Agaricus blazei and Cancer: What Epidemiological Data Shows

Agaricus blazei and Cancer

0 Incidence Studies

The 34% risk reduction quoted in Agaricus blazei marketing comes from a meta-analysis of dietary mushroom intake in general, not from Agaricus blazei. Not one prospective study has ever tracked Agaricus blazei consumption against cancer incidence.

Ba et al., Advances in Nutrition, 2021

17 Studies

in the meta-analysis, all on mushrooms as a food category

19,732

cancer cases pooled across those studies

4 Sources

the entire ABM-specific human literature on cancer benefit

Ba et al., Advances in Nutrition, 2021

View as image ↗

Agaricus blazei Murill (ABM), also called himematsutake or the royal sun mushroom, is one of the most heavily consumed complementary medicines in Japanese oncology. Roughly 300,000 to 500,000 people in Japan take it specifically for the prevention or treatment of cancer.^[10] That adoption rests on a striking body of laboratory and animal work, and on a population-level statistic that, on inspection, is not about Agaricus blazei at all.

This article inventories the epidemiological evidence honestly: what the mushroom data actually shows, what the ABM-specific human data actually shows, and how far apart those two things are.

For a broader view of how Agaricus blazei activates anti-tumor immunity, the mechanistic research is covered in a dedicated article. And the clinical data on ABM as an adjunct during chemotherapy examines intervention trials specifically.

The Mushroom-Cancer Meta-Analysis: What 17 Studies Found

The most comprehensive epidemiological analysis of mushroom consumption and cancer risk was published in 2021 by Ba and colleagues at Penn State College of Medicine.^[1] They systematically searched MEDLINE, Web of Science, and the Cochrane Library for studies published between 1 January 1966 and 31 October 2020, identifying 17 observational studies with data on mushroom intake and cancer risk, covering 19,732 cancer cases.

The pooled results showed a statistically significant inverse association. Comparing the highest to the lowest mushroom consumption groups, the relative risk for total cancer was 0.66 (95% CI: 0.55-0.78). In practical terms, people who ate the most mushrooms had roughly one-third lower risk of developing cancer compared to those who ate the least.

When broken down by cancer type, breast cancer showed the strongest signal. Ten studies examined breast cancer specifically, yielding a pooled relative risk of 0.65 (95% CI: 0.52-0.81). Non-breast cancers, pooled across 13 studies, also showed a significant association (RR: 0.80; 95% CI: 0.66-0.97). When individual sites were examined separately, breast cancer was the only one where the association reached statistical significance, which the authors attributed to the small number of studies available for other cancers.

The analysis found a significant nonlinear dose-response relationship across the seven studies with usable intake data (P-nonlinearity = 0.001). Modelled across that curve, an intake of 18 g/day was associated with 45% lower total cancer risk than an intake of 0 g/day. The paper does not characterise the curve as plateauing, and the small number of contributing studies means the shape of the dose-response relationship should be treated as provisional rather than established.

Eleven of the 17 studies used case-control designs, which are vulnerable to recall bias: people with cancer may remember their dietary history differently than healthy controls. The remaining six were cohort studies, which provide stronger evidence, but the mix of designs is a limitation the authors flag explicitly, along with the wide variation in what each study adjusted for.

Here is the critical caveat, and it is the reason this article exists. This meta-analysis examined mushroom consumption broadly. Fourteen of the 17 studies were conducted in Asian countries, two in Europe, and one in the United States, and the analysis did not resolve results by mushroom species. Whether Agaricus blazei has epidemiological properties different from any other culinary mushroom is simply not answerable from this data.

Specificity Gap

What the Epidemiology Actually Covers

The 34% figure quoted in Agaricus blazei marketing comes from the left-hand column. The right-hand column is every piece of human evidence that is actually about Agaricus blazei. Same rows, so the substitution is visible.

What was studied

Mushrooms as a food category

Studies pooled

17 observational studies

Cancer cases

19,732

Designs

11 case-control, 6 cohort

Total cancer

RR 0.66 (95% CI 0.55–0.78)

Breast cancer

RR 0.65 (95% CI 0.52–0.81), n = 10

Measured cancer incidence?

