Microplastics have been found to interact with the gut microbiome – here’s what health effects they might have

Through the air we breathe and the food we eat, we can’t help but inhale and ingest tiny bits of plastic every day.

These microplastics, as they’re known, have been found in many parts of the human body – including the lungs, placenta and blood vessels. Research has even linked the presence of microplastics to cardiovascular disease and poor health in humans.

Evidence also shows that microplastics can interact with the gut microbiome – and their presence could contribute to inflammatory bowel disease (IBD).

Microplastics are microscopic fragments of plastic that are smaller than 5mm long (and as small as 0.001mm) – and they’re everywhere. Some microplastics are created intentionally, glitter and confetti being obvious everyday examples. Others are created when larger plastic items are worn down (such as when plastic pollution in the ocean or environment is eroded).

Nevertheless, whether they’re shed from plastic chopping boards, in our drinking water or inadvertently added to processed food products, we could consequently be consuming up to 5g every week.

However, we don’t currently know the exact quantities of microplastics a single person may have in their body at any one time. Getting precise measurements of microplastics in human samples can be difficult. This is because other small fragments (such as some fats) in bodily samples can look like plastic to scientific instruments.

While scientists are sure that we’re eating microplastics, there’s also still some debate around their ability to enter our bloodstream and build up in body tissues.

Nevertheless, the fact that we consume them at all is enough for microplastics to meet our metabolic organ – the gut microbiome. Current research suggests that these encounters can reduce the good bacteria in our gut to contribute to IBD.

Microplastics and gut health

Our gut is home to trillions of microorganisms – known as the gut microbiome. Some 500 to 1,000 different microbial species work together in harmony to keep our gut healthy.

A major function of the microbiome is to take what we eat, chew it up and spit out breakdown products. These products are called metabolites and are critical for gut health.

A well-studied group of metabolites are short-chain fatty acids. Short-chain fatty acids garnered attention around a decade ago, when they were found to be produced by good gut bacteria and could help prevent IBD.

IBD is an increasingly common disease, affecting around one in every 123 people in the UK. It can cause severe abdominal pain, diarrhoea, weight loss and fatigue.

One of the gut’s key short-chain fatty acids is butyrate, which is produced by bacteria when they break down dietary fibre. Butyrate has been found to be crucial for gut health, helping to boost immunity and preserve the gut barrier. However, if the gut microbiome is disturbed, microbes that produce butyrate are reduced and gut health is jeopardised.

The gut microbiome faces many challenges that now includes plastic pollutants.

Evidence for how microplastics influence the microbiome and gut health in humans is presently scarce, largely due to the previously mentioned difficulty in measuring microplastics in human samples. But work in mouse models has been more revealing, allowing us to observe the consequences of various types of microplastics in the gut.

A recently published study in the Journal of Hazardous Materials, showed that giving mice a group of polystyrene microplastics of various sizes makes the gut vulnerable to IBD. This happens because key members of the microbiome are reduced, stopping the production of butyrate and increasing the severity of inflammation.

Clearly microplastics are capable of inducing poor gut health. However, whether animal studies accurately capture levels of microplastics found in human tissues remains to be completely understood – something that will hopefully become possible with technological advances. It’s also still not clear exactly how microplastics do this.

Even with bans on intentionally produced microplastics, we still have to fight against those that are produced through wear and tear of plastic-containing materials.

What if we could use our bacteria to help us in this battle? There is some tantalising evidence that some bacteria found in human guts are capable of breaking down some types of microplastics. Although we don’t yet know if this breakdown happens in the gut (or whether it’s a good thing), there is a real, albeit distant, possibility that in collaboration with our microbiome we might be able to fend off some of the ill effects of microplastics.

With ever-growing technological advances, it is plausible that we could, in the future, harness the power of the microbiome to dispose of plastics outside, and inside, our guts.

Nick Ilott receives funding from The Kennedy Trust for Rheumatology Research, The Wellcome Trust, Guts UK, PSC Support and has received funding from Roche for a PhD project jointly with funding from the BBSRC as part of an iCASE DTP.