Parasites and Heavy Metals

This page looks at the idea that parasites and heavy metals are “partners” that build up together in the body and set the stage for cancer. It sets that point, made in a 2026 integrative-oncology presentation, beside the published research: the real and well-documented finding that some parasitic worms of fish and rats soak up lead and cadmium far beyond the levels in their hosts, what the cancer agencies say about heavy metals, how metal levels in people are measured, and what is known about claims that metals can be filtered out of the blood.

What the Presentation Said
Worms That Collect Metals
How the Worms Take Up Metals
Do the Worms Lower Their Host’s Metal Levels?
What Is Known in People
Which Heavy Metals Are Classed as Carcinogens
Measuring Metals in People
Claims About Removing Metals
How the Claim Compares With the Research
What Is Not Known
Connections
Key Research Papers
Featured Videos

What the Presentation Said

The presentation came back to heavy metals several times while discussing parasites and cancer. Its points, in summary:

Parasites were described as feeding on “decay, metals and toxins”, and as harbouring heavy metals together with viruses and bacteria. The speaker called heavy metals and parasites “buddies” that like each other and live in the same environment as cancer.
On that reasoning, the speaker urged treating parasites before viruses, mould or bacteria, and linked a “parasitic detox” and a “heavy metal detox” to a lower risk of cancer and chronic disease. Binders, coffee enemas and diet were described as creating a body “terrain” in which parasites and metals do not thrive.
The speaker stated that 99.9% of the clinic’s patients, and of the general population, carry heavy metals.
A slide was shown with figures for metals said to be removed by a one-hour blood-filtration treatment (extracorporeal blood oxygenation and ozonation, in which blood is run through an outside circuit and exposed to oxygen and ozone): mercury about 70%, cadmium 47%, and aluminium, which the speaker called “a big one”. No study, sample size or measurement method was given for these figures. That device is covered on its own page, Blood Ozone and Ultraviolet Blood Irradiation; this page deals with it only briefly.

No study of parasites and metals in people was cited in the presentation.

Worms That Collect Metals

There is a genuine scientific finding behind the idea that parasites and heavy metals go together — but it comes from environmental science, not from human medicine. Since the 1990s, aquatic ecologists have measured metals in the intestinal worms of wild fish and found that two groups of worms are remarkable metal collectors:

Acanthocephalans, or “thorny-headed worms”, which hook onto the gut wall of fish and other animals.
Cestodes, or tapeworms.

The key measure is the bioconcentration factor: the metal level in the worm divided by the level in the host’s tissue. A factor of 100 means the worm holds 100 times more metal, weight for weight, than the host tissue it is compared with.

The figures reported

In fish caught across Europe, the thorny-headed worm Pomphorhynchus laevis held up to 2,700 times more lead and about 500 times more cadmium than the muscle of its host, the chub. A tapeworm of tench held 75 times more lead and 43 times more cadmium than its host’s muscle (Sures and colleagues, 1997).
Not every parasite does this. In the same work, a roundworm that lives in the swim bladder of eels contained less lead than eel muscle (Sures and colleagues, 1997). A review of this field reports metal levels “several thousand times higher” in thorny-headed worms than in host tissues (Sures, 2003), and a later overview reaches the same conclusion for both thorny-headed worms and tapeworms (Mehana and colleagues, 2020).
In barbel from the Danube, arsenic, cadmium, copper, lead and zinc were all significantly higher in the worms than in host muscle, liver or intestine (Nachev and colleagues, 2010).
In farmed tambaqui in Brazil, a thorny-headed worm held up to about 36 times more iron, 27 times more aluminium and 14 times more zinc than the fish muscle, and also concentrated lead (Jerônimo and colleagues, 2023).
In the rat tapeworm Hymenolepis diminuta, collected from rats near Cairo, lead was 36 times higher than in the rat’s intestinal wall and 29 times higher than in its liver at the more polluted site (Sures and colleagues, 2003).

Because the worms respond quickly and strongly to the metals available in a river or lake, researchers propose using them as bioindicators — living pollution gauges — sometimes more sensitive than the zebra mussels and other organisms traditionally used for that job (Sures and colleagues, 1997; Sures, 2003).

