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Microbiome & Longevity: New Research Suggest Key Links

‘Microbiome’ – Micro meaning very small – Bio meaning life – Me meaning you or me. Remember this term because it is going to become better recognised as an important factor in human health and our longevity. Human microbiome is defined as the collection of genes found in all microbes residing within us – basically all the bacteria, fungi, viruses, and microorganisms inhabiting our bodies. ‘Microbiota’, another term, refers to all microorganisms inhabiting a particular environment like the gut. There are many trillions of these microscopic entities residing in our human gastrointestinal tract, on our skin, and most places. Long have we ignored this micro-environment and rather focused on larger, more readily seen matters, possibly to the detriment of our health and understanding of life. Remember that microbes have been around for a lot longer than we have (billions of years) and are easily the most successful life forms on this planet.  In the current climate, with a global viral pandemic ravaging the world, we are all suddenly more aware of the micro-realm. Indeed, our awareness of microbiome greatly increased around 2002, when gene sequencing technology became available to identify microbes and their influence. Following this there has been a huge explosion in the study of microbiome and humans.

by Robert Sudha Hamilton

Human Microbiota in the Gut

Microbiome and longevity: New research suggest key links, and this is no real surprise when you consider the facts. Science has identified that there are many more microorganisms colonising us than there are human cells forming us. It is a very busy world at the microscopic level. We are, it seems, powerfully influenced by the total genome information contained within all our microbiome rather than just our human cells. The microbiome provides access to millions of genes for all sorts of important biological processes, which are absent in our human cells. We are much more than first thought. There are 300 to 1, 000 species of microorganisms living inside of us, which weigh around 2-3kg, consume 50-65g of sugars per day, and expel 1 to 4 litres of gas per day. 60% of our stools are made up of living and dead bacteria. Obviously, then, our health and longevity are affected by the sum of our microbiome. Every human being has a unique microbiota. Family members will share more microbiome than unrelated individuals. Our symbiotic relationship with these trillions of microbes directly influences the state of our health and how we experience life.

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Ageing & Microbiome

Ageing is the single greatest challenge to our longevity and ageing affects our human microbiome. Our intestinal tract contains the largest surface interacting with microorganisms in the human body. Our gut bacteria maintain a homeostatic metabolism, which allows us to derive energy from the food we eat. We are all familiar with the age-related diseases and conditions which will eventually directly contribute to our demise. These are obesity, cardiovascular disease, cancers, and neuro-degenerative conditions. Many of us eat and drink ourselves to death as we get older, losing the ability to balance the energy coming in and going out. The modern sedentary lifestyle, where we sit down for increasingly long periods in air-conditioned comfort, behind the wheel, behind a desk, in front of countless screens, and at the dining table is literally killing us. Our monkey bodies must be exercised to maintain good health and we need to have a good diet to sustain a diverse microbiota, which means an optimised immune system.

Clear Correlations Emerging Between Gut Microbiome & Good Health

New research, via lab animal studies, has shown clear correlations between gut microbiome status and cognitive changes. In one study conducted at Oregon Health & Science University the gut microbiome in mice was noticeably altered by those mice carrying the genes associated with Alzheimer’s disease, despite the fact that they were all fed the same diet under the same conditions. The disease alters the state of the gut bacteria. At this early stage of research into this exciting realm there is a fair degree of observing changes in both the brain and gut microbiome and wondering which comes first. Epigenetic changes in the hippocampus may be affecting, or affected by, changes in the gut microbiome, according to the research produced by recent studies. Understanding the causal direction of the relationship will illuminate this important research further. Gut bacteria imbalances in the prediabetic stage are shining a light on Type 2 diabetes in human beings (Sharma, 2018). Our metabolism is directly affected by the interaction between gut bacteria and the foods we eat. This process influences blood sugar levels and the synthesis of neurotransmitters. Thus, a condition like Type 2 diabetes emerges slowly over time and can be tracked via the state of our microbiome. However, it is important to note that the complexity of microbiota and the variability within individual human gut microbiome remains a compelling factor.

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Microbiome an Early Warning System

It is highly likely that a bi-directional relationship is at work when we observe the interaction between microbiome and disease within human beings (Haran, 2019). This means that it may not prove to offer a silver bullet in terms of finding a magic probiotic cure for diseases adversely affecting our longevity and quality of life. It may, however, provide an early warning system for those likely to develop serious diseases like Alzheimer’s and Type 2 diabetes.

Our gut microbiome can influence how we feel and think via Vagus nerve stimulation. The interaction between gut bacteria and the foods we eat during metabolism impacts upon our cognitive equilibrium. Neurotransmitters like serotonin and dopamine are directly affected via this process, which can result in whether we feel happy or sad, compelled or overstimulated to eat. Nearly all the serotonin in the body is produced in the gut. Around half of the dopamine is produced there. Therefore, chronic conditions like depression and anxiety are influenced by the state of play within our gut microbiome. Food addictions and overeating can, also, be driven by gut bacteria imbalances. These serious mental health issues can impact negatively on our longevity. Gut microbes can, also, influence what we choose to eat, when we want to eat, and how healthy we are in response to our food choices. Our diet is a major influence in shaping our human microbiome, as different microbes and bacteria are involved with different types of foods. Eating predominantly animal flesh versus a plant-based diet for instance affects the production rate of Short Chain Fatty Acids like Acetate and Butyrate negatively and these are the products of microbial fermentation of plant-based matter (fibre). These are crucial energy sources for the cells that line the gut, and they are anti-inflammatory. There are studies into obesity and gut microbes, which show that certain microbes encourage weight gain. A diet high in processed foods results in a loss of microbiome diversity and those microbes that feed on these types of food remain in abundance to our detriment. Gut microbes play a part in preventing cardiovascular disease through a number of anti-inflammatory measures involving the presence of Butyrate SCFA (Troseid, 2020).

