10 Scientific Benefits of Kissing

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Kissing may be the most primal way we express affection with other humans. We kiss babies on their adorable chubby faces, friends on the cheeks, and lovers on the lips in demonstration of our feelings and desire for closeness. Kissing may be one of the earliest evolutionary mechanisms for social bonding. While there are plenty of obvious pleasures of smooching, there are also some remarkable health benefits, backed by science. Check out these 10 benefits of lip smacking:

1. KISSING RELEASES FEEL-GOOD HORMONES …

Kissing activates the brain’s reward system, releasing neurotransmitters like oxytocin, "the love hormone," and vasopressin, which bonds mothers with babies and romantic partners to each other. It also releases endogenous opioids, dopamine, and other helpful neurohormones to keep our moods balanced.

2. … WHICH HAVE HEALING ABILITIES.

A 2005 study in Neuroendocrinology Letters adds, "Thus, love, pleasure, and lust have a stress-reducing and health-promoting potential, since they carry the ability to heal or facilitate beneficial motivation and behavior." In other words, by reducing your stress hormones, your body can better focus on healing any physiological processes that are exacerbated by stress, and help contribute to more positive mental health and behavior.

3. IT MAKES YOU MORE ALERT.

Kissing often stimulates the release of adrenaline and noradrenaline—not only do these make you feel excited by increasing your heart rate, they make you more alert, as your body prepares for action…of any kind.

4. SMOOCH MORE FOR REDUCED STRESS …

According to affection exchange theory, as mentioned in a 2009 study in the Western Journal of Communication [PDF], physical exchanges of affection, including kissing, "buffer the individual against the physiological effects of stress." The researchers found that expressed affection, of which kissing is a prime example, was directly related to lowering the stress hormone cortisol throughout the day.

5. … WHICH MIGHT HAVE A POSITIVE AFFECT ON YOUR CHOLESTEROL.

The same study authors theorize that if affectionate behavior reduces stress, "then it is logical to predict that it will also effect improvements on physiological parameters that are exacerbated by stress" such as cholesterol. Cholesterol has a number of essential physiological functions, they write, "including maintaining membrane fluidity, producing bile, and contributing to the metabolism of fat-soluble vitamins." It’s also "largely responsible" for the production of steroid hormones, such as cortisol, aldosterone, progesterone, the estrogens, and testosterone.

6. KISSING EVEN IMPROVES ALLERGY SYMPTOMS …

Allergic responses can be aggravated by stress. Since kissing reduces stress by sending those feel-good hormones mentioned earlier to the brain, as well as alleviating cortisol, a 2003 Japanese study in Physiology and Behavior explored the relationship between the stress-lowering activity of kissing on allergic reactions. Ninety participants were evenly divided into three groups: 30 with atopic dermatitis, 30 with allergic rhinitis, and 30 in a control group. In the study, the subjects, whom the authors noted "do not kiss habitually," kissed for 30 minutes with their partner in a private room while listening to soft music. They found that at the end of their smooch sessions, the participants experienced significant relief from skin wheals (hives) and plasma neurotrophin levels (a sign of allergic reaction) associated with Japanese cedar pollen and house dust mites. In 2015, this study won an Ig Nobel prize.

7. … AND MIGHT ALSO BOOST YOUR IMMUNITY.

When you kiss someone on the lips you exchange bacteria. This can either make you sick, or it can help boost your immunity by exposing you to new germs that strengthen your immune system's ability to fight these bacteria. A 2014 study in the journal Microbiome found that couples who kissed frequently were more likely to share the same microbiota in their saliva and on the surface of the tongue. How frequently? At least nine times per day.

8. A KISS A DAY KEEPS THE DENTIST AWAY?

The act of kissing stimulates your salivary glands to produce saliva, the fluid that moistens the mouth to make swallowing easier. Saliva also helps remove cavity-causing particles that stick in your teeth after eating. So while it might be a stretch to say kissing prevents cavities, it can’t hurt.

