Category
📺
TVTranscript
00:00This is not a stomach.
00:30It's a hub of intelligence.
00:35It houses the equivalent of a small pet's brain.
00:40We have 200 million neurons in our gut, about as many as Timmy has in his cortex.
00:46And we can say that Timmy is really very intelligent.
00:52A cat and a dog each have about the same number of nerve cells as the gut.
00:56If they're intelligent, the gut is every bit as smart.
01:02Scientists have some surprises in store for us.
01:05Having rediscovered what common sense has known for a long time, people of a nervous disposition
01:10get butterflies in their stomach, cowards lack guts, and we sometimes act on gut instinct
01:16with the gut feeling of fear in the pit of our stomach.
01:22At times, we get the distinct feeling our brains are not the only captain on board.
01:27But what exactly do scientists know about the interplay between the gut and the brain?
01:37The gut is home, not just to millions of neurons, but also to hundreds of billions of bacteria
01:43that secretly influence our most daring exploits and our personalities.
01:51A voyage into the secret territory of our bowels in search of our second brain.
01:59This story starts at Columbia University in New York City, when Michael Gershon dared to proclaim
02:20that our gut houses a sensitive and intelligent organ.
02:26It's important to focus on the gut, to explain to the world, this is one important organ.
02:32It's not just a repulsive, serpentine, snake-like, disgusting thing, but a vibrant lifeline to success.
02:42So there was a dark age of knowledge of the second brain, and then it was rediscovered, and I helped to rediscover it.
02:50And since it was a renaissance, that makes me the Leonardo of the bowel.
03:00If Leonardo da Vinci had had the chance to use the microscope Michael Gershon uses,
03:04these are some of the neurons he would have observed.
03:07Two hundred million of these neurons line our intestine wall.
03:15They span the length of our digestive tubes, helping us to digest food.
03:29Digestion is surprisingly complicated.
03:33You have to do things that are very hard to do in a laboratory.
03:37Break food down that you eat and make it into tiny little molecules that you can absorb
03:43and use to run your body.
03:45And for that you need a lot of nervous power.
03:53Our two brains resemble each other like brothers.
03:57The upper brain houses the central nervous system,
04:00and the lower brain houses the enteric nervous system.
04:04They even share similar scientific names.
04:12But did evolution really need to equip us with two separate brains?
04:17The reason that evolution would want to have this brain outside is very similar to the reason we all keep
04:26personal computers on our desks.
04:28By peripheralizing it, sending it off to the gut, it's more efficient, more effective.
04:35The brain doesn't have to connect with huge cables to the gut.
04:40It can leave it there.
04:41And you don't have to expand the brain to hold several hundred million more nerve cells.
04:56And you don't have to connect with each other.
05:01Scientist Michel Nunlist, who is based in Nantes in western France,
05:06is one of the world's leading experts on the enteric nervous system.
05:09For Michel, in the history of our two brains, the first brain is not the one we think it is.
05:14The second brain has had its name usurped, really, because I consider it to be the first brain,
05:22the original brain even.
05:23Primitive, multicellular organisms were initially composed of just a digestive tube.
05:29The enteric nervous system developed within this digestive tube.
05:32If we travel back in time, it becomes apparent that our upper brain evolved in order to better feed
05:47ourselves. The appearance of the brain coincided with that of eyes and ears useful for seeking food.
06:02Without dividing the tasks up like this, we would still be spending all our energy digesting,
06:08digesting, and digesting some more.
06:17The turning point in this spectacular evolution of our brain is linked to a technological invention,
06:23the domestication of fire.
06:251.5 million years ago, Homo sapiens was still called Homo ergaster, and he had just invented the barbecue.
06:39Cooking is a form of pre-digestion, so thanks to cooking first, chewing became easier,
06:45and we therefore invested less energy and physical effort.
06:48Secondly, when cooked food arrives in the stomach, digestion is easier,
06:53and we can recuperate 16 times more energy with a lot less investment.
06:57As the first brain worked well, the second brain took advantage of that and was able to develop.
07:02In theory, it could not have happened at all, but it did.
