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Onions: Facts, Nutrition, Health Benefits, and More

Onions are a bulb vegetable that belongs to the same family as leeks, garlic, chives, and shallots. These aromatic vegetables belong to the genus Allium and are part of the lily family. Some even call onions “stinking lilies” because of their distinct and lingering smell.

Onions are one of the most widely cultivated vegetables that are a part of the Allium genus. While you may think onions only come in white, yellow, or red, there are several types of onions you may not be aware of. There are green onions, storage onions, sweet onions, spring onions, yellow, red, and white.

Not only are onions popular worldwide, but they are also one of the most nutritious vegetables. They are antibacterial and contain a wide variety of vitamins, minerals, and nutrients.

Nutrition Facts

Find out the specific nutrient profile of onions below to see how they can benefit your health.


Onions are packed with a variety of nutrients. Some of the macronutrients in one raw red onion include (1):

  • Calories: 87 calories (kcal)
  • Protein: 1.85 grams (g)
  • Fat: 0.197 grams (g)
  • Carbohydrate: 19.6 grams (g)
  • Fiber: 7.82 grams (g)

The types of onions vary slightly in their nutrient profile. For example, while red raw onions contain 19.6 grams of carbohydrates, yellow raw onions provide 12.3 grams of carbohydrates (1).

Redraw onions also give the most amount of fiber compared to white and yellow onions. There is not a huge difference but one red raw onion provides 7.8 grams of fiber, while one yellow onion provides 3.8 grams of fiber (2, 3).

The protein content is nearly identical to all onions ranging from 1-2 grams. All onions provide a wide variety of nutrition.

Vitamins & Minerals

All onions contain a similar amount of vitamins and minerals ranging from only a few milligrams to differentiate. In one red onion, some of the highlighted vitamins and minerals include (3):

  • Calcium: 33.5 milligrams (mg)
  • Magnesium: 22.5 milligrams (mg)
  • Phosphorus: 80.8 milligrams (mg)
  • Potassium: 388 milligrams (mg)
  • Sodium: 1.97 milligrams (mg)
  • Vitamin C: 16 milligrams (mg)

All onions contain the minerals magnesium, phosphorus, calcium, iron, potassium, sodium, zinc, copper, manganese, iodine, and selenium (4). While white raw onions contain 21 mg of calcium, red raw onions provide 33 mg and white raw onions contain 15 mg of calcium.

The vitamins in red raw onions and yellow onions are impressive when it comes to vitamin C. These onions contain a whopping 16 mg of vitamin C or ascorbic acid. They also contain a healthy amount of vitamin B6 or pyridoxine and potassium. Vitamin B6, vitamin C, and potassium are essential vitamins necessary to protect the immune system and much more.

Vitamin B6 helps with storing sugar, fats, and protein in the body and it also helps with the development of the nervous system, skin, nails, and brain (5, 6). The body needs vitamin C to help form collagen, muscles, bone, and even blood vessels. Vitamin C is a crucial vitamin necessary to keep the immune system strong and avoid viruses and other illnesses as well. Potassium helps blood vessels contract and also regulates normal blood pressure (7). Potassium is also necessary to maintain adequate levels of fluid in the cells.

The vitamin content of onions can change with different cooking methods. The vitamins and mineral levels are measured using raw onions. Certain cooking levels and methods, such as high heat or using particular oils can have a drastic influence on the nutrient levels you are consuming (8).

Onions can be a great part of a healthy nutritious diet because of their powerful vitamin and mineral content. Find out some surprising and fun facts below to learn more about this popular bulb vegetable.

Fun Facts

Onions are a bulb vegetable that has their fair share of fun facts along with a plethora of vitamins and minerals to improve your health.

Below are some fun facts about this popular, tear-jerking go-to vegetable.

  • Onion Juice is Antimicrobial: Onions may help fight bacteria.
  • Onions May Help Fight Against Antibiotic Resistance: Antibiotic resistance is a growing issue in America. Onions may be a crucial vegetable to help counter antibiotic resistance (9).
  • Onion consumption has increased by 50% over the last two decades.
  • Onions Contain High Amounts of Sulfuric Compounds: Why should you care? That is the reason onions can make you cry when cutting them.
  • Onions were Discovered More than 5,000 Years Ago: They were first discovered in Central Asia and are one of the most ancient and beneficial food sources.
  • The United States is one of the top three producers of onions.
  • Onions have between eight and fifteen layers.

Health Benefits

What can onions do for your health? It turns out, quite a lot. Onions have natural antimicrobial properties. That means they fight off harmful bacteria rather than attracting them. Because of that and the many vitamins and minerals onions provide, there are many ways onions can benefit your health.

