Polylactic acid – used in food packaging, disposable tableware and clothing – found to alter gut metabolism and harm gut barrier of mice
Microplastics
from a widely used biodegradable material can enter the metabolic cycle of bacteria and cells in the gut after being ingested, a new study has found.
Researchers in China and the United States said the microplastics – from polylactic acid – were found to alter the gut metabolism and damage the gut barrier of mice.
They said this could potentially contribute to conditions like
inflammatory bowel disease
and
diabetes
.
Do you have questions about the biggest topics and trends from around the world? Get the answers with
SCMP Knowledge
, our new platform of curated content with explainers, FAQs, analyses and infographics brought to you by our award-winning team.
“This is the first time in the world that microplastics have been found to enter the body’s metabolic cycle,” the study’s corresponding author Cui Xuejing, an associate researcher with the Chinese Academy of Sciences’ National Centre for Nanoscience and Technology, said on Friday.
In their paper published in the peer-reviewed journal Proceedings of the National Academy of Sciences on May 5, the team wrote: “Biodegradable polylactic acid (PLA) plastics have been praised as an effective solution to the global pollution caused by petroleum-based plastics.
“Their widespread use in food packaging and disposable tableware has resulted in increased oral exposure to PLA microplastics”.
In recent years, microplastics have been found in human lungs, kidneys, blood, placenta and breast milk.
The research team said adults were estimated to consume about 5 grams of microplastics a week from food, tap water, bottled drinks and containers, with infants ingesting even more each week from feeding bottles.
With limited success in reducing the use of plastic,
biodegradable plastics
are used by many in an attempt to address the issue of plastic waste.
PLA – considered more environmentally friendly than conventional plastic since it is made from renewable resources like corn starch and sugar cane – has become the most commonly used biodegradable plastic in the world, found in food packaging, disposable tableware and even clothing.
But there has been little research done into the impact of its microplastics on the human body after they are ingested – an important area of study given that PLA is more brittle than conventional plastic and breaks down into tiny particles more easily.
To study the impact of PLA microplastics on the body, the team from the Chinese Academy of Sciences, Sun Yat-sen University and Columbia University studied exposure in mouse models.
They found that ingested PLA microplastics were degraded in the gut by micro-organisms, allowing them to be incorporated into the metabolic cycle of gut microbiota and the protective epithelial cells that line the skin and organs.
Gut microbiota – particularly the bacteria
Helicobacter muridarum
and
Barnesiella visceriocola
– were found to degrade the PLA microplastics by secreting the enzyme esterase, which breaks the bond of ester compounds in the microplastics.
When the broken-down microplastics were used as a carbon source in the metabolism of gut microbes, they were converted into materials linked to diabetes and hyperuricaemia – where there is an abnormally high level of uric acid in the blood that can cause gout and kidney stones.
In the gut epithelial cells in mice, the microplastic fragments were found to cause decreased production of linear short-chain fatty acids, the gut epithelium’s primary source of energy.
Reduced appetite and weight loss were observed in the mice that ingested the PLA microplastics.
“Although it is unclear how gut microbes distinguish PLA [microplastics], one plausible reason is that frequent consumption of plastics through food and drinks has domesticated gut microbiota to recognise and break down these plastics,” the paper said.
PLA microplastics could promote the growth of detrimental bacteria like
Helicobacter muridarum
, which could replace microbes that ferment conventional dietary fibres, presenting a risk to gut regulation and health.
Cui said the current evidence suggested that the damage caused by PLA microplastic ingestion could be reversible six to 12 months after stopping ingestion, but severe or long-term ingestion could potentially cause irreversible damage.
She said there was no evidence at present that the microplastics remained in the body permanently, but being cautious by reducing exposure was recommended.
Cui noted that research on the safety of biodegradable plastics in the body was still at a relatively early stage, and far more evidence was needed to confirm whether they had strong toxicity in the human body.
She said that since biodegradable plastics still appeared to be better for the environment than conventional ones, it was “too early to rethink the use of degradable plastics to replace traditional plastics”.
More Articles from SCMP
Hong Kong minibus operators hail arrival of over 800 drivers from mainland China
How Ukraine’s Operation Spider’s Web attack on Russia holds important lessons for China
How a Hong Kong French bistro is making a ‘macabre’ fine-dining dish ‘more approachable’
Hong Kong pianist Aristo Sham wins prestigious Van Cliburn international competition
This article originally appeared on the South China Morning Post (www.scmp.com), the leading news media reporting on China and Asia.
Copyright (c) 2025. South China Morning Post Publishers Ltd. All rights reserved.