07:23Cooking our food meant that we could jump some physiological hurdles, in other words,
07:33the constraints linked to the available energy a large brain needed. And from there, from Homo ergaster
07:39onwards, the first brains, which measured 700 to 800 cubic centimeters, gradually evolved, over hundreds
07:45of thousands of thousands of years, into very large brains, like, for example, those of Neanderthal man or Cro-Magnon.
07:55Cro-Magnon, that's you and me. This brain increased to 1,500 to 1,600 cubic centimeters, without any change in body size.
08:03So our brain evolved, and now we can think of something other than our stomachs.
08:19Thinking on one side and digesting on the other, a neat division of tasks in theory. But as always,
08:26the reality is more complex. Firstly, because our two nervous systems, which are connected by the vagus nerve,
08:35are in constant conversation. Secondly, because the brain and the stomach use the same neurotransmitters.
08:42Neurotransmission is the language that nerve cells speak in order to talk to one another.
08:49And neurotransmitters are the words that each nerve cell puts out that another nerve cell can
08:55understand. Now, serotonin is one of the words.
09:03Michael Gershon has dedicated his life to understanding the meaning of the word,
09:07which changes according to the context it's in. And this is what he has discovered.
09:13In the upper brain, serotonin means well-being. In the gut, it sets the pace for intestinal transit
09:20and regulates our immune system. It is depicted here in red, with the cells of our intestine wall in blue.
09:30But surprising as it may seem, 95% of our body's serotonin is produced in our gut.
09:36This serotonin acts on the digestive tube, but also more surprisingly, it is released into the
09:45bloodstream and acts on the brain, in particular in the hypothalamus, which is a zone that manages
09:50our emotions and takes part in the regulation of emotions.
09:53When the gut and brain converse, the messages they exchange transit via the vagus nerve. But we've
10:06known that for a long time now. What researchers have just discovered is that the serotonin that
10:12transits clandestinely via the bloodstream towards the brain interferes with our emotions in a much more
10:18complex way. Destined for the gut, this surplus of information, which in theory has no real business
10:26being in the brain, can sometimes lead to misunderstandings.
10:33We already knew that our emotions could indeed influence our gut. Now what we're seeing is that
10:38our gut can also influence our emotions.
10:40Under normal conditions, the exchanges between gut and brain take place without us even knowing
10:49about it, making it difficult to study them. But as always in science, by observing what goes wrong,
10:56we can gain a better understanding of how things work.
11:01Irritable bowel syndrome, or IBS, is, unfortunately, an obvious case study for examining the communication
11:08problems that sometimes crop up in the brain-gut couple. It's a very common disease, affecting one
11:15in ten people, and is characterized by severe abdominal pain.
11:22The syndrome is characterized by digestive difficulties, abdominal pain, and a disruption
11:26of transit time, but without us being able to find any so-called organic malfunctions from the various
11:31exams we carry out, whether via colonoscopy, gastroscopy, scan. That's why these people can't
11:37understand what's going on, because we usually tell them, well, we've run extensive tests,
11:41and we've found nothing. And they often say, but doctor, I'm in pain, there's something wrong with
11:46me. So it's important to explain to them that currently, we explain these functional disorders
11:51by malfunctions occurring between our brain and our digestive tube.
12:00What is causing these communication problems?
12:02What is sending out the wrong messages? Our upper brain or our lower one?
12:10These questions are mobilizing researchers all over the world.
12:14In Munich, Michael Scheman considers that IBS could originate in the intestine wall.
12:27Along with his team, he's trying to pierce the mysteries of this neuron-packed
12:31area of intestinal skin that lies at the crossroads of often delicious, but sometimes painful, sensations.
12:39It's hard to believe, but inside this sausage, there's an enteric nervous system.
12:44It's a typical Bavarian recipe, white sausage. And this skin is nothing other than a natural
12:50intestine, which contains the enteric nervous system.
12:53More than just dissecting sausages, the researchers are cutting into intestines.
13:02Their work involves measuring the activity of human intestinal neurons.
13:10We're basing our work on the following hypothesis.
13:13One of the causes of IBS is due to a faulty communication
13:17between the mucosal surface and the gut nerves.
13:25To test this hypothesis, Michael Scheman compares the neuronal activity of the submucosal nerves
13:31of healthy patients with those of ill patients.
13:33And this is the result on an ill intestine.
