10 Smart Facts About Your Gut

Colorized scanning electron micrograph of E. coli, a common gut bacteria
Colorized scanning electron micrograph of E. coli, a common gut bacteria
National Institute of Allergy and Infectious Diseases, Flickr // CC BY 2.0

Gut feelings get all the press, but your gut may be more of a thinker than you know. Some scientists now consider it a second brain. While it won’t necessarily help you study for an exam or get a promotion, your gut can influence the chemistry of your mood, emotions, immune system, and long-term health. Research even suggests the gut can “learn” new tricks through conditioning. These powerful connections are part an emerging field of science called neurogastroenterology designed to study the gut-brain link. Here are 10 facts you may not know about your gut.

1. THE GUT DOESN'T NEED THE BRAIN'S INPUT. 

You might think of your gut as a rebel against authority. It doesn’t wait for your brain’s impulses to do the important work of digestion, because it doesn’t need to—it acts as its own “brain.” No other organ, not even the all-powerful heart, can pull that off.

2. THERE ARE MORE THAN 100 MILLION BRAIN CELLS IN YOUR GUT.

Your gut’s power to think for itself is no surprise; there are millions of neurons in its lengthy coils (9 meters of intestines, from esophagus to anus). That’s more neurons than are found in the spinal cord or peripheral nervous system.

3. YOUR GUT HAS ITS OWN NERVOUS SYSTEM.

The enteric nervous system—the controlling mechanism of digestion and elimination—is the overlord of your gut, and functions all on its own. Some scientists see it as part of the central nervous system, while others consider it its own entity. It likely evolved to give the gut the go-ahead when the “got to go” impulse strikes, without requiring the brain’s sign-off, particularly when you consider the helplessness of an infant with its brand-new brain.

4. THERE'S AN INFORMATION HIGHWAY FROM YOUR GUT TO YOUR BRAIN.

There’s one big visceral nerve embedded in your gut—the vagus nerve. Research has revealed that up to 90 percent of its fibers carry information from the gut to the brain, rather than the other way around. In other words, the brain interprets gut signals as emotions. So you really should trust your gut.

5. MOST OF YOUR SEROTONIN IS IN YOUR GUT.

Some 95 percent of your body’s serotonin, that marvelous mood molecule that antidepressant drugs like Prozac keep in your body, can be found in the gut. So, it’s no wonder that diet, medications, and antibiotics can wreak havoc on one’s mood.

6. A HEALTHY GUT MAY PROTECT YOUR BONES.

In a study of the serotonin-gut relationship, scientists discovered an unexpected link between the gut and the bones. Inhibiting the gut’s release of serotonin counteracted the bone-density reduction of osteoporosis in mice. This research is going into studies on new osteoporosis-fighting drugs.

7. RESEARCH SHOWS LINKS BETWEEN AUTISM AND HAVING FEWER STRAINS OF GUT BACTERIA. 

In as many as nine out of 10 cases, autistic people have common gut imbalances such as leaky gut syndrome, irritable bowel syndrome, and fewer strains of “good” bacteria. Research on mice is looking at possible treatments of some of the behavioral disorders of autism by balancing microbes in the guts, though many warn that such treatments can’t produce a “cure” for autism.

8. FOOD REALLY DOES AFFECT YOUR MOOD. 

Different foods, when introduced to the gut via feeding tubes, have been shown to change a person's moods without the person’s awareness of what they were "eating." Fat, for instance, increased feelings of happiness and pleasure (no surprise there) because appeared to trigger the release of dopamine—the brain’s natural opiate. Carbohydrate consumption stimulated the release of serotonin, the “feel good” neurotransmitter.

9. YOUR GUT IS YOUR BEST FRIEND IN COLD AND FLU SEASON.

Not only does your gut hold brain cells, it also houses the bulk of your immune cells—70 percent—in the form of gut associated lymphoid tissue, or GALT, which plays a huge part in killing and expelling pathogens. GALT and your gut microbiome—the trillions of bacteria that live, like an immense microbial universe, in your gut—work hard to help you get over what ails you. That’s all the more reason to be careful with the use of antibiotics, which wipe out the good bacteria along with the bad.

