Benefits of Breastmilk: What’s in it, Anyway?

If you’re currently pregnant, chances are you’ve been thinking about the postpartum period (AKA 4th Trimester) and what feeding your newborn will look like.

I want to start off this blog post by saying no matter what your postpartum feeding journey looks like, you are doing an incredible job. Don’t let anyone make you feel shame or guilt for the decisions you make surrounding feeding yourself and your baby!

That being said, you’ve probably heard from your healthcare providers or friends and family about how breast/chest milk* is rich in nutrients that nourish and protect your baby. But are you aware of all the incredible components that make up breast/chest milk? Or the fact that it changes throughout your postpartum journey? It’s pretty incredible to learn about once you dive in!

*You’ll notice throughout this post that I make an effort to refer to breastmilk/breastfeeding AND chestmilk/chestfeeding. If these terms are new to you or give you pause for any reason, I highly recommend reading this article from Today’s Parent written by lactation consultant, Azura Goodman.

nutrition benefits of Breastmilk / chestmilk

Let’s dive in to what breast/chest milk is usually made up of. And I say usually with some emphasis because the nutritional composition of milk is NOT fixed. It varies based on the stage of milk (how far out from postpartum you are) as well as the breastfeeding or chestfeeding parent’s intake and current nutrient status. Typically, milk is made up of 88% water, 7% carbohydrates, 4% fat, and 1% protein.

Hydration

As you can see from the whopping 88% water content, milk is primarily water. This provides essential hydration for baby and is the reason why infants don’t need any other fluids through at least 12 months of age. Sips of plain water are okay when starting solids at 6 months of age, but breast/chest milk or infant formula should still remain the primary source of fluids and nutrition. Up until 6 months of age, your baby should be exclusively fed breast/chest milk or formula.

Fat

Fat is a crucial nutritional component of milk, providing energy and aiding in growth and development, especially in the development of the nervous system. There are a number of different types of fat present in milk that all provide different benefits, from boosting the immune system to providing energy to developing the gastrointestinal tract. Interestingly, the type of fat present in milk is influenced by the feeding parent’s diet - a great reason to include those brain-building fats like DHA beyond just pregnancy!

The fat content of milk also changes during each feed. The milk at the beginning of each feed is called foremilk while the milk near the end of the feed is called hindmilk. Foremilk is thinner and lower in fat. The fat content slowly increases through the feed, creating a higher-fat hindmilk. Overall, studies have shown that while fat content may change through a single feed, the total fat intake through a 24-hour period remains relatively consistent.

Carbohydrates

Lactose is the primary carbohydrate source in milk and provides an important source of energy (aka calories) that is easily digestible by most infants. The next major carbohydrate source in milk is human milk oligosaccharides (HMOs) which are complex carbohydrates. An important role of HMOs in milk is to provide a source of prebiotics that support a healthy gut microbiome. They are also thought to play a role in regulating the immune system.

Protein

Milk contains whey, casein, and protein building blocks called amino acids all of which support your baby’s growth and development. The ratio of whey to casein changes based on the stage of milk and each form of protein has different roles in the body. Whey protein is easier to digest and makes up a larger percentage of the protein content of milk in the early stages of breastfeeding/chestfeeding. Many of the proteins found in milk support the immune system in addition to aiding growth and development. See the section below on Immune-Support for more details on those components. Unlike the fat content or other components in milk, the protein content remains fairly consistent regardless of the feeding parent’s diet.

Calories

It may go without saying, but milk provides 100% of your baby’s calorie needs in the first 6 months and continues to provide the majority of calorie and nutrition needs up until one year of age. In mature milk, about 50% of calories are from fat and 40% are from carbohydrates.

Vitamins and Minerals

Your milk is rich in vitamins and minerals including iron, calcium, zinc, and water-soluble vitamins. Minerals like iron and calcium are generally not influenced by your diet while water-soluble vitamins like B vitamins are. If you follow a specific diet (vegetarian, vegan, etc), it may be necessary to monitor your diet closely and supplement as needed. Working with a dietitian can be especially helpful if you fall into this category!

Additional Benefits of Breastmilk / Chestmilk that aren’t nutrition

Immune-Support

Milk contains incredible immune-boosting components which protect your baby from illness and infection. These include white blood cells, immunoglobin A (IgA), lactoferrin, and antibodies. Infants fed breast/chest milk are associated with a lower risk of infections and decreased incidence of other conditions like asthma and allergies. You’re essentially giving your baby a handy guide that helps them recognize infections and fight them off. However, that’s not a guarantee that they won’t get sick (if you’ve ever spent time around an infant, you’ll know how ridiculous of a notion that is), but it might certainly help cut down on sick days in your family!

Hormones & Growth Factors

Your milk contains hormones and growth factors that are involved in a myriad of systems in your baby’s body. You might recognize hormones such as insulin, parathyroid hormone, and leptin, among others. Growth factors are involved in the development of the nervous system, regulation of your baby’s metabolism, and maturation of the gut.

Pretty incredible, right? Aside from providing your baby’s sole source of nutrition for those first 6 months postpartum (which on its own feels pretty miraculous), it also helps them stay healthy and continue to develop and grow in that first year of life. And because nutritional science is still such a relatively young field and we’re always learning more, I can almost guarantee there are health benefits to breastmilk / chestmilk beyond what we even know today!

Post updated April 25, 2024

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*The information on this website is provided for educational purposes only and should not be treated as medical advice. Cultivated Nutrition, PLLC makes no guarantees regarding the information provided or how products and foods may work for any individual. If you suffer from a health condition, you should consult your health care practitioner for medical advice before introducing any new products or foods into your health care regimen. Always speak to a qualified practitioner before making any changes to your diet or nutrition. For more information, please read our terms and conditions.