Within our intestines, we harbor some 100 trillion microbial cells, collectively known as the gut microbiome (GM). For better or worse, the GM profoundly influences our health, impacting physiology, metabolism, nutrition, and immune function. GM disruption can promote obesity, diabetes, and chronic inflammatory diseases, including irritable bowel syndrome and Crohn’s disease.1, 2, 3 In short, according to the human microbiome project (HMP), “we are supraorganisms composed of human and microbial components.”4
The HMP was an initiative launched in 2007 by the National Institutes of Health to study the role of microbes in human health and disease. The HMP sparked widespread interest in GM research, but we’re still just beginning to understand the complexities and intricacies of the GM. Nevertheless, preliminary research suggests the transition from being hunter-gathers to sedentary city dwellers resulted in significant GM changes.
For example, researchers recently compared the GMs of traditional Hadza hunter-gatherers of Tanzania with those of urban adults. The results, published in Nature Communications, showed the Hadza having significantly increased GM diversity.5 Notably, the Hadza have higher amounts of Clostridia, a class of gut bacteria, which according to recently published research, protects against food allergies (more on this below).6
The researchers studying the Hadza remarked, “Adaptation to the post-industrialized western lifestyle is coincident with a reduction in GM diversity, and as a result, a decline in GM stability.” Since the gastrointestinal tract is a gateway to pathogenic, metabolic, and immunological diseases, scientists are increasingly interpreting this decline in GM diversity as a major risk factor for degenerative diseases.
Why is Gut Microbiome Diversity Decreasing?
Many aspects of modern lifestyles promote decreased GM diversity, including birthing method (cesarean versus traditional vaginal births), decreased breastfeeding, decreased consumption of dietary fiber, increased early childhood exposure to antibiotics, and increased lifetime exposure to antibiotics. Cesarean births require the use of antibiotics, which is one reason why, according to research recently published by the Canadian Medical Association Journal, cesarean birthed infants exhibit “particularly low bacterial richness and diversity.”7
Antibiotics are notoriously overprescribed in the US, particularly for viral infections (which antibiotics don’t affect). A 2014 study found that doctors prescribe antibiotics for 60% of sore throat cases and 70% of cough cases.8 Dr. Jeffrey Linder, one of the study’s co-authors, says only 10% of sore throat cases are bacterial and multiple studies show antibiotics are ineffective against coughs.9 In short, modern lifestyles and diets are negatively impacting GM diversity.
The Connection Between Gut Microbiome and Food Allergies
According to Food Allergy Research & Education, 15 million Americans suffer from food allergies, including 1 in 13 children.10 Food allergies increased 18% among children from 1997 to 2007.11 Is the increasing food allergies trend related to the decreasing GM diversity trend? According to University of Chicago researchers, yes.
By studying mice raised in perfectly sterile environments, these researchers discovered that Clostridia (the same bacterial strain observed at increased levels among the Hadza and decreased levels among urbanites) protects against food allergies.12 Lead researcher Dr. Cathryn Nagler explained, “The first step is for an allergen to gain access to the blood stream. The presence of Clostridia prevents the allergens from getting into the bloodstream.”13
So what does this mean with respect to the Paleo Lifestyle? For many people, particularly those with a history of antibiotic use, probiotic supplementation may be prudent. Dr. Cordain explains that both probiotic and prebiotic supplements promote healthy gut flora and reduced intestinal permeability for most people, although in some special cases they could agitate the gut.
Moreover, the Paleo Diet contains large amounts of fiber-rich vegetables. Think of fiber as food for the GM. Once inside the gastrointestinal tract, certain vegetable fibers ferment, creating short-chain fatty acids, which promote GM diversity and prevent the overgrowth of antagonistic bacterial strains.14
Remember the human microbiome project (HMP)? Thirty-seven HMP microbiologists were asked a series of questions regarding gut health, including one specific to the Paleo Diet: “Do you believe a high protein-fat diet, so long as it includes a significant amount and diversity of whole plants (fermentation sources) and minimal to no processed carbohydrates, is a strategy for a healthy microbiome?”15 With 1 representing “strongly disagree” and 10 “strongly agree,” the average response was 9.1. In other words, according to the world’s leading GM experts, the Paleo Diet, like the ancestral Hadza diet, promotes healthy, diverse gut microbiomes, thereby protecting against food allergies.
