Why Your Gut Microbiome Changes as You Get Older – And What You Can Do About It

Your gut microbiome is constantly changing. From childhood through adulthood and into old age, the trillions of microorganisms living in your digestive tract respond to your diet, lifestyle, environment, medication and overall health. As we get older, maintaining a healthy and diverse microbiome becomes increasingly important.

Ageing is inevitable, but a decline in gut health does not have to be accepted as an unavoidable part of getting older.

Modern research is revealing just how closely the gut microbiome is connected to immune function, inflammation, digestion, nutrient absorption, metabolic health and even cognitive wellbeing. Understanding these changes gives us an opportunity to take better care of our digestive system and support our health as the years go by.

Your gut microbiome is a living ecosystem

The gut microbiome is made up of trillions of microorganisms, including bacteria, fungi, viruses and other microbes. Together, they form a complex ecosystem that plays an important role in maintaining health.

These microorganisms help us:

• Break down components of food that our own digestive enzymes cannot fully process.

• Produce beneficial substances, including short-chain fatty acids.

• Support the intestinal barrier.

• Communicate with and help regulate the immune system.

• Contribute to the production and availability of certain vitamins and nutrients.

• Maintain a healthy balance between different microbial populations.

A healthy microbiome is not simply about having as many bacteria as possible. It is about having a balanced and diverse community of microorganisms that can perform the many functions required for good health.

This ecosystem is not fixed. It changes throughout our lives, responding to what we eat, where we live, the medicines we take and the way we look after ourselves.

What happens to the gut microbiome as we age?

Research suggests that the composition and activity of the gut microbiome can change as people grow older. However, there is no single microbiome profile that defines healthy ageing. Differences in diet, geography, lifestyle, medication and underlying health all influence the results.

Some studies have found that older adults may experience:

Reduced microbial diversity

A diverse microbiome is generally considered a positive feature of gut health. In some older populations, researchers have observed reduced microbial diversity, although this is not universal.

Changes in beneficial bacteria

Certain bacteria associated with fibre fermentation and the production of short-chain fatty acids may become less abundant in some older adults.

Changes in inflammatory activity

The microbiome interacts with the immune system and the intestinal barrier. Changes in microbial balance may contribute to altered immune signalling and inflammation, although ageing itself is influenced by many other factors.

Changes in digestion and bowel habits

Constipation, reduced appetite, changes in food choices and alterations in digestive function become more common with age. These factors can also influence the microbiome.

The important point is that ageing and gut health influence one another. Changes in the microbiome may affect aspects of health, while changes in health and lifestyle can also reshape the microbiome.

The connection between gut health and inflammation

One of the most important areas of ageing research is the relationship between chronic, low-grade inflammation and the ageing process.

Scientists sometimes use the term inflammaging to describe the gradual increase in inflammatory activity that can occur with age.

The gut is an important part of this conversation.

The intestinal lining acts as a selective barrier. It allows nutrients and other useful substances to pass into the body while helping to keep unwanted material within the digestive tract.

The microbiome plays a role in maintaining this environment. Certain beneficial bacteria produce short-chain fatty acids, particularly butyrate, which is an important energy source for cells lining the colon.

When the balance of the microbiome changes, the production of these beneficial compounds may also change.

This does not mean that every digestive problem causes systemic inflammation, or that a probiotic can reverse ageing. It does mean that supporting the gut environment is a sensible part of a broader approach to healthy ageing.

Why fibre becomes increasingly important

One of the simplest ways to support microbial diversity is to feed the beneficial microorganisms already living in the gut.

Many gut bacteria use dietary fibre as a food source. During fermentation, they produce short-chain fatty acids, including acetate, propionate and butyrate.

These compounds have important functions in the digestive tract and are being studied for their wider metabolic and immune effects.

Unfortunately, many modern diets are low in fibre. Highly processed foods, refined carbohydrates and limited consumption of vegetables can leave the microbiome without the range of substrates it needs.

As we get older, it becomes particularly important to pay attention to the quality of our food.

Consider including:

• A variety of vegetables, rather than relying on just one or two.

• Whole fruits, where appropriate, rather than fruit juices.

• Nuts and seeds.

• Legumes, if tolerated.

