Onions, garlic, leeks, shallots, and chives. They’ve appeared in paintings found inside Egyptian tombs, are referenced in religious texts, and were prized as strength-enhancers by athletes at the Olympic Games in ancient Greece. Also known by their genus name, Allium, these vegetables are the backbone of nearly every culture’s food tradition.
“The healing power of alliums has been recognized for centuries,” says functional-medicine physician Terry Wahls, MD, author of The Wahls Protocol.
Traditional Chinese Medicine and Ayurveda have long celebrated alliums for their antimicrobial, antibacterial, and anti-inflammatory properties. Both healing traditions consider these vegetables stimulating and “heating,” and Ayurveda views them as helpful for stoking the digestive fire it calls agni. Ayurvedic practitioner Vanashree Belgamwar describes their potency: “Sharp, strong, and pungent, alliums are a rajasic [stimulating] food that can support digestion.”
Hundreds of clinical trials underscore alliums’ salutary reputation, including studies showing that a diet rich in alliums lowers the risk of gastric cancer and possibly cancers of the larynx and esophagus.
Some alliums are also heart protective, reducing cholesterol and lowering blood pressure.
“It’s striking how such a humble group of vegetables can be so good for us,” says functional-medicine internist Gregory Plotnikoff, MD, MTS, FACP. “We are conditioned to think that anything this healthful must come in a pill.”
The secret seems to be in the trait that connects all alliums — their naturally occurring sulfur compounds, or organosulfides.
When we eat alliums, these organosulfides help us synthesize glutathione, an essential antioxidant that’s known for neutralizing free radicals, supporting the immune system, and detoxifying the liver.
Organosulfides also nourish mitochondria, the engines that power cells, says Wahls. “Sulfur removes toxins from cells and helps create protein and connective tissue necessary for healthy joints, hair, skin, and tendons.”
Among the most well-studied organosulfides is allicin. Found in garlic, it protects the body’s DNA from mutations, scavenges free radicals, and stomps out tumor growth.
When it comes to their nutrient density, onions and garlic top the list. The latter is so powerful that Wahls considers two cloves equivalent to a cup of any other vegetable. Still, all alliums are beneficial.
Discover just how mighty these humble vegetables really are.
Julia Child once said she found it hard to imagine a civilization without onions. This makes sense, as they’re the third most commonly consumed vegetable worldwide after tomatoes and cabbage.
Their widespread, enduring popularity may be partly due to their capacity to sustain human health. Onions are a rich source of phytonutrients. This includes the flavonoid antioxidant quercetin, which may help lower blood pressure and reduce the risk of heart attack, as well as many types of cancer, particularly colon cancer.
This antioxidant is best known as an anti-inflammatory, and many integrative-healthcare practitioners recommend quercetin for allergy symptoms, because it interrupts the production of the histamine that triggers swollen sinuses, sneezing, and watery eyes.
“I encourage people to eat quercetin-rich foods if they begin to show signs that their histamine is ramping up,” says functional nutritionist Jesse Haas, CNS, LN. “The quercetin in onions is super exciting for people with allergies.” (For more on histamines, see “What You Need to Know About Histamine Intolerance“.)
There’s no recommended dietary allowance for quercetin, but health experts estimate that we need between 5 and 40 mg a day. A medium-size onion contains between 22 and 51 mg.
Although cooking onions may decrease their quercetin levels somewhat, we still absorb two to three times more quercetin from onions than we do from tea and apples, which are other good sources.
In addition to quercetin, onions are an important source of organosulfides — detectable in the potent fragrance released when they’re chopped. An intact onion is nearly odorless because its cell walls isolate the odiferous sulfur compounds into tiny pockets, which keeps them dormant. Cell walls also cordon off the enzymatic catalyst alliinase, which releases sulfur’s sharp smell and taste.
“Onions are a classic example of a vegetable that doesn’t achieve its full flavor potential until its cells are destroyed, first by chopping and then by heat,” explains plant biologist Stephen Goff, PhD.
