Translator: Rhonda Jacobs
Reviewer: Ellen Maloney Imagine this... You have just won
ten million dollars in the lottery. Congratulations. (Laughter) You have just eaten the most delicious,
warm, chocolate brownie that has ever been baked. (Laughter) You... have just had sex. (Laughter) And you... have just done all three at the same time.
Congratulations to you, too. (Laughter) In these situations, our brains
produce chemicals called neurotransmitters which give us these great feelings
of energy, excitement and happiness. And without such chemicals inside of us, we wouldn't feel such emotions
during such pleasant circumstances. So instead, imagine this: You've just been fired. You're about to sit an exam. You have depression. In these situations, our brains, instead,
produce different chemicals, making us feel stressed and anxious. The highs and lows of life
are controlled by our emotions and these chemicals in our brains. This vital organ inside all of us that controls everything
that we feel, think and do. However, as a biologist, I've always
found it strange to comprehend that every feeling, thought,
and action that we have is controlled by a three-pound,
soggy lump of cells inside of our heads, until I discovered
that this might not be the case. The story I want to share with you today
unfolds a fascinating new revelation in our understanding of human physiology, that we each have a second brain, another organ in our body which controls as much
of our physical and mental functions as the brain in our heads, and which may be the key link between
modern disease epidemics, globally, from obesity to cardiovascular disease,
maybe even to mental health. But first, to give you a little
introduction to this story, I want to tell you a little bit
about my background. I was brought up
in a family of psychologists. My mom is a clinical psychologist; my dad a professor
of psychology in a university; my sister even has a PhD in psychology. So when it came to me going to university,
I wanted to study something different. I'd heard enough about the brain
and how it worked at home so I wanted to study something new. I considered what I was interested in, and I figured out
that from a very early age, I'd had a big interest in food. I loved eating food. So, I decided to study human nutrition. And this was great
because I got to study food, how it affected our bodies, how it could contribute to disease, and more importantly, how we could use it
to fight and prevent disease. This story begins back in 1845 with the birth of a curious
young boy in Russia who became an incredible man, but who was forgotten
by history and medicine. Ilya Mechnikov was fascinated
by everything in nature, and by the age of eight,
he was taking notes on all the living things
in his vibrant back garden. He became so good at science
that he discovered the role of phagocytes, some crucial cells in our immune systems,
for which he won the Nobel Prize in 1908. But it was his science
after winning the Nobel Prize that was even more crucial
to our understanding of human health, through a tale of discovery, death,
and self-experimentation. See, everyone in this room
has something in common. We all spent the first
nine months of our existence inside our mothers' wombs. And this was essentially
a sterile environment where no other living things
existed, just you. But as you emerged into this world, you were smothered
in an invisible coating of microbes, friendly microbes
from your mother's birth canal. And these bacteria grew
to form what is now a three-pound invisible organ
inside your large intestine, the same weight as your brain, and which has become known
as our microbiota, or microbiome. And this invisible organ
has grown so much, in fact, that right now, 90 per cent of the cells
in your body are bacterial cells; only ten per cent
are your own human cells. So you are more bacteria
than you are human. (Laughter) This ecosystem of microbes in your gut
is as diverse as the Amazon rainforest. Thousands of species
all with different functions. And your health is incredibly dependent upon the life and vibrancy
of this rainforest. Your gut bacteria digest certain foods, produce essential vitamins and hormones, respond to medicine and infections, control your blood sugar
and blood cholesterol levels. Meaning the types
of bacteria in your intestines can significantly control
your risk of certain diseases from obesity to diabetes,
maybe even osteoporosis. They're involved in just about
every process in your body. They function almost as a second brain. Well, Ilya Mechnikov may have
figured this out himself in 1892. He lived in France, in Paris at the time, where a deadly cholera
epidemic had broken out with thousands of deaths. Naturally, as a scientist, he decided
the best way to study this was to drink a broth of cholera himself. Remarkably, he didn't get sick. So again, as a true scientist,
he needed to increase his sample size, so he recruited a colleague
to do the same thing. This guy didn't get sick either. But when he recruited
another colleague to do the same, this poor guy got critically ill
and very nearly died. By studying cholera under the microscope, Metchnikov found that certain species
of bacteria from the human intestines supported and stimulated cholera's growth,
while other species prevented it. He subsequently claimed that our gut
microbiota, or our gut bacteria, were essential for human health, and that the right balance
of microbes inside of us could help stave off disease. However, popular
understanding at the time, was that the human gut
was a noxious reservoir of toxins. Surgeons had even begun removing
entire sections of human intestines in patients with gut discomfort. Mechnikov's death in 1916 meant that his ideas that our gut
bacteria were good for us were forgotten. A decade later,
antibiotics were discovered, and drastically became overused. C-sections became common. Diets became Westernized. A war was waged on microbes and we spent
a century trying to kill them, which turned our intestinal rainforests
into barren wastelands. This Nobel Prize winner's ideas
were lost in time. Some of the implications of this
were identified recently. See, right now, one in three children
in America are born by C-section, meaning they don't get this initial
innoculum or coating of bacteria that's been designed by evolution
to be in the mother's birth canal. Instead, they're first coated
with other bacteria on the skin or in the hospital environment
which has contributed to up to a 25 per cent
increased risk of obesity, asthma, immune deficiencies and inflammatory
