Search IconSearch

Stop the Tears: Why Onions Are Good for You

Beyond the tell-tale aroma, onions also provide benefits like strong bones and a healthy heart

chopped and whole onions on cutting board

They may bring tears to your eyes and a stench to your breath. But onions also add a lot of flavor to dishes. Whether you like this root vegetable raw or cooked, there are many health benefits to eating onions.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

Why onions are healthy

Onions are part of the Allium family, a group of spicy, sharp root vegetables that includes garlic, leeks and chives. They’re especially high in organosulfur compounds. These chemicals give onions their strong odor and taste (and make you cry). They also have many health benefits. “People have used onions for medicinal purposes for centuries,” says registered dietitian Gillian Culbertson, RD, LD.

Surprising health benefits of onions

With hundreds of varieties — from tangy white onions to sweet Vidalias — it’s easy to add onions to your meals. Getting more of this veggie into your weekly diet may help to:

1. Lower cancer risk

Initial laboratory studies suggest that organosulfur compounds may stop cancer cells from multiplying and growing, causing the cells to die. (Please note that this study hasn’t yet been reproduced in humans, so while the results are promising, we can’t know for sure if the effect will be the same in humans.)

A 2019 study found that consuming 35 pounds of onions and other allium vegetables every year may lower your risk of colorectal (colon) cancer by almost 80%. Most Americans consume about 22 pounds of onions in a year, according to the National Onion Association.

Additional studies suggest that an onion-rich diet may lower your risk of:

2. Fend off chronic conditions

Onions have more than 25 different flavonoids — natural plant substances that have antioxidant properties. They’re also high in vitamin C, another important antioxidant that supports a healthy immune system. “Antioxidants protect against free radicals that cause inflammation and contribute to chronic diseases like cancer, diabetes and heart disease,” explains Culbertson.

For maximum antioxidant benefits, choose colorful red onions, which have flavonoids called anthocyanins that give the vegetable their color. Because research shows an onion’s outer layers have the highest concentration of flavonoids, try to keep as much of that part as possible when removing the skin.


3. Protect against heart disease

Another flavonoid found in onions — quercetin — offers many heart-healthy benefits, especially for people experiencing obesity and metabolic syndrome. “Metabolic syndrome is a combination of risk factors, including excess weight, high blood pressure, high cholesterol and high blood sugar, that increases your risk for heart disease,” says Culbertson.

Onions also appear to have blood-thinning abilities, which can help prevent blood clots that cause heart attacks and strokes.

Because quercetin builds up in your bloodstream over time, consistently consuming onions can lead to greater antioxidant benefits. Different studies indicate that eating more onions may improve heart health by helping to:

4. Strengthen bones

The antioxidants in onions may also reduce bone loss and osteoporosis that often occurs with aging. “Antioxidants minimize the stress that damages healthy cells and speeds up the aging process,” notes Culbertson.

Sipping on onion juice may sound unappetizing. But a 2016 study found that healthy people in middle age and postmenopause who drank 3 ounces of onion juice every day for eight weeks had less bone loss and stronger bones. Another study suggests that women and people assigned female at birth (AFAB) over 50 who eat an onion a day may:

  • Improve bone density by 5%.
  • Reduce their risk of hip fracture by 20%.

5. Fight bacteria

There’s some evidence that quercetin has antibacterial properties, and storing onions for at least three months increases quercetin levels. A 2018 systematic study found that consuming onions may slow or stop the growth of bacteria that cause:

6. Aid digestion

Onions are a rich source of prebiotics and fiber. “Gut bacteria break down insoluble or undigested fiber, causing fermentation,” says Culbertson. “In this way, onions serve as a prebiotic or food source for the bacteria, which aids digestion.”

Unfortunately, this fermentation can also cause gas and bloating. “Cooked onions are easier to digest and less likely to cause digestion problems than raw onions,” shares Culbertson.

What nutrition is in an onion?

A medium 5.3-ounce onion has approximately:

Nutrient-wise, a medium onion has:

  • 34 milligrams of calcium.
  • 28.5 micrograms of folate.
  • 0.31 milligrams of iron.
  • 0.2 micrograms of manganese — 10% of your daily value.
  • 190 milligrams of potassium.
  • 0.26 milligrams of vitamin B6.
  • 12 milligrams of vitamin C — 20% of your daily value!


Should you try onion supplements?

You can buy onion supplements, including onion juice, online and at local stores. But Culbertson cautions that you’ll get more health benefits from onions if you eat the actual vegetable. “It’s always best to get nutrients from foods when possible.”

While your body might appreciate the numerous health benefits of eating onions, those close to you might turn up their noses. The sulfur compounds can make your breath and sweat a little rank. Eating cooked onions instead of raw ones can help. Sauteing, caramelizing, frying or cooking onions lowers the sulfur content. You can also try mints or gum to freshen your breath after a meal.


Learn more about our editorial process.

Related Articles

Assorted whole-grain foods, fruits, vegetables and nuts
June 21, 2024/Nutrition
Eating for Energy: Foods That Fight Fatigue

What’s on your plate can either help power you through your day or put you in nap mode

Person standing in front of oversized nutrition label, reading it
June 19, 2024/Nutrition
What Can You Learn From a Nutrition Label?

Information on serving size, calories and nutrients can help you make healthy choices

Piles of sugar alcohol
June 17, 2024/Nutrition
What You Should Know About Sugar Alcohols

Often labeled as ‘diabetes-friendly’ or ‘calorie-free,’ these sugar substitutes warrant caution

Person prepping mason jars with meals
June 14, 2024/Nutrition
Should You Eat the Same Thing Every Day? Learn the Pros and Cons

Repeating your meals can help simplify meal planning and counting calories, but it could also lead to boredom and nutritional deficiencies

Person looking in fridge, filled with salad, milk, berries, veggies, juice
June 12, 2024/Wellness
Power Up: 10 Ways To Boost Your Energy Naturally

Making certain food and lifestyle choices can help keep your battery full

Big open jar of pickles
May 22, 2024/Nutrition
Are Pickles Good for You?

Pickles are low in fat and calories and rich in some vitamins and minerals, but they’re usually high in sodium

Shirataki Miracle noodles on chopsticks and in red bowl
May 20, 2024/Nutrition
4 Reasons To Give Shirataki (Miracle) Noodles a Try

Fiber-rich shirataki noodles may improve blood sugar, aid in digestion and help with weight loss

Assorted healthy foods spread out over a table and cutting boards
May 20, 2024/Digestive
What To Eat When You Have Diverticular Disease

Reducing inflammation is key when you’re in a flare-up, but so is having a preventive nutritional plan in place when you’re not

Trending Topics

Female and friend jogging outside
How To Increase Your Metabolism for Weight Loss

Focus on your body’s metabolic set point by eating healthy foods, making exercise a part of your routine and reducing stress

stovetop with stainless steel cookware and glassware
5 Ways Forever Chemicals (PFAS) May Affect Your Health

PFAS chemicals may make life easier — but they aren’t always so easy on the human body

jar of rice water and brush, with rice scattered around table
Could Rice Water Be the Secret To Healthier Hair?

While there’s little risk in trying this hair care treatment, there isn’t much science to back up the claims