The 21st century has been referred to as the “era of the gut microbiome” as researchers turn considerable attention to the role trillions of gut bacteria, viruses, and fungi may play in health and disease.
The “gut microbiome” refers to the community of microorganisms living in your intestines. While some microorganisms are harmful to our health (bad or pathogenic microbes), many promote and are even essential for a healthy body (good or beneficial microbes).
An imbalance between the two types of microbes, with a lowering of good ones, or an increase in bad ones, refers to dysbiosis and has been associated with various diseases including immunological diseases, mental health disorders, autoimmune diseases, gastrointestinal (GI) disorders, cardiovascular disease, and cancer.
There is increasing evidence that the gut microbiome lies at the core of many age-associated changes and plays a role in longevity. Studies in mice and macaques have reported gut microbiota-induced inflammageing (inflammation and ageing) and consequently, increased insulin resistance is reversed by restoring A. muciniphila levels and supplementing with butyrate-producing bacteria.
ageing involves a reduction in microbial diversity in the gut, a gradual weakening of the immune system, and cognitive decline. Studies have found a relationship between low bacterial diversity and Crohn’s disease, irritable bowel syndrome (IBS) and colorectal cancer, among other conditions.
The low-level systemic inflammation with ageing (“inflammageing”) increases the risk of chronic diseases and disabilities, including cardiovascular disease, cognitive decline, metabolic disease, frailty, and mortality. When researchers transplanted gut microbes from older mice into younger mice in a 2017 study, the young animals developed inflammation that is indicative of ageing.
Furthermore, ageing is associated with cognitive decline. Gut microbes can communicate with the brain and modulate cognitive functions, via the “gut-brain axis” through neural, immune, and hormonal mediators. Lifestyle and environmental effects on the microbiota can delay (healthy ageing) or accelerate (unhealthy ageing) deterioration in the host and foreshorten life expectancy.
Progressive decline in physiological functions of the alimentary tract associated with ageing changes the internal microenvironment and indirectly affects nutrient intake by older individuals. With age, there is a decrease in digestive enzymes, mucosal immunity, and colonic motility, and an increase in infections, antibiotic use, polypharmacy, and comorbidities.
Three groups of gut microbes are altered among older individuals which are as follows:
- Group 1 taxa (Faecalibacterium, Roseburia, Coprococcus, Eubacterium rectale, Bifidobacterium, and Prevotella) decrease with age and are associated with healthy ageing.
- Group 2 (Eggerthella, Bilophila, Desulphoviobrio, Fusobacterium, Anaerotruncus, Streptococcus, and Escherichia) comprise microbes that increase with age and are associated with unhealthy ageing.
- Group 3 (Akkermansia, Christensenellaceae, Odoribacter, Butyricimonas, Butyribivrio, Barnesiella, Oscillospira) increased with age but are depleted in unhealthy ageing.
Group 2 microbes release metabolites such as trimethylamine (TMA), para-cresol, lithocholic acid (LCA), deoxycholic acid (DCA), lipopolysaccharide (LPS), reactive oxygen species (ROS), and deoxyribonucleic acid (DNA) damageing toxins which increase the risk of cardiovascular disorders, cognitive disorders, inflammation, oxidative stress, osteoporosis, chronic kidney disease, and colorectal cancer.
On the other hand, Group 1 and 3 microorganisms release butyrate, acetate, and short-chain fatty acids (SCFAs), which prevent cognitive disorders, diabetes, obesity, inflammation, barrier function impairments and gut leakiness.
A study published in 2021, in Nature Metabolism, reported that older adults whose mix of gut microbes changed the most over time lived longer than those with fewer changes in their gut microbiota. A gut microbiota that continually transforms as you get older is a sign of healthy ageing.
