The Role of Gut Flora in Aging

In 2014, gut flora was renamed gut microbiota, which, in addition to having anti-inflammatory and anti-tumor effects, is also noteworthy for its anti-aging power, as it has an effect on life expectancy and longevity.

If we consider the weight of the microbiota and its importance in maintaining immunological homeostasis, its anti-inflammatory properties in the prevention of chronic diseases and tumors, and its effect on longevity and anti-aging properties, we may view it as another organ within the human body.

Dr. Debora Nuevo – Neolife Medical Team

We might think of humans as “bacteria transport”.

In 1908, a Ukrainian scientist, Ilya Metchnikoff, Nobel Prize winner and professor at the Pasteur Institute, was the first to propose that bacteria in our gut, called lactic acid bacteria (LAB), had a beneficial effect on our health and were somehow able to promote longevity.  He suggested that by modifying gut flora, we could suppress the aging that resulted from what he called “intestinal auto-intoxication”. Some microorganisms such as Clostridium produce toxic substances like phenols, indoles, and ammonia from the digestion of proteins. By replacing these microbes with other useful ones like Lactobacillus, we might be able to slow the aging process.

gut flora

In 2014, gut flora was renamed gut microbiota, and important new terms emerged, which need to be clarified:

  • Microbiota: set of living microorganisms that reside in an ecological niche, in this case in the human gut.
  • Microbiome: set of microorganisms, their genes, and their metabolites within a given ecological niche.
  • Metagenome: any genetic material present in a sample, i.e. the full set of human and bacterial genome.
  • Dysbiosis: the imbalance between the cells in a human organism and the bacterial cells.
  • Pathobiont: benign endogenous microbes that may cause pathology in an altered ecosystem (dysbiosis).

Types of bacteria in our microbiota

About 90% of bacteria reside in the colon (approximately 100 trillion). It’s been estimated globally that there are about 30 trillion human cells in an adult male, so we could basically think of man as “bacteria transport.”

gut flora

The gut microbiome is immensely diverse, housing over 1000 different species of bacteria. Several studies have found a reduction and loss of this diversity with aging, which would lead to a poor and dysbiotic functioning, enhanced by specific environmental factors and lifestyle.

In simple terms, we may conclude that there are three different groups of gut microbiota, depending on the predominant bacterial genus: Bacteroides (enterotype 1, more associated with a diet rich in proteins and fats), Prevotella (enterotype 2, mainly linked to carbohydrate consumption), and Ruminococcus (enterotype 3). In Europe, the most prevalent enterotype is 1 (56%), followed by type 2 ( 31%).

The role of gut microbiota

Normal human gut microbiota performs nutritional and metabolic functions, and is responsible for antimicrobial protection. It regulates immune response and maintains the entire intestinal mucosa.

  • It’s an important factor in the management of body weight. It’s involved in energy metabolism, regulation of lipogenesis, and storage of body fat. An increase in firmicutes and a decrease in bacteroides can play an important role in obesity. It has also been found that it may play a decisive role in weight loss in anorexia nervosa and even in mental disorders like anxiety or depression.
  • It synthesizes vitamin K and several components of vitamin B, including vitamin B12.
  • The anaerobic bacterial fermentation of carbon fiber hydrates leads to the formation of short-chain fatty acids (SCFAs). These SCFAs are the perfect fuel for colon cells. They also inhibit some proinflammatory cytokines, with the subsequent beneficial anti-inflammatory effect, and induce the apoptosis of cancer cells in colorectal cancer. Additionally, these fatty acids are metabolized in the liver and reduce cholesterol and glucose levels. They also promote cell junctions in the colon and their integrity, accelerating the reepithelialization in lesions and cell differentiation.
  • On the other hand, our microbiota plays a central role in our immune system. The latter starts developing at birth, with the introduction of the microbiota and only matures completely and appropriately in the presence of commensal gut flora. The microbiota has a symbiotic relationship with the human being and maintains a functional intestinal epithelial barrier, which induces the production of anti-inflammatory interleukins. Improving our immunity is a process that occurs over the years, and both the immune system and the microbiota evolve with age. A reduction in the microbiota and its diversity also means an increase in fragility and susceptibility to inflammatory, chronic, or tumor diseases.

What diseases can be linked to dysbiosis?

gut flora

  • The link between some chronic diseases such as inflammatory bowel disease and irritable bowel syndrome is clear. Dysbiosis is thought to be the cause of ulcerative colitis and Crohn’s disease, or at the very least, contribute to its development. Recent studies have shown that patients with active inflammatory disease have significantly lower mean levels of bacteroides than patients in remission or normal subjects. As for irritable bowel syndrome, there seems to be a decrease in the number of bifidobacterium and lactobacillus in subjects who suffer from it.
  • It’s also worth mentioning the presence of a microbiota-gut-brain axis that acts in both directions. On the one hand, if the brain alters intestinal secretion, motility, and permeability, it can alter the microbiota. It, in turn, communicates with the brain by directly stimulating some receptors, affecting the levels of some neurotransmitters like GABA and serotonin. This may change the perception of visceral pain and the control of emotions, but it has also been linked to the pathogenesis of neurological diseases like Parkinson’s or Alzheimer’s disease.
  • A balanced microbiota also plays an important role in the prevention of some types of tumors, like colorectal cancer, hepatocellular carcinoma, or stomach cancer. While it facilitates the proper differentiation of epithelial cells, it also induces the apoptosis of malignant cells. In other words, not only can it be a protective factor against cancer, but it can also facilitate and enhance some chemotherapy treatments.

More specifically, some recent studies in animal models link a bacillus-rich diet to increased longevity compared to other standard E.Coli-rich diets. All of this seems to be due to an antioxidant substance produced by E. Coli, which in this case, seems harmful.

For this reason, in addition to the aforementioned effects (anti-inflammatory and anti-tumor), we may also highlight the anti-aging power of human microbiota, as it is able to modify life expectancy and longevity.

Lastly, if we also consider the weight of the microbiota and its importance in maintaining immunological homeostasis, its anti-inflammatory properties in the prevention of chronic diseases and tumors, and its effect on longevity and anti-aging properties, we may view it as another organ within the human body.


(1) Taylor N. Tibbs, Lacey R. Lopez, Janelle C. Arthur. The influence of the microbiota on immune development, chronic inflammation, and cancer in the context of aging. ,* Microb Cell. 2019 Aug 5; 6(8): 324–334.

(2) Vaiser AM., Koliada AKMarotta F. Gut microbiota: A player in aging and a target for anti-aging intervention. Res REv 2017 May;35:36-45. doi: 10.1016/j.arr.2017.01.001. Epub 2017 Jan 18.

(3) Round JL, Mazmanian SK. The gut microbiome shapes intestinal immune responses during health and disease. Nat Rev Immunol. 2009;9(5):313–323. doi: 10.1038/nri2515