A study in Scientific Reports by Di Liu and Muneshige Shimizu of Tokai University compared four indigestible dietary materials in rats that were also fed polyethylene microplastics. Only the chitosan group showed a significant difference from controls in fecal excretion and in particles left in the gut. The result is interesting, and it comes from a small, short animal experiment.
This guide walks through the design, the numbers, the reason one rate exceeded 100%, and what the authors say about mechanism. It also lists what the study cannot tell us.
Why Researchers Looked at Excretion
The authors wanted to know how long ingested microplastics stay in the digestive tract and whether common dietary materials change that. They report that in control rats, particles lingered in the gut, mainly the cecum, for the week studied, and that they knew of no earlier published work on this question at the time of writing. Their reasoning is that prolonged presence of particles in the gut may matter for gut health, an area they describe as needing more research.
How the Study Was Designed
The team used 30 Sprague-Dawley rats split into five groups of six: a control group, plus groups receiving indigestible dextrin, lactosucrose, chitosan, or eggshell membrane protein. All animals ate a standard AIN-93M laboratory diet containing blue, spherical polyethylene particles averaging 200 micrometers, about 3,300 particles per rat per day.
Dextrin, lactosucrose, and chitosan each replaced 5% of the corn starch, while eggshell membrane protein replaced 5% of the protein. Rats lived in metabolism cages for one week, and researchers counted particles in feces and in the digestive tract. The paper describes its chitosan as an insoluble fiber made from shrimp and crab shell chitin.
What the Researchers Found
The chitosan group produced more feces from the first day. Fecal excretion of particles was higher throughout: 39.6% versus 14.8% in the first 24 hours, and 115.6% versus 83.7% across 144 hours. At dissection, 6.1% of ingested particles remained in the chitosan group’s digestive tract, compared with 12.1% in controls.
| Group | Fecal excretion rate, 0–144 h | Left in digestive tract |
|---|---|---|
| Control | 83.7% ± 3.8% | 12.1% ± 0.5% |
| Chitosan | 115.6% ± 4.5% | 6.1% ± 0.5% |
| Dextrin, lactosucrose, or eggshell membrane protein | Not significantly different from control | Not significantly different from control |
The other three materials did not differ significantly from the control on either particle measure, so chitosan was the only material tested that stood apart on particle counts. Eggshell membrane protein also increased fecal weight from the second day, but its particle counts did not differ significantly from controls.
Read the full paper on Nature or PubMed, and a summary at News-Medical.
Why One Rate Exceeded 100%
A fecal excretion rate above 100% cannot describe a literal outcome. The authors explain that they could not analyze the whole fecal sample, so counts came from portions of it, and they call for better sample volume and pre-treatment methods. The paper reports totals of fecal excretion plus gut retention of 121.7% for chitosan and 95.8% for controls, so the counts are best treated as estimates. Read the figure as a comparison between groups, not an exact percentage.
What the Authors Say About Mechanism
The paper does not directly observe binding. It counts particles, then proposes that chitosan interacts with other gut components. The authors point to earlier work in which high-molecular-weight chitosan formed gel aggregates with oil and bile salts, and they note that chitosan becomes positively charged in gastric juice.
They also caution that polyethylene is nonpolar, so the effect of charge is likely small, and they call for more study of the mechanism across plastic types and sizes. For general background on chitosan’s charge, see our guide to the positive charge of chitosan, and for the wider question, read can chitosan bind microplastics in the digestive tract.
What the Study Does Not Answer
Several limits apply before any result is applied to people:
- It was a one-week experiment with six rats per group.
- It tested one plastic type, polyethylene, in one size and shape.
- It did not test Microplastic Protect or any mushroom-derived chitosan oligosaccharide.
- It did not test other particle sizes or plastics already in tissue.
- It measured particle counts, not clinical outcomes, and it did not set a human dose.
Animal studies suggest questions for future research; they do not set doses or outcomes for people, which is why human studies would be needed to answer them. For broader context, read what we actually know about microplastics and human health and where microplastics actually go.
Where Microplastic Exposure Comes From
The paper’s introduction notes microplastics in table salt, beer, and mineral water, among other foods. Exposure comes from many everyday sources, which is why reducing intake is a practical first step for anyone concerned. Our guides on microplastics in food and water and ways to reduce exposure during meals cover the main routes.
About Microplastic Protect
Microplastic Protect is a dietary supplement made with a 99% pure chitosan oligosaccharide ingredient derived from button mushrooms. A serving is 2 capsules (1,200 mg), and a bottle holds 120 vegetarian capsules. The label directs 2 capsules about 15 minutes before your two largest meals, with water. Compare forms in chitosan vs. chitosan oligosaccharide supplements and mushroom vs. shellfish chitosan, or review the ingredients guide and how to take Microplastic Protect.
It was not part of the study described here. Check with a healthcare professional first if you are pregnant, nursing, taking medication, or managing a medical condition.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Frequently Asked Questions
What is chitosan microplastic excretion?
It refers to the amount of ingested microplastic particles found in feces, measured in this rat study when chitosan was added to the diet. It describes a measured outcome in animals, not an established effect in people.
What did the chitosan microplastic study find?
Rats fed chitosan had higher fecal weight, a higher fecal excretion rate for polyethylene particles, and fewer particles left in the digestive tract than controls. The other three materials did not differ significantly on particle counts.
Why did the excretion rate exceed 100%?
The authors could not analyze the whole fecal sample, so counts came from portions of it. They recommend larger sample volumes and improved pre-treatment.
Was the chitosan study done in humans?
No. It used 30 rats over one week. Results in animals do not confirm the same outcome in people.
Does chitosan affect microplastics already in body tissue?
This study did not examine that. It counted particles in feces and in the digestive tract, not in blood or organs.
Which materials were compared with chitosan?
Indigestible dextrin, lactosucrose, and eggshell membrane protein, along with a control diet.
How long did microplastics stay in the digestive tract?
In control rats, about 12.1% of ingested particles were still in the digestive tract after 144 hours, mainly in the cecum. Human transit and retention were not measured.
Does chitosan bind microplastics?
The authors propose binding in the gut but did not observe it directly, and they call for more mechanism research. See our overview of whether chitosan can bind microplastics for more detail.
What kind of chitosan was used in the study?
The paper describes chitosan as an insoluble fiber made from shrimp and crab shell chitin and does not report testing other sources or forms.
Explore Microplastic Protect
Review the ingredients, serving directions, and pricing for Microplastic Protect on the product page. For formulation, sample, or bulk-supply questions, email steve@chitosanglobal.com or call +1 (423) 202-6145.