed with clinical depression<\/a> also have chronic gut problems,\u201d Shen says. \u201cThe toxic protein clumps that are characteristic of several degenerative brain disorders<\/a> \u2014 like Parkinson\u2019s disease and mad cow disease \u2014 often show up in the gut before the brain, too. We can actually see the neurons there. So, these are real, physical connections.\u201d\u00a0<\/p>\n How does the gut-brain axis work?<\/p>\n Scientists don\u2019t have all the answers to that just yet. But we do know that the gut-brain axis is a two-way street. So, messages can travel in both directions.<\/p>\n Afferent nerve signals travel up to the brain from the gut. \u201cI think of them as cameras and microphones that let the brain know what\u2019s going on down there,\u201d says Shen. What happens when the gut-brain axis malfunctions? Are there any symptoms?<\/p>\n There\u2019s no one tell-tale sign. But here\u2019s an example: The myelin sheath that protects your nerve cells is made up of fats<\/a> that are regulated by metabolism<\/a>. They act as an insulator to protect the electrical signals that travel back and forth. Those sheaths are constantly being recycled and replaced. But if you don\u2019t have a healthy gut-brain axis, that recycling process could be disrupted.<\/p>\n \u201cThis may result in \u2018leaky\u2019 signals, so the neurons have to work extra hard to send them,\u201d Shen explains. \u201cIf the neurons become exhausted, that could start a domino effect, and you\u2019ll end up with other health problems, too. All of these things are connected.\u201d\u00a0<\/p>\n How can\u00a0I\u00a0improve\u00a0my\u00a0gut-brain axis?<\/p>\n Metabolism depends on our digestive organs as well as the bacteria and microbes that live inside us. These are what actually consume our food and help us absorb the nutrients they contain.<\/p>\n \u201cThe gut-brain axis senses all of those elements, too,\u201d notes Shen.<\/p>\n One way to support it is by eating more fiber<\/a> and less sugar<\/a>. That\u2019s because fiber is harder to digest, so much of it arrives intact in the colon, where it provides food for the good bacteria that live there.<\/p>\n \u201cAll of the sugars get absorbed fast by the small intestine, so the good bacteria rely on fiber for their nourishment,\u201d Shen explains. \u201cIf they can\u2019t find any, they start digging into the lining of the large intestine to feed themselves. That can lead to leaky gut syndrome and a host of other problems.\u201d<\/p>\n Fiber also helps with bowel regularity. The gut moves when it feels pressure. So, if there\u2019s not enough volume to your food, you won\u2019t feel that stimulus. This can result in constipation<\/a>.<\/p>\n If the good bacteria die off due to a lack of food, it can also give the bad bacteria a chance to take over<\/a>. So, the right diet can support the gut-brain axis by helping the good bacteria outcompete the bad. Our dietitians recommend filling two-thirds of your plate with vegetables, fruits<\/a>, whole grains<\/a>, beans<\/a>, nuts<\/a> and seeds<\/a>. The remaining one-third can be lean animal protein<\/a> or plant-based protein<\/a>.<\/p>\n Can you reset\u00a0the\u00a0gut-brain axis?<\/p>\n Not exactly. But several methods are available to help physicians improve it. These include:<\/p>\n Probiotics to repopulate the gut<\/a> with healthy bacteria<\/a> \u201cUnder severe disease conditions, a good diet<\/a> has a limited impact,\u201d Shen explains. \u201cSometimes, you need stronger interventions.\u201d\u00a0<\/p>\n How does the gut-brain axis relate to cancer treatment?<\/p>\n Cachexia, or wasting syndrome, is a serious, sometimes irreversible condition that contributes to about a third of all cancer-related deaths. It causes the severe, involuntary loss<\/a> of both fat and muscle, despite efforts to increase calorie intake. Until now, there has been no effective treatment.<\/p>\n But Shen and some of his colleagues are exploring ways to change that. A clinical trial<\/a> featuring the new vagal block electroneuromodulation therapy Shen and his colleagues developed will be opening at UT MD Anderson in May 2026, under the leadership of GI medical oncologist Brandon Smaglo, M.D.<\/a><\/p>\n And Shen recently published a study<\/a> in which LIPUS was used to reduce the inflammation that contributes to cachexia, alleviating some of its symptoms.\u00a0\u00a0<\/p>\n \u201cThe vagus nerve<\/a> regulates the parasympathetic nervous system, which calms you down when you get upset,\u201d notes Shen. \u201cWe developed a wearable skin patch that\u2019s applied to the right side of the neck, where the right vagus nerve is located. By blocking its hyperactivation, we were able to restore liver function, enhance patients\u2019 appetite<\/a>, and reduce systemic inflammation, all of which contribute to cachexia.\u201d\u00a0<\/p>\n
\nEfferent nerve signals travel down from the brain to the gut. \u201cI think of these as loudspeakers that can override the gut\u2019s normal function by issuing new orders,\u201d Shen adds.\u00a0<\/p>\n
\nAnti-inflammatories to calm the system down
\nNeuromodulators, like beta blockers and Botox, to regulate nerve sensitivity
\nLow-intensity pulsed ultrasound (LIPUS), a non-invasive therapy that reduces inflammation<\/a><\/p>\n