The Gut as a Modulator of Aging
In our last blog, we focused on the aging brain – this blog we will explore the gut microbiome as a modulator of healthy aging.
Some people age well and there are a number of factors which influence the aging process – genetics, environment and lifestyle – the last of which offers us the most opportunity to make change.
Our gut microbiota includes the bacterial, fungal and viral organisms that co-exist in our digestive system. As we have discussed in previous blogs (read here, here and here) these organisms are responsible for creating signals which the cells in our body respond to. The signals created can influence the onset of disease, including age-related disease. As we age, our microbiota populations change as well.
Science exploring gut microbiota populations is relatively new. What we do know, is that there is no single universally healthy configuration of microorganisms and that the populations that co-exist with us are in a dynamic state of change according to what we eat and do on any given day.
What we do know:
- There are approximately 2,000 resident bacterial species in our gut/digestive system;
- Similar to fingerprints, no two microbiota populations are exactly alike but there is a common group of microbe types found in everyone, comprising about 30% of the total;
- Throughout the human life span, the gut microbiota population follows some predictable patterns, with rapid change from infancy to age three, stability up until middle-age, and then accelerated change starting in late adulthood;
- Our gut microbiota use both organic and inorganic molecules as substrates for growth – for example, they can break down long-chain polysaccharides and resistant starches that we could not digest by ourselves;
- Changes in the microbial population and its production of signals can alter our susceptibility to obesity, metabolic syndrome, irritable bowel syndrome, and cardiovascular disease;
- Several compounds produced by our microbiota are anti-inflammatory;
- Gut microbiota populations also influence our mood, behaviour and cognition.
What happens when we age?
Age is a progressive loss of homeostasis (balance) and function. Ageing can be seen at a molecular and cellular level, but also a microbial level.
As we age, the presence of protective bacterial species can be reduced, especially when we are exposed to factors which negatively affect the ratio of the microbial populations in our gut. For example, many pharmaceuticals can affect our microbiota, so too can reduced exercise. We may also become more vulnerable to pathogens and disease itself can alter our microbiota – for example diabetes and heart disease (read more here).
What looks different in the microbiota of a person who is aging well?
There are striking similarities in the microbiota profiles of healthy, very aged people from different countries, which has been identified in multiple scientific studies (read more in this review).
As we age, all of us experience changes in microbiota – but those who age well, have certain species present at greater numbers and those who experience unhealthy ageing have a growth in different populations.
The diagram below is from a Nature review (Ghosh et al.) and shows the dynamic changing of the microbiota in healthy and unhealthy aging populations.
Most of us will experience times where we eat poorly, are highly stressed or need to take pharmaceuticals which might negatively affect our microbial balance. The question then becomes:
How do we “rewild” our microbiota?
Interventions to rebuild microbial balance include greater consumption of probiotics and prebiotics – via diets or supplements. Many studies investigating the use of prebiotic and probiotic studies report beneficial effects on host physiology which in include reduction in insulin resistance, zonulin gene expression (a marker of barrier function), inflammation, and levels of brain-derived neurotrophic factor (BDNF), which is upregulated during neuro-inflammation. In addition, improved cognitive function and cardiometabolic health, previously associated with butyrate (produced by “good” bacteria), have been reported.
It is worth noting that responses to dietary changes and an increase in probiotics and prebiotics can be highly personalised – depending on our baseline microbiota composition. It will take longer to restore the “good” species if they are at a lower level in the first place.
It is also important to avoid foods which are highly processed and high in salt, sugar, or fats. We need to replace those with high fibre, nutritious foods, like fruits, vegetables, seeds, beans, and nuts. Daily exercise is also important in the “rewilding” process.
I liken the relationship we have with our gut microbiota to a finely tuned orchestra of 10,000 pieces. Practicing good habits and paying attention to lifestyle choices will create a synchronised masterpiece, ourselves at our very best – and as the violinists age, greater care and attention is needed. The good news is that changes can be made, our guts can be rewilded and in time, who knows which tunes may come out!
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