Vietnamese Coriander and the Anti-Aphrodisiac Claim

Vietnamese tradition holds, firmly and specifically, that eating rau răm dampens sexual desire. This page takes that claim seriously enough to actually check it — and finds two things worth knowing. First, there is no research on it at all, in either direction, and a search aggressive enough to catch a single stray abstract still comes back empty. Second, there is real clinical-trial literature that looks like it might be about this exact question — a human trial on "Polygonum" and sexual performance is genuinely findable — and it is not about this plant, uses a different formula, and points the opposite way. That trap is worth walking through in full, because it is exactly the kind of citation a less careful source would pick up.

Table of Contents

  1. The Claim Itself
  2. What a Real Search Returns
  3. The Kesum Trap: A Different Plant, Same Name
  4. The Sexual-Performance Trial — And Why It Is Not About Rau Răm
  5. A Second Warning: The Retracted Mood Trial
  6. Could There Be a Real Mechanism? Testing the Chemistry Honestly
  7. Botanicals That Actually Have Anti-Androgen Trials
  8. A Non-Pharmacological Explanation Worth Taking Seriously
  9. The Companion Belief: Pregnancy and Menstruation
  10. Where This Leaves You
  11. Key Research Papers
  12. Connections

The Claim Itself

The belief is specific, old and widely shared. In Vietnamese food culture, rau răm is said to suppress ham muốn — sexual desire — strongly enough that eating it in quantity is not neutral. The claim travels with a folk rhyme pairing the herb with hột vịt lộn, the balut-style fertilised duck egg it is always served beside, and it is commonly said that Buddhist monks cultivated and ate rau răm on purpose, to support celibacy. A companion belief, covered separately below, holds that the herb also disturbs menstruation and endangers pregnancy.

This is worth treating as a real question rather than dismissing as folklore or accepting as fact. Traditional food beliefs are sometimes tracking something real — willow bark and aspirin is the model case everyone reaches for — and sometimes they are tracking something else entirely: a cultural association, a coincidence of timing, or a story that became self-sustaining because it was memorable and useful (a monastery has good reason to promote a food story that supports its residents' vows, whether or not the food does anything). The only way to tell the difference is to look.

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The main rau răm page already states plainly that no research exists on this claim. This page pushed harder on that question specifically, because "nobody has looked" is exactly the kind of claim worth re-verifying rather than repeating. Four separate searches were run against the live PubMed database, each combining the plant's two valid scientific names — Persicaria odorata and Polygonum odoratum Lour., title/abstract-scoped so a search cannot be padded by an unrelated paper's MeSH indexing — against every plausible term: libido, aphrodisiac, testosterone, estrogen, androgen, sexual, sperm, fertility, reproductive. A fifth search dropped the Latin entirely and searched the plain-language terms "rau ram" and "Vietnamese coriander" against "libido," "aphrodisiac," "sexual" and "anaphrodisiac," in case something was indexed only under the common name.

The combined result across all five searches: one nominal hit, and it is not real. A single record surfaced for "Persicaria odorata" plus "reproductive" — not because the paper discusses reproduction, but because a co-author's institutional affiliation happens to be a French physiology-of-reproduction research unit. Read the paper itself and it is an antioxidant and cytotoxicity screen with no reproductive or hormonal content whatsoever. Once that false positive is set aside, the true count is zero. No study, in any species, has ever measured what rau răm does to testosterone, estrogen, sperm parameters, libido, menstrual cycling, uterine tissue, or pregnancy outcome.

That is a stronger and more specific statement than "no human trials exist," which is true of nearly every claim on this herb. This is: no trial of any kind, in any organism, on any endpoint remotely related to this specific claim. Compare that to the plant's one genuine mechanism study — isolated rat ileum, reducing smooth-muscle contraction — which at least investigated a real physiological system relevant to a real traditional use (digestion). Nothing comparable exists here. The libido claim has generated no experiment of any kind in the roughly seventy years it has been the subject of published ethnobotanical notice.