Yes — this is incidence data

What gets claimed

Agaricus blazei specifically

Studies pooled

No meta-analysis exists

Cancer cases

No incidence cohort has been run

Designs

1 undocumented origin account, 1 consumer survey, 1 Phase I safety study, 1 non-randomised trial

Total cancer

Not estimated

Breast cancer

Not studied as a standalone question

Measured cancer incidence?

No — nearest endpoint is NK cell activity

Every number in the left column is real, and none of it was collected on Agaricus blazei. The meta-analysis pooled dietary mushroom intake in general populations — 14 of its 17 studies were run in Asian countries, 2 in Europe, 1 in the United States — and it did not resolve results by species. Reading the left column as evidence for the right column is the single most common error in writing about this mushroom.

Sources: Ba et al., Advances in Nutrition, 2021 [ref 1]; Firenzuoli et al., eCAM, 2008 [ref 10]; Talcott et al., BMC Complement Altern Med, 2007 [ref 3]; Ohno et al., eCAM, 2011 [ref 4]; Ahn et al., Int J Gynecol Cancer, 2004 [ref 5].

The Piedade Observation: What Is Actually Documented

The epidemiological story of Agaricus blazei is usually told as an origin myth: residents of Piedade, a rural municipality in São Paulo state, Brazil, ate a local mushroom and had unusually low rates of cancer, diabetes, and heart disease, which prompted Japanese researchers to investigate.

The documented part of that story is narrower. Firenzuoli and colleagues, reviewing the ABM literature in 2008, record that the mushroom is native to a small village named Piedade in the highland Atlantic forest near Tauape, in São Paulo province, and that it was discovered in 1960 by Takatoshi Furumoto, a grower and researcher, who sent it to Japan in 1965 for investigation.^[10]

What that review does not report, and what no peer-reviewed source we could locate reports, is the disease-rate comparison itself. There is no published study of cancer, diabetes, or cardiovascular incidence in Piedade. There is no control population, no standardised measurement, and no adjustment for the many things that differ between a rural Brazilian farming community and whatever it is being implicitly compared to. The low-disease-rate claim circulates widely in supplement marketing and in the introductory paragraphs of papers that cite other papers, but it does not trace back to data.

Fact Check

The Piedade origin story

The claim

“Researchers found that residents of Piedade, Brazil had unusually low rates of cancer because they ate Agaricus blazei, which is what launched the research.”

Repeated throughout supplement marketing and in the framing sections of review articles.

What research shows

Unsupported

The peer-reviewed record documents that Agaricus blazei is native to Piedade and that Takatoshi Furumoto sent samples to Japan in 1965. It does not document any measurement of disease rates in Piedade.

This does not make the claim false. It makes it unmeasured. An ecological observation with no data behind it is a reason to run a study, not a finding in its own right, and in sixty years the study has not been run.

Firenzuoli et al., Evidence-Based Complementary and Alternative Medicine, 2008 [ref 10]

What the origin story did accomplish was to move the mushroom to Japan, where it became the center of ABM research and, eventually, a large commercial market.

Japanese Consumption Patterns: The Survey Data

The scale of ABM use in Japan is genuinely remarkable, and it is well documented. Firenzuoli and colleagues report that 100,000 to 300,000 kg of dried ABM fruiting body is produced in Japan each year, and that roughly 300,000 to 500,000 people take 3-5 g three times daily, typically as a hot-water extract, for the prevention or treatment of cancer.^[10]

A nationwide cross-sectional survey of Japanese cancer patients found a CAM use prevalence of 44.6% (1,382 of 3,100). Among those users, mushroom products were the most frequently consumed category, with Agaricus at 60.6%, followed by AHCC at 8.4% and Ganoderma lucidum at 6.3%.^[4] This is a large, self-selected population making health decisions on the basis of preclinical evidence.

Talcott, Clark, and Lee published in 2007 the only large-scale survey of cancer patients consuming ABM extract.^[3] They mailed questionnaires to 2,346 Japanese consumers of Sen-Sei-Ro, a commercial ABM extract, who self-identified as cancer patients. From those, 782 (33%) returned completed surveys.

