How does human milk change over time?
Human milk changes through lactation: colostrum has less lactose and more protein, transitional milk follows, and mature milk is relatively similar with subtle changes. A review on PubMed Central (NIH) reports that total protein and fat decline gradually over the first 6 months.
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In this article
Does breast milk composition change?
Yes. This summary follows a review of US human milk composition, “Human Milk Nutrient Composition in the United States”, hosted on PubMed Central (NIH). Milk goes through colostrum, transitional milk and mature milk, and composition differs between them.
What is colostrum?
The review describes colostrum as relatively low in lactose and higher in protein. Transitional milk shares some of these traits and reflects a period of accelerated milk production.
How do protein, fat and lactose change?
- Protein: total protein declines gradually over the first 6 months. The whey-to-casein ratio shifts from about 80:20 early in lactation to about 50:50 later.
- Fat: total lipid also declines gradually over the first 6 months.
- Lactose: low in colostrum and transitional milk, higher in mature milk, and at similar levels for up to 6 months.
What about mature milk and energy?
Mature milk is described as relatively similar in composition, with subtle changes over time. The review notes that lipids supply 40 to 55 percent of milk energy depending on the stage of lactation, but it does not give a stage-by-stage energy trend, so we do not state one.
Who to ask about feeding?
For questions about your baby’s feeding, ask a pediatrician, midwife or lactation consultant. This is general information, not medical advice.
People also ask
Does breast milk composition change over time?
Yes. Protein and fat decline gradually over the first 6 months, and lactose is higher in mature milk than in colostrum.
What is different about colostrum?
The review describes it as lower in lactose and higher in protein than later milk.
Is mature milk the same all the way through?
It is described as relatively similar with subtle changes over lactation.
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