The Benefits of Breastmilk Part 1 - Tailored Nourishment For Your Baby


  • Breastmilk provides the ideal amount of nutrients for your baby.
  • Nutrients in breastmilk change as your baby ages. For example colostrum, the first milk, has the highest levels of protein, while mature milk has less protein and more fats and carbohydrates.
  • Breastmilk changes during a feeding: breastmilk at the beginning of a feed is high in ghrelin, a hormone that stimulates appetite. Breastmilk at the end of a feeding is higher in leptin, a hormone that suppresses appetite.
  • Daytime breastmilk has more cortisol than nighttime breastmilk, which makes your baby feel alert.

Breastmilk is nature’s liquid gold. A mom’s body naturally adjusts her breastmilk composition to meet her baby’s nutrient requirements, making your breastmilk unique to you. Breastmilk provides several benefits to your baby.

In the first part of this series, we’ll dive deep on what is in breastmilk and how the nutritional and hormonal composition changes depending on your baby’s age, feeding, and even time of the day.

Nutrients in breastmilk

Breastmilk has the ideal nutrient composition for your baby. Research shows that your breastmilk often contains:

  • 87%-88% water
  • About 7% carbohydrates
  • 3.5-4.5% fat
  • 0.7-1.6% protein

And it provides around 50 to 70 calories/100 mL [1], [2]. 

Carbohydrates in breastmilk

Carbohydrates are different types of sugars that make up the largest portion of macronutrients in breastmilk. They provide the necessary energy for a baby to thrive.

Lactose is the main carbohydrate found in breastmilk. It’s a type of sugar that your baby is able to digest in their developing gastrointestinal tract. It helps your baby absorb calcium and minerals [3]. Lactose intolerance is very rare in babies, and it’s important to note that symptoms of cow’s milk protein allergy (CMPA) are often mistaken for lactose intolerance. True lactose intolerance typically develops after five years of age [4].

Human milk oligosaccharides, also known simply as HMOs, are unique milk sugars only found in breastmilk [5]. There are over 200 different types of HMOs in breastmilk [5]. After lactose and fat, HMOs are the third most abundant component of breastmilk [6].

HMOs don’t provide direct nutrients to your baby, but to your baby’s gut microbiome. Certain gut microbes like Bifidobacterium are able to feed on HMOs for their own energy. This influences both the composition and activity of the gut microbiome. 

When gut microbes feed on HMOs, they produce short-chain fatty acids (SCFAs) such as acetate, butyrate, and propionate. SCFAs help maintain gut integrity and protect against gut inflammation [7].

Fat in breastmilk

Fat makes up the second largest proportion of macronutrients in breastmilk. Not only does it provide energy, it also plays an important role in the development of the central nervous system. 

The main breastmilk fat components are triglycerides. These are digested and provide energy for your baby, and make up around 95%–98% of the total fat in breastmilk [2].

Breastmilk also contains two essential fatty acids:

  • Linoleic acid, an omega-3 fatty acid
  • Linolenic acid, an omega-6 fatty acid 

Linoleic acid has anti-inflammatory properties and is a precursor to the longer chain omega-3s known as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These promote the healthy development of your baby’s brain, nerves, and eyes [8].

Omega-3 and omega-6 fatty acids are considered “essential” because they cannot be created by the human body. They need to be ingested. Your baby gets them from your breastmilk. But you need to get them from food.

In other words, breastmilk fat content is influenced by mom’s diet [2]. 

Research has shown that certain dietary choices by breastfeeding moms can influence the proportion that trans fat makes up in breastmilk. Trans fats can even increase to as high as 7.7% of total fatty acids in breastmilk [9].

Trans fat, also called trans-unsaturated fatty acids or trans-fatty acids, is a type of fat that can be harmful for your baby. It raises bad cholesterol (LDL) and is associated with a higher risk of developing type 2 diabetes. So, decreasing foods high in trans fat can help decrease the proportion it makes up in breastmilk.

Some food sources to avoid that have been found to increase trans fatty acids in breastmilk include prepared and processed foods such as:

  • Bakery items (cakes, pies, breads, rolls, and cookies)
  • Snack foods (chips, pretzels, crackers)
  • Fast foods
  • Margarines 
  • Shortening [9]

Consider selecting foods high in healthy fats, such as omega-3, to ensure higher proportions in breastmilk. 