Cutting an onion breaks down the walls that separate the sulfur compounds from the alliinase. When the two mix, the telltale smell is unleashed. A chopped onion’s flavor is intensified by the amount of time it sits. “The process takes about 10 minutes,” says Goff, “so don’t rush your freshly chopped onions into the sauté pan.”
Those tears many of us shed while chopping are triggered by the organosulfides. Cooking lore is full of no-cry onion hacks — chewing gum, wearing goggles, clamping a slice of bread between your teeth. Yet Goff believes the best way to avoid stinging eyes is to chill onions (for maybe an hour in the fridge) before cutting.
“Every 18-degree F drop in temperature slows the enzymatic activity by half,” he says. “Get them cold and you’ll never cry while chopping onions again.” As they warm up, the sulfuric commingling magic will still happen . . . but your eyes will be spared.
As for eating them, onions fall into two camps — sweet and storage. Sweet onions are milder than storage onions and include Vidalia, Maui, and Walla Walla. Storage onions are more pungent and store well (hence the name); they include the red, white, and yellow onions that most of us are accustomed to using.
The second most popular allium, garlic is by far the most pungent, releasing a hundredfold more fragrant compounds than its relatives. The stinking rose also delivers the most health benefits, and its powerful odor is partly to thank.
When we cut, mince, or press a clove of garlic, the ruptured cellular matrix releases alliin, a sulfur-containing amino acid, and alliinase, an enzyme. Together they make allicin, the compound behind garlic’s potent fragrance and its reputation as a cure-all. (As with onions, wait 10 minutes after you chop the garlic to allow its allicin to blossom.)
Thanks to its curative capacities, garlic is one of the most heavily researched herbal medicines on the planet. Allicin combats more than 300 disease-causing microbes, as well as bacterial and viral infections, including methicillin-resistant staph infections. Research suggests that 1 mg of allicin is the equivalent of 15 international units of penicillin, and one clove of garlic houses up to 13 mg of allicin.
Garlic also helps prevent cancer from taking hold. Studies show allicin not only alters the proteins that tumors need to flourish (thereby slowing their growth), it also encourages apoptosis (cell death) in cancerous cells. Both fresh garlic and aged garlic extract have been found to be protective against gastric, esophageal, and laryngeal cancers specifically.
Garlic also supports the heart. While researchers don’t yet fully understand the mechanism, decades of studies show that garlic is capable of reducing cholesterol and lowering blood pressure.
No doubt garlic’s anti-inflammatory compounds are involved here. Their capacity to reduce levels of C-reactive protein, a key inflammatory marker, gives garlic the potential to address hundreds of illnesses, including most autoimmune disorders. Aged black garlic appears to be especially effective.
Given the power of organosulfides, garlic’s widespread use as a therapeutic is no surprise. “Garlic is the most concentrated source of organosulfides you can eat,” says Wahls. She uses garlic routinely and ups her game if she starts to feel a virus coming on. “If I’m wanting garlic’s antiviral properties, I’ll chew a couple of raw garlic cloves every two hours and chase them down with a big glass of water.”
On that note, even garlic breath is related to its health benefits. Many of its organosulfides waft up the gastrointestinal tract for hours after ingestion. The digestive system is beyond the reach of breath mints, so sometimes the only real option is to wait for garlic to wend its way through. (This can take anywhere from six hours to a couple of days.)
Other sulfur compounds in garlic are absorbed into the bloodstream and excreted through the skin. Wahls’s advice is to make sure everyone in your family is eating garlic, too. “Especially anyone you plan to kiss.”
If you do want to mute the lingering smell of garlic, try eating an apple. The enzymes that make apples turn brown when exposed to oxygen are also able to defuse some of garlic’s odor. Chewing fresh mint or raw lettuce can help, too. Know that the smell of raw garlic lingers longer than cooked.
If you object to the odor enough to avoid garlic altogether, consider supplementing with garlic extract to get its benefits. About 400 mg twice a day is ideal.
