Your gut microbiome is made up of trillions of bacteria, fungi and other microorganisms that play a vital role in digestion, immunity and overall health. While it is influenced by factors such as diet, stress, antibiotics and lifestyle, more and more attention is being paid to how our wider environment shapes the microbiome too, including water quality. One emerging area of concern in the UK is exposure to poor-quality sewage water and how it may affect the balance of microorganisms in the gut.

In this article, Vivere’s Head of Nutrition, Yusra Serdaroglu Aydin, explores the link between sewage water quality and the microbiome. Yusra is a registered dietitian with a background in nutrition, food engineering and culinary arts. Her approach is grounded in science and shaped by a strong understanding of personalised nutrition and the human microbiome.

Here are the five biggest takeaways from this article about the quality of sewage water and your microbiome:

• Exposure to untreated or poorly treated sewage water may introduce harmful bacteria, viruses and pollutants into the body, potentially disrupting the gut microbiome.

• Antibiotic-resistant genes and chemicals found in wastewater may contribute to antimicrobial resistance, which affects both the environment and human health.

• Recreational and occupational contact with contaminated water sources carries a higher risk of microbiome imbalance and related health effects.

• Maintaining a strong, diverse microbiome may reduce vulnerability to the effects of environmental pollutants and pathogens.

• While the UK has strong water quality regulations, sewage spills and runoff still occur, highlighting the importance of public awareness and individual health support.

Sewage water refers to water that has been used in homes, businesses or industrial settings and is often mixed with human waste, chemicals and various pollutants. Ideally, this water is treated before being released back into the environment. However, overflows, leaks and poor management mean that untreated or partially treated sewage can find its way into rivers, lakes and coastal waters.

In the UK, incidents of raw sewage being discharged into natural waterways have become an area getting more and more attention [1] [2]. This raises serious environmental and public health questions, particularly for people who swim, surf or work in or near these waters.

One concern is the transfer of microbial and chemical contaminants from the water to the human body. Whether through skin contact, accidental ingestion or inhalation of water droplets, these exposures may influence the microbiome in subtle or significant ways.

The gut microbiome plays a crucial role in many aspects of health, including:

• Breaking down complex carbohydrates and producing essential vitamins

• Training the immune system and regulating inflammation [3]

• Supporting the gut barrier to prevent harmful substances from entering the bloodstream

• Influencing mental health through the gut-brain axis [4]

When the microbiome is in balance, it helps the body function smoothly [5]. When it is disturbed, known as dysbiosis, it has been linked to a range of conditions such as irritable bowel syndrome, inflammatory bowel disease, allergies, metabolic disorders and even depression [6] [7] [8] [9] [10].

Because of this, any environmental factor that could lead to dysbiosis deserves attention, including the quality of water we are exposed to.

There are several ways in which exposure to contaminated sewage water could affect gut health:

Sewage often contains pathogens such as E. coli, Salmonella, Norovirus and Giardia, which can cause gastrointestinal illness. Even short-term exposure to these pathogens may lead to changes in gut microbial composition, either directly or through the immune response that follows [11] [12] [13].

Wastewater is a recognised reservoir for antibiotic-resistant bacteria and resistance genes. These may originate from human waste, hospitals or agriculture. If these microbes or genetic materials reach the human body, they could influence the balance of the gut microbiome and even make some bacterial infections harder to treat [14] [15] [16] [17] [18] [19].

Wastewater can contain residues of pharmaceuticals, including antibiotics, antidepressants and hormonal treatments. It may also contain heavy metals and industrial chemicals. These substances can impact microbial populations by killing beneficial strains or encouraging harmful ones to thrive [20] [21] [22].

Compounds such as bisphenol A (BPA), found in some plastics and detergents, can interfere with hormonal balance and potentially affect microbial diversity. Long-term exposure to such disruptors in water may have subtle but lasting effects on gut and metabolic health [23] [24] [25] [26] [27] [28] [29].

Certain groups may be more likely to come into contact with poor-quality sewage water, including:

• Recreational water users: Swimmers, surfers and paddleboarders in polluted rivers or coastal waters [30] [31]

• Occupational groups: Farmers, sewage treatment workers, or those in water-related industries, although this is disputed [32]

• People living in flood-prone or rural areas where sewage management is less consistent [33]

In these cases, there may be a higher risk of microbial disruption, infection, or both. It’s also important to note that people with pre-existing gut conditions, weakened immune systems, or those taking regular antibiotics may be more vulnerable to changes in microbiome health from environmental exposures.