13:41This film is the very first visual presentation of the signals that are emitted and received
13:46by the nerve cells of our intestine.
13:50It shows that the neurons of ill patients are far more active than those of the healthy population.
13:57We conclude that these patients are indeed suffering from a hypersensitive nervous system,
14:01a sort of intestinal neurosis, if you like.
14:08Michael Scheman hopes his discovery will soon result in a drug that will normalize this neuronal hyperactivity.
14:23In the meantime, at the University Hospital of Grenoble, Bruno Bonaz has observed that the disease
14:29is often brought on by stress or traumatic events.
14:35He uses a more global method to provide relief for his patients.
14:40Do sit down.
14:45Take slow, calm, deep breaths.
14:49You're feeling serene.
14:52You're smiling.
14:55You're feeling very relaxed.
14:57Nice and relaxed.
15:01Why does the stomach bear the brunt of all that?
15:03I think there are lots of things we carry subconsciously in our stomachs,
15:08which is where the idea of working on that area with hypnosis comes from.
15:11Hypnosis can, in particular, encourage phenomena of adjusting to pain.
15:17It means these patients perceive less pain and their state of hypervigilance is reduced,
15:23so they will perceive less pain.
15:25And now you can feel a pleasant feeling of warmth in the area of your stomach around your abdomen.
15:33Concentrate for a while on the gentle, pleasant warmth you feel in your stomach.
15:37Concentrate for a while on the gentle, pleasant warmth.
15:41If you imagine that the gut is sending signals to the brain that are disturbing,
15:48and the brain finds these signals intolerable,
15:52hypnosis can be used to essentially anesthetize the brain to these signals.
15:59So it's getting the same signals that are bad,
16:02but because of hypnosis, they've suddenly become tolerable.
16:07It's getting the same signals that are in the brain.
16:14Although scientists don't understand the exact mechanisms as yet,
16:18neuroimaging has enabled them to localize the effects of hypnosis
16:21on the brains of patients subjected to intestinal pain.
16:30Here you have four cross-sections of the brain.
16:32When you experience abdominal pain, you activate the zones that are represented here,
16:37like the brain stem here, the thalamus, the insular cortex here,
16:44the anterior cingulate cortex, and the frontal cortex.
16:49And we now know that hypnosis can modulate the activation of these zones that are involved in pain.
16:54So it's clear that hypnosis is not just all in the mind,
17:00but is something that has a neuro-anatomical and functional substratum.
17:12Scientists are only just beginning to understand the secret,
17:15silent conversation that takes place between gut and brain.
17:23Our minds are constantly influenced by our body's internal chemistry.
17:28Even our dreams, the most mysterious expression of our inner lives,
17:33are particularly sensitive to the serotonin emission that happens during our sleep.
17:37One is the most mysterious language.
17:41Could the unconscious, the notion discovered back in ancient times and reinvented by Sigmund Freud,
17:47be located in our gut?
17:50The enteric nervous system can affect how you feel by sending signals to the brain
17:59that do not reach consciousness and can change
18:03change the way the brain perceives the world.
18:08Your ability to think happily, your ability to think well, your ability to resist depression
18:15and anxiety can be very influenced by the messages that the gut sends to the brain.
18:23So to that extent, it's a contributor to your unconscious.
18:33If we don't have emotions or feelings, we become completely irrational.
18:43Freud's approach is fascinating because he said, the ego is not master in its own house.
18:48Well, perhaps not in the brain.
18:50And perhaps the ego's house is down there.
18:53So perhaps that ego is in the gut.
18:54Yes, I like that idea.
18:56Gastric psychoanalyst sounds good to me.
19:03For the time being, gastric psychoanalysis is still on the lookout for a founder.
19:15But so striking is the anatomical similarity between our two brains that scientists are
19:20starting to wonder, very seriously, if the stomach and the head might not share their illnesses
19:25as well.
19:31Certain neurological illnesses, like Parkinson's disease, may even originate in the gut.
19:40The University Hospital of Nantes, which receives 2,000 Parkinson's patients a year, is the ideal
19:46place to study the hypothesis.
19:48We're going to do a few small movements to see the current state of your condition.
19:56Can you do this with your right hand?
20:00Give it a little shake like this.
20:03So that's difficult for you.