In a sub-study of the REIMAGINE (Revealing the Entire Intestinal Microbiota and its Associations with the Genetic, Immunologic, and Neuroendocrine Ecosystem) study, published in Cell Reports, researchers from Cedars-Sinai’s Medically Associated Science and Technology (MAST) Program, ageing produces significant changes in the microbiome of the human small intestine.
With age, Enterobacteriaceae, Lactobacillaceae, Enterococcaceae, and genus Bacteroides increase in abundance in the gut and are associated with disease, like weeks in a garden. As people age, bacteria in the gut change from microbes that prefer oxygen to those that can survive with less oxygen.
Research in rats has shown that an unhealthy gut can affect the barrier function of intestines, and impaired barrier functions have been associated with ageing and age-related conditions such as metabolic diseases, liver disease, inflammatory bowel diseases, and brain and lung problems.
Elder individuals are more likely to suffer from comorbidities and consume medications. Researchers have found that the more medications people consumed, the more Klebsiella bacteria they had in their intestines—Klebsiella can cause hospital-associated infections including surgical site infections, meningitis, and pneumonia, and these bacteria are often resistant to antibiotics.
People with medical conditions have shown tendencies to have more Clostridium bacteria in their intestines, which can cause dangerous C. difficile infections.
An unhealthy gut can give rise to gas, bloating, constipation, diarrhea, abdominal pain, nausea, heartburn, acid reflux, unintentional changes in body weight, sleep disturbances, constant fatigue, skin irritation, food intolerance, mood alterations, and migraines.
- Eat a healthy diet: Consume fibre-rich foods such as vegetables (especially dark, leafy greens, broccoli, asparagus), legumes (such as chickpeas and black beans), whole grains (such as oats and quinoa), nuts (such as almonds and pistachios) and fruits (such as apples, raspberries, bananas, and peaches).
- Consider prebiotics and probiotics: Research indicates that consuming prebiotics and probiotics can boost gut health. Prebiotics provide “food” that promotes the growth of good bacteria, while probiotics are live good bacteria. Foods rich in prebiotics include bananas, asparagus, garlic, chicory, onions, whole grains, and Jerusalem artichokes. Sources of probiotics include fermented foods such as kefir, yogurt, kombucha, tempeh, and sauerkraut.
- Exercise regularly: Exercise promotes gut microbiome diversity by affecting the rate at which material moves through the intestines or reducing gut inflammation, or altering appetite and food processing. Physical activity also promotes heart health and weight maintenance.
- Lower your stress levels: Studies have reported that psychological stressors can disrupt the microorganisms in the intestines. Ways to lower stress include walking, deep breathing, meditating, yoga, and spending time with pets.
- Get enough sleep: Inadequate sleep may adversely impact gut health and increase inflammation. Try to get at least seven to eight hours of sleep daily.
- Eat slowly: Chewing food slowly and thoroughly may reduce the risk of developing diabetes and obesity, decrease digestive discomfort and maintain a healthy gut.
- Stay hydrated: Drinking plenty of water can prevent constipation and has been associated with increased microbial diversity in the gut. A study published in 2022 reported that individuals who drank more water had a lower abundance of gastrointestinal infection-causing microbes in the gut.
- Avoid processed, sugary, refined and fatty foods: A diet high in processed foods, sugars and artificial sweeteners can reduce the number of beneficial microbes and decrease diversity in your gut. Research indicates that this may result in inflammation throughout the body, including the gut.
- Quit smoking and limit alcohol intake: Cigarettes contain lots of chemicals and toxins that are harmful and increase physical stress on the gut microbes. A review published in 2018 reported that smoking also promotes the growth of bad bacteria and lowers the abundance of good bacteria.
- Consume antibiotics only when required: Antibiotics do not differentiate between good and bad bacteria and thus, must be consumed, only as indicated by healthcare professionals. Antibiotics can be damageing to the gut microbiome and immunity.
The Bottom Line
A shift in gut bacteria, tilting towards an increase in bad bacteria, may help drive the ageing process and preserving gut health could help people lead longer and healthier lives.