Diet and Nutrition: Health Benefits of Onions

  • Reviewed By: Christine Mikstas, RD, LD
Reviewed on 9/29/2021

Vitamin C

Vitamin C aids in wound healing and it is an antioxidant.

All kinds are considered a good source of this nutrient. Vitamin C helps your body heal and form blood vessels and other parts of the body. It's also an antioxidant that fights free radicals. Those are molecules your body makes that can sometimes trigger damage. Experts recommend 90 milligrams of vitamin C a day. That's the Daily Value, or the amount of a nutrient you should try to get every day. One average-sized onion has 9% to 18% of your Daily Value.


Onions have both dietary and prebiotic fiber.

Onions have two kinds of fiber: dietary and prebiotic. One cup has 12% of the 21-38 grams you need every day. Fiber helps you feel full longer and have regular bowel movements. And when you feel full, you're less likely to eat as much. That helps lower your risk of obesity. The prebiotic fiber in onions feeds your gut bacteria (probiotics) so they can grow.


Quercetin has anti-inflammatory properties and it helps your body make vitamin E.

All onions have quercetin, a flavonoid or antioxidant compound. Quercetin has anti-inflammatory properties, helps your body make vitamin E, and protects it from many forms of cancer. Every onion has antioxidants, but red and yellow ones have more than white onions.

Vitamin B6

Onions have vitamin B6 that helps your body form red blood cells.

One medium onion has about 8% of your recommended Daily Value. Vitamin B6 helps your body form red blood cells. It also breaks down protein and can be helpful to women with PMS and morning sickness.

Raw Is Healthiest

Eating onions raw or slightly sautéed helps them retain their nutrients.

You'll get the most benefit from onions if you eat them raw. Dice and toss them in salads, omelets, or guacamole. Or add them sliced to sandwiches. You can lightly sauté onions to soften them a bit without losing too much of the good stuff. Cooked onions aren't bad for you -- they just don't have as many nutrients.

Make Quick Pickled Red Onion

Pickled onions are quick and easy to make with red wine vinegar and a pinch of salt.

Slice a red onion and toss it in red wine vinegar and a pinch of salt. Let sit for 15 minutes, tossing every 5 minutes to coat. Top hot dogs, burgers, salads, or tacos with it for extra texture and tang.

Fill Your Fajitas

Onions make a great topping for fajitas.

Lightly sauté sliced onion, bell pepper, and your choice of protein in oil and a few dashes of low-sodium soy or Worcestershire sauce. Serve in corn tortillas or over brown rice with salsa, sour cream, and guacamole. Bonus: Add raw onion to your guacamole.

The Soak Method

Chop onions after soaking them in cold water to minimize watery eyes.

Onions contain a compound that can make your eyes water. Most of it is in the root. If raw onions are too strong for you, chop and soak them in cold water or chill them for 30 minutes to lessen their intense bite. And don't cut into the root.

Storage Tips

Store onions in a cool, dry place.

Store whole onions in a cool, dry, and well-ventilated place, not your refrigerator. Once you cut or peel one, you can keep it in the fridge for 7-10 days. But keep them away from potatoes -- onions make them sprout.

How to Choose Onions

A fresh onion is firm and has no soft spots and has dry outer skin.

Look for a firm one with no soft spots and dry outer skin. It should feel heavy in your hand and have no smell.

Stave Off the Stench

Use lemon juice on your hands to get rid of onion smell.

Still smell onions on your hands long after dinner's over? Rub them with lemon juice.

Diet and Nutrition: Health Benefits of Onions

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