9. IT MAY HELP YOU DETERMINE THE COMPATIBILITY OF YOUR MATE …

Perhaps the way you know you’ve found the one has nothing to do with their eyes, kind words, or the way they romance you, but very subtle cues you pick up through kissing. According to a 2013 study in the Archives of Sexual Behavior, kissing "might facilitate the subconscious appraisal of a potential mate by utilizing pheromonal cues to assess genetic … compatibility, general health, underlying genetic fitness or menstrual cycle phase and fertility." (Note the "might" here—we still haven't found evidence of human pheromones.) In fact, the authors write, in a handful of societies where mouth-to-mouth partner contact is unknown or frowned upon, such as the Mehinaku of Brazil (in fact, only 46 percent of cultures are known to kiss romantically), romantic partners still engage in "kissing traditions of close face-to-face contact involving sniffing, licking or rubbing."

10. … AND IMPROVE YOUR RELATIONSHIP SATISFACTION.

The same study authors suggest that romantic kissing, as well as other forms of physical contact, can strengthen feelings of attachment to the person you're kissing, increasing the feeling of relationship satisfaction between romantic partners. And a 2013 study in the Archives of Sexual Behavior found that more frequent kissing was linked to couples’ perceived feelings about the quality of a relationship—namely, the more kissing, the happier they were—which was not the case for more sex.

For the First Time Ever, a Woman Has Won the Abel Prize—Math's Version of the Nobel Prize

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Every year since 2003, the Norwegian Academy of Science and Letters has bestowed the Abel Prize for excellence and contributions in the field of mathematics. Every year, the recipient has been a man. In 2019, Karen Uhlenbeck crushed that dubious tradition and became the first woman to win the Abel Prize and its $700,000 award.

An emeritus professor at the University of Texas at Austin, Uhlenbeck’s work is focused on gauge theory and geometric analysis—the latter a field she pioneered. Gauge theory supports theoretical physics and is involved in the research of particle physics and string theory. Uhlenbeck is also credited with work that led to greater comprehension of the unification of forces, a primary objective in physics that attempts to link electromagnetic force and weak nuclear force with strong nuclear force in a single theory, which would help us understand the universe.

Mathematician and Abel Prize winner Karen Uhlenbeck is seen in a portrait
Courtesy of the University of Texas at Austin

Uhlenbeck arrived at UT Austin in 1987 and stayed after her retirement in 2014. During that time, she co-founded several programs, including the Saturday Morning Math Group and Distinguished Women in Mathematics lecture series, both in Texas, as well as the Park City Mathematics Institute and the Woman and Mathematics program at the Institute for Advanced Study in Princeton, New Jersey.

She achieved another milestone in her field in 1990, when she became the second woman (and the first since 1932) to host a plenary lecture at the International Congress of Mathematicians.

The Abel Prize, which is modeled after the Nobel Prize, is named after Norwegian mathematician Niels Hendrik Abel. Uhlenbeck will receive the prize in Oslo on May 21.

[h/t New Scientist]

12 Intriguing Facts About the Intestines

When we talk about the belly, gut, or bowels, what we're really talking about are the intestines—long, hollow, coiled tubes that comprise a major part of the digestive tract, running from the stomach to the anus. The intestines begin with the small intestine, divided into three parts whimsically named the duodenum, jejunum, and ileum, which absorb most of the nutrients from what we eat and drink. Food then moves into the large intestine, or colon, which absorbs water from the digested food and expels it into the rectum. That's when sensitive nerves in your rectum create the sensation of needing to poop.

These organs can be the source of intestinal pain, such as in irritable bowel syndrome, but they can also support microbes that are beneficial to your overall health. Here are some more facts about your intestines.

