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

Cover of the book Gut the inside story of our body's most underrated organ by Giulia Enders

Why read this

  • To learn about why you may feel the need to eat certain foods and not others;
  • To know more about the mind-body connection and how your decisions are being influenced by your gut;
  • To learn how to correctly poop, and discover many other curiosities that should help you in your daily life to make smarter decisions for your health.

Why listen to the author

  • Enders is enrolled on a PhD in gastroenterology at Goethe University in Frankfurt, Germany.



Gut (Charming Bowels): The Inside Story – Book Summary

by André D. Ferreira

Reading time: ~14min.

Poop Like Your Ancestors

Pooping in the deep squatting position is the healthiest position. We have a kind of tendon that helps to close the sphincters in the rectum. The closer to the standing position we are, the straighter that tendon is and the more it pulls the end of the intestine, like a thread trying to cut a pipe, reducing the area through which the feces can pass. By deep squatting, as humans always did except until some 200 years ago, the channel becomes straight and wide open.

Those who defecate sitting take sensibly twice as long as those who do it deep squatting. Enders goes as far as suggesting that our current defecating position may be one of the reasons for hemorrhoids and other similar problems. A simple solution to simulate deep squatting on the toilet is to put a support below the feet to raise them, and tilt the trunk slightly forward. Statistically pooping 3 times per week is normal, that is, day in, day out.

Fat is Good. Just Not Too Much

Fat is the best way to concentrate energy (that is, it has the highest energy density, energy / gram). We can think of fat like smartly folded and organized carbohydrates molecules, resulting in a very compact molecule. In the history of human being there have always been periods of hunger, and the fat stored in fat cells meant having life insurance.

But fat has a feature. It is not soluble in water. So it cannot be absorbed and transported in the same manner as the other nutrients and energy sources (glucose), in the blood, or it would float in it as oil floats in water. That’s why we have a specialized fat transportation system — the lymphatic system — whose sole function is to transport fat.

Avoid Eating Grains

Grains / cereals do not want to be eaten. After all, they are the offspring of plants. And effectively for a long time humans did not eat cereals. Only recently have they entered  in our diet. In the US 1 in 100 has celiac disease (meaning that, among other things, gluten can be found in their blood) but many more have celiac sensitivity. The disease can have periods of more or less sensitivity. This sensitivity may be exacerbated by things such as alcohol or stress. When people with this disease stop eating bread and other things with gluten they start to feel better digestion, diarrhea passes, they can focus, among others (see the book “Grain Brain”).

Eat Lactose and Fructose Up to a Limit

Lactose and fructose intolerance are different from celiac disease. The lactose and fructose are sugars. When bacteria and enzymes responsible for breaking lactose into glucose and fructose are overloaded, they are undigested and do not go into the blood. Instead, they follow the path through the small intestine and will be used as food for certain bacteria in the large intestine that can cause gas or abdominal pain. This overload can happen if you ingest too many of these sugars or reduce the number of these bacteria with antibiotics or stress. We all lose some ability to digest lactose as we age but always stay with some and therefore small amounts of lactose are not necessarily bad. The upper daily limit Enders gives is 50 g of fructose which corresponds to about 5 fruit pieces (with no further supply of fructose).


About Vomiting

Before we vomit have you noticed that you tend to salivate more? That’s because it is a way that the human body arranged to protect the precious teeth from the stomach acids that are coming. We should trust the vomit instinct when we have it. The stomach has virus bacteria and harmful substances receptors, that when they sense a too high concentration of those send to the brain sends to stop the party and activates the button to send it all out because the sensors believe the food that is in the stomach does more harm (work to have to eliminate these harmful elements) than good (nutrients that the food would bring).

Saliva is Filtered Blood

Saliva. Did you know it isn’t much more than filtered blood? That’s why there are saliva tests – to know some of the same information can be obtained by blood, and that is also why there saliva-transmissible diseases. Saliva has antibodies and antibacterial substances, hormones, and certain minerals that are not filtered from the blood. The salivary glands release saliva in 4 points inside our mouth. You can feel them, if you want, with your tongue. There are 2 at the top of the cheeks (you should feel little bumps) and other 2 under the tongue.


Digestion works best when there aren’t stress hormones in the blood. Orally taken medicine pills often need to have a greater amount of the active substance as compared to suppositories because the liver eliminates a large part of it before it is absorbed. It also takes longer to be absorbed. This is why, not to overload the liver, children and elderly are many times given suppositories.

What Are Feces?

What are feces? (4/4) Feces = (3/4) water + (1/12) bacteria + (1/12) fibers + (1/12) unwanted substances. So 3/4 are water and the rest is solid matter. Of this solid matter 1/3 are bacteria of the intestinal flora which have already fulfilled their duty, the other 1/3 are undigested fibers and therefore can vary in proportion depending on the amount of them that eat and the other 1/3 are substances that body wanted to throw out like cholesterol and medications.

