Breastmilk Changes During Prolonged Lactation
by Anne Eglash MD, IBCLC, FABM
We know that breastmilk changes are dynamic, with several factors playing a role in composition. Most obviously, human milk starts as colostrum, which is high in protein, immune factors, and beta carotene, while low in water, fat, and overall volume. The milk transitions from colostrum to mature milk over the first 3 weeks of lactation, gradually increasing in fat, carbohydrates, and volume. Breastmilk from a mother with a premature infant is higher in protein during the first month as compared to breastmilk for a term infant. Breastmilk also changes during the day, with higher volumes after mom has gone to sleep at night. During a breastfeeding, milk towards the end of the feeding is higher in fat as compared to the milk ingested at the beginning of the feeding.
Given that we have little information on human milk composition beyond 1-2 years postpartum, a group of researchers sought to analyze total fat, protein, and carbohydrates in breastmilk from mothers nursing for more than 1 year. They collected daytime samples of milk from mothers in the following groups: 1) Under 12 months postpartum, 2) 12-18 months postpartum, 3) 18-24 months postpartum, and 4) above 24 months postpartum. Each group included a range of 26-41 mothers.
- The concentration of carbohydrates, from lactose, decreased significantly after 18 months postpartum.
- Mothers with the highest fat and protein in the milk were past 2 years postpartum.
- Breastmilk from mothers who were over 2 years postpartum had approximately 60% more calories per ounce as compared to breastmilk from mothers who were under 12 months postpartum.
- Women who were nursing their second child had higher protein levels in their breastmilk after 1 year postpartum as compared to women who were nursing their first child.
- If a 2 year old toddler increases his nursing frequency, the protein and fat decrease in his mother’s milk, while the carbohydrates increase.
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Abstract
Human milk (HM) is the first dietary exposure in infancy and the best nutritional option for growth and healthy development of the newborn and infant. The concentrations of macronutrients, namely proteins, carbohydrates and lipids, change during lactation stages. HM has been studied extensively in the first 6 months of lactation, but there are limited data regarding milk composition beyond 1 or 2 years postpartum. The aim of our study was to describe longitudinal changes in HM macronutrient concentrations during the prolonged lactation of healthy mothers from the 1st to the 48th month. For the macronutrient content of milk of mothers breastfeeding for longer than 18 months, fat and protein increased and carbohydrates decreased significantly, compared with milk expressed by women breastfeeding up to 12 months. Moreover, the concentration of fat, protein and carbohydrates in HM over 2 years of lactation from the 24th to the 48th month remained at a stable level. However, analyzed macronutrients were positively (carbohydrate, r = 0.51) or negatively (fat, r = ?0.36 and protein, r = ?0.58) correlated with the amount of feeding. Our results create a greater potential for understanding the nutritional contribution of HM over 2 years of lactation and showed that the source of calories in breast milk for older children is mainly fat, while carbohydrates play a greater role in infant nutrition in the early stage. The observed changes of macronutrient concentrations from the 1st to the 48th month of lactation are probably related to the adaptation of milk composition to the increased energy demand of the intensively growing child.
This study is fascinating. We could create many theories as to why breastmilk calories rise over time. Since children over age 1 consume water separately, there is less need for mothers to have an abundance of free water in her breasts. Less free water in breastmilk leads to higher calorie, more concentrated breastmilk. This is because carbohydrates such as lactose draw more water into the breast. If a breastfeeding mother has less volume of breastmilk, she may be at less risk for mastitis, engorgement, and loss of milk supply, allowing her to nurse her toddler/preschooler longer.
Also, toddlers tend to be picky intermittent eaters, as compared to infants, and nurse for short times. Having a source of highly concentrated calories that can be consumed in 1-2 minutes flat, which usually describes a toddler feeding session, makes sense.
One question is whether consumption of higher fat, higher calorie breastmilk beyond 2 years of age has any influence on the child’s cholesterol and risk of heart disease over time.
Heidi
So with this understanding of milk composition changes related to age of child, how important is it to match age or other factors (such as gestational age) with milk donation. A newborn that receives a two year old child’s milk is not ideal, right?
Of course anything is better than formula…
IABLE
The very best milk for infants is fresh, straight from their mothers. Fresh milk from the breast has the highest protein levels, highest antioxidants, is aged matched, and has immune factors that respond to the germs that both mom and baby have recently encountered or are ill with. Donor milk is second best, certainly better than formula. Age-matching for donor milk is probably advantageous. It is also important to give the freshest milk available (frozen for the least amount of time) to the youngest infants.