20:05So in your day-to-day life, that must hamper all your actions, like eating for example.
20:10It blocks.
20:11It blocks.
20:12He can't lift his arm.
20:13He can't lift his arm, so you have to help him.
20:15Yeah.
20:16He can't feed himself.
20:17For a long time, Parkinson's disease was considered to be a condition that destroyed
20:23neurons located in a particular area of the brain known as the substantia nigra, which
20:29is Latin for black substance.
20:32Yet doctors have observed that the disease is often also accompanied by major digestive
20:36disturbances.
20:38Scientists have therefore put forward the theory that it affects not only brain cells, but also
20:43our gut neurons.
20:44Among certain patients prematurely, before the first motor signs appear, we can find
20:52signs of the digestive tract being effective, such as constipation or an impairment of the
20:57sense of smell.
20:58So, as this is rather premature, some researchers have put forward the hypothesis that the disease
21:04could originate peripherally and then spread gradually along the nervous system and into
21:10the brain and then, in a subsequent stage, become far more widespread in the brain, which
21:15would explain why patients develop intellectual impairment and trouble with balance in the final
21:20phase of its development.
21:29The real origin of the disease, whether it's in the gut or the brain, has not yet been established.
21:35But Michel Nunlist and the neurologist of the University Hospital of Nantes wanted to find out more
21:40about it.
21:41In 2006, they decided to work together to prove that Parkinson's disease can be diagnosed via
21:48a simple intestinal biopsy of the living patient.
21:53Today, that task has been accomplished.
22:00In a simple routine biopsy, there are 150 neurons and their condition reveals a lot about
22:06our brain neurons.
22:10What was observed among Parkinson's patients was that, in these biopsies, lesions typical
22:14of Parkinson's disease were found in the gut neurons, the same lesions that were found
22:19in the central nervous system.
22:25This is an extraordinary result.
22:28Whereas a biopsy of the brain is potentially dangerous for the patient, an intestinal biopsy
22:33is a harmless procedure.
22:39As a gastroenterologist, I would never have imagined taking part in understanding or diagnosing
22:43neurological diseases.
22:45And yet, in the case of Parkinson's disease, we can visualize and give information on what
22:50is happening in the brain, from our brain that is located in the intestine, as though we're
22:54opening a window onto the brain, and that's absolutely fantastic.
23:02What the scientists in Nantes have discovered provides enormous hope.
23:06In two or three years' time, they hope to be able to carry out these routine biopsies on
23:10people at risk.
23:12Given that the digestive symptoms of the disease can occur 20 years before the onset of motor
23:17symptoms, an early diagnosis could enable earlier and therefore more efficient treatment
23:22of the disease.
23:27In the meantime, the idea of looking at the stomach in order to better treat the mind
23:31is starting to gain ground.
23:35The idea of the gut as an open window onto the brain has been shown to be valid for Parkinson's
23:40disease.
23:42The question we'll also be exploring now is to try and see if this hypothesis applies to
23:46other neurodegenerative diseases, and in particular, Alzheimer's disease or other pathologies.
23:52This time, more neurodegenerative ones, but perhaps also behavioural ones, such as autism
23:58and psychiatric pathologies.
24:10On closer inspection, our world resembles a gut, made up of tubes and entrails, in which
24:16fluids, information and signals circulate along increasingly complex networks.
24:26Science is only just starting to take into account the complexity of these exchanges, and their
24:31emerging properties remain to be discovered.
24:40Yet on the other side of the world, traditional Chinese medicine has been based on a vision
24:44of the human body as a whole for thousands of years.
24:50It endeavours to regulate the invisible energy flow that circulates through our bodies.
24:57In Chinese medicine, organs talk to each other and interact via qi, an energy that connects
25:02us to the universe.
25:04The different medical systems are based on their cultural context.
25:12In Western medicine, we concentrate on what is localized, dividing the body into different
25:17parts to study specific functioning.
25:20But Chinese medicine is based on a holistic global vision, and focuses particularly on the
25:25relationship between the different parts of the body.
25:29Each of these two visions has its advantages.
25:46The gut expert of traditional Chinese medicine is called Boji Win.
25:53We are in the CTM Hospital of Canton, the largest hospital in the world, with seven million patients
25:58a year.
