00:00Microbes are everywhere.
00:03On your phone, in your water bottle,
00:07on your hands before you wash them,
00:09on your hands after you wash them,
00:11and literally everywhere else on top of you too.
00:14Microbes are omnipresent at any moment
00:17and there is nothing we can do about it.
00:20So millions of years ago, we made a pact.
00:23We give them shelter and food,
00:25and in turn, they work for us.
00:28But the more we learn about this partnership,
00:30the more it looks like a cold war.
00:34Inside our mother's womb, humans start out sterile.
00:38When we are born and travelling through the birth canal,
00:41billions of our mother's bacteria cover every single part of our bodies.
00:45This is an essential part of human health.
00:48Children born via C-section have a higher rate of asthma,
00:51immune diseases and even leukemia.
00:54So our bodies do not only accept the invasion of microorganisms,
00:58they welcome it.
01:01Over millions of years,
01:03we co-evolved to make the best of our relationship.
01:06Mother's milk, for example, contains special sugars
01:09that are meant to feed and support certain groups of microbes,
01:12work as a decoy for others,
01:14and help to modulate the immune system.
01:17It takes up to two years until a healthy microbe community has formed.
01:21Every human has their own unique microbiome,
01:24made up of bacteria, viruses, fungi and other organisms.
01:28We have three categories of guests on and in our bodies.
01:33One, quiet passengers that do their own thing and are politely ignored.
01:38By being there, they take up space and keep more aggressive intruders in check.
01:43Two, guests that harm us, but with whom we've learned to live.
01:48For example, bacteria that literally create acid that melts our teeth if we don't brush enough.
01:53They want to take up as much space as they can, and we don't want them to.
01:57But we can't get rid of them entirely.
02:00Three, friendly fellows that our bodies want to have around.
02:04Most of them are a community of 380,000 billion bacteria
02:09from up to 5,000 different species that live in our gut.
02:13These gut microorganisms help us digest food
02:16and pull additional calories from things we can't digest ourselves.
02:20Unfortunately, our gut is also the perfect point of attack for intruders,
02:24so it's guarded by an aggressive army, our immune system.
02:28To survive here, our microbiome co-evolved with us to be able to communicate with our body.
02:34The most important part of that is to ask the immune system to not kill them.
02:39But they also have a real motivation to keep our gut healthy,
02:43so some of them produce messenger substances that help to educate the immune system,
02:48and others stimulate the gut cells to regenerate faster.
02:52But over the last few years,
02:54evidence has emerged that the influence of our gut microbiome goes much, much further.
02:59It might even talk directly to our brain.
03:03We've observed a few curious things.
03:0690% of our body's serotonin, an important messenger substance for nerve cells,
03:10is produced in the gut.
03:13Some scientists think the microbiome does this to communicate with the vagus nerve,
03:17the information highway of our nervous system.
03:20Other examples are bacteria that stimulate immune cells in the gut,
03:24so they send a kind of alarm signal to the brain.
03:27Here, it activates immune cells that help the brain recover from injuries.
03:31Since the brain decides when we eat,
03:34the microbiome is interested in a healthy brain.
03:37A new field of science is opening up here,
03:40and we're just on the verge of understanding how these complex systems inside our bodies interact.
03:45But we are starting to see how much our microbiome actually influences us and our behavior.
03:51Take depression, for example.
03:54Healthy rats fed microbes from the guts of depressed people
03:57began showing anxiety-like behavior and symptoms that look like depression.
04:02And in early 2017, a study linked the microbiome to intelligence
04:06by connecting a certain setup of bacteria in newborns with better motor and language skills.
04:12But it might also influence our daily lives.
04:15Tests with fruit flies showed that their microbiome influenced what kinds of food they craved.
04:21This could mean your microbes are able to tell your brain which food it should get them,
04:26although this is not a one-way street.
04:29The seed for our microbiome comes from our mother,
04:32but how it develops and changes is determined by what we eat.
04:36The organisms in our gut feed on different things.
04:39Some like fibers and leafy greens, others go for sugars and starches,
04:44and some love greasy fries and butter.
04:47Our gut is like a garden in which we constantly decide what will grow and blossom.
04:53If we eat healthily, we breed bacteria that like healthy food.
04:58If we eat a lot of fast food, then we breed fast food-loving bacteria.
05:04Life is hard, so we can get trapped in a vicious circle.
05:08You have a stressful time and eat lots of burgers and fries and pizza.
05:13This is awesome for fast food bacteria.
05:15They multiply and multiply and take up space from vegetable-loving bacteria.
05:20But even worse, they send signals to the brain to continue what it's doing.
05:25This makes you want more fast food, which breeds more fast food bacteria,
05:29which makes you crave fast food, and so on.
05:33This kind of self-reinforcing cycle could play a huge role in obesity.
05:38But it's important to stress that you can fight this process
05:41and reverse it by eating healthily and breeding more good bacteria.
05:46Beyond weight gain, our microbiome has also been linked to other serious diseases
05:50like autism, schizophrenia, and cancer.
05:53One of the earliest symptoms of Parkinson's is actually gut problems.
05:58If your body is overrun with bacteria that harm you,
06:01there is often only one solution.
06:03You bring in an army of good guys.
06:06That's very easy.
06:07You just transplant some healthy poop.
06:10You do that by literally transferring poop from a healthy person into your gut.
06:16This method is already used to cure diarrhea
06:19that's caused when C. difficile bacteria take over a gut microbiome.
06:24But we just don't know enough about the complex interplay at work here yet.
06:28For example, a transplant from an overweight donor cured a woman's diarrhea
06:32but contributed to her obesity down the line.
06:35This caused some waves, and another study tried to reverse the effect.
06:40Poop transplants from slim people to obese ones gave them a more diverse microbiome
06:45and made them less sensitive to insulin.
06:47Both things that also happen when people lose weight.
06:51We need to do a lot more science to really understand how our microbes make us healthy or sick.
06:57But whether we like it or not, we need our microbiome, and it needs us.
07:02We'll never have our bodies to ourselves,
07:05but we have gained a powerful ally if we can just keep the peace.
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