Rebecca Boyd
Is there any research on the amount of calcium that is in breastmilk post 1 year. Peds are telling mothers they need to introduce Cows milk at that point because there is no Calcium in their breastmilk after a year.
IABLE
Find out from Peds what their references are for saying that there is no calcium in breastmilk after 1 year. Of course there is calcium in breastmilk after 1 year. One reference, entitled Human Milk Beyond One Year Postpartum: LOWER CONTENT OF PROTEIN, CALCIUM, AND SATURATED VERY LONG–CHAIN FATTY ACIDS from J of Pediatrics Vol 148, issue 1, 2006, describes a small drop in calcium after 1 year, by about 20%, but certainly calcium is still present. It is important to know that young children over 1 year of age need approximately 800mg-1000mg of calcium a day. Many children can get that amount of calcium in 3 servings of dairy products such as yogurt, cheese, ice cream. So if a toddler is nursing, and eats a few servings of dairy a day, there is no need for the child to drink cows milk.
Rebecca Boyd
What about Vegan diets? Is Broccoli and other veggies that contain Calcium or Tofu enough for them?
IABLE
Yes, 3 servings of calcium containing foods a day that are not dairy is fine.
Vanessa
I’m breastfeeding my 2 and a half year old son. I have enjoyed breastfeeding but it’s now due out of necessity. I’m encouraged to know the breast milk has many nutrients but can a growing toddler be fine on just breastmilk alone? My Son is having challenges eating solids he has sensory aversion to mouth and not able to motor plan his mouth coordination. So I feel stuck having to breast feed him since I know he is getting some nutrients. But at times it can be a stressful journey as to him not eating Solids yet. So I’ll be breastfeeding till I see progress with his eating but I’m just wondering if the breastmilk is enough and if he’ll keep growing well.
Caci
One main reason they tell us to introduce foods to 4 months now is for them to develop the motor skills to eat. I think you should continue trying to offer him different foods until he gets comfortable eating solids. Eventually breastmilk will not be enough. He will need to get his nutrients from food.
Tamara
This is incorrect. It’s only recommended to introduce solids around 6 months and only when a baby is showing all the necessary signs of readiness.
R. Konoff
Vanessa, Have you had your child assessed by a feeding therapist (occupational or speech therapist with specialized training)? They could help you help your son progress in his feeding skills and address his sensory challenges. Also, please be sure to monitor if he is growing appropriately. Of course breastmilk continues to be important for toddlers, but typically, by his age, other foods are also being consumed, so if he has stopped growing (or has even lost weight, which sometimes happens), that would be important to know.
Nagham
Hello!! Can u please give us info concerning antibodies in breastmilk for babies after 1 year ? ( exclusively pumping mum
My ped said that the percentage of antibodies decrease significantly after 9 months so our milk is no more important and that the baby can develop more antibodies while playing on the ground for ex than taking his mum milk!!! Is that true?
IABLE
That is ridiculous! When professionals say something like that, ask them for a reference. Not only do antibodies persist in breastmilk until weaning, the antibody levels actually rise after 1 year. This is because breastmilk becomes even more of a superfood, as it becomes less watery (toddlers can drink water on their own after a year). By having less water, breastmilk has more calories/30ml, with higher levels of proteins and fats, and lower carbs. Immunoglobulins are proteins, and their concentrations actually rise after 1 year postpartum. This is why we see less diarrhea, fewer ear infections, less severe RSV in toddlers who are still nursing. Here is a free article reference- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7426452/. Yes, it is true that your child makes antibodies when playing in the dirt, but the child makes the antibodies after first becoming ill. The antibodies in breastmilk help to PROTECT from illness. That is just one role of breastmilk. Breastmilk also modulates your infant’s response to new germs, so that illnesses are less severe. And, while we are at it, let the physician know that the amazing fatty acids designed for infants promote maturity of your little one’s brain, decreasing the risk of seizures, increasing your child’s IQ. Oh, and another thing, your child has a lower risk of heart disease, high cholesterol, insulin resistance, type 2 diabetes, and obesity if they continue to breastfeed beyond a year! Please share this with your physician.