Key Study

Talcott, Clark & Lee (2007) · BMC Complementary and Alternative Medicine

Population

782 Japanese cancer patients who returned surveys, from 2,346 mailed (33% response rate)

Intervention

Self-reported consumption of Sen-Sei-Ro, a commercial Agaricus blazei extract

Comparator

None. There was no control group.

Finding

Respondents expressed consistently positive views, though not extremely so, reporting more benefit for abstract outcomes such as emotional and physical well-being than for relief of specific symptoms. Nearly all had begun taking the extract after their cancer diagnosis.

narrow-scope This is consumption and perception data. It contains no clinical measurement, no control group, and no way to separate product effects from placebo, disease course, or concurrent treatment. A 33% response rate also favours respondents who felt the product helped.

Talcott et al., BMC Complementary and Alternative Medicine, 2007 [ref 3]

The distinction that matters most here is directional. Nearly all respondents began consuming ABM extract after their cancer diagnosis, not before. Whatever this survey captured, it was not prevention. Research from Brazil and Japan on ABM takes different approaches shaped by each country's research tradition.

Clinical Safety Data in Cancer Populations

Ohno and colleagues conducted a Phase I safety study of ABM in cancer survivors, published in 2011.^[4] Seventy-eight patients in complete remission, with no clinical evidence of relapse and no cancer therapy within 30 days of enrolment, received ABM granulated powder at three dose levels: 1.8 g, 3.6 g, or 5.4 g per day for six months (30, 24, and 24 subjects respectively).

Adverse events, graded by NCI-CTCAE version 3.0, occurred in 9 of 78 patients (12%). Most were digestive: nausea and diarrhea. One patient developed a liver dysfunction-related food allergy. None of the adverse events showed a dose-dependent pattern.

On laboratory values, the result is more nuanced than it is often reported. Blood chemistry did shift: red blood cell count, hemoglobin, hematocrit, total cholesterol, total protein, and creatinine all differed significantly from pretreatment values. The authors characterise these changes as mild and transient, noting that laboratory data returned to normal limits without treatment over the course of the study. The conclusion the paper supports is that ABM did not cause problems in most patients within laboratory parameters at the doses tested, which is not the same as no change at all.

This study established basic tolerability, not efficacy. It was not designed to detect whether ABM prevented cancer recurrence, and 78 patients is far too few to identify uncommon adverse events.

The Human Liver Signal

That last point matters, because the severe adverse events reported for ABM in humans have not turned up in trials. They have turned up in case reports, and they have consistently involved the liver.

Human Safety Ledger

Every Published Human Liver Event for Agaricus blazei

The tolerability study and the case reports are almost never cited together. Chronologically, they look like this.

20063 patients with advanced cancer

Serious harm

Severe hepatic damage in all three; two died of fulminant hepatitis. One patient recovered after stopping ABM, then deteriorated again after restarting it.

Mukai et al., Jpn J Clin Oncol [ref 12]

2008Commercial ABM products

Regulatory action

Agaritine measured at up to 1,791 µg/g dry weight in a commercial product; the Japanese Ministry of Health demanded cessation of sales and a voluntary recall.

Firenzuoli et al., eCAM [ref 10]

201178 cancer survivors in complete remission

Tolerability

Adverse events in 9 patients (12%) over six months at 1.8–5.4 g/day, mostly nausea and diarrhoea, none dose-dependent. One liver-dysfunction-related food allergy.

Ohno et al., eCAM [ref 4]

20132 patients with stable malignancy

Serious harm

Drug-induced liver injury confirmed by the Roussel Uclaf Causality Assessment Method, with liver histology closely resembling autoimmune hepatitis. Neither patient had told their physician they were taking ABM.

Hisamochi et al., Clin J Gastroenterol [ref 13]

Five published cases of severe hepatic injury is not a population-level risk estimate, and case reports cannot establish incidence — no one knows the denominator. But it is the same organ every time, in the same population the prevention claims target, and in the 2006 series one patient improved off the product and worsened on rechallenge. That pattern is what pharmacovigilance treats as a signal rather than a coincidence.

