Study Finds Allergy Risk Starts in An Infant’s Gut
Wednesday, October 19, 2016

It takes real guts for newborn Baby to thrive these days.If the beneficial microbes that naturally inhabit an infant’s innards are disrupted during the first weeks of life, a typical newborn can face risk of childhood allergies and asthma that is three times higher than normal, new research shows.

That is the latest in a cascade of findings about the microbiology of motherhood, and the bacteria that live in a baby’s intestines, known collectively as the infant microbiol. Researchers are discovering that bacteria are an intimate part of the bond between mother and child. “It begins at birth,” said Susan Lynch, a Gastroenterology at the University of California, San Francisco.

Humans begin life in the womb germ-free, developing within the sterile amniotic sac isolated from essential microbes. As a baby is squeezed through the muscular chute of the birth canal, it is naturally inoculated with the mother’s microbes, scientists say.

According to more than a dozen recent medical studies, vaginal birth enhances the bacteria in a newborn’s gut, as does breast-feeding and the presence of a dog in the household. Factors that weaken a baby’s gut bacteria include perinatal antibiotics, a cesarean delivery and formula feeding.
Medical microbiologists say a newborn’s personal collection of gut bacteria has a life-long effect on the immune system. Disrupting the numbers, species or growth patterns in this community of microbes in early childhood will alter the child’s developing defense against disease, scientists say.

Researchers have found a connection between the hundreds of microbe species in a baby’s gut and allergy risk. Variations in just four kinds of bacteria—Bactericidal, Lactobacilli, Faecalibacteria and Akkermansia—heightened the risk of allergies and asthma, researchers led by Dr. Lynch at UCSF and her colleagues at the Henry Ford Health System in Detroit reported in September in Nature Medicine. They tracked 298 children from birth through early childhood and documented the relationship between the fledgling microbiome and chronic ailments.

Infants with the lowest levels of critical gut bacteria at the age of one month—who were mostly boys—were more likely to be allergy-prone by their second birth day. They were more likely to show signs of asthma by the time they reached the age of 4 years, the researchers said.

Researchers think gut bacteria could be tuning or mistrusting the immune system. “What we think is going on is that the immune system is not being tweaked in the right way,” said study coauthor Dr. Christine Johnson at the Henry Ford Health System. “We think of allergy and asthma as the canary in the coal mine—one of the first indications that someone’s immune system is not as optimal as it should be.”

From inside the elbow to inside the nose, the human body harbors bacteria that affect our health and well­being. By the latest estimate, these trillions of bacteria outnumber our human cells by about three to one. They are important to digestion, vitamin synthesis, biorhythms, and brain function, to name just a few, new research suggests.

There are 44 species typically living on our forearms, and 19 species in the fold behind our ears. The Belly Button Biodiversity Project, a research consortium based at North Carolina State University, has identified so far 2,368 species that dwell in the human navel. A thousand or more species live in the human gut, according to researchers at the federal Human Microbiome Project.

The natural biochemistry of a mother’s breast milk also appears to boost the infant microbiol. Special sugars in human breast milk feed the infant and the infant’s gut microbes, which foster the child’s growing immune system.

A dog in the home also can boost the diversity of bacteria in the newborn mi­crobiome and lower the risk of allergies, Dr. Lynch and team reported in a 2014 and  study in the Proceedings of the National Academy of Sciences. (Even the practice of cleaning a baby’s pacifier by sucking on it promotes an exchange of bacteria and lowers the baby’s risk of allergies, researchers at Sweden’s University of Gothen­burg found in a 2013 study published in Pediatrics.)

Other common practices, including delivery by C-section or the use of antibiotics, have a substantial effect on gut bacteria at a time when the immune system is still a work in progress.

A third of babies born annually in the U.S., and half of those in China, are delivered surgically. Infants born by C-section miss the wash of maternal microbes and instead are seeded by bacteria from fixtures in the operating room where they are born, microbiologist Maria Gloria Dominguez-Bello and her colleagues at New York University Langone Medical Center reported in 2015 in the journal Microbiome.

“Babies born by C-section get bacteria minutes after birth, but not from the mother,” said Dr. Dominguez-Bello. `We are still trying to understand how big that impact is.”

The average child in the U.S. typically receives about three courses of antibiotics by the age of 2 years. That sharply reduces the richness and diversity of all bacteria species in the infant’s digestive tract, studies suggest.

“IATe are starting to see nitty-gritty differences in the microbiome from birth through early childhood,” said Fredrik Backhed at Sweden’s University of Gothen­burg, who has been tracking 98 mothers and their newborns. It is still too soon to link the changes to later onset of conditions like obesity or diabetes, he cautioned.

Researchers are experimenting with ways to enhance a baby’s internal bacteria in hopes of boosting the infant’s long-term health. At present, there is no strong evidence that perinatal pro­biotics or infant dietary supplements have any substantial long-term immune system benefit, according to the National Center for Complementary and Integrative Health.

As an experiment, Dr. Bello and colleagues started swabbing a few C-section babies with their mother’s vaginal fluids within two minutes of birth, in an attempt to restore a more natural infant microbiome.

Now they are tracking the infants as they grow, comparing them to other babies either born by C-section or delivered vaginally. “We are trying to normalize the mi­crobes,” she said. “This is a natural exposure.”

Robert Lee Hotz. Study Finds Allergy Risk Starts in An infant’s Gut. Baby

press, pp. D1, D4

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