As Chinese people, do our breast milk ingredients have the same composition?

Today we are going to talk about a rather special topic, that is, is all breast milk composed of the same ingredients? First of all, let's talk about the difference between cow's milk and breast milk.

Let's digress a little here - mammals, this is a rather interesting class. When it comes to mammals, many people will think of a series of related concepts, such as warm-blooded animals from the evolution of temperature regulation, and the concept of mammals giving birth to live young from the evolution of reproductive methods. However, mammals, as their name suggests, have a very typical feature: breastfeeding.

That's right, the name of this vertebrate group of mammals comes from the fact that animals in the entire class need to secrete milk through mammary glands to feed their young. As we all know, for living things, food is the basic need to maintain their lives, and for mammal cubs, milk is their only source of nutrition. Because of this, milk is vital to mammals. As a member of the mammal class, we humans naturally need milk to complete the growth of infants and young children.

Is the milk of different animals the same?

The answers are of course different.

Taking the most common milk and breast milk as examples, the figure below shows the difference in casein content between milk and breast milk. We can clearly see the difference between the two [1]

Therefore, we can imagine that there must be differences in the milk of different mammals in nature.

However, this is caused by species differences. After all, Mammals are also a huge class. It has been hundreds of millions of years since their appearance, and the accumulated differences in evolution must be significant.

But if we ask another question, that is, does the milk of the same species have the same composition? For example, does human breast milk have the same composition?

Many people may not be sure.

The answer is: no.

As a human secretion, breast milk itself is affected by the individual's nutritional status, eating habits, lifestyle, etc., as well as factors such as genetic background.

A comprehensive study published in the journal Prostaglandins, Leukotrienes and Essential Fatty Acids, which compiled a comprehensive analysis of 21 studies [2], examined the composition of breast milk in different regions of China.

The locations involved are as follows:

The results showed that the fatty acid content in breast milk of southerners and northerners showed significant differences. The figure below shows some fatty acid data. Because the table is too long, part of the data is intercepted. We can see that the differences in multiple fatty acid components are very significant (p < 0.05).

A similar situation can also be seen in the difference in breast milk between inland and coastal populations (p < 0.05).

Even different levels of social development can affect the composition of breast milk.

It can be seen that even among Chinese people, there will be significant differences in geographical location, such as south and north, coastal and inland, and even the socioeconomic development level will affect the differences in breast milk composition.

The differences are not only reflected in different groups of women, but even for the same person, the composition of breast milk shows obvious differences at different lactation stages.

The following figure shows the crude protein content in breast milk of the same person at different lactation stages [3]

It can be seen that with the increase of lactation time, the crude protein content in breast milk generally shows a downward trend.

There are also differences between the specific amino acids as the lactation time changes.

It can be said that the composition of breast milk is different for different people, and the composition of breast milk is also different for the same person at different lactation times.

Well, now you will understand why milk powder companies are now starting to propose the concept of breast milk formula.

Because breast milk is affected by differences in species itself as well as by factors such as individual level and ethnic group. In this case, a uniform milk powder may not be the best, and the differences in genetic background of the population must be taken into account.

It was under this fact that my country began to establish the Chinese breast milk bank and promote breast milk formula.

Let’s look at the three important components of breast milk: protein/amino acids, fatty acids and other active ingredients

1. Dynamic changes of protein and amino acids in breast milk

JPGN, an international pediatrics journal, systematically reviewed the proteins and amino acids in Chinese breast milk, revealing the dynamic changes of 18 amino acids in nine breast milk stages. The protein and amino acid composition in breast milk is not static, but shows dynamic changes.

2. Distribution of fatty acids in breast milk

The official journal of the International Society for the Study of Fatty Acids systematically reviewed the research on the fatty acid composition of breast milk, focusing on the characteristics of the content of 42 fatty acids in breast milk in different regions of China; it found that the key ratio of the three major fatty acids in Chinese breast milk is 1: 1: 0.7, and more accurately described the ratio of DHA/ARA, an important nutrient for brain development, at 1: 1.69.

3. Other active ingredients

The changes in active ingredients in breast milk published in a professional journal in the field of food nutrition revealed the changes in 11 active protein components in Chinese breast milk in nine stages of breastfeeding, including key nutrients such as lactoferrin and a-lactalbumin.

These studies are currently one of the largest summaries of the composition of Chinese breast milk with the largest sample size. From this, we can see that the composition of each person’s breast milk is really different, and there are still relatively large differences!

1 Kunz C, Lönnerdal B. Human-milk proteins: analysis of casein and casein subunits by anion-exchange chromatography, gel electrophoresis, and specific staining methods[J]. The American journal of clinical nutrition, 1990, 51(1): 37-46.

2 Sun H, Ren Q, Zhao X, et al. Regional similarities and differences in mature human milk fatty acids in Chinese population: A systematic review[J]. Prostaglandins, Leukotrienes and Essential Fatty Acids, 2020, 162.

3 Ren Q, Sun H, Zhao M, et al. Longitudinal Changes in Crude Protein and Amino Acids in Human Milk in Chinese Population: A Systematic Review[J]. Journal of Pediatric Gastroenterology and Nutrition, 2020, 70.