How Breast Milk Changes to Meet Babies' Needs

Mother breastfeeding baby girl at home in New York City

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Breast milk is a liquid source of food made by the human body to nourish babies. The body creates it in response to pregnancy and the suckling of a baby at the breast. However, people who have not been pregnant can also breastfeed with the help of hormones, medications, and stimulation such as pumping.

Breast milk not only provides a child with complete nutrition, it is also a source of protection against illness. Breastfeeding benefits parents and children in a variety of ways, and many of these benefits continue long after breastfeeding has ended.

The dynamic nature of breast milk is fascinating: its composition, color, volume, and taste can all change in response to various factors in both the baby and the breastfeeding parent.

Breast Milk Composition

Breast milk is made up of hundreds of substances, including protein, fat, carbohydrates, vitamins, minerals, water, enzymes, and hormones. This composition isn't constant, however; it varies from parent to parent. It can even change within the same parent, depending on the baby's needs.

Breast milk changes during each feeding, from one feeding to another throughout the day, and over time to meet the needs of a growing child. Here are some of the changes that can occur in the composition of breast milk:

  • Growth spurts cause babies to nurse more often and for longer periods, which helps increase both the volume and fat content of breast milk.
  • What you eat has been shown to affect the flavor of your milk and even influence your baby's taste preferences later in life.
  • The fat content in milk increases throughout each feeding, with the hindmilk providing up to two or three times more fat than the foremilk. Foremilk is thin, watery, and lower in fat, calories, and vitamins A and E than hindmilk.
  • Day vs. night: Breast milk is like a biological clock, literally changing by the hour. For instance, breast milk contains low levels of an amino acid called tryptophan (the precursor to the "sleep" hormone melatonin) in the morning and much higher levels at night. By breastfeeding, you are helping your infant establish their circadian rhythm of being awake during the day and asleep at night.

Parents who pump their milk to feed later may want to mark the time it was pumped when storing it. This way they can feed it at the same time of day to give their baby the time-appropriate factors present in the milk.

  • Beneficial gut bacteria in the parent's gastrointestinal tract may migrate to the mammary glands and get incorporated into breast milk, pointing to a close relationship between the parent's GI health and that of their baby.
  • Antibodies are produced in breast milk when either the parent or child is sick, thereby protecting both of them.

Breast Milk Stages

The production of breast milk begins during pregnancy. When your baby is born, you will have only a small amount of milk for the first day or two. Don't worry; this is more than enough for your newborn. Your baby is getting enough milk if they have one wet diaper on day one, two wet diapers on day two, and so on.

By the third day after delivery, the production of breast milk increases. As your breast milk comes in, you should feel your breasts begin filling up. However, it could take longer (up to five days) for first-time moms .

In the first two weeks after a baby is born, breast milk progresses through three main stages: colostrum, transitional breast milk, and mature breast milk.

Colostrum

Colostrum, the first type of breast milk, is present at the end of pregnancy and during the first few days after a baby is born. The amount of colostrum that your body makes is small, but that small volume contains everything your new baby needs in the first few days of life.

It's usually thick, yellow and sticky, but it can also be thin and white or orange in color. If you are pumping, the thick colostrum may get stuck in the tubing of your pump.

Some moms find it easier to hand-express colostrum into a small cup and then pour it into a bottle. (You should still use your pump to stimulate your breasts and encourage milk production.)

Colostrum is known as "liquid gold" because it's packed with protein, growth factors, white blood cells, and antibodies, especially Immunoglobulin A (IgA) to fight off infections.

It's also a natural laxative that helps prevent jaundice by clearing your baby's body of meconium: the first thick, black, tarry poop.

Colostrum also contains high levels of lactoferrin, a protein that also has immune properties and helps with absorption of iron. Lactoferrin falls during the transition from colostrum to mature milk, but it is present in all forms of breast milk.

Transitional Milk

Transitional breast milk is a combination of colostrum and mature milk. When your breast milk begins to come in (three to five days after delivery), it mixes with colostrum and gradually transitions to mature milk over the course of a few days or a week.

Mature Milk

Milk changes over to mature breast milk by the time a baby is about two weeks old. Compared to colostrum, mature milk is lower in protein but higher in fat and carbohydrates. Mature milk contains about 90% water to meet your baby's fluid needs.

A 2018 study showed that the fat and protein content of breast milk increases after the 18 month mark, while carbohydrates decrease. The authors theorized that these changes are the result of breast milk adapting to the higher energy needs of growing toddlers.

Breast Milk Supply

Your body begins to make breast milk in response to pregnancy and delivery of your child. But to continue making breast milk after your baby is born, you will need to breastfeed or pump.

By removing milk from the breasts, you will stimulate your body to make more milk. The more often you breastfeed or pump, the more milk you will make.

Almost all mothers have the ability to make a healthy breast milk supply. If you're worried about a low milk supply, get help from a physician, lactation consultant, or breastfeeding support group such as La Leche.

Most of the time, correcting your baby's breastfeeding latch and nursing more often will help.

As your baby begins to sleep for longer stretches at night, your body will adjust too. Soon you'll be able to sleep for longer periods without experiencing engorged breasts from not feeding for several hours.

Breast Milk Color

The color of breast milk can change in response to various factors. It's usually white, yellow, or bluish. However, depending on what you eat, it could have a green, orange, brown, or pink hue.

Occasionally, blood from rusty pipe syndrome or cracked nipples can appear in your breast milk. It may be worrisome, but it isn't dangerous. As long as your baby is not refusing the breast, it's safe to continue to breastfeed if your milk changes color.

If you do notice a red or pink tinge to your milk, it's a good idea to consult your doctor or lactation consultant to get any underlying issues checked out before they interfere with breastfeeding.

Medications, including certain antibiotics, can also affect the color of your breast milk. This change in color is not harmful, as long as the medications (and any supplements you take) have been approved by your doctor to use while breastfeeding.

Breast Milk Taste

The flavor of breast milk is described as sweet and creamy. It gets its sweetness from the milk sugar lactose, and it's creamy due to the amount of fat it contains. However, since the foremilk is low in fat, it will appear thin and watery compared to the higher-fat hindmilk.

As noted above, the foods you eat will also contribute to the flavor of your breast milk. A diet high in fruits and vegetables will expose your child to the flavors of these foods through your milk, and can help them accept the taste of fruits and vegetables when they begin eating solids.

Other factors that influence the taste of your breast milk include medications, hormones, exercise, smoking, alcohol, and infections such as mastitis. Freezing and thawing breast milk can also give it a soapy taste which some infants may not like, although it is still perfectly safe to feed.

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9 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Breastfeeding and the use of human milk. Pediatrics. 2012;129(3):e827-41. doi:10.1542/peds.2011-3552

  • American Academy of Pediatrics. New Mother’s Guide To Breastfeeding. Bantam Books, 2011.

  • Lawrence RA, Lawrence RM. Breastfeeding A Guide For The Medical Profession 8th ed. Elsevier Health Sciences, 2015.

  • Riordan J, Wambach K. Breastfeeding and Human Lactation 4th ed. Jones and Bartlett Learning, 2014.