26:01Every day its pharmacy dispenses ten tons of drugs, both Western and traditional Chinese
26:06medicine.
26:09Here, acupuncture needles are used alongside state-of-the-art medical equipment.
26:26The Chinese have been practicing acupuncture for three thousand years, although the gut was
26:31never previously a predominant feature of it, until Dr. Bo discovered abdominal acupuncture
26:36entirely by chance, a new practice in the country of traditions.
26:44It was in 1972.
26:46A lot of students were learning acupuncture, and I had about 20 students trained in Western
26:52medicine.
26:55One day an old worker arrived in a wheelbarrow, complaining of severe back pain.
27:02I applied all the classic acupuncture methods, but nothing worked.
27:06The patient was in such pain, he was sweating profusely.
27:09And I started getting nervous and broke out in a sweat myself, because a lot of my students
27:13were watching me.
27:18With his students gathered around him, the professor could not lose face.
27:23I used two deep acupuncture points located in the stomach, along the Wren meridian.
27:33The patient immediately stopped crying out, and his face suddenly relaxed.
27:41At the time, Professor Bo was highly surprised.
27:45The location of these points in relation to the symptoms was not logical.
27:49He then embarked upon intensive research to understand acupuncture in the abdomen.
27:57And he discovered a highly sensitive zone around the navel.
28:02The umbilical cord is the center of the development of the human body.
28:09Plays a very important role in the growth of the embryo.
28:11Even after the cord has been cut, the navel continues to play a role in coordinating the
28:16whole body.
28:17But we don't know much about this hidden system.
28:23Professor Bo's method is shown on these three illustrations.
28:26He has trained over 5,000 disciples, who now practice abdominal acupuncture in Asia, Europe
28:32and the United States.
28:35On these three images, we can see that the organs and the viscera have a direct relationship
28:42to our emotions and our mental state.
28:45We can see clearly that the gut is closely related to our brain.
28:52Thanks to this discovery, Professor Bo now treats numerous pathologies.
28:56Today, a patient who suffers from depression is consulting him.
29:02Has your condition improved?
29:06Yes, but it came back a while ago because there were problems in my family.
29:13In traditional Chinese medicine, we say that to cure the disease, you have to find the source.
29:18And where is the source?
29:21In the belly.
29:23Lie down.
29:24Let's start the session.
29:38Under Professor Bo's needles, patients suffering from Parkinson's, Alzheimer's and depression
29:44sometimes experience a regression of their symptoms without Western science being able
29:48to understand how the magic works.
29:59Should scientists just accept the idea that there is an energy that is not described in
30:03their medical anatomy books?
30:11To try and better understand how his treatment works, Professor Bo has recorded the MRIs of
30:15healthy patients before and after a session of abdominal acupuncture.
30:24Using functional MRI, we compared the images of the brain of a person before and after a session
30:29of abdominal acupuncture.
30:32After the acupuncture, there is an increase in the number of activated zones.
30:38The results show that abdominal acupuncture can improve cognitive functioning and regulate
30:43emotions.
30:44In both the East and the West, scientists admit that they are a long way from understanding
30:59everything about the brain-gut axis.
31:02But their research so far has led to an astonishing discovery.
31:15One hundred thousand billion bacteria live in our digestive tube.
31:20There are one thousand times more bacteria inside each one of us than stars in our galaxy.
31:27This microcosmos within a macrocosmos is the most concentrated ecosystem on the planet.
31:40There are one hundred times more bacteria in our gut than cells in our whole body.
31:46I am a human being.
31:48My cells come from the egg.
31:51That was the result of the fertilization of the ovum of my mother, by the spermatozoa
31:55of my father.
31:56All those cells that proliferated have made up my body.
31:58Until not very long ago, I thought that was me.
32:01But then I discovered that was not so.
32:03In fact, that's just a little part of me.
32:05There's an enormous part of me that's made up of microscopic bacteria.
32:09I am, in fact, an ecosystem.
32:17We are more bacteria than we are human.
32:21We have many more bacterial cells on our bodies, on our bodies, in our bodies, than we
32:26have human cells.
32:29We have more bacterial DNA than we have human DNA.
32:34So we are like passengers inside a bacterial bus, if you will.
