Gut: The Inside Story of Our Body’s Most Underrated Organ

by Giulia Enders

A more thoroughly researched medical question is that of when a tonsillectomy can or should be carried out. The answer turns out to be—not before the age of seven. Seven is the age by which we have probably seen it all, or all that is important for our immune cells:

Those who need to burp while lying down can make the process easier by lying on their left side. So, if you’re kept awake at night by a bloated stomach and you are lying on your right side, the best thing to do is simply to turn over.

Alcohol can multiply the number of gas-producing bacteria by a factor of up to a thousand.

As soon as we eat something, the liver and pancreas begin to produce these juices and deliver them to the papilla. These juices contain the same agents as the laundry detergent and dish soap you can buy from any supermarket: digestive enzymes and fat solvents. Laundry detergent is effective in removing stains because it “digests out” any fatty, protein-rich, or sugary substances from your laundry, with a little help from the movement of the washing-machine drum, leaving these substances free to be rinsed down the drain with the dirty water.

So, wholegrain bread is not a sugar explosion, but a beneficial sugar store.

Incidentally, our body has to work much harder to restore a healthy balance if a sugar onrush comes suddenly. It pumps out large amounts of various hormones, most importantly insulin.

One way the body does this is by relinking the molecules to form long, complex chains of a substance called glycogen, which is then stored in the liver. Another strategy is to convert the excess sugar into fat and store it in fatty tissue. Sugar is the only substance our body can turn into fat with little effort.

Fat is not soluble in water—it would immediately clog the tiny blood capillaries in the villi of the gut and float on top of the blood in larger vessels, like the oil on spaghetti water. So fat must be absorbed via a different route: the lymphatic system.

Beans may be lacking in methionine, but they are packed with lysine. A wheat tortilla with refried beans and a yummy filling will provide all the amino acids the body needs for healthy protein production.

There are plants that do contain all the necessary amino acids in the necessary quantities. Two of these are soy and quinoa, but others include amaranth, spirulina, buckwheat, and chia seeds.

Symptoms like regular stomachaches, repeated bouts of diarrhea, or severe fatigue do not occur for no reason, and nobody should be expected to just accept them as “one of those things.”

Those who find types 3 or 4 in the toilet bowl may also want to observe how quickly their feces sink in water. Ideally, they should not plummet straight to the bottom, as this would indicate the possibility that they still contain nutrients that have not been digested properly. Feces that sink slowly contain bubbles of gas that keep them afloat in water. These gas bubbles are produced by gut bacteria that mostly perform useful services.

We begin practicing swallowing as unborn babies in the womb. We swallow up to one pint (half a liter) of amniotic fluid a day during this test phase. If something goes wrong at this stage, no harm is done. Since we are completely surrounded by liquid, and our lungs are full of it anyway, we are unable to choke in the normal sense.

Emotions like fear or stress can reduce the ability of the smooth muscle to stretch, making us feel full—or even nauseous—after eating just a small portion of food.

Simple carbohydrates such as sponge cake, rice, or pasta make it through to the small intestine pretty quickly. There, they are digested and rapidly cause an increase in the levels of sugar in our blood.

This explains why we often fancy a sweet dessert after eating meat or fatty, fried foods. Our blood sugar levels are impatient and want to rise quickly, and dessert provides a quick blood sugar fix. Meals rich in carbohydrates may perk us up more quickly, but they do not keep us feeling full for as long as meaty or fatty meals.

There is only one unequivocal exceptional case when it does not see a digestive project through to the end: when we throw up. The small intestine is quite pragmatic when we need to vomit. It does not invest work in something that will not do us any good. It simply sends such stuff straight back by return mail.

An hour after the small intestine has digested something, it begins the cleanup process.

Everyone has heard their little housekeeper at work. It is the rumbling belly, which, contrary to popular belief, does not come mainly from the stomach, but from the small intestine.

Our bellies don’t rumble when we’re hungry, but when there is a long enough break between meals to finally get some cleaning done!

Constant snacking means there is no time for cleaning. This is part of the reason some nutritional scientists recommend we leave five hours between meals.

The large intestine is the tranquil home of our gut flora, which deal with anything that gets swept into the large intestine undigested.

When we are anxious, our brain jockeys the large intestine along, leaving it without sufficient time to reabsorb all that fluid. The result is diarrhea.

The cake’s journey from fork to toilet takes one day on average.

Leisurely digesters should not worry as long as the consistency of their bowel movements is fine and they have no other complaints. On the contrary, one Dutch study showed that those who belong to the once a day or less faction and those who have occasional constipation are less likely to contract certain rectal diseases.

Reflux is the regurgitation of gastric acid and digestive enzymes into the pharyngeal area; in the case of heartburn, those juices travel no farther than the end of the esophagus, causing a burning sensation in the chest.

