How microplastics in the body affect cell metabolism – and why classic “detoxification” reaches its limits here

Dr. Reiner Kraft
6 hours ago
7 min read

I've been concerned about microplastics for a long time. Not because it's a "trendy topic," but because it so inconveniently contradicts many of our usual health-related thought patterns: It's everywhere, it's difficult to measure, and it doesn't behave in biology like a "normal toxin" that can simply be eliminated via the liver/phase II metabolism.

The fundamental question that arises is:

What actually happens in our cells when these particles end up in the body?

The deeper one delves into the literature, the clearer it becomes: microplastics in the body, and especially nanoplastics, are less a classic "poison molecule" and more a foreign particle stress for cells.

1. Microplastics in the human body – the detection

In 2022, it was first clearly demonstrated that plastic particles are detectable in human blood [3]. In this study, various polymer types were identified using pyrolysis-GC/MS.

This was a turning point: microplastics are not just an environmental problem – they are a biological exposure problem .

More recent studies have also shown the presence of microplastics in human sperm, with possible links to sperm quality [8].

2. What happens in the cell: Particle stress instead of molecular toxicology

The central problem: Biotransformation (phase I/II) is designed for soluble molecules – but microplastics are particles/polymers . This changes the entire logic.

What cells typically do with particles:

Endocytosis/Phagocytosis : Particles are "encapsulated" and transported into vesicular systems.
Lysosome bottleneck : Lysosomes are the cell's "recycling furnaces"—but plastic is extremely difficult to biodegrade . This can disrupt autophagy/cellular cleaning (an important metabolic regulator).
Mitochondria/Redox stress : In many toxicological models, a recurring mechanism is oxidative stress , which burdens energy production, membranes and signaling pathways (particularly relevant in tissues with a high metabolic rate).

Important: Much of this comes from cell/animal models and reviews; in humans, the evidence is (still) heterogeneous, mainly because measurement methods vary greatly.

3. Why “detoxification” (biotransformation) only helps to a limited extent here

Here's the point that immediately caught your eye – and that makes the case so difficult:

The particle itself is not "conjugated" or "neutralized" like BPA, alcohol, or medications.
What biotransformation can certainly achieve: Additives and accompanying chemicals (e.g., bisphenols, phthalates, flame retardants) that are attached to or released from plastics. These are molecules and therefore biochemically processable.

Here are studies that show that certain environmental chemicals can be detected in sweat:

BPA in sweat [4]
Phthalates in sweat [5]
PBDE flame retardants in sweat [6]

But: These are molecules , not plastic particles.

Therefore, when someone says "microplastics detox", what they often actually mean is:

(a) reduce exposure +

(b) Reduce/eliminate accompanying chemicals +

(c) Stabilize inflammation/redox.

4. How to measure? The current state – and why comparisons are so difficult

A) Scientific evidence in humans (research)

There are peer-reviewed studies that show plastic components/particles in human samples, e.g., in blood (methods include Py-GC/MS). A well-known example is "Discovery and quantification of plastic particle pollution in human blood" (Environment International, 2022). However, methods, contamination control, measured polymers, and reporting units differ – therefore, "values" between studies are often difficult to compare.

B) Consumer/At-Home Tests (Blueprint Biomarkers)

Bryan Johnson/Blueprint sells a Microplastics Blood Test [2] that reports the number, size, and concentration of particles and offers a comparison to other test participants. According to the product page: “peer-reviewed and independently validated” and CLIA/COLA-certified laboratory.

This is interesting from a practical point of view because it provides, for the first time, something that acts like biomarker tracking – but scientifically, it must be clearly stated: Without public methodological details/publication on the specific assay performance across the board, external classification remains limited.

5. Bryan Johnson's observation: strong reduction – a valuable indicator

As part of his Blueprint Programme , Bryan Johnson reported that he had measured a significant reduction in his microplastic exposure [1]

Johnson himself published that he had measured 85% less microplastic in his ejaculate (165 → 20 particles/mL; Nov 2024 → Jul 2025) and in parallel reported a similar drop in his blood (70 → 10; Oct 2024 → May 2025).
Additionally, the figure of a ~93% reduction in blood particles (e.g., 15 → 1 particle) is circulating in public summaries surrounding Blueprint biomarkers comparisons.

