The Continuing Development of the Bacterial Microbiome After the Age of 3
We’ve known for quite some time that gut flora development from birth through the 3rd year of life has a tremendous impact on health throughout the lifetime. However, not much research has been done on the continuing development of the microbiota in school aged children. Researchers from Denmark and China worked together, analyzing the microbiomes and blood markers of 281 Danish children between the ages of 6 and 9 years, looking at factors like the type of delivery, breast feeding, preschool diet, body mass index and waist size, etc. to see if there were any patterns.[i]
I was not at all surprised by their results, and I imagine you won’t be either. The three main factors that determined the type of gut bacteria found in the children were breastfeeding duration, diet (intake of plant-based proteins and dietary fiber), and the moms’ education levels (which, of course, might have a huge bearing on their children’s diets). That is, diet once again is found to be the most important factor for determining the makeup and health of the gut flora.
A few highlights from the paper:
- The children all fit into one of 3 different “enterotypes” (i.e. composition of gut bacteria), and these were associated with different metabolic profiles. Without getting into excessive detail, children in the E1 (relatively higher amounts of Bacteroides species) and E2 (relatively higher amounts of Prevotella species) groups had greater diversity of bacteria and bacterial genes in comparison to the kids in E3 (relatively greater amounts of Bifidobacterium species). This latter group was also notable in that they had fewer bacterial genes associated with butyrate-producing bacteria.
- Of special interest to those of you with children on the autism spectrum: the children in the E3 group, who were considered to have the least “adult-like” bacterial complexity (i.e. least diversity), not only were poor at utilizing complex carbohydrates like prebiotic fibers (and thus, had lower levels of beneficial short chain fatty acids); they also harbored species that enhanced the biosynthetic pathways for numerous amino acids but not cysteine, which, as many of you may know, is crucial for the creation of glutathione in the body. We’ve known since 2004, when Dr. Jill James, et. al. first published their study[ii] (that my son was actually a part of!) that children on the spectrum have low cysteine and low glutathione levels (and thus, have high levels of oxidative stress and are poor at detoxification) which is a major factors in the population. You do have to wonder if the microbiota alterations found in people on the spectrum is not a factor. ?????
- So…what lifestyle factors were associated with each different group? Well, as I mentioned above, diet was essentially the key factor. The children in E3, who had the less diverse microbiome, had shorter breastfeeding periods and less intake of dietary fiber and plant-based proteins.
- The children in groups E1 and E2 had better glucose responses than E3 when consuming plant-based fiber. The potential reason is that the first two groups produced higher levels of metabolites (like butyrate) that are known to have beneficial effects on glucose and insulin responses. “Together, our findings support the notion that host metabolic benefits of plant-based diets might be conferred by specific bacteria and specific metabolites derived from carbohydrate fermentation.”
A short description of the paper appeared earlier this week on Gut Microbiota for Health, which concludes with the take-away point from today’s post: “…gut microbiota maturation is not complete by the end of the first three years of life and early-life factors have a relevant influence on gut microbiota in school-age children.”[iii]
[i] Zhong, H, et. al. Impact of early events and lifestyle on the gut microbiota and metabolic phenotypes in young school-age children. Microbiome. 2019:7(1):2. 10.1186/s40168-018-0608-z.
[ii] James, SJ, Cutler, P, Melnyk, S, Jernigan, S, Janak, L, Gaylor, DW, Neubrander, JA. Metabolic biomarkers of increased oxidative stress and impaired methylation capacity in children with autism. American Journal of Clinical Nutrition. 2004:80(6):1611-7.