10 Brainy Facts About Your Gut (It’s Smarter Than You Think)

Gut feelings get all the press, but your gut may be more of a thinker than you knew. Scientists now think of it as your 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 smart gut.

1. The gut is the only organ system that can perform its functions without the oversight of the brain.

You might think of your gut as the rebel against authority; it doesn’t wait for your brain’s impulses to do the important work of digestion. 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 over 100 million brain cells in your gut.

Your gut’s power to think for itself is no surprise; there are millions of brain cells, or 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. The 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. (Or else the brain just doesn’t like to get its, er, hands dirty.)

4. The gut sends emotional signals to the brain—suggesting we "feel" with our guts first.

There’s one big, bad 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. GI conditions can be seen as the "mental illness" of 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. Think about that. It’s no wonder that diet, medications, and antibiotics can wreak havoc on one’s mood.

6. A healthy gut may protect your bones.

Colorized scanning electron micrograph of Escherichia coli, a common gut bacteria. Image credit: NIAID via Wikimedia Commons // CC BY 2.0

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. New research shows links between Autism and 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 affects your mood, and not just “comfort food.”

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, right?) as it appears to trigger the release of dopamine—the brain’s natural opiate. Whereas 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 mounting the defense against killing and expelling the foreign invaders of illness. 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, just like your brain.

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, in fact, contribute to the intense difficulty some addicts have trying to kick the habit.

The Surgeon Who Removed His Own Appendix

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iStock

On February 15, 1921, Dr. Evan O’Neill Kane decided to test a theory. At the time, people with heart conditions and other serious ailments could not undergo most basic surgeries because general anesthesia was considered too dangerous. Rather than knocking these patients out, Kane wondered if he could simply give them a local anesthetic.

There was only one way to be sure: Kane decided to give himself an appendectomy.

As the chief surgeon at Kane Summit Hospital in Pennsylvania, Kane could probably perform the procedure blindfolded. The 60-year-old physician had performed more than 4000 appendectomies over his 37-year medical career. (Besides, the timing was right: He had chronic appendicitis and the organ needed to be removed anyway.)

For his experiment, Kane decided to numb the area with novocaine. “Sitting on the operating table propped up by pillows, and with a nurse holding his head forward that he might see, he calmly cut into his abdomen, carefully dissecting the tissues and closing the blood vessels as he worked his way in,” The New York Times reported. “Locating the appendix, he pulled it up, cut [it] off, and bent the stump under.” Finished with the dirty work, he let his assistants tie up the wound.

When a reporter visited a few hours later, Kane declared he was “feeling fine” [PDF].

Overall, he was pleased with the procedure. “I now know exactly how the patient feels when being operated upon under local treatment, and that was one of the objects I had in mind when I determined to perform the operation myself,” Kane later explained to The New York Times [PDF]. “I now fully understand just how to use the anesthesia to best advantage when removing the appendix from a person who has heart or other trouble that prohibits the use of a complete anesthesia.”

This was hardly the beginning—or end—to Kane’s career as his own surgeon. Two years earlier, he had amputated his own infected finger. And 10 years after the self-appendectomy, when he was 70, Kane calmly operated on his own hernia, joking with nurses throughout the whole 50-minute operation. Thirty-six hours later, he was back in the operating room, this time patching up other people.

Kane wouldn't be the last doctor to scoop out his own appendix. In 1961, Leonid Rogozov, the sole physician at the Soviet Union's Antarctic research station, performed an emergency self-appendectomy with the station's meteorologist and mechanic as his assistants [PDF]. More recently, Beirut surgeon Dr. Ira Kahn allegedly removed the organ himself in 1986. Unlike Kane, however, Kahn didn’t put himself under the knife for the sake of a medical experiment: Stuck in a traffic jam and unable to make it to the hospital for emergency surgery, he performed the procedure from the comfort of his car.

10 Smart Facts About Wisdom Teeth

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iStock

Like puberty and your first heartbreak, the painful process of getting your wisdom teeth removed is one of those cumbersome coming-of-age rituals that many people are forced to endure. But why do we have wisdom teeth when they seem to only cause problems? Read on to find out more about the humble third molar—the last tooth many of us get as adults.