• Traditional fermented foods such as live-culture yoghurt, kefir and sauerkraut.

• Whole-food sources of resistant starch, such as cooled potatoes or rice.

Increase fibre gradually, particularly if you are not accustomed to eating much of it. Some people with IBS or other digestive conditions may need to choose their fibre sources carefully.

The goal is not simply to eat more fibre. It is to introduce a variety of foods that provide different types of nourishment for the microbiome.

Protein, healthy fats and the importance of food quality

As we age, maintaining muscle mass, strength and metabolic health becomes increasingly important.

Adequate protein intake, combined with regular resistance exercise, helps support muscle maintenance. Protein-rich foods also provide essential amino acids and other nutrients required by the body.

Quality matters.

Choose minimally processed protein sources that suit your dietary needs, such as eggs, fish, poultry, meat, dairy products or suitable plant sources. Where possible, prioritise good-quality, responsibly produced foods.

Healthy fats also have a role in a balanced diet. Olive oil, oily fish, avocado, nuts and seeds provide valuable fats and other nutrients.

There is no need to build your diet around one fashionable food group or eliminate entire categories without a clear reason. A varied, nutrient-dense diet is generally a more sustainable foundation for long-term health.

The stomach is still the starting point

When we talk about gut health, it is easy to focus entirely on the large intestine and the bacteria living there.

But digestion starts much earlier.

The stomach produces acid that helps break down food, supports protein digestion and contributes to the body's natural defences against ingested microorganisms.

The pancreas and small intestine also play essential roles through digestive enzymes and bile.

If digestion is not functioning properly, the consequences can extend beyond the stomach. Poorly digested food, digestive discomfort and changes in bowel habits can all affect what reaches the microbiome further along the digestive tract.

Persistent reflux, bloating, pain, unexplained weight loss or changes in bowel habits should not simply be dismissed as normal ageing. They deserve proper medical assessment.

It is also important not to assume that everyone with digestive symptoms has insufficient stomach acid. Acid-related problems have different causes and need to be assessed appropriately.

Medication and the ageing microbiome

Medication is another important consideration.

Many people take more medicines as they get older. Some medications can influence the gut microbiome, digestive function or bowel habits.

Antibiotics are a well-known example. They can be essential and sometimes life-saving, but they may also affect beneficial bacteria alongside the microorganisms they are intended to target.

Other medicines, including some acid-suppressing drugs and certain treatments for metabolic conditions, have also been associated with changes in the gut microbiome.

This is not a reason to stop prescribed medication. It is a reason to understand that medication, nutrition and digestive health are connected.

If you are concerned about the effects of a medicine on your digestion, speak to your healthcare practitioner or pharmacist before making any changes.

The role of probiotics as we get older

Probiotics are live microorganisms that, when administered in adequate amounts, can provide a health benefit to the host.

They are not all interchangeable. Different strains have different properties, and the research supporting one strain cannot automatically be applied to another.

This is particularly important when choosing a probiotic.

Spore-forming probiotics are an interesting category because certain Bacillus species produce protective structures called spores. These spores can withstand environmental conditions that would damage many ordinary bacterial cells.

Once they reach suitable conditions, they can germinate and become metabolically active.

Research into spore-forming probiotics is continuing, with studies exploring their potential roles in digestive health and microbial balance. As with all probiotics, benefits depend on the particular strains, formulation, dose and intended use.

For older adults, the priority should be choosing a well-formulated product with clearly identified strains and responsible quality controls, rather than simply selecting the product with the largest number on the label.

Supporting your microbiome with FLORISH

At Sebastian Siebert Supplements, our approach to gut health recognises that the microbiome is an important part of the body's wider health ecosystem.

FLORISH Spore Probiotic with Fulvic Acid combines five spore-forming probiotic strains with fulvic acid.

The recommended adult daily serving of two capsules provides more than four billion spores, together with 300 mg of fulvic acid.

The formulation is designed to provide a combination of spore-based probiotic strains and fulvic acid in one product.

It is important to remember that probiotics are not a replacement for a healthy diet, medical care or the foundations of good digestive health. Individual responses can vary, and people who are seriously ill, immunocompromised or have significant underlying health conditions should seek professional advice before using probiotic supplements.

