Do You Know What's In Breast Milk?

We've heard the mantra "breast is best" repeated a million times over — and while experts are still in agreement that breastfeeding babies for six months or longer is certainly ideal whenever possible, new research suggests that not even breast milk is perfectly pure. According to a study by the Harvard T.H. Chan School of Public Health, significant traces of chemical toxins have been found in breast milk. And in all cases studied, the toxins were being transferred on to each baby.

The presence of the particular chemicals found — perfluorinated alkylate substances (aka PFASs) — are especially worrisome since they've been linked to cancer and have been known to interfere with immune function. They're also a commonly used class of industrial chemicals, according to a press release from Harvard T.H. Chan, which are often used to make a bunch of common household items — like stain-, water-, and grease-resistant products, and have even been found to contaminate certain drinking water sources around the U.S. (So in other words, they're pretty much everywhere.)

But this is perhaps the most troubling part: The PFAS toxins in the study were found to build up over time — by 20 to 30 percent each month — which means that the longer babies breastfeed, the more they're exposed to the toxins. (I know, I know; this all sounds pretty alarming so far, but just read on.)

The presence of toxins in our breasts isn't totally new news — researchers have actually known about it for years. And in her 2012 book, Breasts: A Natural and Unnatural History, author Florence Williams investigated just why, and how, this occurs, by first having her own breast milk tested in Germany. As she later told NPR's Terry Gross, "It turns out that our breasts are almost like sponges, the way they can soak up some of these chemicals, especially the ones that are fat-loving — the ones [that] tend to accumulate in fat tissue. Unfortunately, the breast is also masterful at converting these molecules into food in the way of breast milk."

The problem, of course, has nothing to do with our breasts, at all, or the breast milk they produce. Instead, it has everything to do with the toxins and air pollutants that surround us every day. We've grown so used to chemicals being in so much of what we touch, see, taste, and breathe in that we sometimes forget that they've been tied to everything from giving us cancer to killing off brain cells. As the National Resources Defense Council reports, some 64,000 people die from heart and lung diseases caused by air pollution every year.

As for this recent study, it's important to remember that there's still a ton of research to be done on the matter — and to keep in mind that this research involved a super small sample size in a remote locale. And if you need further reassurance, science has an endless list of proven breastfeeding benefits that will probably do the trick.

Here are just a few of the many reasons why breast milk is still undeniably awesome and important.

1. It Boosts The Immune System, Fighting Off Diseases, Infections, & More

Make no mistake, breast milk has a ton of good stuff in there — including basically all of the protein, sugar, and fat babies need to be healthy. But it's also packed with lots of immune-boosters, like antibodies, immune factors, enzymes, and white blood cells. When mixed together, these help babies fight off lots of diseases (like Crohn's Disease and diabetes) and infections (like ear infections and respiratory ailments). It also helps ward off common conditions like eczema and asthma, as well as sicknesses like vomiting and diarrhea.

2. It Protects Against Childhood Cancers

While a link between breastfeeding and leukemia has been known for years, a recent study in JAMA Pediatrics further backed things up when it found that breastfeeding babies for six months or longer could lower leukemia risks by 19 percent. Considering over 52,000 children are diagnosed with leukemia each year, according to the Leukemia & Lymphoma Society, that 19 percent is pretty significant.

3. It Protects Moms Against A Bunch Of Stuff Too!

According to multiple studies, breastfeeding lowers a mother's risk of developing several cancers, including breast, ovarian, and uterine cancer. It's even been linked to lowering a mom's chance of contracting Type 2 diabetes.

4. It Promotes Bonding Between Mom And Baby

And it's not just about the physical closeness a mom and baby experience during breastfeeding that make the whole thing perfect for bonding. Science has actually proven that when a mom breastfeeds, her body releases oxytocin (aka the "love" hormone), which in turn gives off a chemical surge of feelings ranging from trust to love and affection.

5. It Helps Boosts Brain Activity

A 2013 Brown University study found that babies exclusively breastfed for at least three months had "enhanced development in key parts of the brain," compared to those who were not. As for what those parts of the brain do, exactly? Researchers reported that the sections with the most growth had to do with language, emotional function, and cognition. (So there you are — one more way to turn your kid into a possible baby genius one day.)

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