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Aging is a gut reaction

Well-balanced intestinal microorganisms are the key to longevity

F or the past few decades doctors and researchers have emphasized the importance of naturally fermented foods, such as kimchi and yogurt. These foods have a significant impact on the microorganisms living in our intestines, and research suggests that the state of this flora has a significant effect on overall health. However, the exact mechanisms and association between the community of microorganisms living in the intestines, also called gut microbiota, and aging is still relatively unknown.
Each individual has a unique and vast microbial ecosystem in their body; the gastrointestinal tract itself harbors up to 100 trillion bacteria. These microorganisms play a role in balancing the immune system and their imbalance is associated with many health issuses including cancer, allergies, chronic gastrointestinal diseases, and metabolic disorders such as diabetes and obesity. Such imbalances can be triggered by the use of antibiotics, excessive hygiene, diet and even aging. In fact, after the age of 70, the decline of bodily functions can lead to a decrease in the count and diversity of beneficial species in the gut microbiota, ultimately weakening the body’s defence against disease.

There are approximately 1000 types of bacteria in a healthy adult’s gut ecosystem, the majority of which is composed of phyla Firmicutes and Bacteroidetes. As the most dominant phyla in the gut, the ratio between these two groups of bacteria is informative in determining gut health, according to an article published in Age, an international research journal specializing in the biology of aging. A classification-based analysis by researchers at Kyung-Hee University showed that aging is associated with changes in composition of beneficial bacteria in the gut. Specifically, an increase in Firmicutes, and a reduction of Bacteroidetes was observed The Firmicutes to Bacteroidetes ratio has also previously been shown to be increased with obesity, which can lead to health concerns.

“Inflamm-aging,” as coined by researchers, is chronic, low-grade inflammation that occurs during aging and that involves inflammatory network activation and the release of proteins promoting inflammation. Researchers believe that inflamm-aging may be associated with age-related changes in gut microbiota composition.
Proteins such as lipopolysaccharides (LPS) are a major component of the outer membrane of some bacteria, acting as a protective barrier, and their production is boosted by age. Unfortunately, they can also trigger the body’s immune system and cause inflammation. Levels of LPS production in the gut microbiota, and expression levels of inflamm-aging markers such as p16. P16 is a cell-cycle regulator, and is an inductor of senescence, the process of deterioration with age. With age, p16 expression increases in order to suppress stem cell proliferation and tissue regeneration. Results from the study showed that LPS lead to increased p16 expression in the colon of aged mice, along with increased activation of inflammatory markers. These results indicate that aging can accelerate inflamm-aging by inducing p16 expression in mice by increasing LPS levels in gut microbiota.

Such age-related gut microbiota modifications and imbalances are associated with inflamm-aging and immunosenescence, a decline in the functionality of the immune system. By preventing imbalances in the gut, it may be possible to prevent inflamm-aging and senescence, decrease symptoms and diseases related to aging. A study by University of California, Los Angeles researchers published in Cell Reports in 2015 showed bacterial changes in the intestine and leakage of intestinal tracts before death in fruit flies. Antibiotics, which reduce bacterial levels in the intestine, prevented the age-related increase in bacterial levels and improved intestinal function during aging, significantly prolonging the lifespan of 40 day-old flies. The average lifespan of the fly type Drosophila melanogaster is approximately 50-60 days. These suggests that similar results may be possible in humans through minimizing harmful bacteria which multiplies with age, while preventing the loss of healthy bacteria, and improving intestinal functions.
Although the association between gut microbiota and aging is still relatively undefined, studies suggest that certain diets such as those containing whole grain and high fiber content can contribute to maintaining a balanced intestinal flora, help preventing age-related diseases and promote longevity. For individuals over 70 years of age, focusing on restoring balance and preventing disease-causing inflammation may help thwart age-related issues and symptoms. Although researchers continue the search for novel treatments for age-related issues, keeping a healthy gut environment through diet at an individual level by eating pro and prebiotic foods and avoiding foods causing inflammation can also aid in prevention of disease. This could be particularly relevant for some age groups, such as our baby boomers as they ease their way into retirement.