Why this is valuable: It is (a) about the same person , (b) about two points in time , and (c) with a tracking purpose . Exactly these kinds of N=1 time series can generate hypotheses.

Why it's still not a validation: Details regarding sample handling, contamination controls, reproducibility, and, most importantly, multiple interventions were running in parallel (exposure reduction, possibly other protocols), are (publicly) lacking. Therefore, "cause = sauna" is not proven.

6. Sauna "sweating it out": What the research really says

Johnson attributes his weight loss, among other things, to daily sauna visits.

What does science say?

6.1 Can microplastic particles be excreted via sweat?

There is no robust peer-reviewed evidence that solid polymer particles are excreted in relevant quantities via sweat glands.

6.2 However, what does exist: Studies on chemicals in sweat (plastic-associated)

There are small studies/papers that show that certain environmental chemicals are detectable in sweat and that induced sweating may contribute as an elimination pathway – however, these are not large randomized clinical trials:

Bisphenol A (BPA) was measured in sweat using a blood, urine and sweat design; the paper discusses induced sweating as a potential elimination pathway for BPA (small sample size). [4]
Phthalates (plasticizers) were also tested in blood/urine/sweat; again, they were detected in sweat, but this was a small study. [5]
For PBDE flame retardants, there is also a BUS-like approach for measurement in weld.[6]

In addition, there are more recent studies showing that sweat can contain measurable amounts of certain metals/metalloids. [7] This confirms sweat as an excretion route for some substances, but says nothing directly about microplastic particles.

6.3 How to properly classify Johnson's "sauna effect"

If Johnson suspects sauna as the main driver of his reduction, this hypothesis is plausible in two directions:

Indirectly : Sauna improves inflammatory/metabolic status, which could promote clearance mechanisms (e.g., lymph flow, immune cell turnover) .
Chemicals instead of particles : Saunas might reduce plastic-associated chemicals , not necessarily the particles themselves – and measurement methods might depict chemical signatures/fragments differently in some cases.

However, this remains a hypothesis – current research supports “chemicals in sweat” rather than “microplastics in sweat”.

7. Further considerations & next steps

Even though we are still at the beginning of understanding micro- and nanoplastics in the human body, there are concrete steps that are already making a difference today – plus sensible avenues for anyone who wants to delve deeper.

7.1 Reducing exposure – the biggest lever

Scientific evidence clearly shows that the strongest influencing factor is how much microplastic we ingest in the first place. The less exposure, the lower the potential burden on cells and metabolism.

Practical resources with immediately applicable tips:

➡️ WWF Germany – Tips for avoiding microplastics in everyday life . Concrete, practical measures, e.g., plastic-free packaging, conscious shopping, plastic-free kitchen practices, and more. 🔗 https://www.wwf.de/aktiv-werden/tipps-fuer-den-alltag/tipps-zur-vermeidung-von-mikroplastik

➡️ AOK – Avoiding Microplastics Made Easy: An easy-to-understand guide with 8 practical measures, such as choosing the right drinking water, avoiding plastics in the home, and making conscious consumer choices. 🔗 https://www.aok.de/pk/magazin/nachhaltigkeit/wasser-luft/so-einfach-kann-man-mikroplastik-vermeiden

What you can do right now:

Switch to glass, stainless steel or ceramic instead of plastic in the kitchen and household
Choose plastic-free packaging alternatives when shopping.
Drinking water filtration instead of disposable plastic bottles
Conscious selection of textiles and reduced washing of synthetic clothing

This strategic reduction not only affects microplastic particles, but also reduces the absorption of numerous plastic-associated chemicals – double protection for your body.

7.2 Strengthening the barrier and elimination – a complex but crucial area

A strong biological system can better absorb and regulate stress. This is about:

Gut health

The gut forms one of the most important barriers against external particles. Important factors:

Intestinal wall integrity (e.g., tight junctions)
Microbiome balance
Mucus layer function
Biofilm regulation

These components determine how many particles remain in the body or are expelled.

