The gut flora is a heterogeneous population of micro-organisms that includes bacteria, fungi, and archaea, and that plays important role in the digestion and absorbance of food. Transplantation of fecal microbiota from younger mice (Donor) to older (Recipient) enhanced their health and lifespan (longevity).
During the process of aging, the function of beneficial microbes, that provide necessary nutrients for the body tissues, are severely affected, while harmful microbes, that contribute to the process, such as chronic inflammation and cancer, flourish .
What Evidence Supports the Role of the Gut Flora in Longevity?
Several in vivo studies demonstrated that fecal microbiota transplantation from younger mice (Donor) to older (Recipient) enhanced their health and lifespan. This procedure led to the restoration of healthy microbiota in the recipient suggesting its potential application in the field of longevity.
These conclusions are reinforced through the study of progeria mice, a model characterized by an advanced aging process and that has dysfunctional gut flora (Dysbiosis), like that of progeria patients. The researchers demonstrated that fecal microbiota transplantation from wild-type mice enhanced health span and lifespan in progeroid mouse models .
What Bacteria Are found in the Gut?
The gut contains about 1000 species of bacteria and the most dominant species are Bacteroides, Fusobacterium, Eubacterium, Ruminococcus, Peptococcus, Peptostreptococcus, Bifidobacterium, and Clostridium.
What Are the Good Bacteria in the Gut?
The gut’s most known “good bacteria” are Lactobacillus and Bifidobacterium, also known as probiotics. These bacteria help other gut bacteria by providing them with nutrients that are commonly known as prebiotics .
What Are the Health Benefits of Good Bacteria?
Probiotics have been shown to prevent symptoms of allergies, diabetes type 2 (Diabetes Miletus), autoimmune diseases, rheumatoid arthritis, cancer, diarrhea, constipation, irritable bowel syndrome, Crohn’s disease, and obesity.
Because they produce lactic acid, Lactobacillus and Bifidobacterium also suppress pathogens in healthy individuals through induction of immunomodulatory molecules with antagonistic effects .
What food Help Good Bacteria in the Gut?
To help the growth of good bacteria in the gut, you can consume products that contain probiotics, prebiotics, or both:
1- Probiotics Food
Probiotics are found in yogurt, lactobacillus milk, some cheeses such as Gouda, cheddar, cottage cheese, mozzarella, pickles, sauerkraut, kefir, kimchi, tempeh, kombucha, and miso.
2- Prebiotic food
Prebiotics are found in carrots, quinoa, radishes, onions, chicory roots, konjac roots, oats, yams, garlic, barley, wheat bran, berries, apples, asparagus, bananas, leeks, chia seeds, flax seeds, cocoa, coconut, jicama root, and dandelion greens.
How Does Prebiotics Help Good Bacteria in the Gut?
The most common prebiotics are fructooligosaccharides, galactooligosaccharides, and trans-galactooligosaccharides, but other prebiotics plays important roles in health and aging such as insulin enriched-oligofructose, lactulose, and oligofructose.
They are indigestible carbohydrates that are fermented and broken down by probiotics to obtain survival energy, and short-chain fatty acids such as lactic acid, butyric acid, and propionic acid .
How Does Prebiotics Maintain health and protect against Diseases?
1- Prebiotics’ Effects on Gastrointestinal Disorders
The administration of the prebiotic fructo-oligosaccharides to patients diagnosed with irritable bowel syndrome (IBS) or Crohn’s disease (CD) has been shown to significantly improve the symptoms of the two disorders in randomized double-blind, and placebo-controlled clinical trials .
Additionally, symbiotic therapy using Lactobacillus and Bifidobacterium has been shown to reduce the risk of colorectal cancer by inhibiting the proliferation of colorectal cancer cells .
2- Prebiotics’ Effects on the Immune System
Prebiotics induce the expression of cytokines that promote communication between immune cells leading to improved immune response and protection against infections and other diseases such as cancer and neurodegenerative diseases.
Several studies showed that the administration of fructo-oligosaccharides improves antibody response to viral vaccines , upregulates toll-like receptor 2-mediated immune response , and increased phagocytosis, and the levels of NK cells and the anti-inflammatory IL-10 .
3- Prebiotics’ Effects on the Nervous System
The administration of prebiotics such as non-starch polysaccharides was shown to improve the performance of working and recognition memory and cognitive functions , while another prebiotic known as insulin enriched-oligofructose enhances mood and immediate memory . Lactulose was also shown to improve cognitive function and health-related quality of life .
4- Prebiotics’ Effects on the Cardio-vascular System
The prebiotics inulin has been shown to reduce cardiovascular diseases by reducing the levels of HDL-cholesterol, triglycerides, and lipoprotein A , while lactulose reduces the concentrations of free fatty acids that are originated from colon absorption .
5- Prebiotics’ Effects on the Skin
The administration of galactooligosaccharides with and without probiotics was shown to prevent the reduction in water and keratin caused by phenols that denatures proteins and disrupt disulfide bridges in the skin keratin .