Christopher James Clark, B.B.A. is an award-winning writer, consultant, and chef with specialized knowledge in nutritional science and healing cuisine. He has a Business Administration degree from the University of Michigan and formerly worked as a revenue management analyst for a Fortune 100 company. For the past decade-plus, he has been designing menus, recipes, and food concepts for restaurants and spas, coaching private clients, teaching cooking workshops worldwide, and managing the kitchen for a renowned Greek yoga resort. Clark is the author of the critically acclaimed, award-winning book, Nutritional Grail.
1 Ley, RE., et al. (December 2006). Microbial ecology: human gut microbes associated with obesity. Nature, 444 (7122). Retrieved October 2, 2014 from http://www.ncbi.nlm.nih.gov/pubmed/17183309/
2 Qin, J., et al. (October 2012). A metagenome-wide association study of gut microbiota in type 2 diabetes. Nature, 490 (7418). Retrieved October 2, 2014 from http://www.ncbi.nlm.nih.gov/pubmed/23023125/
3 Frank, DN., et al. (August 2007). Molecular-phylogenetic characterization of microbial community imbalances in human inflammatory bowel diseases. Proceeding of the National Academy of Sciences, 104 (34). Retrieved 2, 2014 from http://www.ncbi.nlm.nih.gov/pubmed/17699621/
4 Turnbaugh, PJ., et al. (October 2007). The human microbiome project: exploring the microbial part of ourselves in a changing world. Nature, 449 (7164). Retrieved October 2, 2014 from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709439/
5 Schnorr, SL., et al. (April 2014). Gut microbiome of the Hadza hunter-gatherers. Nature Communications, 5 (3654). Retrieved October 2, 2014 from http://www.nature.com/ncomms/2014/140415/ncomms4654/full/ncomms4654.html
6 Stefka, AT., et al. (August 2014). Commensal bacteria protect against food allergen sensitization. Proceedings of the National Academy of Sciences, 111 (36). Retrieved October 2, 2014 from http://www.pnas.org/content/111/36/13145
7 Azad, MB., et al. (March 2013). Gut microbiota of healthy Canadian infants: profiles by mode of delivery and infant diet at 4 months. Canadian Medical Association Journal, 185 (5). Retrieved October 2, 2014 from http://www.cmaj.ca/content/185/5/385
8 Barnett, ML., (January 2014). Antibiotic Prescribing to Adults With Sore Throat in the United States, 1997-2010. JAMA Internal Medicine, 174 (1). Retrieved October 2, 2014 from http://archinte.jamanetwork.com/article.aspx?articleid=1745694
9 Singh, M. (October 4, 2013). Despite Many Warnings, Antibiotics Are Still Overprescribed. NPR. Retrieved October 2, 2014 from http://www.npr.org/blogs/health/2013/10/04/229167826/despite-many-warnings-antibiotics-are-still-overprescribed
10 Food Allergy Research & Education. About Food Allergies. Retrieved October 2, 2014 from http://www.foodallergy.org/about-food-allergies
11 Branum, AM., (October 2008). Food Allergy Among U.S. Children: Trends in Prevalence and Hospitalizations. NCHS Data Brief, 10. Retrieved October 2, 2014 from http://www.cdc.gov/nchs/data/databriefs/db10.pdf
12 Stefka, AT., et al. (August 2014). Commensal bacteria protect against food allergen sensitization. Proceedings of the National Academy of Sciences, 111 (36). Retrieved October 2, 2014 from http://www.pnas.org/content/111/36/13145
13 Gallagher, J. (August 26, 2014). Gut bugs ‘help prevent allergies.’ BBC News, Health. Retrieved October 2, 2014 from http://www.bbc.com/news/health-28887088
14 Kaczmarczyk, MM., et al. (August 2012). The health benefits of dietary fiber: Beyond the usual suspects of type 2 diabetes mellitus, cardiovascular disease and colon cancer. Metabolism, 61 (8). Retrieved October 2, 2014 from http://www.sciencedirect.com/science/article/pii/S0026049512000455
15 Leach, J. (September 26, 2012). Guts, Germs and Meals: what 37 microbiologist say about diet. Human Food Project. Retrieved October 2, 2014 from http://humanfoodproject.com/guts-germs-and-meals-what-37-microbiologist-say-about-diet/