32:44At McMaster University in Hamilton, Canada, Stephen Collins is seeking to understand the
32:50functioning of this organized ecosystem that researchers now call microbiota.
32:54We each carry one to two kilos of bacteria inside us.
33:04They generate about 30 percent of our caloric intake.
33:11Because a lot of the food that we eat, we cannot digest.
33:16But the bacteria can digest it for us, and we take the energy.
33:25We offer the bacteria board and lodging, and in exchange they convert our food into energy.
33:34They help us determine what is and isn't toxic for our body.
33:39For the bacteria, survival would be difficult.
33:42The immune system in your gut, which is the biggest immune system in the body, is educated
33:47by what the bacteria inform it, tell it.
33:51So the exposure to lots and lots of bacteria keeps the immune system alert.
33:57As microbes play such a crucial role for our health, it is of critical importance to understand
34:22the mechanisms of microbial colonization.
34:36Inside the mother's womb, the baby lives in a sterile environment, but starting from the
34:41first day of his or her life, he or she will be colonized by hundreds of billions of microbes.
34:47The first bacteria to settle inside the intestine will select the newly arriving bacteria until
34:52things stabilize, making up a personal signature like a sort of fingerprint.
35:05Events such as taking antibiotics, by the mother or by the child, birth by cesarean section, bottle
35:11feeding rather than breast feeding, and an excess of hygiene all reduce bacterial contact and
35:16weaken the infant's microbiota.
35:22I think sometime in the future, I don't know when, that babies will be born with and given
35:28the best possible flora.
35:30That it will be given not only to babies to colonize them properly, but it will be given at various
35:36stages through life, particularly as one gets older, to reinforce the microbiome.
35:43To find the recipe of the ideal microbiota, it is first necessary to know which bacteria
35:51it contains.
35:54At the National Institute of Agronomic Research in France, Dusko Ehrlich endeavors to shed light
36:00on the mysterious population that has lived inside us ever since Eve bit into the apple of knowledge.
36:06In order to do so, he has decided to study the genome of our entire microbiota.
36:15That's right.
36:16Study the genome of an organism made up of 100,000 billion bacteria.
36:22This discrete project, called Program Metahit, is a great deal more ambitious than decoding
36:27the human genome.
36:28Ten years ago, I asked myself, what would be most fun for a microbiologist to do in his
36:36professional life?
36:39And it was very clear, worldwide we had huge sequencing capacity.
36:46Because human genome was sequenced, and genome of monkeys and worms and flies were sequenced.
36:53So, couldn't we use that capacity to sequence not only our genome, but also our metagenome?
37:06The mammoth task ended in 2010, when researchers published the map of the human microbial metagenome,
37:14and ended up with a catalogue of three million genes.
37:20The vast project resulted in a surprising discovery.
37:27We discovered so many things, I couldn't even begin to tell you.
37:34But one of the most surprising discoveries was that we humans can be placed in three groups,
37:45inside the microbial populations that live in our gut.
37:50We call these groups enterotypes.
37:52So, in addition to blood groups, we are divided into three intestinal bacteria groups that Dusko calls enterotypes.
38:10Their difference lies in their capacity to convert food into energy.
38:17All three produce vitamins, but to varying degrees.
38:23The enterotypes doesn't seem to be related to geographical localization, race, sex, age.
38:32And, yes, one could have much closer enterotype to a Japanese than to his own neighbor.
38:40Is it our genes, our environment, our food?
38:46Dusko and his colleagues have not yet understood what determines these three enterotypes.
38:51But they are trying to determine how the thousands of species of bacteria interact with our body.
38:57The scientists' long-term aim is to gain a better understanding of the role bacteria play in the onset of certain chronic diseases.
39:14We're all familiar with blood and urine samples.
39:18Soon, doctors will analyze our stools to find out the exact composition of our microbiota.
39:27It's a revolutionary way of diagnostic.
39:31Well, we see predisposition for diabetes, type 2 diabetes, predisposition for cardiovascular disease, predisposition for liver disease, just by examining microbiota in people.
39:51Studying the bacterial flora of obese people, scientist Patrice Cani made an extremely promising discovery.
40:06He observed that a certain type of bacteria, Ackermansia mucinifila, which abounds in the intestines of a healthy population, is extremely rare in an obese population.