What is Diarrhea and Analyzing Your Stool

After a diarrhea the intestine takes 3 days to be filled, only at the 3rd day do the feces reach the final part of the large intestine. After a diarrhea you should take a pro-biotic to repopulate the intestinal flora. The diarrhea was like a tsunami for the healthy population of bacterias. Many of them were washed away or killed. This can be noted by the color of feces. The stool consistency, classified with the Bristol scale, may also be useful for diagnosis. Here’s a website to help you analyze your feces.

Fibers. There are two kinds: soluble and insoluble. The insoluble are aggressive to the intestines while the soluble are an in-between the insoluble and no fiber. These make the stools softer. They help to circulate them in the intestines. An example of a fruit with plenty of fiber are plums.

We Need Bacteria to Survive

We have about 2 kg of bacteria in our digestive system. The author goes so far as to call them a “microbial organ”. The bacteria that live in our digestive system are really important. For example, you give one rat intestinal bacteria from a mouse overweight, the mouse that received gain weight. The concentration of these bacteria increases the more to the end of it we go.

The author talks about that rigmarole that is told to children to help them eating: “A spoon for Grandpa … Another for grandma … This is for Uncle …” She suggests an alternative version: ” this is for Bacteroides … this is for the Prevotella … ”

We have most of the bacteria in the large intestine. The food that they get is already mostly digested and so the bacteria do not steal anything that is ours. Unlike us, the cows’ bacteria are well on beginning and they are the ones actually eating the vegetables (grass, etc). After eating the vegetables they become food for the cows! So the grass that cows eat is to feed the bacteria, which is their real food. We humans, simply throw them away.

Yogurt is milk pre-digested by bacteria. They leave the lactose in a simple sugar and lactic acid that gives hard consistency to yogurt (coagulates the protein). Thus yogurt saves work to our digestive system compared to drinking milk.

Breast milk is important for babies. It is the most important food supplement, by far. It has all the nutrients they may be lacking and still passes part of the immune capacity of the mother to child. Babies born by vaginal delivery are exposed to a cocktail of bacteria in the vaginal canal that makes life easier for their immune system. This is because the babies’ immune system can practice and create defenses for future threats. Only after the 7th year is that there are noticeable differences between immune systems of a child who was born by Caesarean section and another for normal delivery.

Mind-Body Connection

The supremacy of the brain as the dominant organ is starting to be questioned. The intestine has the 2nd highest concentration signaling substances and network of nerves of the human body. In fact, the intestine and the brain have a highway nerve that directly connect them, the vagus nerve. It was found that, when cut, the state of the intestines no longer have influence on the emotional state of the person. Let’s see a few ways in how they use this direct communication channel.

People with irritable bowel tend to feel more anxiety and / or depression. Indeed, whenever the intestine passes a certain level of discomfort, it sends a message to the brain saying it — “Man this here is not right, see if you can do something.” Inadequate intestinal flora, micro infections, and undiagnosed food intolerances are excellent examples of other things that can make the intestines pass this level of discomfort.

Also the brain talks to the gut and asks it things. One of the subjects on which there is more dialogue is about stress. When we get in the state of fight or flight or when the brain needs energy because we are concerned or thinking too much about our problems, it can ask the gut stop what they’re doing — Hey man I really need some blood in here, I have so many things in line to think about… Can you spare some? — So the intestines get on with the digestion quicker (diarrhea) or if the case is severe, the intestines go to emergency mode — stop digestion altogether and possibly order the stomach to get it all out. However, when a person is constantly stressed, the intestine begins to care less about what the brain tells it — Yeah you keep asking for blood, just wait, will you? It’ll be finished soon — or it would not do any proper digestions. And that’s when the person feels tired or depressed.

Moreover stress changes the weather conditions inside the intestines so that, as time passes, only a certain type of bacteria survive (which aren’t as good functioning). Because of this, the meals and our digestion periods should be exempt of stress.

It’s amazing the interconnectedness of the human body mechanisms. The inflammatory status of our body tells the rest of the body to put on weight in the case of what is causing the inflammation worsens. That’s why many people overweight end up also reveal inflammatory markers above normal, which are the true cause of the ease in getting fat.

On the other hand some of our appetites for certain foods come from intestinal bacteria that are already too long without their snack. It’s a vicious cycle. The more crap you eat, the more you feed the bacteria that like it, and the more willing to eat that crap you become. In fact if then suddenly you start eating healthy food, it creates a bad feeling because you don’t have many bacteria that help digest that healthy food! (Bacteria help digest food by producing e.g. enzymes).

Dealing With 3 Nasty Life-forms

Let’s learn about the 3 life-forms that cause the most frequent troubles in our digestive system:

Dealing With Salmonella

The next topic concerns salmonella. Enders says that they are the bacteria that cause the most problems. They live in the bodies of certain reptiles. These reptiles by walking through fields of grain leave their waste which is eaten by chickens and other similar animals. Finally they end up in you mouth if the bit of meat you ate was raw (or more precisely if it had not been exposed to at least 75 ° C for 10 min.). Also in chickens the same orifice that is used to lay eggs is the same which they use to poop, so the salmonella can be in the egg shell. Moreover, don’t think that freezing kills bacteria… So wash well all that come into contact with raw food and prefer the use of plastic boards for cutting and food prepping as the wood ones are more difficult to wash.