How the Worms Take Up Metals

Thorny-headed worms and tapeworms have no mouth or gut. They absorb everything they need directly through their body surface from the host’s intestinal contents. That feeding style explains much of the metal uptake:

Bile acids carry metals in. According to the review by Sures (2003), the leading explanation is that bile acids in the host’s gut bind metals into fat-soluble complexes that the worms absorb easily through their skin-like surface.
Only adult worms do it. Larval worms living in their small crustacean intermediate hosts take up little metal; uptake begins once the young worm reaches its final host. After four to five weeks, the worms reach a steady level “orders of magnitude” above that of the surrounding water (Sures, 2003; Sures and colleagues, 1997).
Worm sex and worm numbers matter little. In barbel, the number of worms per fish made no difference to how much metal each worm held, and male and female worms differed only for vanadium and zinc (Nachev and colleagues, 2010).

In other words, the worms do not “feed on” metals as food. Metals arrive with the digested food and bile in the host’s gut, and these particular worms absorb them along with the nutrients they take in.

Do the Worms Lower Their Host’s Metal Levels?

If a worm absorbs metal from the host’s gut, the next question is whether the host ends up with less. Studies in fish and rats give mixed answers.

In fish: sometimes lower

In European chub from a Croatian river with low metal pollution, chub infected with a thorny-headed worm had lower copper, cadmium and lead concentrations than uninfected chub (Filipović Marijić and colleagues, 2013).
In perch from a heavily polluted Slovak reservoir, higher metal levels in the worms went with lower levels in the fish, and fish carrying more tapeworms had lower lead (Brázová and colleagues, 2015).
In farmed tambaqui, the higher the metal levels in the worms, the lower they were in fish muscle and liver (Jerônimo and colleagues, 2023).

These authors present the finding mainly as a problem for pollution monitoring: if parasites pull metal out of fish tissue, a survey that ignores infection may underestimate pollution. They do not present it as a health benefit for the fish — heavy parasite loads also damage fish, as the 2020 overview by Mehana and colleagues notes.

In rats: no protection

In a controlled laboratory study, rats were infected with the rat tapeworm and then given lead by mouth. The tapeworms held the highest lead concentrations in the whole system, yet the authors reported that the tapeworm “does not protect” the rat from raised lead exposure: at the same exposure, lead in most host tissues did not differ significantly between infected and uninfected rats (Čadková and colleagues, 2014).
In wild mice and voles from the Czech Ore Mountains, mercury in liver and kidney did not differ significantly between rodents with and without intestinal worms (Jankovská and colleagues, 2023).

So the research shows that some worms concentrate metals; it does not show that worms are a major reservoir of metal in a mammal’s body, nor that they make a mammal’s metal burden either better or worse in a consistent way.

What Is Known in People

Almost all of this research is on fish, freshwater crustaceans and rodents. Searches of PubMed for this page found no study measuring metal concentrations inside parasites taken from people, and no study showing that human intestinal worms or protozoa gather metals in the human body or raise a person’s metal levels.

A few points help put the animal work in context:

The worms studied absorb metals that are already present in the host’s gut. In the research, metal levels in the worms track the pollution of the environment; the worms are an indicator of exposure, not its source (Sures, 2003; Mehana and colleagues, 2020).
No study found for this page linked a parasite’s metal content to cancer in its host, in animals or in people.

The research that does link parasites to human cancer runs along different lines — chronic inflammation, tissue damage and DNA-damaging free radicals caused by a few specific worms such as the blood fluke Schistosoma haematobium and the liver flukes Opisthorchis viverrini and Clonorchis sinensis (Vennervald and Polman, 2009). Metals do not feature in that mechanism. See How Parasites Can Drive Cancer and Parasites Classified as Cancer-Causing Agents.

Which Heavy Metals Are Classed as Carcinogens

The second half of the claim — that heavy metals are part of the cancer picture — has firm support for some metals and some exposures. The International Agency for Research on Cancer (IARC), the cancer agency of the World Health Organization, classifies agents by the strength of evidence that they can cause cancer in humans. Its evaluations of the main metals are:

Group 1, carcinogenic to humans: arsenic and inorganic arsenic compounds, beryllium and its compounds, cadmium and its compounds, chromium(VI) compounds, and nickel compounds, all re-evaluated in International Agency for Research on Cancer Monographs volume 100C (2012).
Group 2A, probably carcinogenic: inorganic lead compounds (volume 87, 2006).
Group 2B, possibly carcinogenic: methylmercury compounds — the form found in fish.
Group 3, not classifiable: metallic mercury and inorganic mercury compounds (volume 58, 1993).