bowel disease in later life. Fortunately, in recent times, we've realized we must
restore our relationship with gut microbes
for our own physical health. However yet, we've still
completely underestimated their role as our second brains. And this is something
that I'm researching. And I learned this first
through the intriguing story of a mouse. If mice become colonized
by the microbe Toxoplasma gondii, an intriguing thing happens: they lose their fear of cats. (Laughter) In fact, they become attracted to cats. (Laughter) In essence, they go a bit mad,
and unfortunately for them, usually end up as dinner for cats. (Laughter) So, this microbe ingested by this animal
takes control of its brain, and changes the way
that it thinks and behaves. So, by delving deep inside the intestinal
jungle of bacteria in our intestines, we've begun to find
some incredible discoveries that are changing our appreciation
for bacteria forever. See, our bellies and brains are physically and biochemically
connected in a number of ways. First of all, our intestines
are physically linked to our brain through the vagus nerve which sends signals in both directions. Interestingly, even though
if this is severed, our intestines can still
continue to function fully without a connection to the brain,
suggesting they have a mind of their own. Secondly, our brains are made up
of a hundred billion neurons which continuously send messages
to tell our bodies how to work and behave. Well, interestingly, our guts
have a hundred million neurons. Thirdly, our microbiomes
are the centerpoint of our immune systems, meaning a disturbance down here can cause subtle immune reactions
all around the body, which if prolonged,
can affect brain health. And finally, do we remember our chocolate-eating, lottery-winning
womanizer here in the front row? He demonstrated for us
the neurotransmitters are these chemicals that can change
the way we think and behave, and how we feel. As it turns out,
most of these neurotransmitters are also produced in our gut, none more so than serotonin,
nature's antidepressant, 90 per cent of which
is produced in our intestines, less than ten per cent
is produced in our brains. Meaning the types
of bacteria inside of you may control the way
that you think and behave. Has stress ever messed with your insides? Have you ever had a gut feeling? Or butterflies in your stomach? You may have to think twice about that. So, you can see, despite my naive
reluctance as a teenager, I've begun to study not only
one brain, but two brains. In the APC Microbiome
Institute in Ireland, we're fascinated in this link
between our belly and our brains, and we research how
our modern diets and lifestyles are impacting this gut-brain relationship, and how we can design interventions
to target the microbiota in order to prevent
and treat chronic diseases. For example, we've shown that the types of fats
that you eat throughout life can drastically change
the types of bacteria that decide to reside in your intestines. In addition, we've shown that by feeding
specific strains of bacteria, it can enhance memory, stress behavior,
and stress hormone levels in animals. And in addition to a number
of other researchers worldwide, we've identified lists of foods
that can act as prebiotics, or foods that can stimulate the growth
of healthy bacteria inside our intestines. To me it's fascinating that our health is so dependent
not only upon nourishing ourselves, but upon feeding other living
microorganisms inside of us, meaning future strategies
to target and treat chronic diseases, including brain health, may depend
on targeting or feeding our gut microbiomes. As it turns out, Ilya Mechnikov
may have known this himself. See, much earlier in his life he married, but his wife quickly became sick
with tuberculosis and died. The stress and trauma of this led Metchnikov to take
an overdoes of opium. Thankfully, he survived. He then re-married, and when his second wife got sick
with the deadly typhoid fever, this time he injected himself
with a deadly tick-borne disease. Thankfully, he survived again. It was only after this, Metchnivok began studying
and appreciating the microbiota. He moved to Paris
to work in the Pasteur Institute where he began hypothesizing
the right balance of microbes in the gut could help stave off disease, and he published a series
of books and lectures describing how to achieve this
and prolong life. Despite the stress and mental turmoil
that he'd experienced in earlier life, he spent the rest of his life dedicated and obsessed with
researching how to prolong human life. He began studying an interesting group
of people in Eastern Europe who were living exceptionally long lives, and he noted that they all drank
bacterial-fermented milk every day and he suggested that
this contributed to their longevity. Interestingly, he began drinking
this bacterial-fermented milk himself, and seemingly lived a healthy life rid of the stress and mental turmoil
he'd experienced in earlier life. Maybe that was just coincidental. He described the time in Paris
as the happiest of his life. But Metchnikov died in France
in 1916 at the age of 71. The life expectancy
in France at the time was 40. As humans, we all need
to adopt a greater appreciation for the microbes inside of us. The incidental war we've waged
on bacteria over the last century has led to bacterial extinction
and sparked an epidemic of modern plagues. I'm here on a Fulbright to research how we can restore
our relationship with microbes, and how this can be used
to prevent and treat chronic diseases. But I feel that we all have
the responsibility and the potential to follow in Ilya Metchnikov's footsteps. Not only to revive his scientific findings
that were lost in time, but to adopt his desire
to prolong healthy, human life. Whether it's by educating ourselves
on the risks and benefits of C-sections, restricting unnecessary antibiotic use, or by adopting a gut-friendly
diet and lifestyle, we can all support the life of microbes
that we've evolved to live alongside. So imagine this: Imagine you've just eaten chocolate,
or won the lottery, sat an exam or just been fired. Imagine your thoughts, your emotions,
your behavior, and your health could be controlled by a hidden organ
that you knew little about. Ilya Metchnikov fought to not only
prolong healthy human life, but healthy microbial life. I feel we can all contribute
to this fight worth fighting for our own health, but more importantly,
for future generations' health by restoring the relationship
between microbe and man. There is some food for thought. Thank you very much. (Applause)
