I would like to talk about a topic today which I do not only find very exciting but also consider important, as it concerns our general well-being. I am talking about the microbiome. I will not go into detail here, cause then I would probably reach the limit of my blog storage. Anyways, I just want to give you a few insights into the functions of our microbiome and its impact on our health. If any questions remain unanswered at the end, don’t hesitate to leave me a comment or send me an email.
What exactly is the microbiome?
As the name implies, it is basically a really small form of life (‘micro’ = small; ‘bio’ = life), colonizing different areas of our body, including the skin [1] and our mouth [2]. In fact, our body is made up of 10-times more bacterial cells than our own ‘human’ cells – that’s at least 100 trillion microorganisms living on and inside of us [3]! Incredible, right? The term ‘bacteria’ might evoke negative associations in some of you but believe me, bacteria can both be bad and good. Microbes actually play an essential part in several biological processes in our body and have a great influence on our health.
The biggest and probably most important microbiome hosted by our body is the one in our gut. An extremely complex interplay – some kind of symbiosis – between a large variety of microbes and your body’s own cells takes place in the digestive tract to keep your digestion on track and to strengthen your immune system. And if this interplay is out of balance, it can lead to severe consequences for our health, ranging from inflammatory bowel disease, asthma, diabetes and obesity to colorectal cancer and even neurolgical dysfunctions [4, 5].
Small, but oh my!
One of the main functions of our gut inhabitants is the breakdown of certain food components that we cannot digest (due to a lack of enzymes) – namely dietary fiber [6, 7]! You might be asking now, how those for us undigestible carbohydrates like pectins can be so important, even though we are unable to digest them? Soluble dietary fiber is broken down by gut bacteria to form the short-chain fatty acids (SCFAs) butyrate, acetate and propionate which are particuarly relevant to maintain our intestinal mucosa [8]. That might sound a bit unspectacular, it is however a crucial process that keeps your gut healthy and protects it from inflammation. And even more: The SCFAs promote the colonization of other beneficial bacteria, while preventing pathogens from settling down in the intestinal wall by interacting with immune cells that also inhabit the gut [9].
Feeding time
The biodiversity of our intestinal microbiota is unique, meaning everyone’s looks different, kind of like a finger print. And as you can imagine, this bacterial finger print largely depends on what we eat – after all, we are talking about our gut here.
The composition of our gut bacteria is, however, os quite dynamic. A change in your diet can cause drastic changes in your gut microbiome within a short period of time. Nevertheless, this change does not have to be beneficial, depending on what you put in your mouth. It was, for instance, shown that a chronic deficiency in dietary fiber can cause a drastic shift in the composition of the gut microbes and that certain types of bacteria begin to degrade the intestinal mucosa for nutrients. This degradation implies an increased risk for infections, as the intestinal mucosa constitutes an essential barrier against pathogens [10]. But not only your gut will suffer under a diet lacking dietary fiber. A reduced amount of dietary fiber in your diet also correlates with increased body weight [11] and promotes the development of respiratory dieseases like asthma [12].
People from countries like the USA, in which large amounts of animal proteins, fats and sugar and minimal dietary fiber are consumed, have a completely different array of gut bacteria than people from countries like Africa, where a lot of grains, legumes and plants are eaten on a daily basis [13, 14]. Now guess which of these two countries has the highest incidence rate for obesity, diabetes, inflammatory bowel diseases and colon cancer! Of course, aside from the gut flora a lot of other factors and biological processes are involved in the course of those diseases, no doubt about that.
Antibiotics and the downfall of the gut flora
(Picture credit: https://www.kratomiq.com/buy-kratom/)
Not only diet influences the life in our gut. The intake for antibiotics can have dramatic consequences for the composition and activity of our intestinal microbiome and therefore our health. Unfortunately, antibiotics do not only act against those nasty germs, but also against the good bacteria in the gut. Children who repeatedly were on antibiotics at a young age show a delayed maturation of the intestinal microbiome than children who were not treated with antibiotics [15]. Several studies were also able to show that the composition of gut bacteria does not recover completely after ingestion of antibiotics like ciprofloxacin [16, 17]. So if you do not necessarily have to take antibiotics, don’t do it!
