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All About Breast Milk

Although breastfeeding can be tough, the benefits of breast milk are endless.
Written by the Theralogix team of Registered Dietitians
There are pros and cons to both breastfeeding and pumping, and it may take some time for you to discover the perfect feeding routine for you and your baby.

There’s only one word for the female body: incredible.  

Your body can provide everything needed to create life from within. And once you welcome that little bundle of joy into the world, your body can provide everything needed to sustain that life for quite some time.  

In fact, breast milk (and maybe a little extra vitamin D) is all your baby needs for up to six months. Learn all about the wonders of breast milk and how you can kickstart your little one’s nutrition from day one.  

What’s so special about breast milk?  

Here’s the thing: fed is always best. The choice to formula feed or breastfeed is extremely personal, and it’s up to each mother/baby duo to decide what works best for them.  

But it’s no secret that breast milk is the gold standard for infant nutrition, balanced with the perfect amount of fat, carbohydrates, protein, and other components to support the growth and development of your little one. It’s also easier for your baby to absorb and digest nutrients from breast milk.  

Research suggests that breastfeeding helps support cognitive development, healthy weight gain, and immune health. And even though you may only breastfeed for a few months to a year, the benefits of breastfeeding may extend far into the future for both you and your baby.   

Does the composition of breast milk change?  

Your breast milk changes from day one to make sure your baby gets the right nutrients to support their rapid growth. When your milk comes in shortly after birth, it progresses through three main phases:  


Colostrum is the first milk you produce after birth. It’s easy for your baby to digest and packed full of nutrients and antibodies to help your little one build a strong immune system. You won’t make very much of this milk, but that’s okay – your newborn’s stomach is only about the size of a marble. Because of its nutrient-rich profile and deep yellow hue, it’s earned the nickname “liquid gold.”  

Transitional milk 

After the first few days, your breasts may feel fuller as you start to produce more milk to keep up with your growing baby. From day five to 14, your milk is in an in-between phase. It’s not colostrum, but it’s also not quite mature milk, either. It’s transitional milk.  

Transitional milk is creamier in texture and higher in fat and calories than colostrum. It also has higher amounts of lactose, a natural sugar that helps give your baby energy.  

Mature milk  

By the end of the first month, transitional milk gives way to mature milk. Along with carbohydrates and fat, mature milk contains the ideal blend of proteins to support digestion, satiety, and optimal growth for your little one. Although the nutritional content of mature breast milk remains fairly consistent, its composition still changes and adapts in a couple of ways.  

  1. Your breast milk changes over the course of each feed. At the beginning of a feed, your milk tends to be a little more watery and lower in fat – this is called foremilk. As your baby continues to feed, your breast milk gradually transitions to hindmilk, which is creamier and higher in fat.  
  1. Your breast milk can change when you or your baby are sick. When you’re feeling under the weather, your body produces specific antibodies to help you recover. These antibodies pass through your breast milk to offer protection for your baby, too. And researchers believe that your baby’s saliva lets you know when they’re getting sick, prompting your body to produce milk with extra immune health benefits.  
  1. Certain foods may change the taste of your breast milk. A diverse diet while breastfeeding is a great way to expose your little one to a variety of flavors early in life, and may make it easier for them to accept solids when the time comes.  

Should you breastfeed or pump your breast milk?  

If you’ve chosen to nourish your little one with breast milk, you have two main options: breastfeeding or pumping. Most women choose a combination of breastfeeding and pumping, although most experts recommend exclusive breastfeeding for the first 4-6 weeks to establish a healthy breastfeeding relationship. But certain circumstances may require you to introduce the pump earlier, like if you’re returning to work, you’re separated from your little one for long periods of time, or your baby has trouble latching.  

There are pros and cons to both breastfeeding and pumping, and it may take some time for you to discover the perfect feeding routine for you and your baby. 

How should you store breast milk?  

If you’re breastfeeding, you’re nourishing your little one right from the source, leaving little room for contamination. But, if you’re pumping, it’s important to follow proper cleaning and storage guidelines to maintain breast milk quality and safety. 

Your little one is still working on building their immune system, so check out these tips to keep your breast milk safe:  

  1. Always use breast milk storage bags or clean, food-grade containers to store expressed or pumped milk. Ensure that any plastic containers you use are BPA-free. Don’t store breast milk in plastic bottle liners or plastic bags that aren’t intended for storing breast milk.  
  1. Store freshly expressed or pumped breast milk:  
  • At room temperature (up to 77°F) for up to four hours 
  • In the refrigerator for up to four days 
  • In the freezer for up to 12 months (although use within 6 months is preferred for optimal quality) 
  1. Label each storage container with the date and practice first in, first out. That means that you use the oldest milk first.  
  1. Thaw breast milk in the refrigerator overnight or under lukewarm running water. Never thaw or heat breast milk in the microwave – this can destroy nutrients in breast milk and create hot spots that may burn your baby’s mouth. Use thawed, refrigerated breast milk within 24 hours. Once you warm breast milk to room temperature, use it within 2 hours. Discard any unused breast milk after this time. Freezing breast milk in smaller amounts can help reduce waste.  
  1. It’s normal for fat to separate from the breast milk when stored. Just swirl the milk gently to mix it back together.  
  1. Follow Centers for Disease Control and Prevention (CDC) guidelines to make sure you properly clean and sanitize your pump equipment and bottles to prevent breast milk contamination.  

Can you donate (or find donated) breast milk? 

Breast milk is a hot commodity. Some women want to provide breast milk for their little ones but may struggle to maintain a healthy milk supply. Families that adopt babies may prefer to feed them breast milk over formula, but don’t have a way to create a milk supply themselves. That’s where breast milk donation can help. 

The FDA and American Academy of Pediatrics (AAP) recommend avoiding internet-based milk sharing sites, but there are plenty of reputable milk banks that properly screen donors for infectious disease and contamination risk. The Human Milk Banking Association of North America (HMBANA) is a great resource to find a milk bank near you and help expand access to safe breast milk for infants and families across the nation.  

Although breastfeeding can be tough, the benefits of breast milk are endless. Your sacrifice of sleep, time, and energy to nourish your little one doesn’t go unnoticed, and your commitment to provide your baby with the best nutrition possible will benefit them for a lifetime.  

Make sure you’re taking care of yourself, too. Check out this blog next: “New Moms: Transitioning from Pregnancy to Breastfeeding Lifestyle Tips.”