Shallots, Antioxidants and Cancer Research

Read this paragraph before the rest of the page. Shallots do not treat cancer. Shallots do not prevent cancer. Nothing on this page should be read as suggesting either, and nothing in the published literature supports either. What exists is a body of population-level observational research on allium-vegetable intake, and a body of laboratory work in which shallot extracts slow the growth of cultured cancer cells. Those are two legitimate kinds of research, and neither one gets you to a claim about what shallots do to a person with cancer or at risk of it.

The antioxidant part of the story is on firmer ground, because it is largely a claim about food composition rather than disease. Shallots really are measurably richer in total phenolics and quercetin than most common onions. That is worth knowing, worth acting on when you choose which allium to cook with, and much less dramatic than the word "antioxidant" has been made to sound.

Table of Contents

1. What This Page Will and Will Not Claim
2. The Antioxidant Chemistry: Two Separate Systems
3. Shallots Versus Onions: The Measured Difference
4. Bioavailability: Does Any of It Get In?
5. Anthocyanins and the Purple Bulb
6. Nrf2: The Indirect Antioxidant Story
7. The Antioxidant-Supplement Cautionary Tale
8. Allium Vegetables and Cancer: The Epidemiology
9. In-Vitro Antiproliferative Work on Shallot
10. Organosulfur Compounds and Cancer Mechanisms
11. What Observational Data Cannot Tell You
12. Cooking, Drying and Frying
13. Practical Guidance
14. What Would Change This Page
15. Cautions
16. Key Research Papers
17. Connections

What This Page Will and Will Not Claim

Being explicit about the boundary makes the rest readable.

What is supported:

• Shallots contain more total phenolics and more quercetin than most common onion varieties. Tier: food-composition analysis.
• Shallot quercetin is absorbed by humans in a measurable, comparatively efficient way. Tier: human pharmacokinetics.
• Shallot extracts slow the proliferation of cultured cancer cells and inhibit angiogenesis in laboratory models. Tier: preliminary — in vitro.
• Populations that eat more allium vegetables have, on average, lower rates of some cancers — most consistently gastric and colorectal. Tier: human observational.

What is not supported, and is not claimed here:

• That eating shallots reduces an individual's cancer risk.
• That shallots or shallot extracts have any role in cancer treatment, alongside or instead of oncological care.
• That shallots' antioxidant content translates into any specific clinical outcome.
• That any dose or preparation of shallot has been established for any purpose.

If you or someone close to you has a cancer diagnosis, the useful pages on this site are the disease pages and the honest answer is that food is supportive care and nothing more. Delaying or declining treatment in favour of a dietary approach is the single most harmful thing this genre of writing causes, and it is the reason this page is worded the way it is.

The Antioxidant Chemistry: Two Separate Systems

A shallot has two chemically unrelated antioxidant systems, and they work in genuinely different ways. Conflating them is why "antioxidant" has become a nearly meaningless word.

Direct radical scavengers: the polyphenols

Quercetin, kaempferol derivatives, anthocyanins and various phenolic acids can donate an electron or a hydrogen atom to a reactive species and neutralize it. This is what chemical antioxidant assays measure — ORAC, FRAP, DPPH and their relatives — and it is why shallots score well on those tests. Leelarungrayub, Rattanapanone, Chanarat and Gebicki published a quantitative evaluation of the antioxidant properties of garlic and shallot preparations in Nutrition in 2006, a direct comparison of the two.

The honest caveat about assay results. A high score in a test tube tells you about chemistry in a test tube. Plasma has its own large antioxidant capacity from urate, albumin and ascorbate, and dietary polyphenols are present in plasma at low nanomolar-to-micromolar concentrations after a meal. The idea that eating high-ORAC foods meaningfully raises your body's radical-scavenging capacity has not held up; the ORAC database was in fact withdrawn by the USDA on the grounds that the values were being misused in marketing. Polyphenols almost certainly do useful things. Direct radical scavenging in vivo is probably not the main one.

Indirect antioxidants: the organosulfur compounds

The sulfur compounds work by a different and more interesting route. Rather than neutralizing radicals themselves, they act as mild electrophilic stressors that activate the Nrf2 pathway, which switches on the cell's own battery of protective enzymes — glutathione S-transferases, NAD(P)H quinone dehydrogenase 1, heme oxygenase-1 and glutamate-cysteine ligase. The cell then makes its own antioxidants, in the right compartments, catalytically, for as long as the response lasts. That is a far better explanation of allium biology than the scavenging story, and it has its own section below.

