The year is 2017, in the west, a co-cultural storm brews that will revolutionise the way that we view nutrition. Developments in metagenomics and metaproteomics, the techniques we use to monitor and understand the bacterial residents of our guts, have revealed the unique super-organism in each of us. These are techniques that allow fast identification of both bacterial species and bacterial function within the body. Following the Human Genome Project, the Human Microbiome Project of 2008 intends to develop a reference set of microbial genome sequences to characterize the superorganism – that being the symbiotic relationship of bacteria and body.
Our true microbial colours are lurid – a diverse range of multitudinous bacterial colonies with a unique interpersonal fingerprint. Your cell count is out-numbered; for every one cell in your body, there are 150 bacterial cells, your metagenome is 150 times that of your genome; you are a 150th of the person you thought you were; cue the early onset of your existential crisis.
People are getting excited over it. The Human Microbiome Project is a National Institute of Health initiative with a modest budget of 115 million dollars. Previous difficulties in culturing procedures of gut bacteria left a paucity of data that makes the microbiological timeline look like some sort of ‘cultural dark age’. New studies present tools that could cast new light through an otherwise opaque microscope.
The implications are huge – we now have unimpeded access to genetic data on unique profiles of bacterial species that can regiment the tools at hand to study complex interspecies relationships and host-bacteria interactions. These have previously been suspected to regulate host morphology, metabolism, cancer predisposition and immune homeostasis. Autoimmune diseases (Crohn’s), diabetes and obesity have demonstrated a causal link between an altered state of bacteria in the gut and disease onset. Lingering in the back of the microbiological mind is the notion that understanding the healthy state of our microbiota will inform ways to modulate it back towards the healthy state during disease. Better yet, there are theoretical benefits in prolonging the healthy state to slow the aging process.
Autoimmune diseases (Crohn’s), diabetes and obesity have demonstrated a causal link between an altered state of bacteria in the gut and disease onset.
‘The aging process’ – what a terrifying trifecta of words. This has long been the view of the western world. Everything we are surrounded by urges us to a state of longevity. It’s in our beauty ideals, in our medical infrastructure and it flows in our vasculature. Diet has always been a way of modulating aging, in calorie restriction or the spirited occupation of fad diets (however brief or pious). However, there is a growing dietary shift that embraces a more holistic approach to dieting. It’s set in a backdrop of anthropogenic overconsumption that could be altering a growing populations microbiological environment.
Veganism is set in a backdrop of anthropogenic overconsumption that could be changing a growing populations microbiological environment.
The number of vegans in Britain has risen by more than 360% over the past decade. In 2013, we witnessed the highest rate of increase in atmospheric CO2 concentrations ever recorded, with the meat industry contributing 18% of all greenhouse gas emissions. Younger generations have opted to orientate their diets in direct opposition to this statistic, with 46% of all vegans of ages 15-34.
Since 2008, studying the relationship between diet and the microbiota has grown in popularity. The commensal species of the microbiota benefit host health by preventing pathogenic colonization, aiding metabolism and regulating immune homeostasis. Early colonisers of the infant GI tract include enterobacter and enterococci, followed by anaerobic Bifidobacteria, Clostridia and Streptococci before adult stage transition (dominated by Firmicutes and Bacteriodes). We characterize our microbiota into distinct ‘enterotypes’ – the delicate ratios of which govern metabolic and immune-regulatory roles.
Younger generations have opted to orientate their diets in direct opposition to this statistic, with 46% of all vegans of ages 15-34.
A study conducted in 2012 in Tubingen, Germany, found that a vegan diet had significantly reduced levels of Bifidobacteria and Bacteriodes, two species that are the most thoroughly characterized within our guts. Given that our gut bacteria are in contact with the largest pool of immune cells in our body, maintaining ratios of bacterial types is essential for the regulation of our immune system. The role of these bacterial subspecies in metabolism, pathogenic protection and immune homeostasis is becoming clearer.
Bacteriodes fragilis species interact with CD4+ T cells via polysaccharide A to progress their development into T helper cells, vital immune components that regulate immune function. This interaction helps to prolong the circulation of IFN-y and IL-4, molecules that help T cells to help other immune cells. Bifidobacteria secrete metabolic enzymes that digest host-derived carbohydrates, enabling them to synthesise short chain fatty acids that protect against pathogenic attack by species such as Salmonella and Clostridium. The presence of Bacteriodes in the gut also produces an antimicrobial effect, producing c-type lectins REGIIIy and REGIIIb, proteins that kill-off invading bacterial species. But we cannot just assign ‘negative’ and ‘beneficial’ functions to species. Our microbiota changes throughout life, and we suspect that it functions more like an ‘organ’ in which all species have a relationship with each other, just like the cellular components of lung or liver tissue. Partitioning bacteria into healthy and unhealthy may not be the full picture.
However, these studies are flecked with glaring flaws in their approach. They were conducted via a myopic lens during the stages of microbiological opinion that diet and microbiota had an exclusively causal relationship. The fact is that the variables affecting the microbiota form an intricate web that we call ‘lifestyle’. The nature of veganism is not a singular change in diet, nor is it a drastic, austere draconian regime over your body. In younger generations it is likely to be a reaction to a growing consciousness of the imperative to lead a more sustainable existence. It’s set in a statistical backdrop of overconsumption. Cue the individual disaffiliation from industrial processes and the adoption of a lifestyle philosophy that places greater weight on the quality of source than the quality of product. The philosophy of veganism acknowledges the individual’s contribution to a ravenous industrial process, and shifts the individual’s lifestyle to a holistically more sustainable approach.
It comes by intuition that those more aware of this concept are more likely to edge towards longevity in other areas of their lifestyle. These folk are statistically more hygiene-conscious, exercising individuals who cannot be used in studies that examine the singular relationship between diet and microbiota. Orientating your diet in opposition of commercial overconsumption is just one way of demonstrating ones disaffiliation from this process – it’s the tip of the iceberg for a growing way of life in younger generations.
Our actual understanding of lifestyle, microbiota, and the way we age is therefore worryingly scarce. We don’t know a lot because we can’t yet. It’s extremely difficult to filter results down to one causal variable when the lifestyles we lead as individuals are so diverse. Species in our gut vary according to hygiene levels in our home, our places of work, and our social groups. Understanding the protective functions of the microbiota is an imperative. However, mapping the result of dietary changes on the microbiota is a slow process. If we are to fully advocate widespread vegetarianism and veganism to prolong our planet for the collective humanity, we best understand the effect it will have on our bacterial counterparts, be it detrimental or beneficial.
J Zimmer et al 2012 A vegetarian or vegan diet substantially alters the human colonic faecal microbiota. European Journal of Clinical Nutrition – https://www.ncbi.nlm.nih.gov/pubmed/21811294
F Baquero and C Nombela 2012 The microbiome as a human organ. Clinical microbiology and Infection – https://www.ncbi.nlm.nih.gov/pubmed/22647038
M Glick-Bauer and Ming-Chin Yeh 2014 The health advantage of a vegan diet: Exploring the gut microbiota connection. Nutrients Journal – https://www.ncbi.nlm.nih.gov/pubmed/25365383