We will continue discussing the effect of chitosan supplementation on the absorption of microplastics. Yesterday we wrote about a Japanese animal study, today we read an Italian human study. According to the latter study, a single dose of 800 milligrams of chitosan causes people to excrete 45 percent more microplastics than normal.

About microplastics
Humans are primarily exposed to microplastics through their food, but can also inhale them. [J Expo Sci Environ Epidemiol. 2024 Mar;34(2):185-96.] The concentration of microplastics is particularly high in the air of enclosed spaces where many people walk back and forth. Relatively large amounts of microplastics are released from the clothing of people moving around.

Well, large amounts... What is large? Through food, humans ingest at least a thousand times more microplastics than through the air. Therefore, when discussing the potential health effects of microplastics, we are primarily referring to food contamination.

Estimates of daily exposure to microplastics in the scientific literature vary widely, but the highest estimates put the exposure at a few hundred milligrams per day.

It should be noted, however, that as far as we know, food mainly contains relatively large plastic particles. We are talking about particles of 50 micrometers and larger.

The body does not absorb those large particles.

Slightly smaller plastic particles that are also present in food, measuring 20-50 micrometers, accumulate in the intestines. In healthy people, they do not penetrate further into the body, or only to a very limited extent, but this does not negate the fact that they may damage the intestinal wall and disrupt the microflora. [Part Fibre Toxicol. 2025 Nov 6;22(1):29.]

According to in vitro studies, even smaller plastic particles in food, measuring 5-10 micrometers and smaller, are absorbed by intestinal cells. [Toxicol In Vitro. 2021 Feb:70:105021.]

In the blood, you actually only find microplastics smaller than 1 micrometer. [Eco Environ Health. 2023 Aug 21;2(4):195-207.] [Environ Int. 2022 May:163:107199.] If you are a stickler for detail, when it comes to such small particles, you no longer refer to them as microplastics, but as nanoplastics.

We actually do not yet fully know where these nanoplastics come from. They likely originate from food, but we do not know to what extent the nanoparticles are already present in food or are formed in the body through degradation processes.

However, it is now clear which organ is most vulnerable to nanoplastics. Researchers find the highest concentration of nanoplastics in the brain. [Nat Med. 2025 Apr;31(4):1114-9.] We are talking about nanoplastics of 100 to 200 nanometers (that is the same as 0.1 to 0.2 micrometers).

In any case, microplastics and nanoplastics penetrate deeper into the body the smaller they are. And that is what makes supplementation with chitosan so interesting.

Study
In 2025, Italian chemist Claudio Casella, affiliated with the University of Pavia, published a small human study involving ten participants. On two occasions, these participants were given an identical meal containing an identical amount of microplastics.

On one occasion, however, the participants ingested 800 milligrams of chitosan just before their meal. That is a reasonable amount.

On the day, 12 hours after the meal, the participants collected their stool samples. The researchers determined the concentration of microplastics in them.

Results
After the participants ingested chitosan, they excreted 45 percent more microplastics than without chitosan.

Click on the table below for a larger version.

The researchers were able to detect particles ranging from 20 to 500 micrometers. They determined that chitosan captured microplastics better as the particles became smaller. It is quite possible that nanoparticles were captured even better by chitosan, but the Italians do not know this for certain.

In an acidic environment, chitosan forms a network of positively charged soluble polymers. These polymers can attach to the microplastics, thereby forming gels. These gels are no longer soluble and can no longer pass through the intestinal wall.

Conclusion
The Italians suspect that there are now enough microplastics present in humans to contribute to disease.

Based on animal studies and measurements in humans, they believe that exposure to high doses of microplastics can cause not only neuropsychiatric symptoms such as anxiety and depression, but also hormonal disturbances, vascular diseases, liver and pancreatic abnormalities, lung and intestinal complaints, and skin and eye problems. They have already coined a name for this group of new diseases: the Microplastic Syndrome. [Microplastics. 2025;4(4):93.]

If this syndrome really does exist, then the Italians already have a treatment. And you guessed it. The Italians have already applied for a patent on that treatment. Because even in Pavia, Italy, nothing comes for free.

Incidentally, the study we are discussing today says nothing yet about the effect of chitosan on the amount of microplastics in the body. We will discuss a report soon showing that such an effect does indeed exist.