Are onions food for you? Adding this nutrient-packed, aromatic vegetable into your meal rotation is a smart (and tasty) move. Onion health benefits are plentiful. Thanks to its nutritional value, accessibility, and delicious flavor, it’s no wonder this versatile bulb is a staple in cuisines across the world and forms the flavor base for a wide variety of dishes. Here’s everything you need to know about onion nutrition, plus how to eat more onions.
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Karen Graham is a registered nutritionist and functional medicine dietitian.
Onion Nutrition Facts
Onions are a vegetable species within the genus allium, along with similar aromatic bulbs like garlic, leeks, chives, and shallots. Here’s what you should know about their nutritional value.
Water – 89.1 gramsEnergy – 40 kcal Protein – 1.1 gramsFat.- 0.1 gramsCarbohydrates – 9.34 gramsFiber – 1.7 gramsSugar – 4.24 gramsSucrose – 0.99 gramsGlucose – 1.97 gramsFructose – 1.29 gramsCalcium – 23 milligramsIron – 0.21 milligramsMagnesium – 10 milligramsPhosphorus – 29 milligramsPotassium – 146 milligramsSodium – 4 milligramsZinc – 0.17 milligramsCopper – 0.039 milligramsManganese – 0.129 milligramsSelenium – 0.5 µgVitamins A, B, C, and K
Nutritional Benefits of Onions
Onions boast a whole bunch of benefits. Here are some key reasons why you should consider adding more onions to your diet.
Improve Heart Health
Eating onions can have a healthy impact on your cardiovascular system. Specifically, research has found that the polyphenol called quercetin that’s in onions helps reduce high blood pressure and triglyceride levels. Darker-colored onions, like red onions and chartreuse onions, contain the highest amounts of quercetin. Research from the American Chemical Society has also found that the “tearless onion” can help protect against heart disease.
Rich in Antioxidants
Onions are packed with disease and free-radical-fighting antioxidants, which help repair and protect damaged cells in your body. They’re one of the best sources of flavonoids (including quercetin), phytochemicals with powerful antioxidant properties.
According to a review published in the Journal of Agriculture and Food Chemistry, onions contain at least 25 different flavonols. “Red and yellow onions are richer in those antioxidants than other types of onions. In fact, yellow onions may contain almost 11 times more antioxidants than white onions,” says Sara Peternell, MNT, a board-certified holistic nutritionist specializing in family nutrition. A diet rich in antioxidants can help reduce inflammation and thwart free-radical damage, which leads to a strong immune system and better overall health.
May Reduce Cancer Risk
There’s been some interesting research conducted on how onions may play an important role in helping to prevent cancer. A study out of the University of Guelph concluded that red onions, specifically, are the most effective at reducing colon and breast cancer cells. This is once again due to the high levels of quercetin and anthocyanin (another type of antioxidant flavonoid).
Another study published in Cancer Prevention Research found that one to seven servings of allium veggies, like onions, is rich in organosulfur and flavonols—compounds that have been found to have tumor-inhibiting components.
Lower Cholesterol
Onion consumption can lower low-density lipoprotein (LDL), otherwise known as “bad” cholesterol. This can help prevent the accumulation and formation of plaque buildup in the arteries, which promotes healthier blood flow and improves cardiovascular health.
Boost Bone Density
One study of perimenopausal and postmenopausal non-Hispanic white women 50 years and older finds that onion consumption seems to have a positive effect on bone density. Those who ate onions also had a 20% decreased risk of hip fracture than those who didn’t eat onions.
Antibacterial Properties
Onions—particularly red and yellow onions—are great natural sources of quercetin. Quercetin is a bioflavonoid that has antioxidant properties and is anti-fungal and antibacterial.
Promote Eye Health
Despite the fact that cutting onions may make your eyes tear up, onions are actually good for your eye health. Onions are chock full of quercetin and sulphur compounds, which help protect the eyes. Quercetin has been used to treat conditions like dry eye and keratoconus, for example.
