Stop the Tears: Why Onions Are Good for You

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.

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:

• Bladder cancer.
• Brain cancer.
• Breast cancer.
• Lung cancer.
• Ovarian cancer.
• Stomach cancer.

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:

• Control high blood pressure.
• Lower cholesterol.
• Prevent metabolic syndrome.
• Reduce chronic inflammation.

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 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:

• E. coli infections.
• Staph infections.
• Stomach ulcers.

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:

• 45 calories.
• 11 grams of carbohydrates.
• 0 grams of cholesterol.
• 0 grams of fat.
• 3 grams of fiber.
• 1 gram of protein.
• 5 milligrams of sodium.

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.