Shallots Versus Onions: The Measured Difference

This is the one shallot-specific nutritional claim on this site that survives scrutiny cleanly, so it is worth stating carefully.

The primary finding. Yang, Meyers, van der Heide and Liu compared phenolic content, antioxidant activity and antiproliferative activity across a range of onion varieties and shallots, in the Journal of Agricultural and Food Chemistry in 2004. Shallots ranked at or near the top of the range for total phenolic content and antioxidant capacity, well above the mild sweet onion types, and their extracts were among the more active in the antiproliferative cell assays. Tier: laboratory food analysis with in-vitro cell work.

Why it is structurally true rather than a fluke. Flavonols concentrate in the outer fleshy layers and dry skin of an allium bulb. A shallot is small and clustered, so it has a much higher surface-to-volume ratio than a large onion — proportionally more of the bulb is outer layer. Add the anthocyanins in the purple skin and flesh, which yellow onions essentially lack, and you get a compositional difference that follows from the plant's shape and pigmentation rather than from a single measurement. Slimestad, Fossen and Vagen's survey "Onions: a source of unique dietary flavonoids" in the same journal in 2007 gives the underlying chemistry.

Two qualifications, because "shallots are higher in antioxidants" is repeated without either.

First, the comparison is against average and sweet onions, not against every onion. Strongly pigmented red onions and pungent yellow varieties test high too. The generalisation that holds is that pungent, deeply coloured alliums carry the most polyphenol — and shallots are reliably both.

Second, "shallot" does not fix the chemistry. Major, Perkovic, Palcic and colleagues showed in Antioxidants in 2022 that the phytochemical and nutritional composition of shallot species — comparing Allium × cornutum, Allium × proliferum and A. cepa Aggregatum Group, all sold locally as shallots — is both genetically and environmentally determined. Fredotovic and colleagues made the same point from the chemistry in Molecules in 2017, comparing the composition and biological activity of Allium cepa and Allium × cornutum methanolic extracts, and again in Plants in 2020 on organosulfur and amino-acid composition. Cultivar, growing conditions, soil and storage all move the numbers.

Bioavailability: Does Any of It Get In?

A food-composition number is only interesting if the compound reaches your bloodstream, and here the shallot has an unusually good answer.

Onion-family quercetin occurs mainly as glucosides — quercetin 4'-glucoside and quercetin 3,4'-diglucoside — and glucosides are absorbed efficiently in the small intestine, considerably better than the rutinoside form found in tea and buckwheat. Wiczkowski, Romaszko, Bucinski and colleagues studied this directly in humans using shallots, identified as Allium cepa L. var. aggregatum, in The Journal of Nutrition in 2008. Nemeth and Piskula reviewed onion flavonoid content, processing, absorption and metabolism in Critical Reviews in Food Science and Nutrition in 2007. Mullen, Edwards and Crozier profiled the methyl-, glucuronyl-, glucosyl- and sulpho-conjugates appearing in human plasma and urine after onion ingestion in the British Journal of Nutrition in 2006, and Lee and Mitchell compared quercetin pharmacokinetics from apples and onions in healthy humans in the Journal of Agricultural and Food Chemistry in 2012. Tier: human pharmacokinetics.

What those studies also show, and marketing omits. What circulates is not quercetin. It is a mixture of glucuronidated, sulfated and methylated metabolites, produced by the intestinal wall and the liver within minutes. Those metabolites have different — often much weaker — activity than the parent compound in the cell assays everyone cites. So a cell-culture experiment that bathes tumour cells in pure quercetin is not modelling what happens when you eat a shallot. This is not a small technicality; it is one of the main reasons polyphenol cell results have translated so poorly into human outcomes.

Anthocyanins and the Purple Bulb

The red-purple colour of Southeast Asian shallots comes from cyanidin glycosides. They contribute to total phenolic and antioxidant measurements, and they are the clearest visible difference between a purple shallot and a yellow onion.

Anthocyanins have their own research literature, mostly on berries, covering vascular function and inflammatory markers, with modest and inconsistent human results. Their bioavailability is poor — substantially worse than quercetin glucosides — and much of their apparent effect may come from colonic metabolites produced by gut bacteria rather than from the intact pigments. See Anthocyanins for that literature.