Some foods high in omega-3 fatty acids include:

  • Certain seafood (salmon, anchovies, tuna, trout, and halibut)
  • Nuts and seeds (chia seeds, flaxseeds, and walnuts)
  • Plant oils (flaxseed oil, olive oil, and soybean oil)

Protein in breastmilk

Protein makes up the smallest percentage of macronutrients in breastmilk. Breastmilk protein is made up of a mixture of whey, casein, and peptides [2]. The proportion of protein in breastmilk is not as influenced by a mom’s diet [10].

Vitamins and minerals in breastmilk

Vitamins and minerals are necessary to help your baby thrive. Breastmilk contains more than 20 minerals, including iron, copper, and zinc. Most minerals are abundant in colostrum and decrease as breastfeeding progresses [2].  

Breastmilk also contains enough vitamins to ensure the normal growth of a baby. However, it does contain low levels of vitamin K and vitamin D.

Vitamin K

Breastmilk is very low in vitamin K, regardless of a mom’s supplementation or diet [11]. Vitamin K is necessary for the proper functioning of cellular components. 

Deficiency in vitamin K can potentially lead to developing bleeding disorder conditions and neurological damage [12]. Vitamin K is often offered as a shot at birth to help increase levels in babies. 

Vitamin D

Babies are born with vitamin D stores for use after birth but are quickly depleted by two months of age [13]. Vitamin D is essential for the absorption of calcium and for other vital cellular functions and is only marginally influenced by mom’s diet and supplementation [13]. 

In babies, a vitamin D deficiency can lead to rickets disease, poor bone development, poor muscle development, and even severe pain. It is recommended that breastfed infants receive 400 international units (10 micrograms) daily of vitamin D [14], [15]. 

Though if vitamin D supplementation for a baby is not ideal, a breastfeeding mom may consider supplementing herself. A research study found that breastfeeding moms who supplemented with 6,400 IU/day of vitamin D3 were able to adequately satisfy their nursing baby’s vitamin D requirements [16]. However, before starting any new supplements or new doses, it’s always best to check with your provider.

How breastmilk changes throughout infancy

One of the benefits of breastmilk is that it’s dynamic. As it turns out, the nutrients in breastmilk change depending on your baby’s age and needs.


Your first milk. It’s liquid gold. Yellow, thick, rich. A mom’s body begins to make colostrum during the last trimester of pregnancy. It’s rich in nutrients specifically for your baby during those early days. Colostrum is thicker than mature milk and it’s richer in immune-boosting components [10]. The highest protein and HMO concentrations occur in colostrum [5].

Transitional Milk

It’s a combination of colostrum and mature milk. Breastmilk will start changing to a whitish color. This is because of the increase in fat content. But it’s normal for breastmilk to still have a yellow hue [2].

Mature Milk

As your baby grows, your breastmilk changes. This is known as mature milk.

Mature milk contains the highest percentage of total carbohydrates, but the least amount of HMOs [5]. Instead, it contains the highest levels of fat, and the lowest percentage of protein [2].

Breastmilk changes during a feed

Not only does breastmilk change throughout your baby’s first year of life, but it also changes during a single feed.

The breastmilk at the beginning of a feed is known as foremilk. This is a watery breastmilk that hydrates your baby. Foremilk is also higher in ghrelin, a hormone that stimulates appetite [17].

The breastmilk at the end of the feeding is known as hindmilk. It’s high in fat and satiates your baby. Fat amounts can be 2–3 times higher in hindmilk than in foremilk [2]. Hindmilk is also higher in leptin, a hormone that suppresses appetite [17].

These differences may help babies learn when they’re full, which could help to explain why breastfed babies have lower rates of childhood and adulthood obesity than formula-fed babies [17]. 

Breastmilk changes during the day

Your breastmilk even changes throughout the day. It changes to be aligned with your baby’s circadian rhythm.

Daytime milk has more cortisol [18]. Cortisol is a hormone that makes your baby feel alert whereas melatonin helps your baby feel sleepy. Differences in these hormones over a 24-hour cycle help babies differentiate day from night [18], [19], resulting in better sleep patterns [20].

In the second part of this series we’ll delve into some of the bioactive compounds that breastmilk contains and how these play a key role in fortifying your baby’s immune system.

>>The Benefits of Breastmilk Part 2 - Immunological Superpowers For Your Baby


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