Sources: Mukai et al., 2006 [ref 12]; Firenzuoli et al., 2008 [ref 10]; Ohno et al., 2011 [ref 4]; Hisamochi et al., 2013 [ref 13].

Mukai and colleagues reported three patients with advanced cancer who developed severe hepatic damage while taking Agaricus blazei extract; two died of fulminant hepatitis.^[12] In one patient, liver function recovered gradually after she stopped taking the product, then deteriorated again after she restarted it. That dechallenge-rechallenge pattern is among the stronger forms of evidence available in a case report. The authors were careful to note that other factors could not be completely ruled out, but concluded that a strong causal relationship was suggested.

Hisamochi and colleagues later described two further cases: a 60-year-old woman with severe hepatitis while taking ABM extract alongside Ganoderma lucidum, and a 75-year-old man with drug-induced liver injury while taking ABM alongside fucoidan.^[13] Both were assessed as compatible with drug-induced liver injury using the Roussel Uclaf Causality Assessment Method, and in both, liver histology closely resembled autoimmune hepatitis. Notably, neither patient had told their physician they were taking a mushroom product. The authors proposed that ABM's immunostimulating action was itself the plausible mechanism of injury, which is an uncomfortable possibility for a product sold for immune stimulation.

Safety

Critical

Hepatic injury has been reported in cancer patients taking ABM

Concern

Five published human cases of severe liver injury are associated with Agaricus blazei extract, including two deaths from fulminant hepatitis. Two further cases showed histology resembling autoimmune hepatitis, and the proposed mechanism is the same immunostimulation the product is sold for. Case reports cannot establish how often this happens, because the number of people exposed is unknown.

What the research says

Anyone taking or considering Agaricus blazei should tell their treating physician, particularly during cancer treatment, and particularly if taking other supplements or hepatotoxic drugs. In the reported cases, several patients had not disclosed their supplement use, which delayed recognition. Liver function monitoring is a reasonable precaution.

Particularly relevant for: Cancer patients, people with existing liver disease, and anyone taking multiple concurrent supplements

What to do

Discuss ABM use with your oncologist or physician before starting, and seek medical attention for jaundice, dark urine, persistent nausea, or right upper abdominal pain.

Mukai et al., Jpn J Clin Oncol, 2006 [ref 12]; Hisamochi et al., Clin J Gastroenterol, 2013 [ref 13]; Ohno et al., eCAM, 2011 [ref 4]

NK Cell Activity: The Ahn 2004 Trial

The largest clinical trial measuring an immune endpoint in cancer patients taking ABM was published by Ahn and colleagues in 2004.^[5] One hundred patients with cervical, ovarian, or endometrial cancer received standard chemotherapy (carboplatin 300 mg/m² plus etoposide 100 mg/m², or carboplatin 300 mg/m² plus taxol 175 mg/m²) every three weeks for at least three cycles, with or without oral ABM extract (Agaricus blazei Murill Kyowa). Thirty-nine patients took the extract; 61 did not.

Natural killer cell activity was significantly higher in the ABM group (P < 0.002). Notably, the effect was specific: no significant difference was observed in lymphokine-activated killer activity, monocyte activity, or the counts of specific immune cell populations. Chemotherapy side effects were also reported as improved in the ABM group, across appetite, alopecia, emotional stability, and general weakness.

Key Study

Ahn et al. (2004) · International Journal of Gynecological Cancer

Population

100 patients with cervical, ovarian, or endometrial cancer receiving carboplatin-based chemotherapy

Intervention

Oral Agaricus blazei Murill Kyowa extract alongside chemotherapy (n = 39)

Comparator

Chemotherapy without the extract (n = 61)

Finding

NK cell activity was significantly higher in the extract group (P < 0.002). Lymphokine-activated killer activity, monocyte activity, and immune cell counts did not differ. Chemotherapy side effects including appetite, alopecia, emotional stability, and general weakness were reported as improved.

preliminary The report describes no randomisation procedure, and labels the comparison group inconsistently as both 'nontreated' and 'placebo'. Group sizes were unequal, patients knew what they were taking, and the primary endpoint was a surrogate immune marker rather than a cancer outcome.

