Are Onions Good for You?

Medically reviewed by Natalie Butler, RD, LD on April 25, 2016Written by Jacquelyn Cafasso

Onions on a cutting board

The sulfur-containing compounds in onions can make your breath stink and your eyes water. But did you know they’re also responsible for the onion’s powerful health-promoting effects? Onions are members of the allium family, like garlic. The brown, white, or red-skinned bulbs are a staple in cuisines around the world. They add a pungent kick to any meal.

Like all veggies, onions are a healthy part of a well-balanced diet. But the benefits of onions are more extraordinary than most people know. Onions are low in calories and high in vitamin C. They’re also rich in unique anti-inflammatory and antioxidant compounds.

Read on to find out why including more onions in your diet is nothing to cry about.

Nutritious benefits of eating onions 

A source of unique dietary flavonoids

Onions are one of the richest sources of dietary flavonoids, powerful phytochemicals. These are polyphenolic compounds that may decrease the risk of cancer, cardiovascular, and inflammatory diseases. Flavonoids are types of compounds known as antioxidants. Antioxidants help delay or slow the oxidative damage to cells in the body. Flavonoids are most concentrated in the outer layers of the onion, so don’t peel them too much.

One of the most important flavonoid compounds found in onions is known as quercetin. Quercetin has been researched extensively for its anticancer effects. For example, a recent study found that quercetin helped slow down tumor growth in mice with pancreatic tumors.

Quercetin has also been found to play a role in decreasing blood pressure. High blood pressure is a major risk factor for developing cardiovascular diseases. These include:

  • stroke
  • heart failure
  • coronary artery disease
  • peripheral artery disease

High in organosulfurs

Onions contain a variety of sulfur compounds. The sulfur gives them their characteristic pungent smell. But these sulfur compounds may help reduce inflammation and even help tone down the symptoms of asthma, arthritis, and heart disease.

A 2010 review published in Molecular Aspects of Medicine found that the regular consumption of organosulfur compounds found in onions and garlic may prevent the development of cardiovascular disease. The thiosulfinates found in onions are thought to act as natural blood thinners by keeping blood platelets from collecting in the blood. This decreases your risk of heart attack and stroke.

Rich source of chromium

Onions contain a large amount of the trace mineral chromium. Chromium is thought to assist in regulating blood sugar and enhancing the action of insulin. It has also been found to be directly involved in carbohydrate, fat, and protein metabolism. This is especially important for people who suffer from insulin resistance, or type 2 diabetes.

Vitamin C

Onions are a great source of vitamin C. Vitamin C is an antioxidant and plays an important role in immune function. Vitamin C also improves the absorption of nonheme iron. Nonheme iron is the type of iron that is found in plant-based foods, like spinach. Sautée spinach and onions together to help prevent iron-deficiency anemia.

Improving bone density

Several studies have found a link between onion intake and bone density. The benefit is especially important for menopausal women, who often experience loss of bone density to the point of osteoporosis.

A study in women ages 50 and older, for example, found that women who ate onions at least once a day had a 5 percent greater bone density than women who only consumed onions once a month or less. The researchers also found that frequent onion consumers could decrease their risk of hip fracture by more than 20 percent compared to women who didn’t eat onions at all.

How to incorporate more onion into your diet

Many people fear cutting onions because of their tendency to bring on tears during preparation. To fight crying when slicing an onion, chill them for an hour or so before preparation. Cooling slows the activity of the enzyme that produces allyl sulfate, which is what results in tears. If you don’t have the time, you can always invest in some goggles to protect your eyes while you slice and dice.

Onions can add a flavor to any soup, stew, dip, or sauce. They can be used as a topping for your favorite sandwich or burger, but onions also make an excellent side dish. The flavonoids in onion are more concentrated in the outer layers of the flesh, just below the skin. To maximize the health benefits, peel off as little of the fleshy, edible portion as possible when preparing an onion and let it rest for five minutes before cooking.

You can eat onions raw or cooked. Raw onions tend to have a strong and pungent flavor, while sautéing, sweating, or roasting onions really brings out their sweetness. Try these side dish recipes to get your daily onion dose:

  • A simple, yet perfect, tomato and onion salad can accompany you to any family barbeque. View the recipe.
  • Onions for breakfast might not sound appetizing at first, but they are actually a great addition to a breakfast omelet. Try making an omelet with turmeric, tomato, and onions for a healthy start to your day. View the recipe.
  • Have extra onions? Try pickling them and storing them in a jar for later. Tangy yet sweet pickled onions only take a few minutes to prepare. View the recipe.
  • Red cabbage and onions with apples and apricots is a vibrant side dish perfect for autumn. View the recipe.
  • If you’re in need of a hearty dip for a Mexican-inspired dinner, look no further than your standard guacamole salsa. This combination of avocado, cilantro, tomato, and red onion is delicious, and also full of nutrients. View the recipe.
  • If you’re a fan of vegetables with lots of flavor, sautéing together some onions, spinach, and mushrooms makes an excellent side dish for steak or chicken. View the recipe.
  • A bread made from onions? Yep, that’s right. This “raw” onion bread is a favorite amongst raw foodies. It calls for onion, sunflower seeds, flax, and olive oil and can be topped with hummus, sliced avocado, or anything else you desire. View the recipe.

Next steps

It’s time to get over your fear of cutting onions. They’re too beneficial to pass up. Rich in antioxidants, vitamin C, flavonoids, and more, onions can help you:

  • reduce the risk of heart attack, stroke, and cancer
  • reduce inflammation
  • improve glucose tolerance in people with diabetes
  • maintain healthy bones
  • stimulate the immune system
  • prevent iron-deficiency anemia

Soups, omelets, dips, and side dishes aren’t complete without an onion or two. Make sure to stock up on your favorite variety of onions next time you’re at the grocery store. 

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