10. YOUR GUT CAN BECOME ADDICTED TO OPIATES.

Inside your gut are opiate receptors, which are also found in the brain. The gut is just as susceptible to addiction as the brain and may contribute to the intense difficulty some addicts have trying to kick the habit.

Why Do We Get Shivers Up Our Spines?

iStock.com/martin-dm
iStock.com/martin-dm

Picture this: You're sitting on your couch in the dark alone, watching a scary movie. The killer is walking toward an unsuspecting victim, then suddenly jumps out at her. In that moment, the hairs on your body stand up, and you get a shiver down your spine. When you go for a walk on a crisp morning, the same thing happens. When the music swells during your favorite song, you get the shivers again, this time with the little goosebumps on your arms that appear when you get that sensation.

There's a good reason for shivers and goosebumps: they're your body's response to emotion or stress. We got this from our animal ancestors. When they were cold, the hair on their bodies would stand up—the movement of the arrector pili muscle would cause the skin to contract, raising each hair—to provide an extra layer of insulation. This response is also in play when animals feel threatened: their natural reaction is to try to look bigger than their attacker, so their skin and hair expand to play up that effect. The part of the brain called the hypothalamus is what controls this reaction.

So why do goosebumps—also known as cutis anserina or piloerection—appear, aside from the functional purpose of looking larger or creating insulation? It's because our emotions are also connected with the hypothalamus, so sometimes goosebumps are just our body reacting to our brain's signals of intense emotion.

When we feel things like love, fear, or sadness, the hypothalamus sends a signal to our bodies that produces adrenaline in our blood. The signal triggers the arrector pili muscles to contract, and then we have goosebumps caused by emotion. The sudden adrenaline rush may also cause sweaty palms, tears, increased blood pressure, or shivers.

When we listen to music and get shivers, it is a mixture of subjective emotions toward the music and physiological arousal. If we hear a song we get excited about, or a song that makes us sad, the hypothalamus reacts to the sudden change in emotion and we physically feel the shiver along our spine.

This article was republished in 2019.

10 Facts About the Lungs

iStock/pixelfit
iStock/pixelfit

Every cell in your body needs oxygen in order to function properly. Your lungs are obviously crucial in achieving this goal—once you take air into your lungs, oxygen enters the bloodstream and moves through your body. Each cell makes a trade, exchanging oxygen for carbon dioxide—which your bloodstream then transports back to the lungs. When you exhale, you’re actually expelling carbon dioxide (CO2), nitrogen, and water vapor.

So how does your body make this happen? Bronchial tubes connect your lungs to your throat and mouth. These are lined with tiny little hairs called cilia that move in wave-like patterns, which pushes mucus up your throat. At the base of the bronchial tubes are tiny air sacs that hold the air you breathe in, called alveoli. Your right lung has three balloon-like sections, called lobes, which are full of spongy tissue. Your left lung has only two lobes, to make room for the heart. They sit in a special membrane called the pleura, that separates your lungs from the wall of your chest. Altogether, your lungs are a highly efficient machine—and they do a lot more than you might think.

1. Taking in oxygen is only one of your lungs' most important jobs. 

Yes, you need oxygen to live, but if you didn’t expel the carbon dioxide in your lungs, you would die. Carbon dioxide acts as an acid in the body and is generated by muscle action, Wendie Howland, a nurse with Howland Health Consulting, tells Mental Floss. “Your body operates optimally at a fairly narrow pH range, and when you generate extra CO2 by, say, running up the stairs, you bring your pH into the normal range almost immediately by excreting CO2 by breathing deeply.” So exhaling that more toxic CO2 is as important as taking in oxygen.