Enhance Gut Health
Onions are beneficial for gut health due to their high content of prebiotics. This includes both inulin and fructooligosaccharides, which are beneficial gut bacteria that promote a healthy microbiome. The growth of good bacteria ultimately improves digestion and helps your body better absorb nutrients. Plus, the antimicrobial properties of the sulfur compounds in onions can help maintain a balanced gut flora by keeping bad bacteria at bay.
Anti-Inflammatory Properties
Onions have anti-inflammatory properties, too. This means that they can have soothing and calming effects. In fact, they prevent inflammation-inducing leukotrienes, prostaglandins and histamines in both osteoarthritis and rheumatoid arthritis.
Versatile Vegetable
Onion is a super versatile vegetable. You can use it to add flavor to many meals, from soups to burgers and beyond. You can also add onions to dips and salsas. You can eat it raw, cook it, or even caramelize it. Fried onions are another option, albeit a less healthy version. But, whichever way you choose, there are endless ways to incorporate onions into your diet.
Long-Lasting (When Stored Properly)
Whole onions should last in your pantry or other cool, dry, dark place (not the fridge) for about two weeks—but don’t store them next to potatoes, which emit gas and moisture that can quickly spoil onions. If you have leftover onion that’s already been cut, pop it in a resealable bag in the fridge to stay fresh for about a week (you can also store it in a container in the freezer).
How to Cook With Onions
Raw yellow onions tend to be the sweetest variety, making them a great addition to salsas. Cooked yellow onions make a savory base for soups, stews, and sauces. Onions are also delicious on their own, roasted, grilled, or sautéed.
Top sandwiches and burgers with grilled (or raw!) onions to up the zest factor. For a tangy burst of flavor—and beautiful color—add pickled red onions to grain bowls, fish or pork tacos, or alongside any meaty main. If you’re a little uneasy about adding onions to your at-home menu, start by keeping the cooking process simple. Weis recommends slicing the onions into discs, brushing them with olive oil, seasoning with salt and pepper, and grilling both sides.
Check out these creative recipes—starring the humble onion—that are bursting with flavor and nutrients.
Caramelized Onion Apple Tart
Con Poulos
These easy caramelized onion apple tarts pack a lot of flavor without too much work, thanks to frozen puff pastry. Serve as an appetizer or alongside a salad for a full meal.
Deeply Caramelized Onion Dip
Jennifer Causey
Patience is the key to this delectable dip: Cook the onions low and slow, stirring frequently—no shortcuts allowed. Serve with thick-cut potato chips and crisp veggies.
Tapenade and Red Onion Pizza
Victor Protasio
The salty tapenade goes well with the sweet, sautéed onions. Besides, you can never go wrong with pizza. Pair with a peppery arugula salad to round out the meal.
Rich French Onion Soup
bonchan/Getty Images
This French classic is easy to make and takes half the time. What’s not to love? If you don’t like Swiss cheese, you can try gruyere instead.
Possible Downsides of Onions
It’s true that onions aren’t for everyone. For starters, eating onions can cause bad breath. The odor from onions lingers long after you eat them, too. But that’s not all that can happen. While bad breath is one thing, stomach issues are another. Some people are very sensitive to the oligosaccharides, a fructan found in onions.
The green tops of scallions are not usually a problem for people with onion intolerances, Graham says. So, if you are sensitive to onions but want to eat them, the scallions may be a good place to start to add onion flavor and nutrients into meals.
Karen Graham, RDN, a functional medicine dietitian, says that onions can be problematic for many people, causing gas, bloating, constipation, and diarrhea. In her practice, about 30% of people tested for food intolerances have an issue with onions.
Beyond digestive issues, some people are also allergic to onions. Onion allergy can cause contact dermatitis (skin rashes and itchiness), rhinoconjunctivitis (runny nose, sneezing, red eyes, etc.) and asthma.
