Breastmilk and microbes: Breastfeeding is much more than …. feeding

Breastfeeding shapes the infant microbiome as it contains live beneficial bacteria that support the development of a healthy microbial community

Breastfeeding is a dynamic process that helps to shape the infant gut microbiome, the community of bacteria, viruses, fungi, and other gut microorganisms. Breast milk, which is rich in beneficial bacteria and prebiotics, plays a crucial role in establishing and shaping the early life gut microbiome. The dynamic nature of breastfeeding, including the introduction of new bacterial populations and the enrichment of the milk with beneficial bacteria from the maternal gut, helps to ensure that the infant receives the right balance of nutrients and beneficial bacteria to support the development of a healthy microbial community

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Breastfeeding is a dynamic process

Not just feeding

Breast milk is more than just a source of nutrition for infants – it also plays a crucial role in shaping the development of the infant microbiome. Human milk oligosaccharides (HMOs), a type of carbohydrate found in breast milk, have been shown to alter developmental trajectories by influencing the composition and function of the intestinal microbiota during the first year of life. HMOs are not digested by the infant, but are fermented by gut bacteria, leading to the production of short-chain fatty acids that have a variety of health benefits. By supporting the growth of beneficial bacteria and inhibiting the growth of harmful bacteria, HMOs promote a healthy microbial community in the infant gut. This, in turn, has a positive impact on the overall health and development of the infant.

From early life gut maturation...

... to adult life disease risk

The microbiome is diverse and unique to each individual, and it is influenced by various factors such as diet, environment, and genetics.

Some of the most important roles of the microbiome during the first year of life in terms of health include:

Digestion

The microbiome plays a crucial role in the digestion of food and the absorption of nutrients. It helps to break down complex sugars and fibers that the body cannot digest on its own and also produces certain vitamins, such as vitamin K and B-vitamins.

Immunity

The microbiome helps to protect the body against illness and infection by producing antimicrobial substances and stimulating the immune system. It also helps to prevent the overgrowth of harmful bacteria and other microorganisms.

Metabolism

The microbiome plays a role in metabolism by influencing the production and breakdown of certain hormones and chemicals in the body. It has also been linked to the development of obesity and other metabolic disorders.

Mental health

The microbiome has been found to play a role in mental health and has been linked to conditions such as depression, anxiety, and autism.

Allergies and asthma

A healthy microbiome has been shown to reduce the risk of developing allergies and asthma.

Skin health

The microbiome has a role in maintaining the health of the skin by protecting against infections and influencing the production of oils and other substances that keep the skin hydrated and healthy.

Postbiotics

Postbiotics are metabolic byproducts produced by the microbiome that have various health benefits. For example, certain postbiotics have been found to have anti-inflammatory effects and have been linked to the prevention of certain diseases.

Neonatal development

The microbiome plays a crucial role in the development of newborns, especially in the first few months of life. A healthy microbiome can help to support growth and development and reduce the risk of certain health issues.

Breast milk shapes the infant microbiome

It contains a diverse array of beneficial bacteria to enrich infant's gut

Human breast milk (HBM) was once thought to be sterile, but it is now known to contain commensal and probiotic bacteria such as Lactobacillus fermentum and Lactobacillus gasseri. HBM contains about 1000 colony-forming units of various bacterial species per milliliter, and infants receive around 800,000 bacteria from breast milk each day. This diversity of bacteria in breast milk can help to establish and shape the infant gut microbiota, the community of bacteria, viruses, fungi, and other microorganisms that live in the gut. The infant microbiome begins to develop in utero, but is largely influenced by the environment after birth through mechanisms such as vaginal flora during delivery and breastfeeding. Breastfeeding status is a key factor that determines the composition and diversity of the infant gut microbiota, and the gut microbiota of breastfed infants is typically more diverse than that of formula-fed infants. HBM contains various bacterial species including Staphylococcus, Streptococcus, Bifidobacterium, Lactobacillus, and Enterobacteriaceae, and the composition of breast milk can vary based on factors such as the stage of lactation and the mother’s diet and lifestyle. Colostrum, the first form of breast milk produced after childbirth, contains a more diverse number of bacterial species than transitional or mature milk. This diversity of bacteria in colostrum can help to establish and shape the infant gut microbiota during the critical early stages of life.

Breast milk also contains prebiotics

Food for bacteria

In addition to its well-known nutrients and beneficial bacteria, breast milk also contains prebiotics, which are non-digestible compounds that feed and support the growth of beneficial bacteria in the infant gut. Prebiotics play a crucial role in supporting the development and maintenance of a healthy microbiome, and they have been linked to a range of health benefits in infants and adults.