2. Think of your lungs as big ol' buckets.

Rather than thinking of your lungs as big balloons, Cascari says, “Think of your lungs as buckets of blood with air bubbles going through them.” In fact, your lungs contain as much blood as the entire rest of your body, which is why your center of gravity is above your waist. They produce blood cells as well. Every time your heart beats, it sends an equal amount of blood to your lungs as it does everywhere else in your body. “It’s this incredible system that can respire—an exchange of gas from the air into the blood and the lungs—without leaking. The fact that that goes on day in day out for our whole life is pretty amazing,” he says.

3. Your lungs are huge.

Your lungs are one of your biggest organs, but you might be surprised to learn that if you spread out the surface area of the alveoli, the sacs where oxygen and blood interface, you could cover an entire tennis court, Schroeder says.

4. Without mucus, your lungs would dry up. 

You may not be a big fan of mucus when it’s clogging your chest or nose during a cold, but it’s a “highly underrated, powerful infection-fighting agent in your body with some pretty cool features," says Ray Casciari, a pulmonologist at St. Joseph Hospital in Orange, California. “It’s actually cleaner than blood,” Casciari reveals. “If you take bacteria and expose it to mucus, the mucus will stop the growth of the bacteria. Whereas blood will actually support the growth of the bacteria.” (In fact, researchers in laboratories often deliberately use blood to grow bacteria.) Your mucus is such an important protective agent that you’d die without it. “If you didn’t have mucus in your lungs, you would dehydrate, losing so much water through evaporation that you would die within minutes,” he says. On the other hand, too much mucus production is dangerous.

5. Whatever you inhale quickly goes from your lungs to your brain. 

In under seven seconds, to be precise. Because of your lungs’ enormous surface area and “its intimate relationship with blood vessels that surround it,” says Scott Schroeder, director of Pediatric Pulmonary Medicine at the Floating Hospital of Tufts Medical Center, an inhalation of smoke or a vaporized medicine can reach the brain very quickly.

6. Coughing isn't always bad for your lungs.

Even when you aren’t sick, a normal person coughs about 10 times per day, says Schroeder—whether due to a sticky piece of food, an allergen you accidentally inhale, or your own mucus generated by exercise.

7. Asthma isn't just one disease affecting lung function.

Asthma, which causes wheezing, coughing, and shortness of breath, is actually a number of different illnesses under one name, Schroeder says. The good news is that deaths due to asthma are very uncommon, and have decreased significantly over the last 20 years, he reports (with one notable exception—African-American men age 18–24). But it doesn’t affect everyone equally. Women are much more likely to develop asthma as adults than men, especially if they are overweight. And people in urban areas are more likely to suffer from asthma than those in rural areas, likely due to increased particulate matter in the air from car exhaust and industrial pollutants.

8. Exercise can make asthma—and your lung function—better.

Asthma is actually improved by cardiovascular exercise. Schroeder says there are no sports that people with asthma cannot participate in, “except scuba diving, but I don’t consider that a sport.”

9. You can get lung cancer even if you've never smoked.

“You can spend your whole life in a very clean environment, never having smoked, and still get lung cancer,” Casciari says. Not all lung cancer is caused by cigarette smoking (though the majority is). Casciari cites occupational exposure, radiation exposure, and potential genetic risk factors, although researchers are still exploring the role genetics play. “Folks tend to think of their lungs very little, and when they do, they think, ‘I don’t smoke, so I’m ok,’ but that’s not completely true.”

10. Breakthroughs in lung cancer treatments has improved survival rates. 

For decades, toxic chemotherapy has been the best medicine for treating lung cancer, but it comes with intense side effects. However, several new breakthroughs have recently improved outcomes for patients, says Casciari. Thoracic CT scans, for example, improve survival by 20 percent by providing earlier diagnosis and treatments. Furthermore, new minimally invasive surgery techniques have made recovery from lung cancer surgery much easier, with people being discharged on the same day of surgery. Finally, immunotherapies that target specific cancer markers and harness the immune system itself to fight cancer cells have improved outcomes—and decreased side effects—for lung cancer patients.

This story was first published in 2017.

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