Recent evidences shows development of gut microbiota during infancy affects several metabolic, immune, and endocrine pathways in humans. An inbalance in gut microbiota diversity or function, also known as dysbiosis, not only affects early child growth and development, but is also related with the development of chronic, non-communicable diseases in later life. Maternal diet in pregnancy, mode of delivery, breastfeeding and timing of introduction of solids food all influences gut microbiota composition. Breastfeeding is the most influential factor on gut microbiome composition. There is difference in population of gut microbiome population of breastfed and formula fed infant. There also are evidences showing breastfed infant being less susceptible to communicable and non communicable diseases as compared to formula fed infants. Child undernutrition is a major public health challenge prevalent in low- and middle-income countries. Undernourished children face adverse health consequences that can be intergenerational. Complementary feeding practices started during 6 months which do not meet the WHO’s guiding principles lacking in quantity, quality of food will lead to undernutrition, restrict growth, child development of the child. First 1000 days of life from conception to 2 years are very crucial for a child’s physical and mental development. Establishment of the gut microbiome during early life is a complex process with lasting implications on an individual’s health. This review will summarize the evidence on how IYCF (Infant young child feeding practices) broadly impacts early life gut microbiome composition and function.
Introduction
Infancy is a critical period for establishment of the gut microbiome, and is known to have a long-term impact on health and risk for disease. Microbial colonization of the gastrointestinal (GI) tract is fundamentally linked to metabolic programming, immunologic maturation, and proper gastrointestinal development. Any disturbances in colonization of gut microbiome may lead to many illness like allergy, asthma, inflammatory bowl disease , Diabetes, obesity ,food allergy and many more illness. The healthy fetus is devoid of microbial organisms, but upon birth our gastrointestinal (GI) tract becomes colonized with a multitude of microbes, gradually developing into a complex microbial community during the first year of life. Human milk plays an important role in the development of the infant’s gut microbiome. Up to 88% of the genera are shared between human milk and the breastfed infant’s stool, supporting direct transmission (1).
In addition to direct transmission of the milk microbial community, breastfed infants receive nutrients, human milk oligosaccharides (HMOs), immune cells, antibodies, and secreted proteins that can further modulate the infant’s gut microbiome.
Maternal diet and microbiome
There is evidence to suggest that maternal diet may play a critical role in shaping the microbiome during pregnancy and in neonates independent of maternal body habitus. Maternal dietary intake during pregnancy is associated with maternal gut, vaginal, and milk microbiome composition . thus neonatal microbiome is influenced by the maternal diet. (3,4) Fruit and vegetable consumption also influences the maternal microbiome. Maternal overweight/obesity status has also been associated with alterations in the infant gut microbiome .Increases in pre-pregnancy body mass index (BMI) have been associated with alterations in the maternal gut microbiome. Studies have shown that pregnant mothers in first trimester who were obese prior to pregnancy were found to have a higher relative abundance of Firmicutes and a lower relative abundance of Proteobacteria compared to their normal body weight counterparts (5).This Firmicutes increase the efficiency of energy extraction and promote the absorption of calories .
Breastfeeding and microbiome
Breastfeeding shapes the gut microbiota in early life, both directly by exposure of the neonate to the milk microbiota and indirectly, via maternal milk factors that affect bacterial growth and metabolism such as human milk oligosaccharides, secretory IgA, and anti-microbial factors. There are differences in gut microbiota variety of exclusive breastfed and non breastfed infants. Benefits of breastfeeding is due to its effect on infant gut micobiota. Beneficial bacteria are transferred from breastmilk and also from skin around mothers areola. The gut microbiome in breastfed infants is usually dominated by bifidobacteria and Lactobacillus species, while formula-fed infants harbor a more diverse gut microbiota that resembles that of older children .The retrograde flow and the entero-mammary pathway are accepted as the two primary source of origin of milk microbiota . In retrograde flow there is transmission of microbes from infants mouth to mammary duct during suckling and in enteromammary pathway there is translocation of maternal gut bacteria through intestinal epithelial barrier to reach mammary gland via lympathic circulation. Several factors can influence the composition of the human milk microbiota (HMM) maternal age, parity, socioeconomic status, antibiotic use, probiotics during pregnancy and type of delivery. The human milk microbiota is the second integral source of microbes after birth canal and the mammary glands , periareolar skin and the infants mouth can influence its composition. Bifidobacterium and Lactobaccillus has a probiotic role. Few strains of lactobacillus also has antioxidant and anticancer activities. Human milk microbiota can influence infants health in two ways 1) by promoting intestinal immune homeostasis and 2)fascilitating digestive process. Human milk provide antigenic stimuli that promotes intestinal immune maturation system. Microbes produce SCFA by fermentation of HMO (Human milk oligosaccharides) which has a immunomodulatoy effect on host physiology. Many factors like diet, ethnicity, location, medication can impart variability in milk microbiota. Thus breastfed infant is protected from various bacteria and virus as compared to formulafed infants. There are lower incidences of gastrointestinal infection and upper respiratory inection in breastfed infants. There are lower chances of asthma, diabetes, obesity in these infants as compared to formula fed infants.
Complementary Feeding and Gut microbiome
Complementary feeding period is a period when solid food are first introduced to infants after 6 months of age. Introducing correct food is crucial for infants growth and development. Diversified diet will provide essential micronutrients and will also help growth of diverse gut microbiome. The complementary feeding period offers a unique opportunity to shape the gut microbiome, potentially influencing outcomes like growth trajectories, obesity risk, immune function, and allergic disease development. As complementary feeding progress milk based component is replaced by fruits ,vegetables, fibres, meat, pulses and cereals which effects growth and development . These food influences gut microbiota ,increases alpha diversity and increases bacteria that produce SCFAs and BCFAs. This “natural” development of the gut microbiota and its metabolites is associated with healthy growth, neuro, bone development, and appropriate immune system regulation.
Processed food can significantly effect gut microbiota. These food have less fibres, preservatives, colours, emulsifier and other chemicals which can cause negative effects. Processed food can decrease diversity and increase harmful bacteria. The ultra processed food high in fats, high in sugars and salt additives and acellular nutrients ,low in vitamins .They weaken the gut barrier, disrupt hormonal regulation, and increase the risk of inflammation and related diseases .Food additives have toxic effect on microbiota and artificial sweetners are known to be etiological factor to inflammatory bowel disease.
Thus ultraprocessed food causes change in microbiota composition, promoting the growth of inflammatory bacteria associated with conditions such as type 2 diabetes, cardiovascular diseases, and metabolic disorders.
Conclusion
Dysbiosis or imbalance in gut microbiota can be caused by factors like maternal diet, maternal obesity, mode of delivery, introduction of formula milk, inappropriate complementary food, introduction of ultraprocessed foods. Dysbiosis is linked with inflammatory bowl diseases, obesity, diabetes ,metabolic syndrome, depression and anxiety. Breastfeeding and correct complementary food plays a crucial role in protection of all these conditions. Formula fed infants have different gastrointestinal microbiome and health outcomes as compared to breastfed infants. Children consuming excess ultraprocessed food are also seen suffering from anxiety, depression and other mental issues. This may be related to dysbiosis and its effect on gut brain axis. Introducing probiotics like lactobacillus and bifidobacterium,probiotics like dietary fibres, synbiotics, postbiotics (SCFA)can have a protective effect against mental disorders by beneficial gut microbiota and suppressing harmful ones.
Author Name
Dr Bina ketan Bharadva
MBBS,IBCLC
Lactation consultant and Infant young child nutrition counselor
Perinatal mental health counselor