C-sections, allergies, and probiotics

Student guest post by Shylo Wardyn

I recently read the book ‘Good Germs, Bad Germs’ by Jessica Snyder Sachs. I became intrigued by parts of her book that discussed how babies become colonized with bacteria during birth. The most interesting part was the differences between vaginally-delivered and Caesarean-delivered babies. It was not something I had ever thought of before. With my interest piqued, I did a Google scholar search to see what kind of research was being done on this topic. I stumbled upon an article looking at C-sections and risk of childhood allergies, namely asthma. I realized this would be the perfect topic for this assignment!

A little background information:

Asthma is a chronic inflammatory disorder of the airways that affects both children and adults. It is not known why some people develop asthma and others don’t. Rates of asthma have more than doubled from 1980 to 2004 in children <18, but since 2001 have held steady. It is noteworthy to mention that the definition of asthma was altered in 2001, as well (Moorman, et al., 2007). A Caesarean section (C-section) is a surgical procedure in which an incision is made through the mother's abdomen and uterus to deliver one or more babies. While C-sections are traditionally done when a vaginal delivery poses risk to the mother or baby, women can also elect to have a C-section instead of a normal delivery. C-section delivery rates account for 31.8% of all births in the United States; 2007 marked the 11th consecutive year of increase and a record high for the US (Hamilton B.E., 2009). The neonatal period is critical for bacterial colonization of the intestines. Infants delivered vaginally acquire their intestinal flora from their mother's vaginal and fecal flora, generally species of Bacteroides, Lactobaccilus and Bifidobacteria. This intestinal flora colonization is delayed in Caesarean delivered infants; consequently, their gut flora is abnormal for weeks to months. One study found that in Caesarean delivered infants at the age of 6 months, the colonization rate of Bacteroides was half that of infants in the vaginally delivered group (Grölund, 1999). The research: Gut normal flora has a significant impact on the immune system; normal flora strains have been shown to induce the production of IL-10, which has an important regulatory role in the development of the allergic immune response (Kalliomaki & Isolauri, 2003). This is the biological hypothesis behind the proposed association between C-sections and asthma. This issue has been studied, but results are conflicting. I found two meta-analyses that looked at the research to date. Thavagnanam (S. Thavagnanam, 2007) found a 20% increase in the risk of asthma in children who had been delivered by Caesarean. While Bager et al. also found a moderate increase in the risk of asthma after Caesarean, they did not attribute this to the increasing rates of C-sections (Bager, Wohlfahrt, & Westergaard, 2008). They felt that for this to be the case, C-section deliveries should be associated with all allergic outcomes, not just some of them. I felt that they discredited their study by stating this; they still found a biologically plausible and significant association between C-section delivery and asthma. A more recent Norwegian population-based cohort study confirmed a moderate association between C-section and asthma (Tollanes, Moster, Daltveit, & Irgens, 2008). Probiotics and general remarks: While there clearly needs to be more research about the exact role of gut flora in the development of allergies, an interesting area of research is in probiotics. Probiotics are cultures of beneficial bacteria of the normal gut flora. Studies have shown that probiotics administered to pregnant women and their newborns lead to lower rates of development of allergic diseases (including asthma). However, these studies looked at high-risk children; those that had a first degree relative or parent with any allergic disease (Kalliomaki, et al., 2001; Kuitunen, et al., 2009). I couldn't find any randomized placebo-controlled trials with babies delivered by C-section as the group of interest. I think that would be a great study and would answer a lot of questions. While it seems this is still a new area of research, I think the studies speak for themselves. If this information was more widely disseminated, maybe some women would think twice before electing to have a C-section. Maybe in the future, parents will be advised to give their newborns that were delivered by C-section probiotics. Or maybe everyone will be prescribed probiotics after taking broad-spectrum antibiotics....but that is for another blog! Bager, P., Wohlfahrt, J., & Westergaard, T. (2008). Caesarean delivery and risk of atopy and allergic disease: meta-analyses. Clin Exp Allergy, 38(4), 634-642. Grölund, M.-M. L., Olli-Pekka; Eerola, Erkki; Kero, Pentti. (1999). Fecal Microflora in Healthy Infants Born by Different Methods of Delivery: Permanent Changes in Intestinal Flora After Cesarean Delivery. Journal of Pediatric Gastroenterology & Nutrition, 28(1), 19-25. Hamilton B.E., J. A. M., S.J. Ventura. (2009). Births: Preliminary Data for 2007. Kalliomaki, M., & Isolauri, E. (2003). Role of intestinal flora in the development of allergy. Curr Opin Allergy Clin Immunol, 3(1), 15-20. Kalliomaki, M., Salminen, S., Arvilommi, H., Kero, P., Koskinen, P., & Isolauri, E. (2001). Probiotics in primary prevention of atopic disease: a randomised placebo-controlled trial. Lancet, 357(9262), 1076-1079. Kuitunen, M., Kukkonen, K., Juntunen-Backman, K., Korpela, R., Poussa, T., Tuure, T., et al. (2009). Probiotics prevent IgE-associated allergy until age 5 years in cesarean-delivered children but not in the total cohort. J Allergy Clin Immunol, 123(2), 335-341. Moorman, J. E., Rudd, R. A., Johnson, C. A., King, M., Minor, P., Bailey, C., et al. (2007). National surveillance for asthma--United States, 1980-2004. MMWR Surveill Summ, 56(8), 1-54. S. Thavagnanam, J. F., A. Bromleyz, M. D. Shields and C. R. Cardwell. (2007). A meta-analysis of the association between Caesarean section and childhood asthma. Clinical and Experimental Allergy, 38, 629-633. Tollanes, M. C., Moster, D., Daltveit, A. K., & Irgens, L. M. (2008). Cesarean section and risk of severe childhood asthma: a population-based cohort study. J Pediatr, 153(1), 112-116.