Nagham
Thats great thank u so much!! Every breastfeeding and exclusively pumping mum need to hear and be reminded about this!! Do you think there is a certain minimum required “ml” of breastmilk to give all that benefits after 1 year? For ex if we give 1 cup of liquid full fat cow milk and another cup of breastmilk for a total of 500 ml daily is good? I mean by supplementing we can still get all the benefits u cited?
IABLE
Hi, the benefits of breastfeeding/breastmilk are for the most part dose related, so the more the better. I am not aware of prescribed volumes that protect from ‘X’ or ‘Y’
Liz
Can you source for how many calories are in milk after 1 year of age? I find this really interesting.
IABLE
This is a good article that shows changes in milk after 1 year- https://pubmed.ncbi.nlm.nih.gov/34520401/
Emily T
Do you have any research on breastmilk & breastfeeding when you’re pregnant? My supply drops drastically when I’m pregnant and I’m wondering if the concentration increases at all or if the nutritional value changes I’m breastfeeding my 1 year old & and I am newly pregnant. My son is very allergic to dairy and refuses all formula/dairy free milks.
IABLE
It is normal for breastmilk volume to decline during pregnancy, as the breast remodels for the next infant. The breastmilk is not higher in calories during that time. However, for children over the age of 1, cows milk or milk substitutes are not required. There are many countries around the world that do not feed their children milk from another animal after age 1, but rather feed the child and offer water for fluid. The only advantage of cows milk is calcium and protein, which can be ingested thru food rather than milk. Here is a reasonable article with more details- https://www.livescience.com/49551-should-kids-drink-milk.html
Tesha
My baby is almost 3yr I was curious about how it changed over the years for her. I’ve nursed 6 kids. This is the longest I’ve nursed 1 baby. I had back to back babies though so I’ve been nursing for 9 years consecutively. This is the last baby. So there is no competition for the “boombahs” ( breast). I plan on her deciding when she wants to be weaned. Dose lactation for 9 years have any difference?
IABLE
Every time you have a new baby, your milk ‘starts from scratch’ with colostrum first, then mature milk for a year. Every year after 12 months postpartum the calories increase in breastmilk. Congrats on your lactation journey!
Natalie
My husband and I are adopting a newborn baby girl in 6 months. I am currently breastfeeding my 9 month old son. Due to the age and gender difference, would I still be able to breastfeed my adopted daughter, particularly if I supplemented donor breastmilk for her first several months of life from a donor who matched her age and gender?
IABLE
Congratulations on your upcoming adoption and continuing to breastfeed your son! We generally don’t give individual medical advice on this blog. However, I would say in general that for a term healthy newborn, there is no need to age-match milk. Milk banks who are members of the Human Milk Banking Association of North America do not age match donor milk to the age of the recipient. Your milk would be absolutely fine for your newborn adoptee!
J
hi there. is it true that because breast milk composition changes to meet the requirement of the baby as they grow, therefore there is no need to increase the volume / amount of ounces given to the baby? pumped milk fed in bottle. chilled not frozen. I have been giving 4oz from 2 months old till now my baby is 8 months. thank you
IABLE
Hi, not needing to increase the volume of breastmilk per serving from 2 months to 8 months is completely normal. This does not have to do with difference in calories or other nutrients in milk. This is because babies don’t need as many calories per kg/body weight as they get older, because they are growing more slowly over time. Babies grow the fastest in the first 4 months of life, so their calorie needs are super high in the first 4 months. Those calorie needs slow down after 4 months so the volume of breastmilk does not need to increase. I am assuming your baby is growing well.
Sandra Arita
Hi my toddler is currently 22 months … he stills breastfeeds… he has been a picky eater lately… but he does eat here and there. Does my breast milk fill up those gaps of nutrition for him you think??? Iv just been stressed out because he’s been picky and not eating as much as I would want him to.
IABLE
Hi, we cannot give personal advice on this platform. I suggest that you talk to your physician, or a knowledgeable dietitian about your infant’s diet.
Mariya K
What factors increase the caloric/fat content in breastmilk as baby grows? (I.e., hormones?) I am currently pumping and baby no longer breastfeeds directly. How does the body know to continue to make milk that meets the baby’s growing nutrition needs?
IABLE
Breastmilk stays remarkably similar in its make-up the first year. The calories do not increase in breastmilk over time. This is because babies need fewer calories/kg of body weight as they age in the first year and beyond.