40:18He therefore wanted to examine the purpose it serves.
40:23To do so, his team fed mice a fat-rich diet and watched how they got fatter, with and without Ackermansia.
40:32The experiment yielded incredible results.
40:37By ingesting the same quantity of energy of fat-rich food, the animals which received the bacteria took twice as long to get fatter.
40:46What we were able to demonstrate is that the adipose tissue of the animals that received a fat-rich diet, but were treated with the bacteria, stopped less energy.
40:53Ackermansia lives in the mucus layer that lines and protects our intestinal cells, and that enables it to converse with our cells.
41:12Scientists have succeeded in finding out how these bacteria communicate with the cells of the intestinal wall of mice.
41:31In this experiment, we are analysing the mouse's genes.
41:37What we were able to demonstrate is that the bacteria, Ackermansia, was able to activate the mouse's genes that induce an increase in the mouse's capacity to burn fat.
41:46With the result that the mouse gets half as fat, as half the body fat, of a mouse that does not receive the bacteria.
41:57This test tube may well contain the goose that lays the golden egg.
42:06We will soon be eating this living bacteria, either in a yogurt or by popping a pill.
42:12But will it really help us fight obesity?
42:15From a therapeutic point of view, the aim is to improve the conditions of patients suffering from obesity and type 2 diabetes.
42:24The aim is not, and besides, it would never work, to say to people that we can administer this bacteria to them,
42:30and they can eat whatever they want, and still be protected from obesity.
42:33I don't think that's possible.
42:35Today, scientists estimate that obesity is due 10% to genetic factors, 10% to bacteria, and 80% to our behavior.
42:52It therefore greatly depends on our own will.
42:57But when we talk about will, does that necessarily mean we are the only ones to decide?
43:04Is our brain the mastermind of our personality, or is it acting under influence?
43:13It is here, in Stephen Collins' ultra-sterile laboratory, that the answer may lie.
43:22If you take a germ-free mouse that has no bacteria, the mouse behaves in a very strange way.
43:28It takes risks. It is almost irresponsible.
43:33When you put bacteria into these mice, their behavior changes.
43:37They take no more risks. They are very careful.
43:40Why is this?
43:42So maybe the bacteria are saying, look, we want to survive, so you better behave well.
43:48But Stephen Collins does not stop at this simple observation.
43:52In this experiment, he chose two lines of mouse, one rather active and daring, the other rather calm.
43:59Then, he administered to each line the microbiota of the other line of mouse.
44:05We took mice who were very quiet, and we put their microbiota into mice that are notoriously aggressive.
44:16And these are Swiss mice.
44:18And the Swiss mice became calmer.
44:28Then we did the other experiment.
44:30We took mice who were very quiet, and then we gave them the microbiota from the aggressive mice.
44:36And the calm became more aggressive.
44:43That's the experimental evidence that the microbiota influenced the brain.
44:51Who we are is not determined solely by us as humans.
45:11We're being influenced by our ancestors.
45:14You know, the bacteria that were present on this earth for millions of years before us,
45:21that have acquired a genetic repertoire that's much greater than ours.
45:26And now we find that they influence who we are and how we are.
45:31The results of Stephen Collins' demonstration have toured the world.
45:49In Europe, other scientists are making mice more adventurous simply by making them eat bacteria.
45:56We already knew about a few of those features among a certain number of parasites, not bacteria but small eukaryotes,
46:05which live inside organisms and change the behavior of these organisms by serving their own interests.
46:12The example of toxoplasmosis is an amusing one because when these small parasites are present in mice,
46:18they remove the mice's fear of cats.
46:21Certain studies even suggest that the mice are sexually attracted to the cats, which is strange.
46:26Of course, that results in them getting eaten by the cat,
46:30which serves the interests of the toxoplasma because toxoplasma develops well in cats.
46:36And there are many examples of this.
46:54It's very common for parasites living in the gut of their host organism to alter its behavior.
47:00It shows to what extent there is an interaction between what happens in a person's gut
47:07and what that person's brain will order them to do.
47:12But before concluding that we are being manipulated by bacteria,
47:24it is necessary to prove that what happens in mice can be transposed to humans.