A 2025 synopsis by International Agency for Research on Cancer scientists describes how these evaluations combine human studies, animal experiments and mechanism data, for arsenic, cadmium, cobalt and antimony (de Conti and colleagues, 2025).

Cadmium as an example

The strongest human evidence comes from workers: occupational cadmium exposure is linked to lung cancer. Links to prostate and kidney cancer are weaker, and other sites are considered equivocal. Cadmium is poorly mutagenic and is thought to act mostly by indirect or epigenetic means (Waalkes, 2003).
A systematic review of newer worker studies found a lower relative risk of lung cancer in groups exposed to cadmium without arsenic and nickel, did not confirm the prostate cancer link, and found no increased cancer risk in the environmentally exposed populations studied (Verougstraete and colleagues, 2003).
Tobacco smoke is a major everyday source. Inhaled cadmium builds up in the lungs and the body, with a biological half-life of one to two decades, and smokers have higher blood and urine cadmium than non-smokers (Richter and colleagues, 2017).

The point that the dose and the setting matter is central to this research: the clearest cancer risks come from high, long-term exposures such as industrial work, contaminated drinking water (for arsenic) and smoking. More detail is on the site’s Toxic Minerals pages.

Measuring Metals in People

The presentation stated that 99.9% of patients and of the general population “have heavy metals”. No source was given for that figure, and none was found for this page. What national surveys do show is that small amounts of lead, mercury, cadmium and arsenic can be measured in the blood or urine of most people, because these metals occur naturally and in food, water, air and tobacco smoke.

The U.S. Centers for Disease Control and Prevention (CDC) runs the National Report on Human Exposure to Environmental Chemicals, based on blood and urine samples from the National Health and Nutrition Examination Survey. The U.S. Centers for Disease Control and Prevention states that “the measurement of an environmental chemical in a person’s blood or urine is a measure of exposure; it does not by itself mean that the chemical causes disease or an adverse effect.” Whether a level matters depends on how high it is compared with reference values and known harm thresholds — see the Heavy Metals Panel page for the specimens and action levels used.

“Provoked” urine tests

Some practitioners give a chelating drug (a drug that binds metals so they are passed in the urine) and then measure metals in the urine. Because the drug itself pulls extra metal into the urine, results look high compared with normal reference ranges, which were set on unprovoked samples. The American College of Medical Toxicology’s 2010 position statement says that post-challenge urinary metal testing “has not been scientifically validated, has no demonstrated benefit, and may be harmful” when used to assess and treat people in whom metal poisoning is suspected (American College of Medical Toxicology, 2010).

Claims About Removing Metals

The blood-filtration figures

The presentation’s figures — mercury about 70% and cadmium 47% removed by extracorporeal blood oxygenation and ozonation — could not be traced to any published study. A PubMed search for this page found one related publication: a 2025 single-patient case report of an 88-year-old woman who received two series of three treatments. Her urine “toxin to creatinine” ratios were measured before and after; heavy-metal values fell by an average of 25.7%, with all values falling except nickel. The authors note there was no control for ongoing exposure (Bennett and colleagues, 2025). That report measured urine excretion, not the amount of metal taken out of the blood, did not report mercury or cadmium removal figures matching the presentation’s, and, as a single uncontrolled case, cannot show that the treatment caused the change. The device and its safety record are covered on Blood Ozone and Ultraviolet Blood Irradiation.

Chelation: a real treatment with real risks

For proven lead poisoning, chelating drugs are an established treatment that increases urinary and biliary excretion of lead. They also remove other metals and minerals, such as zinc and, in some cases, calcium. The U.S. Centers for Disease Control and Prevention reported three deaths between 2003 and 2005 from cardiac arrest caused by low blood calcium during chelation therapy; the report points to the drug edetate disodium, which carries an established risk of low blood calcium (Centers for Disease Control and Prevention, 2006). No clinical trial found for this page tested chelation, binders or any “heavy metal detox” as a way to prevent or treat cancer.