For shallots the practical implication is narrow and worth acting on: if you are choosing between shallot types, the deeply pigmented small Asian ones carry compounds the pale European ones largely do not. That is a real reason to prefer them, alongside the better reason that they taste more concentrated.

Nrf2: The Indirect Antioxidant Story

This is the most scientifically interesting part of allium biology and the part least discussed outside the literature.

How it works. Nrf2 is a transcription factor held inactive in the cytoplasm by its partner Keap1 and continuously degraded. Keap1 is rich in reactive cysteine residues. When an electrophilic compound modifies those cysteines, Nrf2 escapes degradation, moves to the nucleus, and switches on genes carrying an antioxidant response element — glutathione S-transferases, NAD(P)H quinone dehydrogenase 1, heme oxygenase-1, glutamate-cysteine ligase. Kensler, Wakabayashi and Biswal reviewed the pathway in the Annual Review of Pharmacology and Toxicology in 2007.

Where alliums come in. Thiosulfinates and their breakdown products are exactly the kind of thiol-reactive electrophiles that modify Keap1 cysteines. Chen, Pung, Leong and colleagues demonstrated induction of detoxifying enzymes by garlic organosulfur compounds through Nrf2, in Free Radical Biology and Medicine in 2004. Tier: preliminary — cell culture.

Why this framing is better. Three reasons. It is catalytic rather than stoichiometric — one signalling event induces enzymes that neutralize many molecules, rather than one antioxidant molecule quenching one radical. It works at the low concentrations food actually delivers. And it explains why alliums might matter without requiring the implausible claim that a vegetable meaningfully raises plasma antioxidant capacity.

Why it still is not a health claim. Nrf2 induction is a cell-culture observation. Whether a portion of shallot induces these enzymes in human tissue, by how much, for how long, and with what consequence, has not been established. There is also a real complication: Nrf2 signalling is protective in normal cells but constitutively active Nrf2 helps established tumours resist chemotherapy and oxidative stress. "Activate Nrf2" is not unambiguously good news, which is one more reason the shallot-and-cancer story cannot be simplified into advice.

The Antioxidant-Supplement Cautionary Tale

Before the cancer epidemiology, it is worth remembering what happened the last time an observational antioxidant association was turned into an intervention. This history is the strongest available argument for caution about every claim on this page.

Cohort studies in the 1980s and 1990s consistently found that people with higher intakes of beta-carotene, vitamin E and selenium had less cancer. Large randomized trials followed. The Alpha-Tocopherol Beta-Carotene trial and the Beta-Carotene and Retinol Efficacy Trial both found more lung cancer in smokers given beta-carotene. The SELECT trial, reported by Klein and colleagues in JAMA in 2011, found that vitamin E supplementation significantly increased prostate cancer risk. Bjelakovic, Nikolova, Gluud, Simonetti and Gluud published a systematic review and meta-analysis of mortality in randomized trials of antioxidant supplements for primary and secondary prevention, in JAMA in 2007, and found no mortality benefit — with a signal of increased mortality for some agents. Tier: large randomized controlled trials and meta-analyses of them.

The lesson, stated plainly. A strong, replicated observational association between an antioxidant-rich diet and lower cancer risk repeatedly failed to reproduce when the antioxidant was isolated and given as a supplement — and sometimes reversed. This is why this site does not recommend shallot extract capsules, and it is why "shallots are high in antioxidants" is presented here as a fact about food quality rather than as a health intervention.

Allium Vegetables and Cancer: The Epidemiology

Tier: human observational — cohort and case-control studies, pooled. Association, never causation.

Gastric cancer. This is the most consistent signal in the field. Zhou, Zhuang, Hu and colleagues published a meta-analysis in Gastroenterology in 2011 reporting that consumption of large amounts of allium vegetables was associated with reduced gastric cancer risk. Guercio, Galeone, Turati and La Vecchia published a critical review of the experimental and epidemiological evidence on gastric cancer and allium vegetable intake in Nutrition and Cancer in 2014 — and "critical" is the operative word: they examine the weaknesses as well as the signal.

Colorectal cancer. Turati, Guercio, Pelucchi, La Vecchia and Galeone published a meta-analysis of observational studies on colorectal cancer and adenomatous polyps in relation to allium vegetable intake in Molecular Nutrition and Food Research in 2014. Wu, Shi, Fang and colleagues reported a hospital-based matched case-control study in China finding allium vegetables associated with reduced colorectal cancer risk, in the Asia-Pacific Journal of Clinical Oncology in 2019.