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The human body is now perceived as an ecosystem with a colony of interactive microorganisms and a host of human cells. Thus, getting the balance right in terms of diet and environmental factors is pretty important.  The foundation for this is laid right at the start via in-utero development and maternal diet. The mother’s breast milk is a vital part of establishing the right composition of microbiota within the infant. How we are born affects the microbiome make-up with a vaginal birth delivering the mother’s microbiota, but a caesarean section involves bacteria from the skin of those handling the baby post-delivery (Dominguez-Bello, 2010). This can impact upon health issues in later life, according to recent studies. Diet and lifestyle through early childhood is a determining force in shaping the composition of microbiome within an individual.

A reduction in microbiota diversity is a key indicator in ageing human beings (Joshi, 2017). Contributing factors are limited dietary pattern, reduced mobility, lessening immune strength, gut morphology changes, increased use of medications, reduced intestinal functionality, and recurrent infections. A decrease in Bifidobacterium and Lactobacillus, and an increase in Enterobacteriaceae have been observed, more generally, via the process of ageing in studies done globally.  Antibiotics dramatically change the microbiota because they kill off a lot of good bacteria along with the targeted bad bacteria. Therefore, too many antibiotics over a prolonged period has serious consequences for our gut bacteria. Pharmaceutical drugs can, also, be affected by a person’s microbiota and can have higher toxicity in individuals due to the drug’s interaction with their unique gut bacteria.

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Ageing is a complex process involving physiological, metabolic, and immunological functioning within organisms. It is most noticeably accompanied by inflammation and metabolic dysfunction. Chronic inflammation is a key indicator of the human ageing process. The gut bacteria, which are involved in maintaining immune tolerance, decrease as we age, and those bacteria involved in infection and intestinal inflammation increase in prevalence. Our gut microbiome performs important roles in the breakdown of food, metabolism and storage of lipids, vitamin synthesis, and the prevention of infection by harmful microbes. Getting older sees a decline in the effectiveness of all of these activities.

There Are Things We Can Do to Promote Good Gut Bacteria

Our immune system can benefit from a healthy dietary input, which promotes good gut bacteria via polyphenolic antioxidants. The recent discoveries in the body’s micro-realm, as they relate to our biological functioning, fundamentally alters the perception of how we interact with our environment as human beings. Our body’s immune system is deeply dependent upon its interaction with its bacteria – the microbiota. Colon cancer, another common disease related to ageing and adversely affecting longevity, shows a strong microbiome change. The interaction between microbiome, immune system, and epithelial cells lining the colon reveals bad bacteria making proteins with greater carcinogenic potential. The eco system within the body gets out of balance and the likelihood of colon cancer is increased, especially as we age.

The Human Microbiome Project is a study begun in 2007 and it has been charting the state of microbiota in people with different diseases. The data derived from this project is providing the necessary information to gain insight into the relationship between our health and microbiome. This process is incredibly complex, like much of the finer functioning of our biology.

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Short Chain Fatty Acids (SCFA) are produced via dietary fibres being fermented in the colon. Butyric acid is one SCFA, which has an important role to play for the normal functioning of the colon. Human beings only have about 20 genes which will encode proteins responsible for the breaking down of these carbohydrates, whereas one bacterial species Bacteroides has 260 genes for the same task. Gut bacteria are efficiently breaking down fibre, which assists in ensuring a process free from bloating, constipation, gas, and diarrhea. The right dietary fibre can improve the production of SCFA and improve the positive interaction between microbiome and immune system for better health. A study carried out at the University of Queensland (Comino, Williams, & Gidley, 2018) has confirmed this understanding and result.

The more we understand the role of microbiome in the healthy human being and in those suffering from disease the greater the positive impact upon longevity. The new research suggests key links in many of the most prevalent conditions adversely affecting ageing. The modern health scourges like heart disease, cancer, diabetes, depression, and neurodegenerative conditions all show the link to depleted microbiome diversity in various guises. Ageing is accompanied, more generally, by a diminishing balance of good versus bad gut bacteria. The next level of scientific understanding may take us further into comprehending unique microbiome signatures in each of us. Right now, however, we can take steps to ensure that we feed ourselves with an appropriate dietary fibre for optimal health. Good digestion and a fully functioning immune system are dependent upon it.


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Sharma S, Tripathi P. Gut microbiome and type 2 diabetes: where we are and where to go? J Nutr Biochem. 2019 Jan;63:101-108. doi: 10.1016/j.jnutbio.2018.10.003. Epub 2018 Oct 11. PMID: 30366260.

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Delivery mode shapes the acquisition and structure of the initial microbiota across multiple body habitats in newborns

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Sudha Hamilton is a natural health writer, historian, and chef. His published titles include: House Therapy: Discover Who You Really Are At Home; Healing Our Wellbeing; and Sacred Chef.

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