The gut flora is essential for health, aging, and longevity and its unbalance (Dysbiosis) can lead to severe health consequences through the lack of availability of quality nutrients that are necessary for preventing diseases such as infections, cardiovascular diseases, nervous system, gastrointestinal, skin, and immune disorders that significantly promote aging, reduces the quality of life, and shorten longevity.
Therefore, the consumption of probiotics and prebiotics can considerably prevent these consequences and ensure a longer and high quality of life.
 Davani-Davari, D., Negahdaripour, M., Karimzadeh, I., Seifan, M., Mohkam, M., Masoumi, S.J., Berenjian, A. and Ghasemi, Y., 2019. Prebiotics: definition, types, sources, mechanisms, and clinical applications. Foods, 8(3), p.92.
 Lindsay, J.O., Whelan, K., Stagg, A.J., Gobin, P., Al-Hassi, H.O., Rayment, N., Kamm, M.A., Knight, S.C. and Forbes, A., 2006. Clinical, microbiological, and immunological effects of fructo-oligosaccharide in patients with Crohn’s disease. Gut, 55(3), pp.348-355.
 Silk, D.B.A., Davis, A., Vulevic, J., Tzortzis, G. and Gibson, G.R., 2009. Clinical trial: the effects of a trans‐galactooligosaccharide prebiotic on faecal microbiota and symptoms in irritable bowel syndrome. Alimentary pharmacology & therapeutics, 29(5), pp.508-518.
 Rafter, J., Bennett, M., Caderni, G., Clune, Y., Hughes, R., Karlsson, P.C., Klinder, A., O’Riordan, M., O’Sullivan, G.C., Pool-Zobel, B. and Rechkemmer, G., 2007. Dietary synbiotics reduce cancer risk factors in polypectomized and colon cancer patients. The American journal of clinical nutrition, 85(2), pp.488-496.
 Langkamp‐henken, B., Bender, B.S., Gardner, E.M., Herrlinger‐garcia, K.A., Kelley, M.J., Murasko, D.M., Schaller, J.P., Stechmiller, J.K., Thomas, D.J. and Wood, S.M., 2004. Nutritional formula enhanced immune function and reduced days of symptoms of upper respiratory tract infection in seniors. Journal of the American Geriatrics Society, 52(1), pp.3-12.
 Lomax, A.R., Cheung, L.V., Noakes, P.S., Miles, E.A. and Calder, P.C., 2015. Inulin-type β2-1 fructans have some effect on the antibody response to seasonal influenza vaccination in healthy middle-aged humans. Frontiers in immunology, 6, p.490.
 Clarke, S.T., Green-Johnson, J.M., Brooks, S.P., Ramdath, D.D., Bercik, P., Avila, C., Inglis, G.D., Green, J., Yanke, L.J., Selinger, L.B. and Kalmokoff, M., 2016. β2-1 Fructan supplementation alters host immune responses in a manner consistent with increased exposure to microbial components: results from a double-blinded, randomised, cross-over study in healthy adults. British journal of nutrition, 115(10), pp.1748-1759.
 Vulevic, J., Drakoularakou, A., Yaqoob, P., Tzortzis, G. and Gibson, G.R., 2008. Modulation of the fecal microflora profile and immune function by a novel trans-galactooligosaccharide mixture (B-GOS) in healthy elderly volunteers. The American journal of clinical nutrition, 88(5), pp.1438-1446.
 Best, T., Howe, P., Bryan, J., Buckley, J. and Scholey, A., 2015. Acute effects of a dietary non-starch polysaccharide supplement on cognitive performance in healthy middle-aged adults. Nutritional neuroscience, 18(2), pp.76-86.
 Smith, A.P., Sutherland, D. and Hewlett, P., 2015. An investigation of the acute effects of oligofructose-enriched inulin on subjective wellbeing, mood and cognitive performance. Nutrients, 7(11), pp.8887-8896.
 Prasad, S., Dhiman, R.K., Duseja, A., Chawla, Y.K., Sharma, A. and Agarwal, R., 2007. Lactulose improves cognitive functions and health‐related quality of life in patients with cirrhosis who have minimal hepatic encephalopathy. Hepatology, 45(3), pp.549-559.
 Russo, F., Chimienti, G., Riezzo, G., Pepe, G., Petrosillo, G., Chiloiro, M. and Marconi, E., 2008. Inulin-enriched pasta affects lipid profile and Lp (a) concentrations in Italian young healthy male volunteers. European journal of nutrition, 47(8), pp.453-459.
 Brighenti, F., Vuksan, V., Rao, A.V., Cunnane, S.C., Ocana, A., Corey, P. and Vezina, C., 1991. Specific types of colonic fermentation may raise low-density-lipoprotein-cholesterol concentrations. The American journal of clinical nutrition, 54(1), pp.141-147.
 Kano, M., Masuoka, N., Kaga, C., Sugimoto, S., Iizuka, R., Manabe, K., Sone, T., Oeda, K., Nonaka, C., Miyazaki, K. and Ishikawa, F., 2013. Consecutive intake of fermented milk containing Bifidobacterium breve strain Yakult and galacto-oligosaccharides benefits skin condition in healthy adult women. Bioscience of microbiota, food and health, 32(1), pp.33-39.