Ahn et al., International Journal of Gynecological Cancer, 2004 [ref 5]

The limitations are substantial. The paper describes no randomisation procedure and refers to the comparison group inconsistently, as both a "nontreated" and a "placebo" group, which are not the same thing. Patients in the ABM group knew they were taking a supplement, so placebo effects cannot be excluded from the subjective side-effect measures. Group sizes were unequal. And NK cell activity is a surrogate marker: higher activity does not automatically translate to longer survival or reduced recurrence. With those caveats stated, this remains the only substantial human trial measuring immune biomarkers during active cancer treatment with ABM. The details of NK cell enhancement in cancer patients taking royal sun mushroom are explored in a separate article.

What Preclinical Models Show About Cancer Types

While epidemiological data is sparse, laboratory and animal studies have examined ABM against specific cancer types, providing biological plausibility for the mechanistic story.

Yu and colleagues demonstrated in 2009 that the broth fraction of ABM inhibited proliferation in both androgen-dependent and androgen-independent prostate cancer cell lines.^[6] Caspase 3 activity and DNA fragmentation were enhanced most in androgen-independent PC3 cells. In severe combined immunodeficient mice bearing PC3 xenografts, oral supplementation with the broth fraction (the one with a higher beta-glucan ratio) significantly suppressed tumor growth without adverse effects, with reduced proliferating cell nuclear antigen staining and reduced tumor microvessel density, indicating both antiproliferative and antiangiogenic activity.

Xu and colleagues published two studies on colorectal cancer. The 2024 study found that ABM polysaccharide (ABMP) significantly promoted CD8+ T cell activity in a co-culture system (P < 0.05) and inhibited the growth of intraperitoneal MC38 tumors in mice, but did not suppress subcutaneous tumors, suggesting the effect is tumor-stage dependent. Lipid-related spectral signal in the peritoneal tumor microenvironment fell after treatment while omega-3 polyunsaturated fatty acid content rose.^[7] Their 2025 follow-up, using 14 weeks of preventive ABMP intervention, found the anticancer effect was age-dependent: 8-month-old mice showed stronger tumor suppression than 12-month-old mice, again with reduced lipid content in the tumor microenvironment of the younger animals.^[8]

Not all preclinical data is positive, and the negative result is instructive. Ziliotto and colleagues tested ABM in a 20-week rat model of colon carcinogenesis, feeding crude A. blazei at 5% of the diet after dimethylhydrazine treatment.^[9] It did not suppress aberrant crypt foci development or crypt multiplicity, and there were no differences in colon tumor incidence between the treated groups. Their in vitro screen against nine human cancer cell lines found antitumor activity with dichloromethane/methanol and hexanic extracts at 250 µg/ml, but none at all with aqueous, methanol, ethyl acetate, or n-butanolic extracts. Since hot-water extracts are the dominant commercial form, this is a meaningful mismatch between what shows activity in a dish and what people actually swallow.

Evidence Position

1. Cell studiescompleted

   Extensive. Activity is extraction-method dependent: organic extracts active, aqueous extracts not (Ziliotto 2009).

2. Animal studiescompleted

   Positive in prostate xenograft (Yu 2009) and intraperitoneal colorectal models (Xu 2024, 2025); null in a rat colon carcinogenesis model (Ziliotto 2009).

3. Human case reportscompleted

   Five published cases, all hepatic injury, two fatal (Mukai 2006; Hisamochi 2013).

4. Small human trialscurrent

   One Phase I tolerability study in 78 survivors (Ohno 2011) and one non-randomised trial of 100 patients measuring NK activity (Ahn 2004).

5. Large randomised trialsmissing

   None. No randomised trial has measured a cancer outcome with ABM.

6. Meta-analysis of ABMmissing

   None. The 2021 meta-analysis often cited for ABM pooled dietary mushroom intake in general.

ABM has a deep preclinical base and a shallow clinical one. The highest rung reached with a cancer-relevant endpoint is a non-randomised trial measuring a surrogate immune marker in 39 treated patients. The rungs above it are empty.

