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Alliums and Cancer, powerful and potent

Allium vegetables and spices including onion, garlic, leek and bunching onion fill the image, ready to be cooked with insparsed parsley to combat cancer.

They’re crisp and tasty and some may even bring you to tears when cooking… All for good reason! Nutrients and compounds found in plants of the Allium family are correlated with clear anti-cancer activity.

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Together with treatments prescribed and follow-up by licensed doctors, they will help you in the quest to prevent or fend off cancer.

A powerfully pungent family: smelly sulfur

Members of the Allium family have developed strong, volatile compounds as a way to repel pests both large and small.

The strong smell that is released whenever a leaf is crushed or a bulb wounded is a combination of compounds that become airborne when individual cells are destroyed.

These are enzymes called alliin lyase (or alliinase) and LF-synthase, released together with organosulfides. In intact cells, they’re stored separately, but when sent out into the air, they react and produce sulfenic acid. This particular type of sulfuric acid wafts up to the eyes and nose and triggers painful, tear-bringing messages in the body.

It is a particularly effective way to repel large herbivores and omnivores and also small insects like aphids and such. Plants of this class also show bactericidal, antiviral and fungicidal activity, thus impacting even the microscopic world.

Phenols and flavonoids

Flavonoids are a sub-class of phenols. The specific type of flavonoid in plants of the Allium family is called a flavenol.

Two of the most present flavenol compounds in the allium family are quercetin and kaempferol.

Quercetin and kaempferol are pigments, which means they impart color to the plant parts they’re in: yellow and red.

Alliums vs. Cancer

Collectively, organosulfides and phenols influence cancer in various ways and ingesting food items that contain them will lead you to benefit from some of their capabilities.

  • Note: although scientists increasingly value and consider the importance of one’s diet in preventing and curing cancer, it is critical to consult a doctor for every decision taken related to this disease. Self-treatment in the case of cancer is not an option.

How do these compounds affect cancer in the body? Let’s take a look at how these compounds impact the development of a cancer, from the prevention stage all the way to the influence on an active declared cancer.

Flavonols and organosulfides from onions, garlic, leek, chives and shallots (or scallions) may help:

  • scavenge free radicals – free radicals are molecules with an electric charge which leads them to steal electrons from neighboring cells and molecules, damaging their structure. Sometimes the damage affects the DNA of a cell, producing a mutation that may lead to cancer. Scavenging free radicals means that allium beneficial compounds trap and stabilize the charged molecule, neutralizing it. This is what is called “antioxidant activity“.


  • fight off bacteria, fungus and viruses – these microbes sometimes induce cancers when left untreated for too long or when the body is subject to multiple attacks on health. This activity is “antimicrobial” and in some respects “antibiotic“.


  • reduce severity and quantity of mutations – activity of allium compounds reduces occurrence of mutations and decreases their severity. This is “antimutagenic” activity.


  • help repair defects and mutations in cell DNA, thus reversing potentially cancerous cells into normal, healthier cells.


  • block or limit multiplication of cancerous cells – Allium plant family compounds reduce the capacity of cancerous cells to multiply. This property is called “antiproliferation“.


  • disrupt communication of and between cancer cells – cells naturally communicate with their environment, sending off messages about their needs. Interrupting this keeps tumors from being able to coax more nutrients from the blood flow, among other examples.


  • decrease inflammation – cancer is a form of permanent inflammation. Inflammatory response is useful in the case of wounds, but for cancers it just makes more of the body’s resources available for the malignant cells to use. This property goes by the name “anti-inflammatory“.


  • reduce onset and formation of tumors – cancer cells multiply and form nodes which are called tumors. Allium compounds that work against this are called “antitumorigenic” agents.


  • trigger or induce apoptosis – apoptosis is cell death. Old or damaged cells naturally undergo apoptosis, but cancer cells seem to “forget” to die. For these, a trigger is needed that starts the process of cell death, turning the cells into nutrients and waste that are absorbed by or flushed from the body.

Most of these were observed and documented in vitro against individual cells in a laboratory. Real-life in vivo situations differ from controlled-environment protocols, so a lot of research is still needed to definitively prove this activity.

How to prepare onion, garlic, leek, chives & shallot for top cancer-fighting impact

Eating these raw is best, but it’s also the most difficult given their strong taste and low digestibility for weak stomachs.

  • Try to include them chopped in preparations like guacamole, gazpacho, sprinkle them on salads or insert them in salad dressings or cottage cheese dips in moderate amounts if the taste is overbearing.

Cooked Alliums, whether steamed, fried, boiled, baked or else still retain some effectiveness, since quercetin, kaempferol and organosulfides are heat-resistant. However, the “cocktail” effect isn’t as powerful since many other compounds are destroyed by heat (vitamin C, for instance).

  • Note that when boiling, some of the compounds leak into the cooking water. This is fine if you’re preparing soup, but if you throw that water away, the amount of remaining beneficial nutrients decreases.

Incidentally, different portions of allium bulbs have been analyzed: the darker outwards layers, the center-most part, and the lower part closest to the roots are where these compounds are most concentrated. Try to slice as close to the roots as you can!

It has been documented that, for alliums, active ingredients vary in proportion and amount for each variety, even within a single species. As a general rule of thumb, the more colorful the bulb or leaf, the more active ingredients it contains. After all, the flavonols here are also pigments used as dyes in some countries.

But don’t focus all your attention to a single variety, even if its the darkest and most colorful: in some cases the ratios of active compounds will protect more against one type of cancer than the other. So you’ll want to vary varieties, too – pun intended!


Growing plants of the Allium family to access their cancer-related benefits

Apart from the therapeutic effect of growing a garden, having your own onion and garlic patch will ensure you have access to healthy, fresh, organic food.

Plants of the Allium family are very easy to grow:

Smart tip on which onions are healthiest

The darker the color of the onion, the more flavenols it usually contains.

Smart tip about alliums and cancer

Remember to talk to your doctor before making any drastic changes to your diet if you’re undergoing therapy. It’s important because the potent compounds of alliums, in rare cases, may interfere with medicines you might be taking.

Image credits (edits Gaspard Lorthiois):
CC BY-NC 2.0: Shelley & Dave Gunn
CC BY-NC-ND 2.0: darkcell, Meg Cotner
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