1. THEY HAVEN’T SERVED ANY PURPOSE FOR HUNDREDS OF THOUSANDS OF YEARS.

Imagine, for a moment, that you’re a prehistoric man or woman. You subsist largely on raw meat, roots, and leaves. You’d need some pretty powerful chompers to cut up your food, right? That was where your third molars—also known as wisdom teeth—came in. Today, our palates are a little more refined, and we prefer softer foods (think avocado toast and smoothies). Plus, modern cooking tools have put our wisdom teeth out of business.

They’re not just pointless, though—they’re also problematic. Wisdom teeth are a “scar of human evolution,” according to Princeton University researcher Alan Mann. About 800,000 to 200,000 years ago, early humans’ brains started growing at a rapid pace—so much so that they ballooned to three times their original size. When that happened, it changed the shape of the braincase (the back part of the skull) and its position relative to the dental arcade (rows of teeth). The dental arcade shortened, and suddenly there was no longer enough room for third molars. And since the genes that determine the makeup of our teeth evolve separately from those that control brain development, humans were stuck dealing with the consequences of a crowded mouth, according to Live Science.

2. NATURE MAY EVENTUALLY SORT IT OUT, THOUGH.

On the bright side, scientists say evolution may eventually take care of the problem, meaning that people in the future would not develop wisdom teeth. It’s anyone’s guess as to when this will occur, though. “On the evolutionary scale, if I had to predict down the road—centuries probably—wisdom teeth are going to be one of the things that humans probably won’t have anymore,” Dr. William McCormick, assistant clinical professor at West Virginia University’s School of Dentistry, tells Mental Floss.

3. THE NUMBER OF WISDOM TEETH VARIES FROM PERSON TO PERSON ...

It’s possible that you have one, two, three, four, or none at all. Another possibility, although it’s rare, is to have more than four wisdom teeth, which are called supernumerary teeth. “In my career, I have seen two cases where patients have had fourth molars—or two sets of wisdom teeth,” McCormick says. (Comparatively, humans’ ancestors had quite the mouthful, with 12 wisdom teeth in total.)

According to McCormick, genetic factors like jaw size might determine the number of wisdom teeth that a person has. Your lineage may also have something to do with it. Practically no Aboriginal Tasmanians have third molars, but almost 100 percent of indigenous Mexicans have at least one wisdom tooth. African Americans and Asian Americans are also more likely than people of European descent to have fewer than four wisdom teeth. This variation can be attributed to a random genetic mutation that arose thousands of years ago, thereby preventing the formation of wisdom teeth. This mutation is more prevalent in certain populations.

4. ... AS DOES THE NUMBER OF ROOTS THAT EACH TOOTH HAS.

The roots are the part of the tooth that form first, and then push the bud (the part that's visible in your mouth) through your gums. While wisdom teeth typically have two or three roots, they can have more. McCormick says he personally removed his wife’s wisdom teeth in the ‘70s and was surprised to see that one of them had five roots. “It looked like a spider. It was not a pleasant extraction,” he says.

For that reason, if wisdom teeth need to be removed, it’s easier to do so before the roots start to take hold. “When the roots are totally formed, they’re anchored like a tree that’s been in your backyard for 100 years,” says Dr. Ron Good, an orthodontist in southwestern Pennsylvania who runs a family practice with his brother, Dr. Bob Good. On the other hand, surgeons want some roots to grab hold of, because removing a tiny tooth bud is “like extracting a marble,” Dr. Ron tells Mental Floss.

5. YOUR WISDOM TEETH CAN ERUPT AT ANY TIME.

According to Guinness World Records, the oldest person to ever grow a wisdom tooth was 94 years old. McCormick says there's a wide variation in ages when eruption occurs; he once had a 65-year-old patient with dentures whose wisdom tooth had started to erupt (poke through the gums). “They’re crazy little beasts. You never know what you’re going to see.”

Apparently, wisdom teeth have been acting erratically for thousands of years. Aristotle documented this phenomenon in his book The History of Animals: “Cases have been known in women upwards of 80 years old where at the very close of life the wisdom-teeth have come up, causing great pain in their coming; and cases have been known of the like phenomenon in men too.”

In most cases, though, wisdom teeth erupt when you’re in your late teens or early twenties.

6. THE FIRST IMPACTED TOOTH WAS RECORDED ABOUT 15,000 YEARS AGO.

When wisdom teeth don’t have enough room to grow normally, they get stuck in the jaw and fail to erupt. These are called impacted teeth. The oldest known case of an impacted tooth was found in the skeleton of a 25- to 35-year-old woman who died some 15,000 years ago. This case cast doubt on the theory that impacted teeth are a modern ailment, caused by recent changes in our dietary habits.