Yu et al., 2009 [ref 6]; Xu et al., 2024 [ref 7] and 2025 [ref 8]; Ziliotto et al., 2009 [ref 9]; Mukai et al., 2006 [ref 12]; Hisamochi et al., 2013 [ref 13]; Ohno et al., 2011 [ref 4]; Ahn et al., 2004 [ref 5]

The Agaritine Question

Any discussion of ABM and cancer prevention must address agaritine, a hydrazine compound found in Agaricus species. Firenzuoli and colleagues raised this concern in their 2008 review, describing agaritine and its derivatives as "a well-known carcinogenic and toxic substance in animals" that "must be completely and fully evaluated".^[10]

This is not purely theoretical. The same review reports agaritine measured at up to 1,791 µg/g dry weight in a commercial ABM product, a level that prompted the Japanese Ministry of Health to demand a cessation of sales and a voluntary recall.

Agaritine is present in common button mushrooms (Agaricus bisporus) as well as ABM, and it degrades substantially during cooking and drying, so fresh mushrooms contain more than processed products. Dietary exposure from ordinary culinary mushrooms is generally considered low-risk by food safety authorities. But concentrated extracts taken at 3-5 g three times daily for months are not ordinary dietary exposure, and the paradox of consuming a potentially carcinogenic compound in a mushroom marketed for cancer prevention is not resolved by pointing at button mushrooms.

There is a further complication that undercuts the whole exercise of generalising about "ABM". Hetland and colleagues, reviewing the immunological literature in 2008, reported novel findings pointing to highly different biological potency between ABM extracts of different source and manufacture.^[11] If commercial preparations differ substantially in potency, and if agaritine content varies enough to trigger a product recall, then epidemiological data on "Agaricus blazei consumption" would be measuring a moving target even if someone collected it.

Where the Epidemiological Evidence Stands

The epidemiological case for mushrooms and cancer prevention is real but non-specific. The Ba et al. 2021 meta-analysis provides the strongest population-level evidence, showing a consistent inverse association across 17 studies and 19,732 cancer cases. That association applies to mushrooms as a food category.

For Agaricus blazei in particular, the human evidence consists of one origin account whose central claim was never measured, one consumer survey without clinical endpoints, one Phase I tolerability study with no efficacy measurement, one non-randomised trial measuring a surrogate immune marker, and five case reports of liver injury.

Hetland summarised the mechanistic state of knowledge in 2011: ABM is rich in immunomodulating beta-glucans and has shown antitumor, anti-infection, and antiallergic properties in mouse models, mediated through stimulation of innate immune cells including monocytes, NK cells, and dendritic cells, and through amelioration of a skewed Th1/Th2 balance.^[2] The biological mechanisms are plausible. The preclinical data is extensive. The human epidemiological data does not exist.

Research Gap

What would settle the question

What would it take to know whether Agaricus blazei prevents cancer?

○

A prospective cohort tracking ABM consumption specifically, not mushrooms generally

Every existing cohort measured dietary mushroom intake as a category. None separated species.

○

Cancer incidence as the endpoint, not an immune marker

The closest human endpoint reached so far is NK cell activity in 39 patients.

○

A standardised, characterised extract

Potency differs substantially between commercial preparations (Hetland 2008), and agaritine content has varied enough to trigger a product recall.

○

Adjustment for confounders that travel with supplement use

Health-conscious behaviour, income, and healthcare access all correlate with taking a daily supplement for years.

◑

Safety surveillance with a known denominator

A Phase I study established six-month tolerability in 78 patients, but hepatic injury cases have only ever surfaced through spontaneous reports.

No rung above 'small human trial' has been attempted in the roughly sixty years since the mushroom reached Japan.·A prospective incidence cohort would need 10 or more years of follow-up. None has been started.

Ba et al., 2021 [ref 1]; Hetland et al., 2008 [ref 11]; Ohno et al., 2011 [ref 4]; Firenzuoli et al., 2008 [ref 10]

Until those studies exist, the epidemiological case for ABM and cancer prevention rests on extrapolation from general mushroom data and inference from preclinical models. That is a reason for interest. It is not a reason for confidence.

