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Thierry Hennet

Breast Milk: The Swiss Army Knife of Bodily Fluids

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Thierry Hennet

We here at mental_floss appreciate urine, and blood is vital. But for sheer versatility, you just can’t beat breast milk. So say scientists today in the journal Trends in Biochemical Sciences, who characterize the fluid as a food, a fertilizer, an umbrella, a clock, a remote control, and a wastebasket.

“Breastfed at Tiffany’s”—that’s the actual name of the journal article—compiles the findings of more than 70 research papers on breast milk and breastfeeding. While the research on the substance is plentiful, the chemistry of the stuff itself remains elusive. Most mammal milk contains around 30 to 50 different sugar molecules. Human milk has more than 200. This complexity is both fascinating and frustrating to chemists.

“Despite its recognized benefits, the structural richness of breast milk has also impeded the characterization of the multiple effects of milk components on infant physiology,” the authors write.

A new mother can make up to 4 1/2 cups of milk per day, a process that requires a tremendous amount of energy. But it’s worth it, the authors write, because of all the things breast milk can do.

To begin with the obvious: Breast milk is terrific nourishment for a fast-growing newborn human. In particular, the rich milk called colostrum, which a mother typically makes just before and after a baby’s birth, has high concentrations of proteins and beneficial carbohydrates.

Breast milk is also a form of protection for infant and mother. Studies have shown that “the ultimate personalized medicine,” as the researchers describe it, decreases infant mortality, can reduce a child’s risk of later obesity, and can even help protect mothers against later breast and ovarian cancer.

Breast milk also helps support the growth of healthy bacteria in a baby’s gut. At birth, each person is equipped with only the bacteria they collected as they exited their mother. (Some have suggested supplementing this bacterial load through a technique called "vaginal seeding," but the jury is still out on its effectiveness.) In order to protect yourself and develop a healthy microbiome, you’re going to need more than that, and you’re going to need to feed them. The plentiful sugar compounds in breast milk give brand-new baby bacteria the sustenance they need to survive and grow.

“Infants don't have the machinery to digest these sugars so they are literally for the bacteria,” paper co-author Thierry Hennet said in a press statement. “It's like a seeding ground, and breast milk is the fertilizer.”

And breast milk contains vitally important antibodies called immunoglobulins, as well as proteins called cytokines, defensins, and lactoferrins, all of which help strengthen and build a baby’s fragile immune system.

As a clock, breast milk helps regulate both hormone circulation in a woman and weaning in her baby. During pregnancy, an ebb and flow of hormones keep a woman from lactating too soon. Once the baby is born, chemicals in the milk itself trigger a decrease in those hormones, allowing a free flow of milk to the baby.

For milk sugars to be absorbed in the gut, they must first be processed by an enzyme called lactase. Our bodies make lactase until we’re around 2 or 3 years old. When that tap shuts off, the sugars proceed, unprocessed, into our gut, where they can cause bloating, cramps, and nausea (a.k.a. lactose intolerance). That intolerance is a not-so-subtle sign for a child’s body that it’s time to stop breastfeeding.

Breast milk also operates as a remote control for a baby’s growth. The hormones leptin, insulin-like growth factor 1, and adiponectin contribute to an infant’s fat storage, metabolism, and overall body growth.

Lastly, there’s the wastebasket function, which is as undesirable as it sounds. Harmful chemicals, including pesticides, heavy metals, and medications, can accumulate in a mother’s breasts and breast milk, then pass into her child.

Breast milk's other claim to fame? It influenced the scientific name for humans, mice, cows, weasels, and everything in between. According to the authors, “Breast milk is ultimately why Carolus Linnaeus, as the father of seven children, chose the term Mammalia to define our own class of animals in the tree of life.”

Of course, breastfeeding is not an option or the right choice for every mother. Experts agree that baby formula, designed specifically to meet infants' nutritional needs, is a safe alternative. 

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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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science
Are Sex, Drugs, and Rock 'n' Roll Really Linked? Researchers Investigate
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Around the world, sex, drugs, and rock 'n' roll are said to go hand-in-hand. But do they? As PsyPost reports, a pair of Pennsylvania psychologists recently dove into the empirical evidence tying the three together, asking college students to talk about their drug use, sex lives, and music preferences and talents to suss out whether people who play and enjoy rock music really do have more active sex lives and drug use.

Published in the journal Human Ethnology Bulletin, the study [PDF] of 467 students relied on self-reporting, which isn't typically the most reliable evidence—people are wont to exaggerate how often they've had sex, for instance—but the survey also asked them about their desires, posing questions like "If you could, how frequently would you have sex?" It also asked about how often the students drank and what drugs they had tried in their lifetimes. They also described their musical experience and what kind of music they listened to.

The results were mixed, but the researchers identified a relationship between liking faster, "harder" music and having more sex and doing more drugs. Acoustic indie rock aficionados weren't getting quite as wild as heavy metal fans. High-tempo-music lovers were more likely to have taken hallucinogenic drugs like LSD, for example, and tended to have had more sexual partners in the previous year than people who favored slower types of music. According to the study, previous research has found that attention-seeking people are more likely to enjoy "hard" music.

The study didn't have a diverse enough group either in age or in ethnicity to really begin to make sweeping generalizations about humans, especially since college students (the participants were between 18 and 25) tend to engage in more risky behaviors in general. But this could lay the groundwork for future research into the topic. Until then, it might be more accurate to change the phrase to "sex, drugs, and heavy metal."

[h/t PsyPost]

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