Broader reviews. Galeone, Pelucchi, Levi and colleagues examined onion and garlic use and human cancer in The American Journal of Clinical Nutrition in 2006. Nicastro, Ross and Milner reviewed garlic and onions and their cancer prevention properties in Cancer Prevention Research in 2015 — a careful piece worth reading precisely because it is unenthusiastic where the evidence is weak. Sengupta, Ghosh and Bhattacharjee gave an overview of allium vegetables in cancer prevention in the Asian Pacific Journal of Cancer Prevention in 2004.

Three things to notice about this whole body of work.

1. It is about the allium category, not the shallot. Food-frequency questionnaires ask about onions and garlic. Shallots are usually not a separate line item, and in the Southeast Asian populations that eat the most shallots they are consumed as part of a spice paste rather than as a countable vegetable. The shallot's contribution is invisible in the data.
2. Case-control designs dominate, and they are the weakest design here. Asking people with a cancer diagnosis to recall their diet from years earlier invites recall bias, and hospital controls are rarely representative.
3. The strongest signal is in the highest-intake groups, typically Chinese and Mediterranean populations eating far more allium than a Western average. Effects seen at the top of an intake distribution do not predict what a marginal increase does for someone in the middle.

In-Vitro Antiproliferative Work on Shallot

Tier: preliminary — cell culture and laboratory models. None of this is evidence about people.

Anti-angiogenesis. Seyfi, Mostafaie, Mansouri and colleagues reported in-vitro and in-vivo anti-angiogenesis effects of shallot (Allium ascalonicum), identifying a heat-stable, flavonoid-rich fraction that potently inhibited angiogenesis, in Toxicology in Vitro in 2010. Angiogenesis inhibition is a legitimate anticancer mechanism — several approved drugs work this way — which is exactly why the distinction between a laboratory fraction and a vegetable matters so much here.

Anticancer and anti-inflammatory activity of shallot extract. Mohammadi-Motlagh, Mostafaie and Mansouri reported anticancer and anti-inflammatory activities of shallot (Allium ascalonicum) extract in Archives of Medical Science in 2011. Note the provenance caution that applies across the Iranian shallot literature: verify whether the plant used was A. cepa Aggregatum Group or A. hirtifolium / A. stipitatum, since "shallot" in Persian-language sources frequently means the latter.

Antiproliferative activity in the varietal comparison. The Yang 2004 study included antiproliferative assays alongside its chemical measurements, and shallot extracts were among the more active. Fredotovic and colleagues' work on Allium cepa and Allium × cornutum extracts in Molecules in 2017 similarly included biological-activity assays.

Why cell-culture antiproliferation is such a weak signal. Four reasons, all of which apply to essentially every plant extract that has ever been tested. The concentrations used are typically far above anything achievable in human plasma from food. Crude extracts contain cytotoxic compounds that would harm normal cells at the same concentrations — and cytotoxicity assays often do not distinguish "selectively kills cancer cells" from "kills cells." The parent compounds are metabolized before they reach any tissue in a real body. And a cell in a flask has no immune system, no stroma, no blood supply and no capacity to metastasize, which is to say it is missing most of what makes cancer difficult. Detergent kills cancer cells in a dish.

Organosulfur Compounds and Cancer Mechanisms

The mechanistic literature on allium organosulfur compounds and cancer biology is large and largely built on garlic-derived compounds. It is worth knowing because it is where the shallot claims ultimately come from.

Powolny and Singh reviewed multitargeted prevention and therapy of cancer by diallyl trisulfide and related allium-vegetable-derived organosulfur compounds in Cancer Letters in 2008. Hosono and colleagues reported that diallyl trisulfide suppresses proliferation and induces apoptosis in human colon cancer cells through oxidative modification of beta-tubulin, in the Journal of Biological Chemistry in 2005 — a well-characterized molecular mechanism. Proposed routes include phase-II detoxification enzyme induction via Nrf2, cell-cycle arrest, apoptosis induction, histone deacetylase inhibition and inhibition of carcinogen activation. Tier: preliminary — cell and animal.