Treating parasites first

The advice to treat parasites before viruses or bacteria because parasites “harbour” metals has no clinical trial behind it in the literature searched for this page; the claim that parasites carry bacteria and viruses is examined on Do Parasites Harbour Bacteria and Viruses?. Decisions about cancer treatment, antiparasitic medicines and metal testing belong with a clinician.

How the Claim Compares With the Research

Supported

Some parasites really do concentrate heavy metals. Thorny-headed worms and tapeworms of fish and rats hold lead and cadmium at tens to thousands of times their hosts’ tissue levels (Sures and colleagues, 1997; Sures, 2003; Sures and colleagues, 2003).
Several heavy metals are classed as human carcinogens — arsenic, cadmium, chromium(VI), nickel and beryllium in International Agency for Research on Cancer Group 1, inorganic lead in Group 2A.
Low levels of several metals can be measured in most people.

Supported only in part

“Parasites harbour heavy metals”: true for certain worm groups in fish and rodents, not for all parasites (an eel roundworm held less lead than its host), and not studied in people.
“Heavy metals, parasites and cancer share the same environment”: polluted waters can hold both metal-laden fish and metal-laden worms, but no study found links the two to cancer together. The cancer risk from metals is tied to dose and setting, mainly occupational, water-borne and tobacco exposures.

Contradicted by the studies found

The idea that parasites “feed on” metals: the research describes passive absorption of metals dissolved in the host’s gut contents along with nutrients, not metals as food.
The figure that 99.9% of people “have heavy metals” as a sign of disease: the U.S. Centers for Disease Control and Prevention states that a measurable level is a measure of exposure and does not by itself mean harm.

No research found

No published source for the blood-filtration removal figures (mercury 70%, cadmium 47%); the only related publication found is a single uncontrolled case report with different measures and smaller changes.
No study of metal content in human parasites, and no study showing that treating parasites changes a person’s metal levels.
No clinical trial testing a “parasitic detox” or “heavy metal detox” for cancer prevention, and none testing a parasites-first treatment order.

What Is Not Known

Whether any parasite of humans concentrates metals the way fish thorny-headed worms do. The question has not been studied directly.
Whether metal-laden worms in food fish affect the metal levels of people who eat the fish. No human data on this were found.
How much the presence of parasites skews metal readings in wildlife surveys — a practical problem the fish researchers themselves raise.
Whether extracorporeal blood oxygenation and ozonation removes metals from the body at all; no controlled study measuring this was found.
Whether low, everyday metal exposures, as opposed to high occupational ones, raise cancer risk; for cadmium, the environmental studies reviewed did not show an increased risk (Verougstraete and colleagues, 2003).