Common in French cuisine, leeks are a type of onion that does not form a bulb. Instead, they look like gargantuan green onions, with large, thick leaves that grow above ground while their tender heads stay buried in soil, where they’re protected from the sun.
Leeks are a good source of oligosaccharides, a type of carbohydrate that acts as a prebiotic. (Onions and garlic also contain them.) Prebiotics feed the healthy bacteria in the colon. “Prebiotics selectively stimulate beneficial microorganisms in the colon, which may improve digestion, among other health benefits,” says Haas.
A leek requires a little extra care to clean. To remove dirt and debris before cooking, try slitting the white part lengthwise, from top to bottom. Rinse the head under running water while gently pulling apart the layers to rid them of grit. If you’re still seeing dirt, slice the leeks, then throw them in a colander and give them a good rinse.
All parts of leeks are edible, but it’s the white portion that develops the most flavor. Often found in stocks and soups, leeks have a mild taste that imparts a sweet, earthy dimension.
In addition to sulfur compounds, scallions are a rich source of vitamin K, which aids in blood clotting. They look like a more delicate version of the leek, and both the green and white portions are edible. The green end is milder and more tender; it’s a lovely garnish when you want some onion flavor but don’t need the full wallop of raw red or white onion. Use the white portions as you would larger onions.
Like garlic bulbs, shallots feature one head that segments into several cloves, each wrapped in a thin skin. They boast some of the highest concentrations of antioxidants in the allium family.
Flavorwise, they contain notes of both onion and garlic, minus the sulfuric sharpness. Like leeks, they’re common in French cooking (they’re nearly ubiquitous in vinaigrettes), and they bring an earthy nuance to dishes.
When cooking, treat shallots as you would garlic — use low heat and avoid browning. Like garlic, shallots tend to dry quickly, so store them in a cool, dark place.
A slender, bright-green herb, chives are generally used fresh to impart a hint of onion flavor to a recipe — often egg or salad dishes — without overpowering other delicate ingredients. They’re another great source of vitamin K. Use sharp scissors to cut fresh chives into a dish while it’s still warm, and refrigerate the remaining delicate stems in a protective bag for up to a week.
The Raw and the Cooked
Alliums deliver a distinctively bitter bite, to the point that researchers have speculated that their organosulfides evolved to repel pests and grazing animals. The word “allium” can even be traced to a Greek word meaning “to avoid.”
Fortunately for our health, our tastebuds have evolved to appreciate them — perhaps because our cooking traditions are full of ways to make alliums more palatable. Put them to the best use with these kitchen tricks.
Slice bulbs along their long axis, root to tip, to lessen the bite of raw onions. Longitudinal cuts do less damage to the cell walls, which releases fewer sulfur compounds.
Rinse chopped raw onions under running water to wash away some of the sulfur compounds — this reduces the organosulfides. If a milder onion taste makes a dish more palatable, some is better than none.
Sauté onions to help break down the vegetables’ harsher compounds and produce a milder flavor. Again, you won’t get quite as many organosulfides, but you’ll still benefit from many of the nutrients, including fiber.
Cook onions for up to an hour or so and they’ll caramelize, creating a sweet, umami-infused flavor.
Let cut garlic sit for up to 10 minutes before cooking to increase its flavor and release its allicin. Dial it down by adding it right to the pan, or by chopping cloves in thin slices. Fewer cuts mean less allicin is released.
Rub a halved clove of garlic around the inside of a salad bowl or on a slice of freshly toasted sandwich bread when you want just a hint of the flavor.
Add garlic to pans on low to medium heat and take care not to burn it, which makes it bitter.
Roast garlic to deactivate alliinase and bring out a sweet mellowness. “You’ll often see an entire head of roasted garlic on my plate,” says Wahls. “Just pop it in the oven at whatever temperature you are baking other dishes.”
This article originally appeared as “All About Alliums” in the October 2021 issue of Experience Life.