Dealing With Helicobacter

Another danger. Helicobacter are bacteria living in the stomach of about half of the human population. However there are some bacteria who have a certain gene disabled and thus are harmless. The ones that don’t create long term irritation and will destroy the stomach walls in certain places, causing ulcers. The minority causes more serious problems (1% of people with this bacteria develop stomach cancer because their stomach is constantly restoring the cells that the bacteria destroys, so some end up being created defective — that’s very simply put how cancer develops).

Enders states that there is a simple test by which one can detect whether a person has that bacteria. Their elimination is by antibiotics … Still it raises the question of how was it possible that this bacteria already in cohabits with us for 50 000 years. A logical theory is that it also brings benefits. Some say that they bring immunity benefits, but it is not yet clear.

Dealing With Roundworms

Roundworms and why we should change underwear daily. One of the way worms propagate is by the eggs that lay on the anus and then, because of the itching that it produces, we scratch it. Then, and especially at night, we may inadvertently take our fingers to the mouth or near there and the eggs go into the mouth where they start developing into roundworms again.

Pro and Prebiotics

The following topics are about the pro and prebiotics, which are different things. Probiotics are living beneficial bacteria that we eat. Pre biotics are nutrients that feed the good bacteria that live inside us.


Probiotics are living beneficial bacteria that we can take to temporarily improve our gut’s flora. But how are probiotics and other good bacteria beneficial exactly?

1) Some of them produce fatty acids that protect the intestinal villi, so that they can absorb nutrients to their maximum efficiency and stay healthy longer.

2) They do not leave much room for bad bacteria to establish, because they do not get along. In fact, from time to time, the good bacteria produce antibiotics to ward them out of there.

3) They don’t let bad bacteria feed, especially if it’s food that they like. Hence the importance of constantly making healthy decisions in regards to food.

4) They help against diarrhea, irritable bowel.

5) They help the immune system to be in shape (scientists found that people who take probiotics catch fewer colds and the ones they do catch are less severe).

However, most of the probiotics must be taken regularly because these bacteria do not settle for a long time inside us. They’re like very well-meaning tourists. So it’s been more of a treatment than a thing to stay. But the author says that this is changing and so we should pay attention to the market.


Prebiotics are more suited to daily life as they strengthen our good bacteria that are actually established inside us. An example of a prebiotic are natural fibers. But we should not start eating lots of fiber suddenly since it would cause a sudden uprising in flora, as they wouldn’t be used to it. There are also pre biotics for sale in the pharmacy, but this is an area far less developed than the pro-biotics.

About Hygiene

Then Enders raises an interesting point of view. Eliminate all bacteria from our life is not necessarily beneficial. In fact, from a certain perspective, the higher a country’s hygienic standards, the higher the number of allergies and autoimmune diseases therein. The author argues that hygiene should be more about reducing the number of bacteria, not eliminating them completely (except in cases of sick people) since not only 95% of them are harmless, but few of them serve for the immune system to practice. For example a few thousand salmonella are child’s play to our immune system. The problem is when they’re millions. Domestic hygiene is based on either one or a combination of these things: 1) diluting; 2) drying; 3) heating and 4) cleaning.

1) Diluting means basically reducing the concentration of the bacteria until it reaches a point where it is too low in number to do harm, and our immune system can take care of it. Ventilate the room of the house, run water over the food. Sponges and cloths would traumatize those who saw them under the microscope. They are warm, moist, and have leftover food … What else is missing for life? You should always run the sponges with water after using them to remove large debris, to dilute the amount of food for the bacteria that are there, and to dilute the number of bacteria as well.

2) No water, no life. Some beings die if they dry. Still, even if it doesn’t kill everything, by drying things you are still preventing those that survive to reproduce. Because even if they survive they should be in a hibernation state. This also applies to foods. That’s why foods last much longer in dry conditions as compared to wet.

3) High temperature. A temperature of 50-60 °C kills most of bacteria. That’s the minimum temperature suitable for washing underwear or other clothes that may have many bacteria like towels that are wet for a long time. It takes 70 °C to kill salmonella, and at 75 °C almost all are dead.

4) Cleaning agents. Using detergents either helps washing away (diluting principle) or may kill bacteria.

Understand Antibiotics

Antibiotics. These are meant to kill bacteria, not viruses (viruses are not living things). Antibiotics have the side effect of killing both good and bad bacteria. So one of the things that usually happen very often after taking antibiotics is diarrhea, which contains many of our recently killed intestinal bacteria. This means taking antibiotics changes our intestinal flora (that is bacterial composition).

When you take an antibiotic you’re not killing all the bacteria and those that aren’t, are resistant. So the more antibiotics you take the more resistant to that antibiotic are the bacteria that exist in your intestines. Anyway in cases of serious illness it may be beneficial to take antibiotics and take them early to avoid the worsening of the disease. Then there is also the fact that we may be inadvertently taking antibiotics by eating meat from animals which have taken them to survive in the unclean environments in which they were created.

That’s one of the advantages of organic meat because for meat to be considered bio/organic the animal must not have taken more antibiotics throughout its life that a low limit imposed by a standard. The same applies to fruit shells.

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