Lungs & Mucous Membranes

Airborne microplastic particles become lodged in the respiratory tract. Healthy mucous membranes and respiratory function reduce absorption.

Redox balance & inflammation regulation

Environmental stressors often act via oxidative stress pathways. This means:

Antioxidant capacity
Endogenous inflammation regulation
Genetic variants (SNP profiles in the redox system)

… play a role in how well a system can cope with stress.

These issues are biologically complex and vary from person to person .

👉 This is exactly where my longevity coaching training comes in: scientific mechanisms + individual assessments + concrete interventions to strengthen barrier systems, redox regulation and micro-stress resilience.

8.3 For proactive users: Prevention check

For everyone who wants to actively do something for their health now – without immediately entering comprehensive coaching programs:

👉 Prevention check with functional laser spectroscopy: This check provides a non-invasive, functional picture of your cell metabolism, including:

Inflammatory state
oxidative stress
Cell energy efficiency

While it doesn't directly measure microplastic pollution, it shows early on which direction your system is trending – which is an excellent first step for prevention strategies.

Why this is valuable: Many stress reactions operate via inflammatory/oxidative mechanisms. An early functional assessment helps to intervene more effectively.

8.4 For anyone who wants to delve deeper

If you want to delve deeper, further coaching and intervention pathways are available, such as the Full Body Reset Program . This includes, among other things, biomarker-based analyses and DNA/genetics-based assessments.

These tools allow for the systematic analysis and targeted addressing of individual metabolic profiles, stress variants, genetic predispositions, and adaptive capacities.

References

[1] Bryan Johnson – Post: “I eliminated 85% of microplastics from my ejaculate.” (own publication, repost/archived) URL: https://posts.bryanjohnson.com/tweets/i-eliminated-85-of-microplastics-from-my-ejaculat/

[2] Blueprint – Microplastics Test (product page, test description/assay claims) URL: https://blueprint.bryanjohnson.com/products/microplastics-test

[3] Leslie et al. (2022) – Discovery and quantification of plastic particle pollution in human blood (PDF)URL: https://www.wacaprogram.org/sites/default/files/knowdoc/Leslie%20et%20al%202022.pdf

[4] Genuis et al. (2012) – Human Excretion of Bisphenol A: Blood, Urine, and Sweat (BUS) Study (PDF)URL: https://onlinelibrary.wiley.com/doi/pdf/10.1155/2012/185731

[5] Genuis et al. – Human Elimination of Phthalate Compounds: Blood, Urine, and Sweat (BUS) Study (PDF)URL: https://www.researchgate.net/profile/Stephen-Genuis/publication/233850050_Human_Elimination_of_Phthalate_Compounds_Blood_Urine_ and_Sweat_BUS_Study/links/00b4951a2120eb51fa000000/Human-Elimination-of-Phthalate-Compounds-Blood-Urine-and-Sweat-BUS-Study.pdf

[6] Human Excretion of Polybrominated Diphenyl Ether Flame Retardants: Blood, Urine, and Sweat Study (ePDF)URL: https://onlinelibrary.wiley.com/doi/epdf/10.1155/2017/3676089

[7] MDPI IJERPH (2022) – Excretion of Ni, Pb, Cu, As, and Hg in Sweat under Two Sweating Conditions URL: https://www.mdpi.com/1660-4601/19/7/4323

[8] MDPI Toxics (2025) – The Presence of Microplastics in Human Semen and Their Associations with Semen Quality URL: https://www.mdpi.com/2305-6304/13/7/566

[9] WWF Germany – Tips for avoiding microplastics in everyday life

This article explains how microplastics occur in everyday life and what specific behavioral changes can help reduce intake – e.g., buying unpackaged goods, avoiding plastic, or reducing waste. https://www.wwf.de/aktiv-werden/tipps-fuer-den-alltag/tipps-zur-vermeidung-von-mikroplastik

[10] AOK – 8 tips for minimizing microplastics in everyday life, water & air

Another well-structured guide with practical, immediately applicable measures – from choosing drinking water and making conscious consumer choices to everyday behavior. https://www.aok.de/pk/magazin/nachhaltigkeit/wasser-luft/so-einfach-kann-man-mikroplastik-vermeiden