Besides adding great flavor to your food, onions offer serious health benefits.  They are full of vitamins, minerals, and fiber; they are also one of the best sources of the antioxidant flavonoid called quercetin as well as beneficial organic sulfur compounds.

Quercetin is a pigment that adds color to many fruits and vegetables and is found mainly in the skin and leaves of plants.  The greatest concentration of quercetin in onions is in the outer layers, with red onions having the most, then yellow, with white having the least.

Antioxidants, including quercetin, help prevent inflammation that can lead to can lead to chronic disease.  The many health benefits of onions include:

Heart Health

The sulfur compounds in onions act as a natural blood thinner to help prevent blood clots that can lead to heart attack or stroke.  They also help reduce cholesterol.  The quercetin in onions helps prevent plaque buildup in your arteries, which can reduce blood flow and can also lead to heart attack and stroke.

Cancer Risk Reduction

Quercetin can inhibit the growth of cancer cells in breast, colon, prostate, ovarian, endometrial, and lung tumors.  It can also help stop the processes involved in cancer cell proliferation and mutations.

Fighting Allergies

Quercetin appears to be a natural antihistamine as well as anti-inflammatory, helping to fight seasonal and food allergies, as well as asthma and skin reactions.  Quercetin can stabilize the production of histamines which cause symptoms like sneezing, watery eyes, and itching in allergic reactions.

Brain Health

The antioxidant properties of quercetin also protect the brain from oxidation and inflammation to reduce the risk of dementia and Alzheimer’s.

Gut Health +

Onions are rich in inulin, which is a type of fiber that acts as a prebiotic to feed the good bacteria (probiotics) in your gut.  Inulin also helps prevent constipation, improve blood sugar regulation, boost nutrient absorption, and support healthy bone density.


The quercetin in onions fights the growth of dangerous bacteria like E. coli and Staphylococcus aureus.  Research is continuing to determine how onions affect bacteria in the body.

Onions are versatile and can be enjoyed in as many ways as you can imagine.  The quercetin and sulfur compounds are greatest when the onions are raw, but are also available in cooked onions.  Dice them and use them raw in salsas and guacamole; raw slices are great in salads and sandwiches; you can caramelize them, saute them, stir-fry them, or roast them; add them to everything from omelets and sauces to casseroles, vegetables, and grains or seeds like quinoa and rice.

What’s good to know is that the beneficial quercetin in onions is also found in other plant foods including apples, berries, cherries, grapes, red wine, bell peppers, tomatoes, asparagus, citrus fruits, broccoli, cabbage, Brussels sprouts, kale, spinach, shallots, scallions, black and green tea.  The average American gets about 5 to 40 milligrams of quercetin per day, but if you’re on a plant-based diet you may be getting as much as 500 mg every day, and you should aim for up to 1000 daily mg.

The next time you have tacos or a veggie burger, don’t hold the onions!


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