In the weeks after your baby is born, you’ll undoubtedly spend a lot of time snuggled up to your new love for feedings and skin-to-skin contact. You may have taken a breastfeeding course, met with a lactation consultant, or read countless articles about all that comes with nourishing a newborn. The information can be both exciting and overwhelming—just like being a new mom!

Breast milk is a living substance packed full of a startling amount of nutrients and living cells (even stem cells!), among other incredible properties. Your body is designed to make this food to provide the perfect nourishment for your little one, but breast milk is more complex than you probably ever realized.

Here are five fascinating facts about breastfeeding and human milk, the perfect food for your baby.

1. Breast milk is packed with immunity.

What is special about breast milk? The immunity it provides, among other health benefits!

White blood cells protect the body from illness and disease. Around week 16 of your pregnancy, you begin making a yellowish milk called colostrum, the earliest form of breast milk. It contains 1 to 5 million white blood cells per milliliter. Even on the low end of the spectrum, that’s 100 times more than what your blood carries!

No wonder colostrum is referred to as “liquid gold”! By six months postpartum, the white blood cell count drops to 100,000 cells per milliliter—10 times your own concentration. 

Most immune factors decrease after the first year of breastfeeding. Second-year milk, however, sees higher concentrations of lysozyme, an immune factor that attacks bacterial cell walls, protects babies against Salmonella and E. coli, reduces inflammation, and promotes healthy intestinal flora.

Breast milk has also been known to be effective in healing eye infections and ear infections, as well as helping cuts and burns to heal more quickly. Some mothers even use breast milk to provide sore, cracked nipples relief and faster healing. Breast milk is truly a miracle liquid with many uses!

2. The nutrition composition is always changing.

The number of calories and nutrients (carbohydrates, fats, and protein) in breast milk changes from week to week and throughout the day, based on your baby’s needs. 

Newborns can easily digest colostrum’s chemical composition, which revs up their digestive system and helps them pass those first few stools. Colostrum contains 10 times more beta-carotene than mature milk, as well as higher vitamin E and zinc levels for rapid skin and eye development.

The amount of breast milk will increase two to five days after birth. When your breast milk supply starts increasing, the milk is called transitional milk, and it may have a blue tint to it. Mature milk comes in 10-14 days after birth. Mature milk is 3–5 percent fat, packed with vitamins and minerals for your baby’s growth and development.

Over the course of one feeding, the fat content of mature milk can range from 1 percent at the beginning to 5 percent at the end. This change serves as a form of appetite control for little eaters. Mature breast milk is also high in cholesterol, which is important for nerve conduction in the brain and thought to be heart-protective for babies as they grow and develop.

On average, breast milk contains 1.2 grams of fat per ounce, but that varies from person to person and throughout the day. Similarly, protein and lactose levels vary throughout the day. After a year of breastfeeding, the fat content increases to provide for the increased caloric needs of your growing child.

3. Breast milk is a potent cocktail of hormones.

Studies confirm that hormone-level fluctuation triggers certain developmental milestones, such as opening the eyes, reproductive organ development, and growth spurts. Here’s what we know about how some breast milk hormones influence your baby’s development: 

• Melatonin – Varies throughout the day to help your baby wake, sleep, and form a circadian rhythm.
• Thyroxine – Increases over the first week to mature your baby’s intestines and metabolism.
• Epidermal Growth Factor – Found in colostrum and helps develop your baby’s GI tract, also helpful for preemies.
• Leptin – High for the first 180 days to control weight and appetite, influences healthy microbial flora.
• Endorphins – Diminish pain (no wonder ill or injured babies find mother’s milk comforting).

By design, babies often fall asleep soon after they start eating. Each time you breastfeed, you release the relaxation and bonding hormone oxytocin, which has a calming effect on you and your baby, decreasing heart rate and blood pressure for you both. The benefits of this hormone extend long after your baby weans, with a decreased risk of heart disease for both of you!

4. Microbial content varies from day to day.

Over 150 sugars (oligosaccharides) feed your baby’s intestinal microbes to keep healthy digestive bacteria flourishing in your baby's digestive tract. Bacteria from your body transfer through your milk to help your baby establish their own gut flora and immune system. The precise microbial makeup changes from day to day and season to season.

According to biologist Katie Hinde, a baby’s suckling at the breast during a feeding session creates a vacuum; the ensuing “baby spit backwash” delivers messages to the mother’s mammary gland receptors. If a particular pathogen is identified, the mother’s body begins to produce antibodies to fight it, which then travel back to the baby’s body.

This explains why there can be a significant change in the color of breast milk when your baby is sick. Your body adjusts to provide milk that is closer to the nutrient-dense colostrum that you first produced in order to provide illness-fighting antibodies to your baby. Grab your breast pump and check out how your breast milk changes color the next time your little one's sick!

5. Flavors fluctuate and influence your baby’s palate.

Incredibly, your baby can detect the unique scent and taste of your breast milk—and prefer it. Mature human breast milk tastes “sweet and a little nutty, with an almost vanilla-like flavor.” Breast milk can taste saltier after having mastitis, during the last few months of pregnancy, or when milk consumption falls below a certain amount—a change in flavor that may affect your baby’s desire to wean.

Early breast milk experiences deliver unspoken cultural messages to our offspring and help babies determine their own taste preferences. Whatever you eat transfers subtleties of flavor in your milk—be it spicy, sweet, or salty—for up to eight hours after ingestion. You can think of the variations as the different flavors in an exciting meal. Exclusively breastfed babies may have adventurous palates when starting solid foods because of their exposure to a wide variety of flavors.

“You have information about your whole lifespan that could be in your milk,” Hinde explains, pointing to the fact that vegetarian mothers who ate meat as teenagers still pass on those fatty acids to their infants. “Milk is telling the baby about the world its mother has lived in.”  

For Baby AND Mom!

Breast milk is a complex, ever-changing, ever-fascinating substance, designed to give your baby just what they need. Breastfeeding is a wonderful gift for your baby, but don’t forget there are benefits for you too! Breastfeeding promotes faster healing after delivery, stronger bones, reduced anxiety, and bonding time with your baby.

And that's just the start! Studies show that breastfeeding (especially extended breastfeeding or continued breastfeeding) can reduce the risk of breast and ovarian cancer. (Developing a protective factor against breast cancer is incredible, but always remember to do breast self-exams even while nursing!)

Remember, your milk composition isn’t the only thing changing with breastfeeding; breastfeeding mothers may lose weight or gain weight, and their breasts will certainly change. Wearing comfortable, supportive, and flattering nursing clothes that feel good will make your breastfeeding journey much more enjoyable. Moms and babies deserve the softest clothes!

To learn how to find the perfect nursing bra, especially important if you're exclusively breastfeeding or exclusively pumping, click here. Kindred Bravely has a variety of nursing bras and maternity bras to meet your needs, including our patented hands-free pumping and nursing bra and nursing sports bra!

What were you surprised to learn about breastmilk? Please comment below!

Disclaimer: This content is not intended to be a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your health care provider. For more great information, consult the parenting website for the American Academy of Pediatrics (AAP).