7. SOME PHYSICIANS SAY THAT IMPACTED WISDOM TEETH SHOULD BE SURGICALLY REMOVED ...

Many people get their wisdom teeth removed, even if there isn’t any pain or discernible problem aside from impacting. Known as prophylactic surgery, this preventative practice is common in the U.S., but in recent years there has been some debate as to whether it’s necessary. One popular theory holds that most people either have problems with their wisdom teeth or will at some point in the future. “It’s hard to get a percentage, but probably 75 to 80 percent of people do not meet the criteria of being able to successfully maintain their wisdom teeth,” Dr. Louis K. Rafetto, who headed a task force on wisdom teeth, told The New York Times in 2011.

About 3.5 million extraction surgeries are performed each year, and according to another estimate, that adds up to be 10 million individual wisdom teeth pulled annually. Dr. Ron and Dr. Bob, of Good Orthodontics, are both of the opinion that wisdom teeth are ticking time bombs. “In our mind, we feel that wisdom teeth, in general, are of no value and are only potential problems,” Dr. Bob says. He added that third molars can interfere with your bite and cause your teeth to wear down, and in some cases, can also cause cysts, tumors, nerve damage, periodontal disease (affecting the gums and other areas around the teeth) and TMJ disorders (affecting the jaw joint). Plus, if your teeth are too crowded and you aren’t able to brush and floss them normally, it can lead to additional issues, such as gum disease and cavities.

8. ... WHILE OTHERS SAY YOU SHOULD AVOID IT.

Dental practitioners in the UK put an end to routine wisdom tooth extractions in 1998, citing a study at the University of York that reportedly found no scientific evidence to support the practice, according to the The Miami Herald.

Opposition is building in the U.S., too. Retired dentist Dr. Jay Friedman told How Stuff Works that only about 12 percent of wisdom teeth eventually cause problems. He compared that rate to the 7 to 14 percent of people who experience appendicitis, yet appendixes aren’t removed until they become a medical issue. If this seems to contradict Raffeto's statistics, it’s because there isn’t a whole lot of concrete data on the subject, and much of it is conflicting—so it really comes down to the individual physician’s and patient's preferences. “Ask three dentists the same question, and you’re going to get four different answers,” McCormick says with a laugh.

Like Friedman, McCormick doesn't support wisdom tooth removal unless there’s an infection, abscess, or other problem. “You have to weigh the surgical risk with what you’re going to try to accomplish,” he says. Like any surgery, wisdom tooth extraction poses a risk, although more serious complications, like fractured jaws and death, are extremely rare. McCormick says some possible side effects include nerve damage, infection, and dry socket (an infection of the tooth socket).

Despite the differing opinions in the dental community, McCormick, Dr. Ron, and Dr. Bob agreed that there’s no prescriptive rule for wisdom tooth removal, and that each patient should be evaluated on a case-by-case basis.

9. THEY’RE CALLED LOVE TEETH IN KOREAN.

In English, the name wisdom tooth conveys the idea that third molars come in later than other teeth, at a time when you’re older and (hopefully) wiser. Other languages don’t follow the same convention. In Korean, for example, the poetic name for third molars translates to “love teeth,” because it's around this time (late teens and early 20s) that one typically experiences their first love. The Japanese language also has a creative word for it: oyashirazu, or “unknown to parents,” since most people have already moved away from home by the time their wisdom teeth come in.

10. THEY’RE USED IN STEM CELL RESEARCH.

It turns out wisdom teeth aren't all bad. Although some of the research is still in the experimental phase, scientists are studying dental stem cells—which were discovered in 2003—to see if they can potentially be used to repair and regenerate tissue.

One study on mice, at the University of Pittsburgh’s School of Medicine, found that stem cells taken from wisdom teeth could someday be used to repair corneas that have been scarred by infection or injury. Any clinical applications for humans would require more research, though.

"There are studies with dental pulp cells being used to treat neurological disorders and problems in the eye and other things,” Dr. Pamela Robey, of the National Institute of Dental and Craniofacial Research, told CNN. “The problem is, these studies have really not been that rigorous ... the science needs a lot more work.”

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