Human breast milk is a medical marvel in many ways. For one, scientists have discovered that it's the most complicated milk substance produced by any mammal. Milk contains sugars, known as oligosaccharides, and a study in 2010 found that human breast milk contains over 200 kinds, versus an average of 30 to 50 in the milk of cows or mice. The complexity of the sugars, the research team thinks, likely helps the immune system of the baby develop, fight infections, set up its gut microbiology, and many other important chores. But sugars aren't the only element in breast milk. It also contains proteins, and one of them seems to be useful beyond just nourishing babies: for the battle against cancer.

The protein itself is alpha-lactalbumin, and researchers have turned it into a substance called HAMLET (Human Alpha-lactalbumin Made LEthal to Tumour cells [sic]). And in tests in 2010, it killed 40 different kinds of cancer cells while leaving healthy cells untouched. Trials are still continuing, but HAMLET, and by extension breast milk itself, is hoped to be one of the many therapies that could help cancer patients in the future.

Premature babies can endure a lot of medical issues, but it seems that their mothers, if they choose to and are able to breastfeed, might be able to help them play metabolic catch-up with full-term babies. Research released by Penn State this month has found that the breastmilk the body produces for premature babies is a bit different than what's produced for full-term ones, and that the difference seems to help boost the premies' metabolic performance.

They looked at the breast milk of mothers who'd had premature children — born between 27 and 37 weeks gestation — and noticed that it has a different selection of microRNA in it. MicroRNAs are tiny bits of RNA, an acid that's involved in the body's gene expression, and the ones in breast milk will be passed on to babies. The breast milk of moms of premature babies contains microRNA that's angled towards helping gastrointestinal function and fat storage. It helps premature babies gain weight faster and face less developmental delays. This is particularly important as a discovery because premie babies in the ICU often drink donated milk, which might be depriving them of a personalized diet that's like spinach to Popeye.

Research published in June ACS Infectious Diseases has found that sugars found in some breast milk go to war against Group B strep bacteria — and win. The small study was focused on Strep B because those bacteria are known to be seriously damaging to pregnancies and infants, and whether or not it can be transmitted to a child via breastfeeding is a big concern. What the researchers found was intriguing and a big sign for further research: In some women's breast milk, sugars went forth and broke up Strep B colonies, preventing them from spreading and protecting the babies from infection.

The really weird thing, which we can't explain yet, is that the researchers found this result in some women but not others. Why remains a mystery. Now research needs to be done on all the factors that might affect this Strep B battleground in breast milk — and whether the sugars involved could be used in other ways, to help fight infection in antibiotics.

Recent research from Canada found a direct link between women eating peanuts while breastfeeding and their children's allergies to peanuts as they grew. They asked the parents of 347 babies about whether they'd eaten peanuts during the breastfeeding period and when they might have introduced peanuts into their children's lives, and then tested the kids themselves for peanut sensitivity once they hit seven years of age. The results show that, if you want your child to avoid a peanut allergy (and you don't have one yourself), one of your best bets is to eat peanuts while breastfeeding, then introduce peanut products before your infant is a year old.

But the important thing, the study noted, was that you had to do both; just having peanut-tasting milk made children (and not introducing peanuts once the child is weaned) a bit more likely to develop peanut allergies, not less. Understanding how children develop allergies in response to environmental triggers remains an odd science, but it seems that breast milk may be part of a mother's protective arsenal.

The sugars within breast milk are attracting attention not just for their many benefits for babies, but for their potential aid for adults. One of the most interesting elements of breast milk are its sugars, or oligosaccharides, for the reason that babies can't actually digest them. They pass into the babies' gastrointestinal system, where, according to a review of the science from 2012, they feed healthy microbiomes, lower the risk of infections and viruses, boost the immune system, and help give babies good ingredients for brain development. And the superfood industry is interested in its potential applications for adults.

One start-up, Sugarlogix, think that these kinds of sugars, known as "pre-biotics," might be good for adult gut health too, as they could create a welcoming environment for healthy bacteria to grow. There are hundreds of types of breast milk sugars, but it's focusing on one, 2′-fucosyllactose, which may improve human immune response. It wouldn't be a sweetener, but will operate purely as a digestive boost, rather like yogurt, but with more interesting origins.