1. The intestines were named by medieval anatomists.

Medieval anatomists had a pretty good understanding of the physiology of the gut, and are the ones who gave the intestinal sections their names, which are still used today in modern anatomy. When they weren't moralizing about the organs, they got metaphorical about them. In 1535, the Spanish doctor Andrés Laguna noted that because the intestines "carry the chyle and all the excrement through the entire region of the stomach as if through the Ocean Sea," they could be likened to "those tall ships which as soon as they have crossed the ocean come to Rouen with their cargoes on their way to Paris but transfer their cargoes at Rouen into small boats for the last stage of the journey up the Seine."

2. Leonardo da Vinci believed the intestines helped you breathe.

Leonardo mistakenly believed the digestive system aided respiratory function. In 1490, he wrote in his unpublished notebooks, "The compressed intestines with the condensed air which is generated in them, thrust the diaphragm upwards; the diaphragm compresses the lungs and expresses the air." While that isn't anatomically accurate, it is true that the opening of the lungs is helped by the relaxation of stomach muscles, which does draw down the diaphragm.

3. Your intestines could cover two tennis courts ...

Your intestines take up a whole lot of square footage inside you. "The surface area of the intestines, if laid out flat, would cover two tennis courts," Colby Zaph, a professor of immunology in the department of biochemistry and molecular biology at Melbourne's Monash University, tells Mental Floss. The small intestine alone is about 20 feet long, and the large intestine about 5 feet long.

4. ... and they're pretty athletic.

The process of moving food through your intestines requires a wave-like pattern of muscular action, known as peristalsis, which you can see in action during surgery in this YouTube video.

5. Your intestines can fold like a telescope—but that's not something you want to happen.

Intussusception is the name of a condition where a part of your intestine folds in on itself, usually between the lower part of the small intestine and the beginning of the large intestine. It often presents as severe intestinal pain and requires immediate medical attention. It's very rare, and in children may be related to a viral infection. In adults, it's more commonly a symptom of an abnormal growth or polyp.

6. Intestines are very discriminating.

"The intestines have to discriminate between good things—food, water, vitamins, good bacteria—and bad things, such as infectious organisms like viruses, parasites and bad bacteria," Zaph says. Researchers don't entirely know how the intestines do this. Zaph says that while your intestines are designed to keep dangerous bacteria contained, infectious microbes can sometimes penetrate your immune system through your intestines.

7. The small intestine is covered in "fingers" ...

The lining of the small intestine is blanketed in tiny finger-like protrusions known as villi. These villi are then covered in even tinier protrusions called microvilli, which help capture food particles to absorb nutrients, and move food on to the large intestine.

8. ... And you can't live without it.

Your small intestine "is the sole point of food and water absorption," Zaph says. Without it, "you'd have to be fed through the blood."

9. The intestines house your microbiome. 

The microbiome is made up of all kinds of microorganisms, including bacteria, viruses, fungi, and protozoans, "and probably used to include worm parasites too," says Zaph. So in a way, he adds, "we are constantly infected with something, but it [can be] helpful, not harmful."

10. Intestines are sensitive to change.

Zaph says that many factors change the composition of the microbiome, including antibiotics, foods we eat, stress, and infections. But in general, most people's microbiomes return to a stable state after these events. "The microbiome composition is different between people and affected by diseases. But we still don't know whether the different microbiomes cause disease, or are a result in the development of disease," he says.

11. Transferring bacteria from one gut to another can transfer disease—or maybe cure it.

"Studies in mice show that transplanting microbes from obese mice can transfer obesity to thin mice," Zaph says. But transplanting microbes from healthy people into sick people can be a powerful treatment for some intestinal infections, like that of the bacteria Clostridium difficile, he adds. Research is pouring out on how the microbiome affects various diseases, including multiple sclerosis, Parkinson's, and even autism.

12. The microbes in your intestines might influence how you respond to medical treatments.

Some people don't respond to cancer drugs as effectively as others, Zaph says. "One reason is that different microbiomes can metabolize the drugs differently." This has huge ramifications for chemotherapy and new cancer treatments called checkpoint inhibitors. As scientists learn more about how different bacteria metabolize drugs, they could possibly improve how effective existing cancer treatments are.

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