47:33In order to modify human intestinal flora, we have two tools.
47:37Antibiotics to kill bad bacteria and probiotics to develop good ones.
47:46Probiotics are yeast and live bacteria that are supposedly beneficial for health.
47:51They can be found in yogurts, for example.
47:56There is still some doubt as to their real efficacy,
47:59given that research on them is in part funded by those who market them.
48:02In Europe, food industry groups have been asked to remove all allegations of health benefits
48:07from their probiotic-enriched milk-based products.
48:13What's more, evaluating the efficacy of probiotics is no easy matter.
48:21Life is not simple, even among bacteria.
48:24One single bacterium is a factory that makes thousands of molecules.
48:27And generally, to make things even more difficult,
48:30a preparation of probiotic bacteria contains several of these bacteria,
48:34increasing the complexity even more.
48:36So we're a long way from the classic one molecule, one action standard.
48:40We don't understand exactly how it works.
48:50We know how to kill the bad ones with antibiotics,
48:53and how to try to favor the good ones by giving probiotics.
48:57But in fact, for the moment, we really don't understand very much.
49:00At the Center for Neurobiology of Stress in Los Angeles,
49:15Kirsten Tillich was also skeptical.
49:18How could taking probiotics have an effect on stress response?
49:21To find out more, Kirsten and her team tested the effect of probiotics on the brains of healthy women.
49:34What we decided to do is look at healthy women who had no pain, no discomfort,
49:38no gastrointestinal, no anxiety or depression.
49:42And the task that we chose is a task that's been used to look at how people respond to emotionally negative images.
50:01And we thought, well, let's see if changing what's in the gut can change the responsiveness to these images.
50:07For two weeks, scientists gave a group of 60 perfectly healthy women yogurts, with and without probiotics.
50:24Then they looked to see if their brains responded differently to stress.
50:31You ready to start the task?
50:33Okay, here we go.
50:37So what we found was that in people who took the probiotic, a network of brain regions was less active.
50:44So it implies that the people who took probiotics are less reactive to those images.
50:50We know that in the brain, something is changing in the way that they're responding to their environment,
50:56and specifically to negative or potentially threatening things in their environment.
51:00So this is the first study that has shown that if you give a probiotic, it changes something in the brain.
51:08This is incredibly exciting to us, that with this simple food that I could go to the market and buy,
51:14potentially I could change something that's going on in my brain.
51:16But even the most enthusiastic scientists recommend exercising caution in the face of this very recent research,
51:29especially given that, as yet, we don't know much about the side effects of bacteria on our body.
51:34But all agree that they have an effect both on our health and on our brains.
51:39We now have to recognize that a certain component input into our brain comes from bacteria.
51:53It doesn't mean we are controlled by bacteria, but they certainly have an influence in who we are,
52:04in how we behave, and how we react.
52:08So I think we now have to consider that we have a third brain.
52:14We have the big brain, we have the little brain, and now we have the intelligence of bacteria.
52:23In science, we don't just progress by making discoveries, we also progress by changing models or paradigms.
52:37What we are is linked to our history and our environments.
52:41These environments are external, and we're now discovering internal, and that's wonderful.
52:53We tend to think, here we are, we're all humans, we sit staring at our screens with a strong sense of our own individuality,
53:04thinking that ecosystems are outside, the forests, the fields, the Amazon, that that's not us.
53:11But in reality, things don't work like that.
53:14We have this bacterial flora inside of us, and it also exists outside of us too.
53:18So in fact, we're bathing in a bacterial ecosystem that penetrates us and is part of us.
53:28There's no longer this separation between ourselves and what is not ourselves,
53:32between the exterior, between me and the others.
53:35There's one absolutely remarkable biological continuity.
53:39Scientists' vision of our body has changed.
53:49What we formally took for the ultimate foundation of reality, our individuality,
53:56is very probably the reflection of a more complex reality,
54:01essentially made up of messages, networks, and still very mysterious connections.
54:06We are now thousands of genes, billions of neurons, and hundreds of billions of bacteria.
54:17We are a multitude of links and information.
54:22Their overwhelming complexity reaches far beyond the confines of our own selves.
54:28of our own selves.
54:58of our own selves than the others.
54:59We are Darren давайте with