Connections

Key Research Papers

Sures B, Taraschewski H, Siddall R. Heavy metal concentrations in adult acanthocephalans and cestodes compared to their fish hosts and to established free-living bioindicators. Parassitologia. 1997;39(3):213-8. PubMed PMID: 9802069
Sures B. Accumulation of heavy metals by intestinal helminths in fish: an overview and perspective. Parasitology. 2003;126 Suppl:S53-60. PubMed PMID: 14667172
Mehana EE, Khafaga AF, Elblehi SS, Abd El-Hack ME, Naiel MAE, Bin-Jumah M, Othman SI, Allam AA. Biomonitoring of Heavy Metal Pollution Using Acanthocephalans Parasite in Ecosystem: An Updated Overview. Animals (Basel). 2020;10(5):811. PubMed PMID: 32392878
Nachev M, Zimmermann S, Rigaud T, Sures B. Is metal accumulation in Pomphorhynchus laevis dependent on parasite sex or infrapopulation size? Parasitology. 2010;137(8):1239-48. PubMed PMID: 20380766
Jerônimo GT, Porto EL, Bolson MA, Sargentini-Júnior É, Martins ML, da Cruz MG. Bioaccumulation of trace metals in Neoechinorhynchus buttnerae and in its fish host tambaqui (Colossoma macropomum) from fish farms. Environmental Science and Pollution Research International. 2023;30(11):30183-30196. PubMed PMID: 36422778
Sures B, Scheible T, Bashtar AR, Taraschewski H. Lead concentrations in Hymenolepis diminuta adults and Taenia taeniaeformis larvae compared to their rat hosts (Rattus norvegicus) sampled from the city of Cairo, Egypt. Parasitology. 2003;127(Pt 5):483-7. PubMed PMID: 14653537
Filipović Marijić V, Vardić Smrzlić I, Raspor B. Effect of acanthocephalan infection on metal, total protein and metallothionein concentrations in European chub from a Sava River section with low metal contamination. The Science of the Total Environment. 2013;463-464:772-80. PubMed PMID: 23856403
Brázová T, Hanzelová V, Miklisová D, Šalamún P, Vidal-Martínez VM. Host-parasite relationships as determinants of heavy metal concentrations in perch (Perca fluviatilis) and its intestinal parasite infection. Ecotoxicology and Environmental Safety. 2015;122:551-6. PubMed PMID: 26432028
Čadková Z, Miholová D, Száková J, Válek P, Jankovská I, Langrová I. Is the tapeworm able to affect tissue Pb-concentrations in white rat? Parasitology. 2014;141(6):826-36. PubMed PMID: 24709293
Jankovská I, Karešová V, Michlová T, Kunc P, Knížková I, Ševčík R, Sloup V, Langrová I. Significance of Intestinal Helminth Infection and Animal Sex for Mercury Concentrations in Two Rodent Species. Journal of Wildlife Diseases. 2023;59(3):504-508. PubMed PMID: 37270297
Vennervald BJ, Polman K. Helminths and malignancy. Parasite Immunology. 2009;31(11):686-96. PubMed PMID: 19825108
de Conti A, Madia F, Schubauer-Berigan MK, Benbrahim-Tallaa L. Carcinogenicity of some metals evaluated by the IARC Monographs: A synopsis of the evaluations of arsenic, cadmium, cobalt, and antimony. Toxicology and Applied Pharmacology. 2025;504:117506. PubMed PMID: 40780533
Waalkes MP. Cadmium carcinogenesis. Mutation Research. 2003;533(1-2):107-20. PubMed PMID: 14643415
Verougstraete V, Lison D, Hotz P. Cadmium, lung and prostate cancer: a systematic review of recent epidemiological data. Journal of Toxicology and Environmental Health, Part B, Critical Reviews. 2003;6(3):227-55. PubMed PMID: 12746140
Richter P, Faroon O, Pappas RS. Cadmium and Cadmium/Zinc Ratios and Tobacco-Related Morbidities. International Journal of Environmental Research and Public Health. 2017;14(10):1154. PubMed PMID: 28961214
American College of Medical Toxicology. American College of Medical Toxicology position statement on post-chelator challenge urinary metal testing. Journal of Medical Toxicology. 2010;6(1):74-5. PubMed PMID: 20354920
Centers for Disease Control and Prevention (CDC). Deaths associated with hypocalcemia from chelation therapy—Texas, Pennsylvania, and Oregon, 2003-2005. MMWR Morbidity and Mortality Weekly Report. 2006;55(8):204-7. PubMed PMID: 16511441
Bennett SJ, Kuo J, Wang S, Salway RJ. Observed Reduction in Urinary Toxin Excretion With Extracorporeal Blood Oxygenation and Ozonation (EBOO) Treatment in an 88-Year-Old With Chronic Anemia: A Case Report. Cureus. 2025;17(12):e99948. PubMed PMID: 41583215

PubMed Topic Searches

Other Sources

International Agency for Research on Cancer. IARC Monographs Volume 100C: Arsenic, Metals, Fibres, and Dusts (2012). https://publications.iarc.who.int/120
International Agency for Research on Cancer. IARC Monographs Volume 87: Inorganic and Organic Lead Compounds (2006). https://publications.iarc.who.int/105
International Agency for Research on Cancer. IARC Monographs Volume 58: Mercury and Mercury Compounds, summary and evaluation (1993). https://inchem.org/documents/iarc/vol58/mono58-3.html
Centers for Disease Control and Prevention. National Report on Human Exposure to Environmental Chemicals: At a glance. https://www.cdc.gov/environmental-exposure-report/about/index.html