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The Kesum Trap: A Different Plant, Same Name

Here is where this page earns its keep. Malay and Indonesian speakers call rau răm daun kesum or simply kesum — a name already noted on the main page. What is not noted there, and matters a great deal for exactly this claim, is that kesum is also the common name of a completely different plant: Persicaria minor (Huds.) Opiz, synonym Polygonum minus Huds., sometimes called pygmy smartweed or small water pepper in English. It is a distinct species in the same genus, native to the same region, used in some of the same dishes (it too turns up in asam laksa in parts of Malaysia), and — this is the load-bearing fact — it has a real, substantial, commercially-developed pharmacology research program in Malaysia that Persicaria odorata does not.

A live search confirms these are cleanly separate literatures, not an artefact of sloppy indexing. Title/abstract-scoped searches for "Persicaria odorata" and "Persicaria minor" return non-overlapping sets of papers; the same is true for "Polygonum odoratum" against "Polygonum minus." Not one PMID appears in both lists. Malaysian research groups — chiefly at Universiti Sains Malaysia and Universiti Kebangsaan Malaysia — have developed standardised Polygonum minus extracts under at least two commercial brand names, Biokesum® and LineMinus™, and tested them for antioxidant activity, anti-stress and cortisol effects in a zebrafish model, cognitive and mood outcomes in a human trial, and — the one that matters most here — sexual performance in men.

None of that is rau răm. If a marketer, a supplement label, or a casually-sourced blog post cites "Polygonum" research on sexual function, mood or cognition, there is a real chance it is describing Polygonum minus, not Polygonum odoratum — two plants that share a Malay common name, a genus, and a region, and nothing else relevant to this claim. The next two sections walk through exactly what that research says, because it is real, it is findable, and reading it correctly requires knowing which plant it is actually about.

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The Sexual-Performance Trial — And Why It Is Not About Rau Răm

In 2014, a genuine randomized, double-blind, placebo-controlled human trial was published under the title "Effects of a Proprietary Freeze-Dried Water Extract of Eurycoma longifolia (Physta) and Polygonum minus on Sexual Performance and Well-Being in Men." Men aged 40–65 took a 300 mg daily combination product for twelve weeks; twelve completed on the active arm, fourteen on placebo. The active group showed statistically significant improvement (p < 0.05) on the Sexual Intercourse Attempt diary, the Erection Hardness Scale, the Sexual Health Inventory for Men, and the Aging Male Symptom scale, with no attributable adverse events.

Read that result carefully and three things stand out, each of them a distinct trap:

Put together: this is a real trial, of a real product, showing a real result — about a different plant, in a blend with a named aphrodisiac, pointing away from the claim it might seem to support. It belongs in this article as a warning, not as evidence, and every one of those three qualifications needs to travel with it wherever it is cited.

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A Second Warning: The Retracted Mood Trial

The same confusable plant carries a second cautionary tale, this one about research integrity rather than species identity. In 2015, a Malaysian group published a randomized, double-blind, placebo-controlled trial of Polygonum minus extract (branded LineMinus™) on cognitive function and psychosocial status in thirty-five middle-aged women, reporting improvements on a digit-span memory test, a quality-of-life subscale, and (in participants with good baseline mood) verbal and full-scale IQ scores on the Wechsler Abbreviated Scale of Intelligence.

Two years later, in 2017, the journal retracted the paper. The retraction notice is a bare formal statement — it names the article being withdrawn and gives no public reason. This page will not guess at one; a confident explanation would be exactly the kind of invented number the rest of this site's evidence standards refuse to produce. What can be said honestly: a real, published, peer-reviewed human trial of a Polygonum minus extract on cognitive and mood outcomes was formally withdrawn by its own journal, and any citation trail that still includes it without noting the retraction is out of date. It is included here specifically so a reader who encounters it elsewhere recognises it.

A separate, non-retracted Polygonum minus study is worth a brief mention for completeness: a 2022 zebrafish experiment testing the same standardised extract (Biokesum®) in a chronic-stress model found reduced cortisol and a significant change on one of four behavioural anxiety measures, comparable in direction to the antidepressant fluoxetine used as a positive control. It is animal data, on the wrong plant, for a mood claim — not a sexual-function claim — and it is mentioned here only to complete the picture of how much real pharmacology attaches to Polygonum minus that has nothing to do with rau răm.