The shallot problem with all of it. Diallyl trisulfide is a garlic compound. It derives from allicin, which derives from alliin, which is garlic's dominant cysteine sulfoxide. Shallots are dominated by isoalliin and produce propenyl- and propyl-derived compounds instead. The families are related and the mechanisms may well overlap — but the specific molecules in the specific papers are not the molecules a shallot makes. When a shallot page cites diallyl trisulfide research, that is a substitution, and it should be labelled as one.

What Observational Data Cannot Tell You

This section is short and it is the most important methodological point on the page.

People who eat a lot of allium vegetables are not a random sample. They eat more vegetables generally, more fibre, more legumes; they eat less ultra-processed food; they are more likely to cook from raw ingredients; in many cohorts they smoke less, drink less and are more physically active. Statistical adjustment can account for the confounders that were measured, imperfectly, and can do nothing at all about the ones that were not. Residual confounding is the default expectation in nutritional epidemiology, not an edge case.

On top of that, gastric cancer — the site with the strongest allium association — has a dominant known cause in Helicobacter pylori infection, alongside salt intake, smoking and preserved-food consumption. Populations differ enormously in H. pylori prevalence and in salt-preservation habits, and both correlate with the kind of diet in which allium intake varies. Untangling the allium contribution from that is genuinely hard, and the honest reviews in this literature say so.

The intervention trials of isolated antioxidants, described above, are the empirical demonstration that these concerns are not academic. That is why this page ends where it does.

Cooking, Drying and Frying

How you treat a shallot substantially changes its chemistry, which matters for anyone eating them with polyphenols in mind.

Ratseewo, Chumroenphat, Li and colleagues measured changes in chemical composition, volatile compounds and bioactive-compound retention in shallots under different drying methods, in Food Chemistry: X in 2025. The broad picture across allium processing research:

• Raw: full flavonol content, active alliinase, maximum thiosulfinate formation on cutting, vitamin C intact.
• Chopped and rested ten minutes, then cooked: alliinase has run to completion before heat destroys it, so the sulfur products are formed; flavonols largely survive, being reasonably heat-stable.
• Dropped whole or sliced straight into hot fat: alliinase is denatured before it acts, so little thiosulfinate forms; the flavonols remain.
• Deep-fried into crisps: enzyme destroyed, volatiles driven off, sugars caramelized, oil absorbed. Delicious, and the least chemically intact form.
• Boiled with the water discarded: water-soluble flavonol glucosides leach into the cooking liquid. If the liquid is part of the dish, as in a soup or a curry, nothing is lost.
• Pickled: a good compromise — close to raw, keeps well, and the tradition exists across Vietnam and Thailand for good reason.

Practical Guidance

• Choose small, deeply pigmented shallots when you have the choice. More anthocyanin, more flavonol per gram, better flavour.
• Peel conservatively. Papery skin off; keep the fleshy layer beneath it, which is the most flavonol-dense edible tissue in the bulb.
• Eat some raw or pickled. Vinaigrettes, quick pickles, sambals with raw shallot.
• Keep the cooking liquid. Curries, soups and braises retain what boiling would otherwise pour down the sink.
• Eat a range of coloured vegetables, not a single hero food. Every serious analysis of the diet-and-cancer literature points at overall dietary pattern rather than at any one item. Shallots earn their place in that pattern; they do not carry it.
• Do not buy shallot extract, "high-ORAC" shallot powder, or any allium antioxidant supplement. No established dose, no standardization, no human efficacy data, a real chance of the wrong species, and a randomized-trial history in this exact category that should give anyone pause.
• If you have a cancer diagnosis, tell your oncology team about every supplement you take. Concentrated antioxidants and Nrf2 activators have plausible interactions with radiotherapy and with several chemotherapy agents, whose mechanisms depend on oxidative damage. This is a real interaction concern and not a formality. Food-level shallot in cooking is not the issue; capsules are.

What Would Change This Page

• A cohort study that measured shallot intake as a distinct item, ideally in a Southeast Asian population where intake is high and lifelong, rather than folding it into "onions."
• Human data on whether a realistic portion of shallot induces Nrf2-dependent enzymes in accessible human tissue, and for how long.
• Quantitative characterisation of which thiosulfinates shallots actually produce, in what amounts, so that the garlic mechanistic literature could be assessed for transferability instead of assumed to transfer.