A Look into Obesity and Gut Microbiota

Student guest post by Liz Stepniak

In the United States, the obesity epidemic is rapidly spreading. Since 1980 the prevalence of obesity has increased over 75%. Currently, over half the population is overweight, and nearly 1 in every 3 adults is clinically obese. Research has also been proliferating, exploring a plethora of possibilities to better understand and treat this growing epidemic. One of the recent trends in obesity research has been investigating the role of the microbiota in the gut and differences in the composition of these bacteria between obese and non-obese individuals. Could this be a potential treatment for obesity? Like many things in research, not all studies come to the same conclusion that there is an important role of gut microbiota in obesity.

Obesity is a result of alterations in the body’s regulation of energy intake, expenditure, and storage. During a time when a large portion of the population worked in manual labor and it was necessary to conserve calories for long periods of time; this was an efficient mechanism. Currently, the majority of people do not have manual labor positions, so our energy expenditure is much lower but our bodies are still conserving those calories leading to an imbalance in regulating energy intake and expenditure and an overall increase in weight gain.

An important site to explore the regulation of energy intake and storage is the digestive system, specifically: the gut. The human gut has over 5,000 species of bacteria. There are three main phyla found in the gut: Firmicutes, Bacteriodetes, and Actinobacteria. One of the roles that bacteria plays in the gut is to help extract calories from what we eat, help store these calories for later use, and provide energy and nutrients for the production of new bacteria to continue this job. So, it is biologically plausible that if this was the primary job of one of these groups of bacteria or a certain bacteria phyla were more proficient in this job; that this could help explain a possible link to obesity.

The field of understanding metabolic balance and its role in obesity expanded with a December 2006 paper which discovered that an obesity-associated gut microbiome had an increased capacity for energy harvest. This study demonstrated overt differences between microbiomes of obese and non-obese mice and also indicated that this trait was transmissible among mice. Research has also shown that maintaining a proper ratio between Firmicutes and Bacteriodetes is necessary to maintain good health. Another study found that obese people have higher amounts of Firmicutes and lean people had higher amounts of Bacteriodetes. This study also found that the composition of bacteria shifted as the obese subjects lost weight. Enter: the probiotics push. An attempt to alter the composition of the microbiota in the gut.

This idea was spread further in April of 2008, when the Mayo Clinic published a paper which examined the role that bacteria play in the human gastrointestinal tract for regulating weight and obesity. Through experiments using mouse models, the investigators suggested that the manipulation of gut microbiota could be a useful strategy for regulating energy balance in obese people. They clearly state that this would not be a substitute for proper diet and exercise; this was to be approached as a novel tactic to treating obesity.

However, not all research has agreed upon a link between gut microbiota and obesity. A group of investigators at the University of Aberdeen Rowett contradicted this research and claimed there was no link between gut bacteria and a person’s BMI level. This was a small study, only 33 obese participants and 14 participants of average weight and they only changed the carbohydrate portion of the diet. They further comment on this finding to say that they’re not ruling out the possibility that a more detailed analysis of the gut bacterial community may reveal differences between obese and normal weight people in some different bacteria species that make up the Bacteroides and Firmicutes groups, which is directly linked to the diet. Essentially, the authors question whether there is an important difference linked to obesity in the composition of gut microbiota or if the composition is merely altered by diet.

Recently, I have seen several mentions of probiotics in the news, articles on maintaining proper digestive health, and frequent literature regarding gut microbiota and obesity. Although there have been multiple studies showing an association between gut microbiota and obesity, there is a significant amount of research needed to confidently classify the link between the role of gut bacteria and obesity. The big question remains whether this is just another short-lived trend in obesity treatment or if it has the ability to be sustained and make a positive impact in the obesity epidemic.

Maybe one day the answer to solving the obesity epidemic will be uncovered….

Until then… in the words of Michael Pollan: “Eat Food. Not Too Much. Mostly Plants.” And exercise!!

Works Cited:

CDC: Obesity and Overweight.

Mayo Clinic (2008). Could Changing The Bacteria In Your Digestive System Be An Obesity Treatment? ScienceDaily.

Duncan SH et al. (2008). Human colonic microbiota associated with diet, obesity and weight loss. International Journal of Obesity 32, 1720-1724

Turnbaugh PJ et al. An obesity-associated guy microbiome with increased capacity for energy harvest. Nature 444, 1027-1021.

Grimes M. Jan 26, 2010 NaturalNews.com: Bacteria in the Gut Shown to Reduce Obesity

DiBaise JK et al (2008). Gut microbiota and its possible relationship with obesity. Mayo Clin Proc 83: 460-469.