8 Surprising Health Benefits of Onions (And Why You Should Eat More of Them)

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Why You Should Add More Onions to Your Diet (Hint: They're Seriously Good for You)

Onions are more than a delicious base for soups, stews, and sauces—they're a nutritional powerhouse with worth that extends way beyond the kitchen. Because of their ubiquity, versatility, and dense nutrient profile, onions are a worldwide culinary staple.

We asked certified nutrition experts Sara Peternell, MNT, and Karen Graham, RDN, to break down why onions deserve a regular spot in your diet—and how to enjoy them at home.

Onion Nutrition Facts

Before diving into the health perks, let’s take a quick look at what’s inside one medium raw yellow onion (about 143 grams):

• Calories: 54
• Protein: 1.2g
• Fat: 0.1g
• Carbs: 12.3g
• Fiber: 3.8g
• Sugar: 8.3g
• Potassium: 260mg
• Vitamin C, calcium, iron, and magnesium – all in small but beneficial amounts.

1. Onions Enhance Heart Health

The most important benefit of onions may be their ability to enhance heart health. Onions—especially red and chartreuse ones—are rich in quercetin, a polyphenol that can lower blood pressure and levels of LDL ("bad") cholesterol. This can reduce your risk of developing plaque in the arteries and promote cardiovascular function in general.

Fun Fact: "Tearless onions" also turn out to be heart-healthy, according to the American Chemical Society.

2. Loaded With Antioxidants That Combat Disease

Onions contain over 25 types of flavonols, making them one of the densest vegetable sources of antioxidants. Antioxidants counteract free radicals, reduce inflammation, and protect your cells from damage—essential to keeping chronic diseases at bay, including cancer.

Pro Tip: Yellow onions contain up to 11 times more antioxidants than white onions.

3. May Support Blood Sugar and Metabolic Health

Some research indicates that onions may help with blood sugar control. Raw onions in diabetic patients have been found to exhibit hypoglycemic activity—lowering fasting glucose levels. Bioactive compounds like quercetin have also been found to increase insulin sensitivity.

4. Boost Bone Density (Especially for Women)

Onions might help with healthier bones with age. In a study of perimenopausal and postmenopausal women, daily consumption of onions was associated with higher bone density and a 20% reduced risk of hip fracture.

5. Fight Infections Naturally

Onions, particularly red and yellow, contain high levels of quercetin, with additional antibacterial, antiviral, and antifungal activity. Quercetin together with vitamin C may even help to ward off respiratory infections by inhibiting viral replication.

6. Maintain Eye Health

While onions may make your eyes tear up, they're also good for you! Onions are rich in quercetin and sulfur compounds that reduce oxidative stress on eye tissues and can help cure diseases like dry eye and keratoconus.

7. Support a Healthy Gut Microbiome

Onions have many prebiotics, like inulin and fructooligosaccharides, that supply energy to help the good gut bacteria grow. A balanced gut microbiome is necessary for efficient digestion, nutrient uptake, and even immunity.

8. Reduce Inflammation

Chronic inflammation is linked to nearly all the big diseases, from arthritis to heart disease. Onions lower inflammatory markers like prostaglandins and histamines, and therefore are a natural anti-inflammatory food—especially useful for those with osteoporosis or rheumatoid arthritis.

Are There Any Side Effects of Eating Onions?

Yes—onions aren't suitable for everyone. Some people are intolerant to fructans (an onion carbohydrate), which leads to bloating, gas, and stomach upset. Others may even have a true onion allergy, causing skin, respiratory, or asthmatic symptoms.

Tip: The green tops of green onions (scallions) are easier to digest and still provide flavor and nutrients.

How to Cook (and Enjoy) More Onions

You don't need to entirely revamp your meals to benefit from onions. Try these easy methods to incorporate more onions:

• Raw: Toss sliced onions with salads, salsas, or burgers.
• Grilled: Brush olive oil over onion slices and grill for a smoky, sweet flavor.
• Pickled: Use pickled red onions as a tangy topper for tacos, grain bowls, or sandwiches.
• Caramelized: Make caramelized onion tarts with apples using frozen puff pastry as a speedy appetizer or side dish.
• Soups & Stews: Start your soups and sauces with sautéed yellow onions for more depth and flavor.

Tips for Storing Onions

Whole onions: Store in a cool, dry, dark place (not the fridge) for two weeks.

Chop onions: Refrigerate in an airtight container for up to 7 days.

Freezer option: Chopped, refrigerator-frozen onions will be usable in later cooked recipes.

Last Word: Are Onions Good for You? Absolutely.

From boosting heart and bone health to supporting immunity, digestion, and metabolism, the benefits of onions go way beyond taste. If you’re not already adding them to your meals, now’s the time to start.