by Lisa Guthrie
March 06, 2013
Scientists studying gut microbiota, described as a vast and mysterious “new organ,” have made an important discovery that will give expectant and new mothers yet another reason to give birth vaginally and breastfeed their babies.
Microbiota is an array of microorganisms that live on and in our bodies. The greatest concentration of these bacteria—as many as 1,000 different kinds numbering in the tens of trillions—live in the gut. They are important not only for digestive health, but also affect other aspects of our wellbeing. The uterus is a sterile environment (free of microorganisms), and so too is the infant gut. Birth marks the beginning of the “colonization” process, whereby bacteria populate an area without causing harm. A study published in the February 11, 2013 issue of the Canadian Medical Association Journal found that babies born vaginally are exposed to different bacteria during birth compared to babies born surgically (C-section). Babies also test positive for different types of bacteria depending on how they are fed. For example, after just three days, the bacteria in the gut of breastfed infants is quite different from that of formula-fed babies.
A team of Canadian researchers examined 24 full-term infants (37–41 weeks’ gestation)—12 boys and 12 girls. Six infants were born by C-section. At the time of fecal sampling—when the infants were 4 months old—10 were exclusively breastfed, five were partially breastfed (supplemented with formula), and nine were not breastfed at all. Exclusive breastfeeding was more common among infants delivered vaginally compared to those born by C-section (44 percent versus 33 percent).
How the researchers studied the bacteria was unique. In the past, gut microbiota was grown in laboratory cultures and individual organisms were identified. But about 80 percent of intestinal bacteria can’t be grown in cultures. Now new technology using DNA sequencing allows scientists to thoroughly find and study the microbes, and even analyze groups they call “microbial communities.” Researchers have used the new DNA technology to look at adult bacteria, but very little research has been done in infants. Until now.
The researchers in this study identified bacteria in the fecal samples and compared the gut microbiota of babies born vaginally with those born by C-section, and breastfed babies with those who were formula-fed.
The researchers found that babies born by C-section (even if they were breastfed) lacked specific bacteria found in infants born vaginally—bacteria that they pick up as they passed through the birth canal. Cesarean-born babies miss that exposure, so their gut microbiota is different. Some of the absent bacteria are considered “seed” bacteria on which other bacteria colonies grow as the microbiota evolves, making the results even more significant.
When formula-fed infants were compared with babies who were exclusively or partially breastfed, the researchers found significant differences in their gut bacteria. The authors point out that breastfeeding promotes a “healthy” gut microbiota by giving babies substances that encourage the growth of beneficial bacteria.
Arguably gut bacteria play a basic and important role in the quality of our health by promoting a stable intestinal tract, stimulating development of the immune system, providing protection against disease-causing bacteria, and contributing to the absorption of nutrients and the use of energy. When the gut microbiota is disrupted, negative effects have been documented, including inflammatory bowel disease, diabetes, obesity, cancer, allergies, and asthma. It’s no coincidence that these are some of the very disorders breastfeeding protects against.
The research team that studied the origin of the gut microbiota overtly says: “The potential long-term consequences of decisions regarding mode of delivery and infant diet are not to be underestimated. Infants born by cesarean delivery are at increased risk of asthma, obesity, and type-1 diabetes, whereas breastfeeding is variably protective against these and other disorders. These long-term health consequences may be partially attributable to disruption of the gut microbiota.”
The researchers emphasize the importance of understanding more about the gut microbiota and its influence on health as it may directly impact parents’ and physicians’ decisions on infants’ delivery and diet.
“Our study addresses an important knowledge gap, since the infant gut microbiota has rarely been characterized with sequencing methods that provide sufficient coverage of the entire bacterial community. Our findings are particularly timely given the recent affirmation of the gut microbiota as a ‘super organ’ with diverse roles in health and disease, and the increasing concern over rising rates of cesarean delivery and insufficient exclusive breastfeeding,” writes research leader Dr. Anita Kozyrskyj of the University of Alberta.
The Centers for Disease Control and Prevention reports that one in three U.S. births are by C-section. And while some are medically indicated, many are not. Add to that the fact that 77 percent of mothers in the U.S. initiate breastfeeding, but only 39 percent breastfeed exclusively for three months and only 25 percent breastfeed for one year.
Given these facts, the best choices a mother can make for the long-term health of her baby are to opt for a vaginal birth and to breastfeed for at least a year (exclusively for the first six months).
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