The Bottom Line

Mushroom consumption broadly is associated with lower cancer risk in observational studies, with the strongest evidence for breast cancer (35% risk reduction in the highest consumption groups across 10 studies). None of that data is about Agaricus blazei. For ABM specifically, the human evidence is one consumer survey, one Phase I tolerability study, one non-randomised trial measuring an immune marker, and five case reports of severe liver injury including two deaths. The biological mechanisms are plausible and well documented in preclinical models, but the gap between "ABM activates NK cells in a lab" and "ABM prevents cancer in populations" has not been bridged by human data, and the widely repeated Piedade low-cancer-rate story turns out never to have been measured.

Frequently Asked Questions

Does Agaricus blazei prevent cancer?

No human study has demonstrated that Agaricus blazei prevents cancer, and no prospective study has ever tracked ABM consumption against cancer incidence. A 2021 meta-analysis of 17 observational studies found that higher mushroom consumption (all species combined, 19,732 cancer cases) was associated with 34% lower cancer risk (Ba et al., 2021), but that data is about mushrooms as a food category. Preclinical studies show ABM activates NK cells and suppresses tumor growth in some mouse models, and fails to in others.

What is the evidence for Agaricus blazei and breast cancer?

The Ba et al. 2021 meta-analysis found that the highest mushroom consumers had 35% lower breast cancer risk across 10 studies (pooled RR: 0.65; 95% CI: 0.52-0.81), and breast cancer was the only site with a statistically significant individual association. This data covers all mushroom species, not ABM specifically. No published study has examined ABM consumption and breast cancer incidence as a standalone question.

Is Agaricus blazei safe for cancer patients?

The picture is mixed and worth taking seriously. A Phase I study of 78 cancer patients in remission found ABM powder (1.8-5.4 g/day for 6 months) caused adverse events in 12% of patients, mostly nausea and diarrhea, with no dose-dependent toxicity (Ohno et al., 2011). Separately, five published case reports describe severe liver injury in people taking ABM extract, including two deaths from fulminant hepatitis (Mukai et al., 2006) and two cases of drug-induced liver injury resembling autoimmune hepatitis (Hisamochi et al., 2013). Case reports cannot establish how common this is, but the pattern is consistent enough to warrant physician involvement.

Did people in Piedade, Brazil really have low cancer rates from eating this mushroom?

There is no published study measuring cancer rates in Piedade. The peer-reviewed record documents that Agaricus blazei is native to the Piedade area of São Paulo state and that Takatoshi Furumoto sent samples to Japan in 1965 for investigation (Firenzuoli et al., 2008). The low-disease-rate comparison that usually accompanies this story has no data behind it: no control population, no standardised measurement, and no adjustment for confounders.

How popular is Agaricus blazei among cancer patients in Japan?

A nationwide cross-sectional survey found that 44.6% of Japanese cancer patients (1,382 of 3,100) used complementary therapies, and among those users, Agaricus products were the most frequently consumed at 60.6%, ahead of AHCC (8.4%) and Ganoderma lucidum (6.3%). Japan produces an estimated 100,000-300,000 kg of dried ABM annually, with 300,000-500,000 people taking it for cancer prevention or treatment (Ohno et al., 2011; Firenzuoli et al., 2008).

Does Agaricus blazei boost NK cell activity in cancer patients?

In one non-randomised trial of 100 gynecological cancer patients, those receiving ABM extract alongside chemotherapy had significantly higher NK cell activity (P < 0.002) compared to the group not receiving it (Ahn et al., 2004). The effect was specific to NK activity; lymphokine-activated killer activity, monocyte activity, and immune cell counts did not differ. NK cell activity is a surrogate immune marker, and whether this translates to improved cancer outcomes has not been tested.

Does Agaricus blazei contain carcinogens?

Agaricus blazei contains agaritine, a hydrazine derivative described in a 2008 review as a well-known carcinogenic and toxic substance in animals. The same review reported agaritine measured at up to 1,791 µg/g dry weight in one commercial product, prompting the Japanese Ministry of Health to demand cessation of sales and a voluntary recall. Agaritine is also present in common button mushrooms and degrades substantially during cooking and drying, but concentrated extracts taken daily for months are a different exposure from culinary use (Firenzuoli et al., 2008).