Why fulvic acid is part of the conversation

Fulvic acid is a naturally occurring component of humic substances. It has attracted scientific interest because of its chemical properties and its interactions with minerals and other compounds.

Laboratory research has explored a range of possible biological activities, but human clinical evidence remains limited in several areas. It is therefore important not to assume that findings from laboratory studies automatically translate into proven health benefits in people.

FLORISH includes fulvic acid as part of its formulation, while FULFIXER provides a separate capsule-based fulvic acid supplement for those who wish to consider it as part of their wider supplement routine.

As with any supplement, check the ingredients, follow the product directions and consult a qualified healthcare professional if you take prescription medicines or have an existing medical condition.

The lifestyle habits that support a healthier gut

Supplements can be useful additions, but they cannot compensate for a lifestyle that consistently works against digestive health.

There are several practical habits worth prioritising.

1. Eat a wider variety of whole foods

The microbiome benefits from dietary variety. Try to include different vegetables, fruits, nuts, seeds and other fibre-containing foods throughout the week.

2. Move your body regularly

Physical activity supports bowel function, metabolic health and general wellbeing. Walking, cycling, swimming and resistance training can all form part of a healthy routine.

3. Prioritise sleep

Sleep and the gut microbiome appear to influence one another. Regular sleep patterns and sufficient rest are important parts of overall health.

4. Spend time outdoors

Time in natural environments provides opportunities for movement, sunlight exposure and contact with a wider range of environmental microorganisms. Research into the relationship between biodiversity, environmental exposure and human health is developing.

5. Manage ongoing stress

The gut and brain communicate through complex pathways. Chronic stress can influence digestive symptoms and gut function. Relaxation, social connection, time outdoors and appropriate exercise can all help support wellbeing.

6. Be thoughtful about antibiotics

Antibiotics should be used when clinically appropriate, not unnecessarily. Never avoid a prescribed antibiotic when it is needed, but discuss concerns and recovery support with your healthcare practitioner.

7. Review your supplement routine

More supplements do not automatically mean better health. Consider what you actually need, whether you are taking appropriate doses and whether products could interact with medicines or one another.

Healthy ageing starts with the basics

There is no single supplement, diet or routine that can stop the ageing process.

However, there is growing recognition that the gut microbiome is an important part of healthy ageing. Its relationship with digestion, the immune system, metabolism and inflammation makes it worth looking after throughout life.

The most effective starting point is often surprisingly simple: eat real food, include a variety of fibre sources, maintain adequate protein intake, move regularly, sleep well and take care of your digestive health.

A well-chosen probiotic such as FLORISH may be considered as part of that broader approach, alongside a balanced diet and healthy lifestyle.

We should not wait until digestive problems become persistent before paying attention to our gut. The habits we build today can help support our health for years to come.

Take care of your gut, and you are taking care of one of the most important foundations of your overall wellbeing.

Important note

This article is intended for general educational purposes and is not a substitute for individual medical advice, diagnosis or treatment. People with persistent digestive symptoms, significant medical conditions or concerns about medication and supplements should consult an appropriately qualified healthcare professional.

References and further reading

1. O'Toole PW, Jeffery IB. Gut microbiota and aging. Science. 2015;350(6265):1214–1215. doi:10.1126/science.aac8469.

2. Claesson MJ, et al. Gut microbiota composition correlates with diet and health in the elderly. Nature. 2012;488:178–184. doi:10.1038/nature11319.

3. Vaiserman AM, Koliada AK, Marotta F. Gut microbiota: A player in aging and a target for anti-aging intervention. Ageing Research Reviews. 2017;35:36–45.

4. Rooks MG, Garrett WS. Gut microbiota, metabolites and host immunity. Nature Reviews Immunology. 2016;16:341–352.

5. Koh A, De Vadder F, Kovatcheva-Datchary P, Bäckhed F. From dietary fibre to host physiology: Short-chain fatty acids as key bacterial metabolites. Cell. 2016;165(6):1332–1345.

6. Cryan JF, et al. The microbiota-gut-brain axis. Physiological Reviews. 2019;99(4):1877–2013.

7. National Center for Complementary and Integrative Health (NCCIH). Probiotics: What You Need To Know.