Some examples of prebiotics that are found in human milk include:

Lactose: Lactose is a disaccharide that is broken down by lactase, an enzyme present in the small intestine, into its component monosaccharides, glucose and galactose. These monosaccharides can then be absorbed and used for energy.
Lacto-N-biose (Gal-1-3GlcNAc): Lacto-N-biose is a structural component of some HMOs .
N-acetyllactosamine (Gal-1-4GlcNAc): Like lacto-N-biose, N-acetyllactosamine is a structural component of some HMOs
Fucose: Fucose is a monosaccharide that can be linked to other sugars to form fucosylated HMOs. It plays a role in the immune system by serving as a ligand for certain receptors on immune cells.
Sialic acid: Sialic acid is a monosaccharide derivative that can be linked to other sugars to form sialylated HMOs. It plays a role in the immune system by serving as a ligand for certain receptors on immune cells.
20-fucosyllactose (20-FL): 20-FL is an HMO that is fucosylated at the terminal position. It serves as a ligand for certain receptors on immune cells.
Lactodifucopentaose: Lactodifucopentaose is an HMO that is fucosylated at the terminal position.
Lacto-N-tetraose: Lacto-N-tetraose is an HMO that contains N-acetylglucosamine at the terminal position.
20-sialyllactose: 20-sialyllactose is an HMO that is sialylated at the terminal position.

What factors influence gut microbiota shaping

Some of them

The infant microbiome begins to develop in utero, but it is largely influenced by the environment after birth. This means that the types of bacteria and other microorganisms present in the infant microbiome are influenced by various factors such as diet, environment, mode of delivery, and other exposures.

Gestation

During pregnancy, the developing fetus is exposed to bacteria and other microorganisms from the mother's microbiome, which can influence the development of the infant microbiome.

Breastfeeding

Breast milk contains a range of beneficial bacteria and prebiotics that can help to support the development of a healthy microbiome in infants. Formula-fed infants may have a different microbiome than breastfed infants, as formula does not contain the same types of bacteria and prebiotics found in breast milk.

Solids introduction

The age at which solids are introduced can also influence the infant microbiome. Introducing solids earlier or later than recommended may alter the types of bacteria present in the infant microbiome.

Mode of delivery

The infant microbiome is largely shaped by the environment after birth. For example, infants who are born via cesarean section may have a different microbiome than infants born vaginally, as they are exposed to different types of bacteria during delivery.

Antibiotics

Antibiotic treatments can also alter the microbiome, as they can kill both harmful and beneficial bacteria

Geographic location

Geographic location can also play a role in shaping the infant microbiome, as different regions of the world have different bacterial exposures and exposures to different types of bacteria can affect the infant microbiome.

Children update milk composition through saliva

Every time they touch the nipple with their lips introduce new antigens to the mother

The process of breastfeeding is a dynamic one, and several factors can influence the composition of breast milk. One interesting aspect of breastfeeding is that children can help to update the milk composition through saliva when they touch the nipple with their lips. This helps to introduce new antigens and molecules to the milk, which can alter the microbiome of the breast milk and the infant.

It is important to note that the transfer of antigens bacteria from the infant’s mouth to the breast milk is a normal part of the breastfeeding process and does not necessarily indicate a problem with milk hygiene. In fact, this transfer of bacteria can be beneficial for the infant’s developing microbiome, as it helps to expose the infant to a diverse array of bacteria that can support the development of a healthy microbiome.

Mothers ship microbes from their gut to the breast

By engulfing them with dendritic cells that reside in the gut

One interesting aspect of this process is that mothers can engulf gut microbes with dendritic cells and enrich the milk with these microbes, contributing to the diversity of bacteria in the milk. Dendritic cells are immune cells that are found throughout the body, including in the gut. They have the ability to engulf and internalize bacteria and other microorganisms, which can then be presented to the immune system for further evaluation. This process, known as phagocytosis, allows the body to identify and respond to potentially harmful microorganisms and helps to maintain a healthy microbiome. During breastfeeding, dendritic cells in the mother’s gut can engulf bacteria and other microorganisms and transport them to the mammary gland, where they can be incorporated into the breast milk. This process can help to enrich the milk with a diverse array of bacteria and other microorganisms, which can contribute to the diversity of the infant microbiome.