Should I take Agaricus blazei if I have cancer?

That is a decision for you and your treating physician, not something this article can answer. This is research summary, not medical advice. What the evidence supports saying is narrow: no human study has shown that ABM treats or prevents cancer; the one trial measuring an immune marker during chemotherapy was not randomised; and severe hepatic injury has been reported in cancer patients taking ABM extract, in several cases without their physicians knowing they were taking it. If you are using or considering ABM, tell your oncologist.

Sources & References

1. 1RTHM-00671·Ba, Djibril M et al. (2021). “Higher Mushroom Consumption Is Associated with Lower Risk of Cancer: A Systematic Review and Meta-Analysis of Observational Studies..” Advances in nutrition (Bethesda.Study breakdown →PubMed →↩
2. 2RTHM-00215·Hetland, Geir et al. (2011). “The Mushroom Agaricus blazei Murill Elicits Medicinal Effects on Tumor, Infection, Allergy, and Inflammation through Its Modulation of Innate Immunity and Amelioration of Th1/Th2 Imbalance and Inflammation..” Advances in pharmacological sciences.Study breakdown →PubMed →↩
3. 3RTHM-00121·Talcott, James A et al. (2007). “Measuring perceived effects of drinking an extract of basidiomycetes Agaricus blazei Murill: a survey of Japanese consumers with cancer..” BMC complementary and alternative medicine.Study breakdown →PubMed →↩
4. 4RTHM-00229·Ohno, Satoshi et al. (2011). “Phase I Clinical Study of the Dietary Supplement, Agaricus blazei Murill, in Cancer Patients in Remission..” Evidence-based complementary and alternative medicine : eCAM.Study breakdown →PubMed →↩
5. 5RTHM-00066·Ahn, W-S et al. (2004). “Natural killer cell activity and quality of life were improved by consumption of a mushroom extract, Agaricus blazei Murill Kyowa, in gynecological cancer patients undergoing chemotherapy..” International journal of gynecological cancer : official journal of the International Gynecological Cancer Society.Study breakdown →PubMed →↩
6. 6RTHM-00172·Yu, Ching-Han et al. (2009). “Inhibitory mechanisms of Agaricus blazei Murill on the growth of prostate cancer in vitro and in vivo..” The Journal of nutritional biochemistry.Study breakdown →PubMed →↩
7. 7RTHM-00916·Xu, Yongzhao et al. (2024). “Preventive intervention with Agaricus blazei murill polysaccharide exerts anti-tumor immune effect on intraperitoneal metastasis colorectal cancer..” International journal of biological macromolecules.Study breakdown →PubMed →↩
8. 8RTHM-00955·Xu, Yongzhao et al. (2025). “The Age-Dependent Anticancer Efficacy of Agaricus blazei Murill Polysaccharide in Colon Cancer..” Molecular nutrition & food research.Study breakdown →PubMed →↩
9. 9RTHM-00174·Ziliotto, Liane et al. (2009). “Screening for in vitro and in vivo antitumor activities of the mushroom Agaricus blazei..” Nutrition and cancer.Study breakdown →PubMed →↩
10. 10RTHM-00131·Firenzuoli, F et al. (2008). “The Medicinal Mushroom Agaricus blazei Murrill: Review of Literature and Pharmaco-Toxicological Problems..” Evidence-based complementary and alternative medicine : eCAM.Study breakdown →PubMed →↩
11. 11RTHM-00133·Hetland, G et al. (2008). “Effects of the medicinal mushroom Agaricus blazei Murill on immunity, infection and cancer..” Scandinavian journal of immunology.Study breakdown →PubMed →↩
12. 12RTHM-00105·Mukai, Hirofumi et al. (2006). “An alternative medicine, Agaricus blazei, may have induced severe hepatic dysfunction in cancer patients..” Japanese journal of clinical oncology.Study breakdown →PubMed →↩
13. 13RTHM-00287·Hisamochi, Akiko et al. (2013). “Drug-induced liver injury associated with Agaricus blazei Murill which is very similar to autoimmune hepatitis..” Clinical journal of gastroenterology.Study breakdown →PubMed →↩