The gut and the mind
Up to this point, I mainly discussed the aspect of healthy digestion, but did you know that our digestive tract is tighly connected with our brain? If our gut is not well – for instance due to inflammation that results from the dysbiosis in our microbiome – certain signaling molecules including neurotransmitter and factors of the immune system are sent from the gut to the brain [18]. And this may have a strong effect on our mental well-being. Recent scientific studies revealed a connection between the gut microbiome and different mental disorders, like depression [19], Alzeimer’s Disease [20] and interestingly autism [21].
Gimme all the veggies!
Diet has a great impact on our physical and mental state of health by acting either directly or indirectly through our microbiome. Despite the complexity of the microbiome, it is certain to say that a plant-based diet, rich in unprocessed grains, legumes, fruit and vegetables, positively affects the gut flora and thereby our overall health. So if you are considering living off chips, chocolates and cookies over the weekend, maybe you should think again and listen to your gut!
If you like these kind of posts, let me know in the comments below. And in case you have suggestions for future posts about health-related topics, please write them down as well.
References:
[1] Grice et al. Topographical and temporal diversity of the human skin microbiome (2009), Science
[2] Nasidze et al. Global diversity in the human salivary microbiome (2009), Genome Res
[3] Whitman et al. Prokaryotes: The unseen majority (1998), Proc Natl Acad Sci
[4] Blumberg and Powrie. Microbiota, disease, and back to health: A metastable journey (2016), Sci Transl Med
[5] Turnbaugh et al. An obesity-associated gut microbiome with increased capacity for energy harvest (2006), Nature
[6] Sonnenburg et al. Glycan foraging in vivo by an intestine-adapted bacterial symbiont (2005), Science
[7] Sawicki et al. Dietary fiber and the human gut microbiota: Application of evidence mapping methodology (2017), Nutrients
[8] Wong et al. Colonic health: fermentation and short chain fatty acids (2006), JCG
[9] Kau et al. Human nutrition, the gut microbiome, and immune system (2011), Nature
[10] Desai et al. A dietary fiber-deprived gut microbiota degrades the colonic barrier and enhances pathogen susceptibilty (2016), Cell
[11] Ley et al. Microbial ecology: Human gut microbes associated with obesity (2006), Nature
[12] Trompette et al. Gut microbiota metabolism of dietary fiber influences allergic airway disease and hematopoiesis (2013), Nature Medicine
[13] Yatsunenko, T. et al. Human gut microbiome viewed across age and geography (2012), Nature
[14] De Filippo et al. Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa (2010), Proc Natl Acad Sci
[15] Langdon et al. The effects of antibiotics on the microbiome throughout development and alternative approaches for therapeutic modulation (2016), Genome Med
[16] Dethlefsen et al. The pervasive effects of an antibiotic on the human gut microbiota, as revealed by deep 16S rRNA sequencing (2008), PLoS Biol
[17] Jernberg et al. Long-term ecological impacts of antibiotic administration on the human intestinal microbiota (2007), ISME J
[18] Clapp et al. Gut microbiota’s effect on mental health: The gut-brain axis (2017), Clin Pract
[19] Foster, McVey Neufeld. Gut–brain axis: how the microbiome influences anxiety and depression (2013), Trends Neurosci
[20] Zhao et al. Secretory products of the human GI tract microbiome and their potential impact on Alzheimer’s Disease (AD): Detection of Lipopolysaccharide (LPS) in AD hippocampus (2017), Front Cell Infect Microbiol
[21] Mayer et al. Altered brain–gut axis in autism: comorbidity or causative mechanisms? (2014), Bioessays
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