Overall, the process of breastfeeding involves the transfer of bacteria and other microorganisms from the mother to the infant, and the role of dendritic cells in engulfing and enriching the milk with these microbes is an important aspect of this process. This transfer of bacteria can help to shape the infant microbiome and support the development of a healthy microbiome.

Milk has different composition between two feedings

Thus ensuring that the infant receives the a developmental updated mixture

Breast milk is a dynamic and highly nutritious substance that changes composition to meet the updated needs of the infant. One of the most striking features of breast milk is its ability to change composition between feedings to ensure that the infant receives the right balance of nutrients and beneficial bacteria.

Breast milk is composed of a complex mixture of nutrients, including proteins, fats, carbohydrates, vitamins, and minerals, as well as a range of beneficial bacteria and other microorganisms. The composition of breast milk changes over time to meet the changing needs of the infant, and it is especially responsive to the infant’s needs in the first few months of life.

For example, the composition of breast milk changes over the course of a feeding to meet the infant’s changing needs. The foremilk, which is produced at the beginning of a feeding, is thin and watery and contains more lactose and other carbohydrates. The hindmilk, which is produced later in the feeding, is thicker and creamier and contains more fat and other nutrients. This change in the composition helps to ensure that the infant receives the right balance of nutrients and energy to support their growth and development.

Breast milk also changes composition over the course of the day and over the course of the infant’s development to meet the infant’s changing needs. For example, breast milk produced at night may contain higher levels of certain hormones and other substances that help to promote sleep and relaxation in infants.

Tips for keeping the milk nutritious

Seasonal, clean and varied are the keys

Eat a diverse and healthy diet

A healthy and varied diet can help to support the production of breast milk and may increase the levels of probiotics and prebiotics in breast milk. Aim to include a variety of whole, unprocessed foods in your diet, including fruits, vegetables, whole grains, and lean proteins

Include seasonal vegetables

Seasonal vegetables are fresher and more nutrient-dense than out-of-season produce, and they may contain a wider range of beneficial nutrients and phytochemicals

Avoid processed foods

Processed foods are often high in additives, preservatives, and other artificial ingredients. Limiting your intake of processed foods and focusing on whole, unprocessed foods may help to improve the quality of breast milk

Exercise regularly

Regular physical activity can help to improve overall health and wellness, and has positive effects on breast milk production and quality

Take probiotics

Taking probiotics may help to increase the levels of beneficial bacteria in the gut, which may be reflected in the breast milk

Eat prebiotic-rich foods

Prebiotics are compounds that serve as a food source for beneficial bacteria. Including prebiotic-rich foods in your diet, such as onions, garlic, asparagus, and leeks, may help to increase the levels of prebiotics in breast milk

Stay hydrated

Drinking plenty of water and other fluids can help to support the production of breast milk and may help to improve its quality

Avoid pesticides

Pesticides, such as glyphosate, can be harmful to both human health and the environment. Limiting your exposure to pesticides, such as by choosing organic produce or growing your own fruits and vegetables, may help to reduce the levels of pesticides in breast milk

Avoid heavy metals

Heavy metals, such as lead and mercury, can be harmful to health and may be present in certain foods and the environment. Limiting your exposure to heavy metals, such as by avoiding certain types of fish or not smoking, may help to reduce the levels of heavy metals in breast milk

Choose healthy fats

Healthy fats, such as olive oil, avocado, and nuts, are an important part of a healthy diet and support the production and quality of breast milk

Heinig, M. Jane. “Host defense benefits of breastfeeding for the infant: effect of breastfeeding duration and exclusivity.” Pediatric Clinics of North America 48.1 (2001): 105-123.

Stewart, Christopher J. “Breastfeeding promotes bifidobacterial immunomodulatory metabolites.” Nature Microbiology 6.11 (2021): 1335-1336.

Oddy, Wendy H. “Breastfeeding, childhood asthma, and allergic disease.” Annals of Nutrition and Metabolism 70.Suppl. 2 (2017): 26-36.

Laouar, Amale. “Maternal leukocytes and infant immune programming during breastfeeding.” Trends in immunology 41.3 (2020): 225-239.

Donnet-Hughes, Anne, et al. “Potential role of the intestinal microbiota of the mother in neonatal immune education.” Proceedings of the Nutrition Society 69.3 (2010): 407-415.

Bravi, Francesca, et al. “Impact of maternal nutrition on breast-milk composition: a systematic review.” The American journal of clinical nutrition 104.3 (2016): 646-662.

Theodoros Prevedoros

BIOCHEMIST MSc

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