Although it's not always possible to avoid environmental exposure completely, there are steps individuals can take to support and protect their microbiome:

Fibre feeds beneficial gut bacteria. Eating a wide range of plant-based foods, including vegetables, fruits, legumes and whole grains, supports microbial diversity [34] [35] [36].

Live yoghurt, kefir, sauerkraut and kimchi can help introduce beneficial bacteria to the gut, which may help rebalance the microbiome if it has been disrupted [37] [38] [39].

Ensure your drinking water is filtered and comes from a reliable source. If using private water supplies, test them regularly for contaminants [40] [41].

After swimming or working in natural waters, shower thoroughly and avoid swallowing water. Cuts or grazes should be cleaned and covered.

If your microbiome has been disturbed due to illness or exposure, science-backed probiotics and prebiotics may help restore balance. Consult a qualified practitioner before starting any new supplement [35] [42].

The UK has strict standards for drinking water, and organisations like the Environment Agency and Ofwat monitor sewage treatment [43] [44] [45]. However, recent news headlines and environmental campaigns have raised concerns about the frequency and severity of untreated sewage discharges, especially following heavy rain.

The long-term health effects of such exposures are still being studied, but the presence of pathogens, antibiotic-resistant bacteria and chemical residues in the water we interact with cannot be ignored. Raising awareness and empowering individuals with knowledge about microbiome health is a practical step in reducing potential risk.

“The quality of the water we interact with, including sewage-contaminated sources, can influence the delicate balance of the gut microbiome. While exposure may not always result in obvious symptoms, the subtle shifts in microbial diversity and function could have wider implications for our health over time. Supporting your microbiome through good nutrition, smart hygiene habits and staying informed about environmental issues is an investment in long-term wellbeing”.

Vivere helps you take control of your health with personalised insights from state-of-the-art gut microbiome testing, nutritional guidance, science-backed supplements and expert support. Sign up today and start living better, for longer.

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[2] Raw sewage spills into England rivers and seas doubles in 2023 - BBC News

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[4] Beyond the brain: The gut microbiome and Alzheimer’s disease | National Institute on Aging

[5] What defines a healthy gut microbiome? - PMC

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[16] Detection of Antibiotic Resistance Genes in Source and Drinking Water Samples from a First Nations Community in Canada - PMC

[17] Private and well drinking water are reservoirs for antimicrobial resistant bacteria - Nature

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[22] Human Health Risks due to Exposure to Water Pollution: A Review - MDPI

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[25] Occurrence and seasonal disparity of emerging endocrine disrupting chemicals in a drinking water supply system and associated health risk | Scientific Reports

[26] Endocrine disrupting chemicals in the environment: Environmental sources, biological effects, remediation techniques, and perspective - ScienceDirect

[27] Water contamination by endocrine disruptors: Impacts, microbiological aspects and trends for environmental protection - ScienceDirect

[28] Environmental Endocrine Disruptors and Endometriosis - PMC

[29] Endocrine disruptor contaminants in water and their adverse effects in humans - ScienceDirect

[30] Alterations in the human skin microbiome after ocean water exposure - PMC

[31] Take part in ‘Poo-Sticks’ river swimming study! - European Centre for Environment and Human Health | ECEHH

[32] The resistome and microbiome of wastewater treatment plant workers – The AWARE study - ScienceDirect

[33] Microbial risks associated with exposure to pathogens in contaminated urban flood water - ScienceDirect

[34] The Science: How Your Diet Affects Your Gut Microbiome - Vivere

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[36] Nutrition Plan - Vivere

[37] Fermented Foods - Vivere

[38] Fermented-food diet increases microbiome diversity, decreases inflammatory proteins, study finds - Stanford

[39] Unpacking Food Fermentation: Clinically Relevant Tools for Fermented Food Identification and Consumption - PMC

[40] Making waves: From tap to gut- exploring the impact of drinking water on gut microbiota - ScienceDirect

[41] Drinking Water Source and Intake Are Associated with Distinct Gut Microbiota Signatures in US and UK Populations - PubMed

[42] Probiotics & Prebiotics - Vivere

[43] Drinking Water Standards and Regulations - DWI

[44] Environment Agency Water Hub

[45] Pollution and water quality - Ofwat