Note what is deliberately not on that list: a trial of shallots for cancer prevention or treatment. Such a trial would be neither feasible nor ethical on the current evidence, and its absence is not a gap waiting to be filled.

Cautions

Shallots are not a cancer treatment or a cancer prevention strategy. If you have a cancer diagnosis, no dietary change substitutes for oncological care, and delay is measured in outcomes. Eat well because eating well helps you tolerate treatment.

Supplement interactions with cancer treatment. Tell your oncology team about every supplement. Concentrated antioxidants and Nrf2 activators may plausibly interfere with radiotherapy and with chemotherapy agents that work through oxidative damage. Culinary shallots are not the concern; extract capsules are.

FODMAP intolerance and IBS. Shallots are high in fructans and are excluded during the elimination phase of a low-FODMAP diet; they reliably trigger bloating, wind and pain in people with irritable bowel syndrome. Shallot-infused oil with the solids strained out is generally tolerated, because fructans are not oil-soluble. See Irritable Bowel Syndrome.

Reflux and gastritis. Alliums, especially raw, are a common reflux trigger — relevant because this page suggests eating some raw. See GERD.

Anticoagulants, antiplatelets and surgery. Culinary shallots are fine on warfarin, a direct oral anticoagulant, clopidogrel or aspirin. Concentrated allium or quercetin supplements should be cleared with your prescriber and stopped one to two weeks before planned surgery.

Botulism risk from alliums in oil. Alliums held in oil at room temperature create the anaerobic, low-acid conditions Clostridium botulinum requires; garlic-in-oil has caused documented outbreaks. Refrigerate shallot oil or confit immediately, use within a few days, or freeze in portions.

Allergy and contact dermatitis. Allium allergy is uncommon but real and can cause oral allergy symptoms, rhinitis, asthma or, rarely, anaphylaxis. Occupational contact dermatitis is well documented in cooks and food handlers.

Toxic to dogs and cats. All alliums cause oxidative damage to red blood cells in dogs and cats, producing Heinz-body haemolytic anaemia; cats are especially sensitive. Cooked shallots, shallot powder, fried crisps and leftovers all count. Contact a vet if a pet eats a meaningful quantity.

Key Research Papers

Each entry names the plant and the study type. Links are PubMed topic searches so you see each paper alongside related work.

