While seemingly unsettling, the greeting party welcoming your baby into this new world includes scores of uninvited guests: bacteria. Before baby even gets discharged from the hospital, legions of bacteria are already making a home on and in his body—but there’s no reason to panic. The collective community of these microorganisms is known as the microbiome, and it’s an influential factor in your lovebug’s immune system development and other areas of health.
Try as parents might, mom and dad won’t entirely succeed at blocking baby’s exposure to bacteria—the microorganisms are simply too numerous and widespread. So, let out a sigh of relief as your two-and four-legged family members interact, and don’t be afraid to bring your little buddy outside to explore. “My kids certainly had a blast crawling around in the garden,” says Jennifer Kloesz, MD, medical director of the neonatal intensive care unit at Magee- Womens Hospital of UPMC.
As for balancing the intake of microbes with avoiding pathogens, common sense prevails, suggests Stephen Eppes, MD, vice chair of the department of pediatrics and director of pediatric infectious diseases at Christiana Care Health System in Wilmington, Delaware. “It’s impractical to try to keep everything out of a baby’s mouth,” he says. Acknowledge and accept that putting things in his mouth is the way your tot gets to know the world and understand its myriad objects.
It’s true, of course, that some bacteria can make babies sick. But consider, surprising as it may sound, the ill effects of a too-clean upbringing.
A baby’s first couple of years are the prime time of his immunological development, explains Carla Davis, MD, allergy and immunology specialist at Texas Children’s Hospital in Houston. Every day as your baby learns the sights, sounds and smells of his new world, his immune system is also learning—and microbes are important teachers.
Infants possess more naive T cells—the cells responsible for vetting new microbes that the body has never before encountered—than older children or adults. “These naive cells are learning what’s part of the body and what’s not part of the body,” says Davis.
Bacteria act as a vesicle of sorts for the delivery of molecules known as antigens, which travel on and in bacteria and stimulate an immune response. The immune system’s T cells and other agents travel throughout the body encountering these antigens and, in many cases, can learn to tolerate them.
In the gut, diversity of microbial species is central to good health. Many different microbes swimming and swarming around together is more favorable than having only a small number of species dominate, and diversity appears positively correlated with better education of the immune system, Kloesz says. While we may all carry harmful bacteria like E. coli at any given time, beneficial bacteria help keep these pathogenic species in check.
Without early exposure to different bacteria and the antigens they carry, though, the immune system will not learn. And that means that when exposure to these antigens occurs later in life, there’s a greater likelihood the immune system will not tolerate them, thus contributing to the onset of allergies, asthma and even more serious autoimmune diseases and conditions.
With the thousand-plus species of bacteria found on and in the human body come hundreds of thousands of antigens that can shape immune system development. “We used to think that the in utero environment was sterile until the time of delivery, but we know now that that’s not true,” says Eppes.
Through sophisticated diagnostic means, we’ve seen how bacteria have left their fingerprints all over babies before they’re even born. There are bacteria in the placenta. There are bacteria in the amniotic fluid. Meconium, baby’s first stool discharged after birth, contains bacteria.
Knowing this is all the more reason for expectant mothers to consider the health of their own microbiomes. From before birth, a mother’s microbiome influences that of her baby’s. If her microbial state of health is dysbiotic (meaning the microbial populations are imbalanced), her baby could have greater genetic predisposition to develop conditions caused by an agitated immune system, Davis explains.
Simply eating well can help maintain a healthy, balanced gut microbiome during pregnancy. Fermented dairy products, like yogurt, and other fermented foods, like kimchi, deliver big doses of live, beneficial bacteria. And your practitioner might be able to recommend a beneficial probiotic supplement as well.
Nurse to health
Once baby is born, breastfeeding can play a big role in establishing and populating the gut with good microbes, accounting for up to some 40 percent of intestinal microbes, Eppes says. Mother’s milk can help maintain baby’s microbial health throughout infancy, too.
“Breastfeeding is really key,” says Kloesz. “If you breastfeed, you’re going to have less ear infections and less bacterial and viral infections to begin with.” Breast milk contains beneficial bacteria, such as Lactobacillus and Bifidobacterium, which can help keep harmful bacteria at bay. It’s replete with human milk oligosaccharides, or HMOs—substances that can, among other things, nourish good bacteria and help them flourish in the gut.
Davis notes that, for mothers who can’t breastfeed, there are infant formulas available containing some of these HMOs and probiotics. But we still can’t replicate every beneficial substance within breast milk, and bacteria, it seems, prefer the real thing.
For as much influence as our microbiomes have on our health, there’s still a lot we do not know. Eppes points out that most of our understanding of the microbiome stems from research conducted within only the past 10 or 15 years, making it still a very new field of medicine. But a lot of dollars are going into microbiome research, and according to Kloesz, over the next decade “we’re going to have a much better idea of what’s the right combination and what’s the right population of bacteria that makes sense for the best intestinal health and development.”
Still, we understand enough to know that bacteria play a major role in your baby’s health. Even in its infancy, research on the microbiome has already revealed the extent that bacteria shape baby’s health—from before birth to well beyond. Just remember that even if your baby ingests and rolls amok in microbes throughout infancy, she may still develop allergies and autoimmune conditions. Microbial exposure can only mitigate, not eliminate, these outcomes. In addition to bacterial influence, Davis says genetic and environmental factors also affect development and immunological health. It’s the combination of these components that will guide many health outcomes.