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Could There Be a Real Mechanism? Testing the Chemistry Honestly

Absence of research is not automatically absence of plausibility, so it is worth asking directly: does rau răm's actual chemistry give any reason to expect a hormonal or sexual effect, even an untested one?

The documented compounds, covered in more chemical detail on the essential-oil page, are dominated by aliphatic aldehydes (decanal, dodecanal) responsible for the aroma, the sesquiterpene dialdehyde polygodial responsible for the peppery bite, and a background of common dietary flavonoids and phenolics — quercetin, myricetin, gallic acid, catechins. None of that chemistry is unusual; the same flavonoid class is present in tea, onions, apples, and dozens of other foods eaten in far larger quantities than a garnish herb, and dietary flavonoids as a category have been studied elsewhere for weak, inconsistent, dose-dependent interactions with hormone-related pathways — a large and genuinely mixed literature that says essentially nothing about any one minor dietary source in isolation.

This page will not attempt to turn that into an argument either way, and it is worth saying explicitly why not. Two of the papers describing this herb's phenolic content report it as milligrams of quercetin- or gallic-acid-equivalent per gram of concentrated ethanolic extract — not per gram of fresh leaf, and with no published extraction yield that would let a reader convert one figure into the other. Building a dose calculation from an extract concentration to a culinary-garnish exposure, without that conversion factor, would be inventing a number this page cannot stand behind. So it refuses to: there is no responsible way to say whether a normal serving of rau răm delivers a chemically meaningful dose of anything hormonally active, and no source claiming otherwise has done that arithmetic honestly either.

What can be said cleanly: nothing in rau răm's known chemistry is a recognised anti-androgen, anti-estrogen, or libido-suppressing compound class in the way the next section's comparator herbs contain recognised ones. The plant's chemistry gives no particular reason to expect the folk claim to be true, and no particular reason to expect it to be false. It has simply never been tested.

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Botanicals That Actually Have Anti-Androgen Trials

It helps to know what real evidence for a claim like this actually looks like, because it throws rau răm's total absence of data into sharper relief. A small number of common plants genuinely have been tested for anti-androgen or libido-related effects, in humans, with named mechanisms:

None of this means spearmint or licorice are strong or reliable anti-androgen treatments — the spearmint trial itself is small, short, and mixed on its own primary clinical endpoint. The point is narrower and more useful: these are what a genuine, if modest, evidence base for a claim like this looks like. Rau răm does not have one.

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A Non-Pharmacological Explanation Worth Taking Seriously

If there is no chemistry and no trial, why has the belief persisted for generations across an entire food culture? One answer that does not require any pharmacology at all is worth naming, because sexology research supports it as a real, measurable phenomenon: expectation itself can alter genital arousal response.

A 2016 study in the Journal of Sexual Medicine used a conditioning paradigm — pairing sexual imagery with a physical stimulus, then measuring genital response (penile circumference in men, vaginal pulse amplitude in women) under different cognitive framing instructions — and found that a deliberate cognitive strategy to upregulate expectation of sexual reward measurably increased genital arousal response in both sexes. The mechanism runs in both directions: if upregulating expectation increases measured arousal, the reverse — a culturally reinforced expectation that a food will dampen desire — is a physiologically plausible route to the same outcome showing up as real, even with zero pharmacological involvement from the food itself.

This is speculation about mechanism, not a claim that this is what is actually happening with rau răm — nobody has tested that either, and this page will not pretend otherwise. But it is a genuinely different, non-mystical, evidence-grounded way a widely-shared belief about a specific food could produce a real subjective effect on the people who hold it, entirely independent of whether the plant does anything at all. A monastery that tells its residents rau răm supports their vows, and residents who eat it believing that, do not need the plant to do anything for the belief to feel confirmed.

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The Companion Belief: Pregnancy and Menstruation

The libido claim travels with a related one: that rau răm in quantity disturbs menstruation and can cause miscarriage, and that pregnant women should avoid it. This is the same shape of claim — an emmenagogue and abortifacient reputation — attached to many warming, aromatic culinary herbs across many traditions, and it carries the same evidentiary status as the libido belief: no study of any kind, in any species, has examined rau răm and uterine activity, menstrual cycling, or pregnancy outcome. It is not "unproven" in the sense of having failed a test. It has never been given one.

