Health Benefits of Onions

Medically Reviewed by Dany Paul Baby, MD on November 27, 2022
3 min read

Onions belong to the genus Allium and are closely related to garlic, shallots, and leeks. Most people consume roughly 20 pounds of this pungent vegetable per year, eating them raw, cooked, pickled, or powdered. There are many varieties of onions to choose from, including yellow, red, white, purple, Spanish, and Vidalia onions. 

Onions are a good source of vitamins, minerals, and fiber and are known to offer a variety of health benefits, such as:

Lower Risk of Cancer

Many kinds of onions contain a wealth of chemicals that help fight cancer. Onions are among the richest food sources of a nutrient called quercetin, which is known to prohibit the activity or creation of cancer-causing elements. A quercetin-rich diet has been associated with a lower risk of developing lung cancer.

Lower Risk of Heart Disease and Stroke

Onions contain organic sulfur compounds. These compounds are the reason why onions have such a sharp, strong taste and smell. Organic sulfur compounds help reduce the level of cholesterol in your body and may also help break down blood clots, lowering your risk for heart disease and stroke. You should eat onions raw rather than cooked to get the most sulfur compounds from them.

Diabetes Control

Both the quercetin and organic sulfur compounds found in onions are known to promote insulin production, making them a helpful vegetable choice for those with diabetes.

Lower Risk of Alzheimer’s Disease

Flavonoids come from plants and are found in particular abundance in onions. One study has found that those who consume a long-term diet high in flavonoids decrease their risk of getting Alzheimer’s disease.

Nutrients Per Serving

A ½ -cup serving of chopped, raw white onion contains:

Onions are also a good source of:

Things to Watch Out For

Likely the only negative effect you will notice from eating onions is that they can affect your body odor. When your body breaks down the sulfur compounds found in onions, they can react to sweat on your skin, creating what is generally considered to be an unpleasant body odor.

For those with Irritable Bowel Syndrome, onions may increase gas and bloating. If so, their consumption should be limited.

Try to prepare onions close to the time you will serve them. Their flavor lessens, and their smell grows stronger the longer they sit after cutting.

Many people’s eyes tear up when cutting onions. To avoid this problem, you can cut onions under water or chill them for 30 minutes before cutting. When you do cut an onion, leave the root end intact, as this part of the onion holds the most organic sulfuric compounds, which are what make you cry.

You can sauté, braise, boil, steam, bake, grill, caramelize, roast, or fry onions. 

You can preserve onions by freezing, pickling, canning, or dehydrating them. Note that if onions have been frozen, they should only be used for cooking.

Onions offer a flavor boost to any dish and can be eaten at breakfast, lunch, and dinner. Here are some ways to add more onions to your diet:

  • Mix diced onion, jalapeño, tomato, and cilantro with lime juice for a spicy guacamole dip.
  • Combine rice with caramelized onions and broth for a rice dish with a little sweetness.
  • Bread fresh-cut onions then fry them to make delicious onion rings.
  • Mix grated onions with rice vinegar, soy sauce, sugar, and vegetable oil for a refreshing salad dressing.
  • Add cooked onions to omelets, frittatas, and quiches.
  • Add onions to stir fry dishes.
  • When making chili, add onions to kick up the flavor.
  • Try adding caramelized onions to savory baked goods like cornbread, focaccia, and cheddar biscuits.

Show Sources


The American Journal of Chemical Nutrition: “Long-term dietary flavonoid intake and risk of Alzheimer disease and related dementias in the Framingham Offspring Cohort.”

Clemson Cooperative Extension: “Onion, Leek, Shallot, & Garlic.”

ESHA Research, Inc., Salem, Oregon: “Onion, white, fresh, chpd.”

Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy: “Know Your Onions: Peeling Powerful Nutrition Benefits.”

Illinois State University: “Vegetable Component.”

Journal of Agricultural and Food Chemistry: “Onions: A Source of Unique Dietary Flavonoids.”

Michigan State University Extension: “Onions: those versatile edible bulbs.”

National Onion Association: “Cutting, Preparation Tips, and More.”

North Dakota State University: “Field to Fork Onions!”

North Dakota State University: “Prairie Fare: Onions Add Flavor, Potential Health Benefits to Your Menu.”

Tufts University: “Are Raw Onions More Nutritious Than Cooked Onions?”

The University of Arizona Campus Health Service: “Irritable Bowel Syndrome: Diet and Stress.”

University of Nebraska-Lincoln: “Cooking with Onions without Crying.”

Wexner Medical Center: “5 foods and drinks that affect body odor.”


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