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Infants who are breastfed perform better on intelligence tests, are less likely to suffer from obesity, and are less prone to diabetes later in life. Additionally, breast milk plays a role in shaping the immune system and helps combat many infections. Hence, the World Health Organization recommends exclusive breastfeeding for the first six months of a baby’s life, with continued breastfeeding along with appropriate complementary foods for two years or more. However, the mechanisms that make breast milk so beneficial are still being studied.
Scientists from the University of Cincinnati reviewed existing research to understand how breastfeeding helps reduce viral load and prevent complications in infants.
Respiratory Syncytial Virus and Breast Milk
Respiratory syncytial infection, or RSV infection, stands as a leading cause of lower respiratory tract infections. Over half of children contract RSV infection during their first year of life, and by the age of two, 90% of children will have experienced it. The primary danger of the virus lies in its complications, notably bronchiolitis – inflammation of the smallest airways. Of all hospitalizations and deaths due to RSV infection, 45% occur in children under 6 months of age. Besides its immediate impact on health, RSV infection can also influence the long-term development of immunity.
Infants who are breastfed tend to endure RSV infection much more easily and typically do not experience complications. This is why researchers have focused on studying the protective effect of breast milk against the respiratory syncytial virus.
Breast Milk Contains Oligosaccharides
Breast milk harbors numerous biologically active components beneficial for infants, among which human milk oligosaccharides (HMOs) stand as paramount. While the antiviral properties of these compounds have been studied, this review focuses on the lesser-acknowledged roles of HMOs in countering RSV infection and proposes potential protective mechanisms.
Oligosaccharides are synthesized from lactose and play diverse roles in infant development. The concentration and composition of HMOs vary depending on race, genetic factors, environment, duration of pregnancy, and lactation period. They resist digestion: 95-99% reach the colon intact. Here, their work begins: they modulate the microbiome, inhibit pathogen binding, and reduce inflammation. They also bolster the immune system by interacting with immune cells, acting as signaling molecules.
Antiviral Effect of Oligosaccharides
Research indicates that lower levels of lacto-N-fucopentaose II (LNFP-II) oligosaccharide in maternal milk and infant feces were associated with more severe symptoms and complications of RSV infection. Additionally, HMOs demonstrate antiviral properties by binding to clinically significant viruses, including rotavirus, norovirus, human immunodeficiency virus (HIV), and influenza. Despite breast milk’s ability to transmit viruses, it rarely causes illness in infants. Scientists believe this is due to the antiviral properties of oligosaccharides.
The structural diversity of HMOs provides a broad spectrum of protection against viral infections. Consequently, they may even prevent emerging diseases, such as COVID-19. Acetate produced by gut bacteria in response to specific oligosaccharides may enhance the immune response against RSV infection. Animal studies indicate that acetate supplements can protect against lung inflammation caused by respiratory syncytial virus. Clinical observations of infants with bronchiolitis indicate that high levels of fecal acetate are associated with milder symptoms.
Scientific Conclusions
Oligosaccharides represent a promising approach in combating RSV virus due to their direct antiviral action and modulation of gut microbiota. Large cohort studies are needed to determine the specific oligosaccharides that protect against RSV infection and understand the mechanisms of their action. Additionally, it is important to further study the impact of synthetic HMOs, which can be used in formulas if natural breastfeeding is not possible.