The practical guidance is the same one the main page already gives, and it holds regardless of which direction the belief runs: culinary garnish amounts are what the cuisine has always used, with generations of ordinary exposure behind them and no signal of harm; medicinal-strength quantities or extracts have no safety data at any level and should not be taken during pregnancy on that basis alone, not because a specific harm has been demonstrated, but because nothing has been ruled out either.

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Where This Leaves You

Three findings, stated as plainly as the evidence allows:

  1. The claim is untested, not disproven. A search deliberately built to catch even a single stray record on rau răm and sexual function, in either direction, returns nothing real.
  2. The nearest-sounding real research is about a different plant. Polygonum minus ("kesum") has an actual clinical-trial history touching sexual performance and mood — one trial not retracted and pointing toward improved performance in a blend with a known aphrodisiac, one trial retracted outright — and confusing it with Polygonum odoratum (rau răm) is an easy, specific, documented mistake to make.
  3. There is no basis, chemical or clinical, to act on the folk belief either way. Eating rau răm as Vietnamese cuisine has always used it is simply eating a garnish herb. Taking it deliberately to suppress desire, or avoiding it deliberately because you want the opposite, both assume a pharmacological effect that has never been demonstrated to exist.

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Key Research Papers

  1. Udani JK, George AA, Musthapa M, Pakdaman MN, Abas A. Effects of a proprietary freeze-dried water extract of Eurycoma longifolia (Physta) and Polygonum minus on sexual performance and well-being in men: a randomized, double-blind, placebo-controlled study. Evidence-Based Complementary and Alternative Medicine. 2014;2014:179529. — PubMed. Different species, blended formula, opposite direction — see full discussion above.
  2. Shahar S, Aziz AF, Ismail SN, et al. The effect of Polygonum minus extract on cognitive and psychosocial parameters according to mood status among middle-aged women: a randomized, double-blind, placebo-controlled study. Clinical Interventions in Aging. 2015;10:1505–1520. [RETRACTED 2017] — PubMed.
  3. Retraction notice for the above. Clinical Interventions in Aging. 2017;12:1635. — PubMed.
  4. Abdul Rahim N, Nordin N, Ahmad Rasedi NIS, et al. Behavioral and cortisol analysis of the anti-stress effect of Polygonum minus (Huds) extracts in chronic unpredictable stress (CUS) zebrafish model. Comparative Biochemistry and Physiology C. 2022;256:109303. — PubMed.
  5. Grant P. Spearmint herbal tea has significant anti-androgen effects in polycystic ovarian syndrome: a randomized controlled trial. Phytotherapy Research. 2010;24(2):186–188. — PubMed. A real human anti-androgen RCT — on a different, well-characterised botanical.
  6. Update on plant-derived anti-androgens (review). International Journal of Endocrinology and Metabolism. 2012. — PubMed. Surveys the genuine plant anti-androgen literature; rau răm is not in it.
  7. Assessment of endocrine disruption potential of essential oils of culinary herbs and spices involving glucocorticoid, androgen and vitamin D receptors. Food & Function. 2018. — PubMed. Shows the receptor-binding assay methodology that exists and has never been applied to rau răm.
  8. Brom M, Laan E, Everaerd W, Spinhoven P, Trimbos B, Both S. The influence of emotion upregulation on the expectation of sexual reward. Journal of Sexual Medicine. 2016;13(1):105–119. — PubMed.
  9. Duangjai A, Parseatsook K, Sajjapong W, Saokaew S. Assessment of Polygonum odoratum Lour. leaf extract on rat's ileum contraction and the mechanisms involved. Journal of Medicinal Food. 2020;23(11):1169–1175. — PubMed. The one real mechanism study that exists on this actual species — digestive smooth muscle, not hormones.
  10. Khuayjarernpanishk T, Sookying S, Duangjai A, et al. Anticancer activities of Polygonum odoratum Lour.: a systematic review. Frontiers in Pharmacology. 2022;13:875016. — PubMed. The one systematic review that exists on this species covers cancer cell lines, not reproduction.

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Connections

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