1. Shallot vs onion, food analysis with in-vitro cell work. Yang J, Meyers KJ, van der Heide J, Liu RH. Varietal differences in phenolic content and antioxidant and antiproliferative activities of onions. Journal of Agricultural and Food Chemistry, 2004. Find on PubMed
2. Shallot, human pharmacokinetics. Wiczkowski W, Romaszko J, Bucinski A, et al. Quercetin from shallots (Allium cepa L. var. aggregatum) is more bioavailable than its glucosides. The Journal of Nutrition, 2008. Find on PubMed
3. Shallot vs garlic, chemical assay. Leelarungrayub N, Rattanapanone V, Chanarat N, Gebicki JM. Quantitative evaluation of the antioxidant properties of garlic and shallot preparations. Nutrition, 2006. Find on PubMed
4. Shallot, in vitro and animal. Seyfi P, Mostafaie A, Mansouri K, et al. In-vitro and in-vivo anti-angiogenesis effect of shallot (Allium ascalonicum): a heat-stable and flavonoid-rich fraction of shallot extract potently inhibits angiogenesis. Toxicology in Vitro, 2010. Find on PubMed
5. Shallot, in vitro. Mohammadi-Motlagh HR, Mostafaie A, Mansouri K. Anticancer and anti-inflammatory activities of shallot (Allium ascalonicum) extract. Archives of Medical Science, 2011. Find on PubMed
6. Shallot species, composition. Major N, Perkovic J, Palcic I, et al. The phytochemical and nutritional composition of shallot species is genetically and environmentally dependent. Antioxidants, 2022. Find on PubMed
7. Onion and hybrid, composition and activity. Fredotovic Z, Sprung M, Soldo B, et al. Chemical composition and biological activity of Allium cepa L. and Allium × cornutum methanolic extracts. Molecules, 2017. Find on PubMed
8. Onion flavonoid chemistry. Slimestad R, Fossen T, Vagen IM. Onions: a source of unique dietary flavonoids. Journal of Agricultural and Food Chemistry, 2007. Find on PubMed
9. Human observational, meta-analysis. Zhou Y, Zhuang W, Hu W, et al. Consumption of large amounts of allium vegetables reduces risk for gastric cancer with a meta-analysis. Gastroenterology, 2011. Find on PubMed
10. Human observational, critical review. Guercio V, Galeone C, Turati F, La Vecchia C. Gastric cancer and allium vegetable intake: a critical review of the experimental and epidemiologic evidence. Nutrition and Cancer, 2014. Find on PubMed
11. Human observational, meta-analysis. Turati F, Guercio V, Pelucchi C, La Vecchia C, Galeone C. Colorectal cancer and adenomatous polyps in relation to allium vegetables intake: a meta-analysis of observational studies. Molecular Nutrition and Food Research, 2014. Find on PubMed
12. Human observational, case-control. Wu X, Shi J, Fang WX, et al. Allium vegetables are associated with reduced risk of colorectal cancer: a hospital-based matched case-control study in China. Asia-Pacific Journal of Clinical Oncology, 2019. Find on PubMed
13. Human observational, review. Galeone C, Pelucchi C, Levi F, et al. Onion and garlic use and human cancer. The American Journal of Clinical Nutrition, 2006. Find on PubMed
14. Review. Nicastro HL, Ross SA, Milner JA. Garlic and onions: their cancer prevention properties. Cancer Prevention Research, 2015. Find on PubMed
15. Garlic compound, mechanism. Powolny AA, Singh SV. Multitargeted prevention and therapy of cancer by diallyl trisulfide and related allium vegetable-derived organosulfur compounds. Cancer Letters, 2008. Find on PubMed
16. Garlic compound, mechanism. Hosono T, et al. Diallyl trisulfide suppresses the proliferation and induces apoptosis of human colon cancer cells through oxidative modification of beta-tubulin. Journal of Biological Chemistry, 2005. Find on PubMed
17. Mechanism, cell culture. Chen C, Pung D, Leong V, et al. Induction of detoxifying enzymes by garlic organosulfur compounds through transcription factor Nrf2. Free Radical Biology and Medicine, 2004. Find on PubMed
18. Pathway review. Kensler TW, Wakabayashi N, Biswal S. Cell survival responses to environmental stresses via the Keap1-Nrf2-ARE pathway. Annual Review of Pharmacology and Toxicology, 2007. Find on PubMed
19. Randomized trials, the cautionary evidence. Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C. Mortality in randomized trials of antioxidant supplements for primary and secondary prevention: systematic review and meta-analysis. JAMA, 2007. Find on PubMed
20. Randomized trial, harm. Klein EA, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA, 2011. Find on PubMed

Live PubMed searches

1. Allium ascalonicum antioxidant activity
2. Shallot antiproliferative and apoptosis studies
3. Anthocyanins in red onion and shallot
4. Allium compounds and Nrf2 induction
5. Allium vegetables and cancer risk in cohort studies
6. Quercetin metabolites and their activity in plasma

Connections

• All Herbs
• Shallot Benefits hub — the evidence tiers and the three plants called "shallot."
• Shallot (Allium ascalonicum) — botany, taxonomy, active compounds and culinary use.
• Quercetin — the flavonol shallots supply in a well-absorbed form.
• Anthocyanins — the pigments behind the purple bulb and part of its phenolic edge.
• Antioxidants — why the word means less than it appears to.
• Garlic — the source of the diallyl-sulfide mechanistic literature this page declines to borrow silently.
• Onions — the shallot's own species and the comparison used in the varietal studies.
• Stomach Cancer — the site with the strongest allium epidemiological association, and its real risk factors.
• Colorectal Cancer — the other site with pooled observational data.
• Helicobacter pylori — the dominant known cause of gastric cancer, and a major confounder in the allium data.
• Vitamin C — a shallot nutrient, and another antioxidant whose supplement trials disappointed.
• Turmeric — a parallel case of strong in-vitro anticancer data that has not translated in humans.

This page is educational and is not medical advice. Shallots do not treat or prevent cancer, and no claim on this page should be read that way: the human data is observational and concerns allium vegetables as a category, while the shallot-specific work is confined to cell culture and laboratory models. If you have a cancer diagnosis, no food or supplement substitutes for oncological care, and delay causes harm. Tell your oncology team about every supplement you take — concentrated antioxidants have plausible interactions with radiotherapy and with chemotherapy agents that work through oxidative damage. Culinary shallots in your cooking are not the concern; capsules are.

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