Practical tips to help with heartburn and reflux are based on trying to get those two nervous systems back on the right path. Chewing gum or sipping tea can help the digestive tract because small, repeated swallows help nudge the nerves in the right direction—down toward the stomach, not back up.

Cigarette smoke stimulates areas of the brain that are also activated by eating. This may lead to a sense of satisfaction, but it also tricks the brain into producing more gastric acid for no practical reason, as well as causing the sphincter between the esophagus and the stomach to relax. This is why giving up smoking often helps reduce reflux and heartburn complaints.

Neutralizing stomach acid should not be used as a long-term strategy, however. Stomach acid is useful for combating the harmful effects of allergens and bacteria from our food, and is instrumental in digesting proteins.

Vomiting is not a stomach stumble: it happens according to a precise plan.

The brain responds to the alarm, activates the area responsible for vomiting, and switches the body to emergency mode.

We turn pale as the blood drains from our cheeks and is sent to the abdomen. Our blood pressure drops and our heart rate falls.

we feel that unmistakable sign: saliva, and lots of it. The mouth begins producing saliva in great quantities as soon as it receives information from the brain about the emergency that’s underway. This saliva is meant to protect our teeth from the corrosive ...

Our lungs take a particularly large breath before our airways are closed. The stomach and the opening to the esophagus suddenly relax and—bam!—the diaphragm and abdominal muscles abruptly press upward, squeezing us like a tube of toothpaste.

Currently, the best explanation of motion sickness is this: when the information sent to the brain from the eyes is at odds with that sent by the ears, the brain cannot understand what is going on and slams on every emergency brake at its disposal.

When a passenger reads a book in a moving car or train, their eyes register “hardly any motion,” while the balance sensors in the ears say “lots of motion.”

When people throw up from nerves, it is simply their digestive tract trying to do its best to help.

1. For travel sickness, keep your eyes fixed on the horizon far ahead. This helps the eyes and balance sensors coordinate their information better.

Doctors do not know how or why P6 works. The point is located two to three finger-breadths below the wrist, right between the two prominent tendons of the lower arm.

The best results are produced by psyllium seed husks and the rather more pleasant-tasting plum. Both contain not only fiber, but also agents that draw extra fluids into the gut—making the whole business smoother.

There are two kinds of fiber: water-soluble and insoluble. The latter is better at stimulating movement through the digestive system, but it can often cause stomachaches. Water-soluble fiber does not provide quite such a powerful push, but it does make the contents of the gut softer and easier to deal with.

The gut not only possesses an unimaginable number of nerves, those nerves are also unimaginably different from those of the rest of the body.

Were the gut solely responsible for transporting food and producing the occasional burp, such a sophisticated nervous system would be an odd waste of energy. Nobody would create such a neural network just to enable us to break wind. There must be more to it than that.

Regions they can end up in, however, include the insula, the limbic system, the prefrontal cortex, the amygdala, the hippocampus, and the anterior cingulate cortex. Any neuroscientists reading this will be up in arms when I roughly define the responsibilities of these brain regions as, respectively, self-awareness, emotion, morality, fear, memory, and motivation. This does not mean that our guts control our moral thinking, but it allows for the possibility that the gut might have a certain influence on it.

The vagus nerve is the fastest and most important route from the gut to the brain. It runs through the diaphragm, between the lungs and the heart, up along the esophagus, through the neck to the brain.

If the brain permanently thinks it is in an emergency situation, it begins to take undue advantage of the gut’s compliance. When that happens, the gut is forced to send unpleasant signals to the brain to say it is no longer willing to be exploited. This negative stimulus can cause fatigue, loss of appetite, general malaise, or diarrhea.

The altered circumstances stress creates in the gut allow different bacteria to survive there than in periods of low stress. We could say stress changes the weather in the gut. Tough guys who have no problem with turbulence will reproduce successfully—and at the end of the day they are not likely to spread good cheer in the gut. If this theory is true, that would make us not just the victims of our own gut bacteria, but also the gardeners of our inner world. It would also mean that our gut is capable of making us feel the negative effects long after the period of stress is over.

The researchers gave the mice a cocktail of antibiotics that affect only the gut, wiping out their entire gut flora. They then fed the animals with gut bacteria typical of the other strain. Behavior tests showed they had swapped roles—the BALB/c mice became more gregarious and the NIH Swiss mice were more timid. This shows that the gut can influence behavior—at least in mice.

The earlier in life mealtime calm is introduced, the better. Stress of any kind activates nerves that inhibit the digestive process, which means we not only extract less energy from our food, we also take longer to digest it, putting the gut under unnecessary extra strain.

Lactobacillus plantarum and Bifidobacterium infantis could already be recommended as a pain treatment for patients with irritable bowel syndrome. Many patients with a low pain threshold in the gut currently take substances designed to treat diarrhea, constipation, or cramps. That might help with the symptoms, but it does not address the cause of the problem.