Onions May Lower Inflammation

Onions are a potent anti-inflammatory vegetable, much like many other vegetables in the same family and elsewhere. Vegetables in general are a crucial piece of a healthy diet to not only keep weight down but to lower inflammation and avoid disease. All disease is driven by too much inflammation in the body (10, 11).

The reason onions are so powerful at lowering inflammation is that they are full of vitamins, minerals, antioxidants, and special compounds that lower inflammation. Onions provide a range of therapeutic and pharmacological benefits. Eating more onions may help to lower oxidative stress in the body and they may even protect the immune system from disease (12).

There is even some research on how onions may help those who develop Covid-19. With so many unknowns after the pandemic, more research is emerging on how we can defend our bodies with quality nutrition and what may be the most helpful to fight off the virus. The study points to evidence saying that onions may not only be anti-inflammatory but also anti-viral and anti-thrombotic (13). Onions have been used for centuries as a part of medicinal treatment for many ailments. Although more research is necessary, onions may have a powerful benefit for the human body and disease prevention.

Onions May Reduce the Risk of Cancer

The benefits of onions and the entire Allium species may even range to cancer prevention. Onions, along with shallots, garlic, chives, and leeks may help to reduce the risk of cancer due to their nutritional profiles.

Although more research is necessary due to some conflicting information, there may be some benefits to consuming onions and reducing colorectal cancer, stomach cancer, esophageal cancer, prostate cancer, and potentially others as well (14).

Another reason garlic and onions may be a helpful aid to prevent cancer is that they have antimicrobial properties. Some studies suggest that sulfur compounds may slow or stop tumor growth (15).

Onions May Protect the Heart and Reduce the Risk of Hypertension

Since onions are an anti-inflammatory food, they may have a drastic medicinal effect on the heart. Due to their antioxidant properties and rich vitamin profile, onions may even help reduce the risk of high blood pressure or hypertension (16). Hypertension is one of the most common diseases in the United States, right behind heart disease.

Onions may even provide an overall improvement to blood lipid profiles, lowering triglycerides, reducing cholesterol, and lowering the risk of heart disease or heart attacks (17). Cardiovascular disease is the leading cause of death in the world. Adding a wide variety of nutrition to your everyday diet along with lifestyle changes can improve the chances of avoiding this common chronic disease.

Ways to Consume Onions

Onions are a staple in tons of dishes all over the world. They add a ton of flavor to foods and can be enjoyed by several varieties of cooking methods.

If you aren’t eating onions everyday already, here are some ways and ideas you can try to add them to your diet.

Slice/chop them and enjoy them raw in:

  • Salads
  • Salsas
  • Guacamole
  • Sandwich topping
  • Blend with salad dressings or sweet-savory jams

Try them caramelized by:

  • Adding to salads
  • Put on baked goods such as focaccia bread
  • Use for burgers, pizzas, or sandwiches toppings (cheesesteaks anyone?)
  • Add to egg dishes like scrambled eggs, omelets, or frittatas
  • Blend with dips and condiments such as french onion dip or hummus
  • Incorporate into pasta dishes

Try cooking or sautéing onions into recipes such as:

  • Soups like french onion soup, bean soup, or chicken noodle
  • Cook with potatoes
  • Make onion rings
  • Grill them with other vegetables or protein sources
  • Add as a garnish to any dish you’d like
  • Use as a staple for sauces like tomato or marinara sauce

Potential Risks of Eating Onions

There are typically none to very minimal risks when it comes to eating onions. However, they may cause adverse effects for some people.

  • They may cause digestive issues: For people with digestive conditions like irritable bowel syndrome (IBS) or for those who follow a low FODMAP diet, onions may need to be avoided. Onions have been noted to cause digestion issues like gas, upset stomach, and bloating for persons with conditions like such. They are considered a FODMAP food (high in fermentable oligo-, di-, monosaccharides, and polyols short-chain carbohydrates) (18).
  • They may cause watery eyes: When onions are cut, they release certain compounds that cause irritation around the eyes (19). This is why they can make certain people cry when chopping them up. You can try chilling them before cutting them up if they typically cause this issue for you.
  • They can cause bad breath: If you have ever enjoyed onions before, then you are probably aware that they can cause halitosis, also referred to as bad breath. This won’t impact your health, but you can try brushing your teeth, chewing gum/mints, or use mouthwash after eating them to help combat the smell (20).

Frequently Asked Questions

What is the best way to store onions?

The best way to store an onion is by refrigerating them at 40 degrees Fahrenheit or below. By storing them at this temperature they can last in the fridge for up to one year. If you don’t have enough room in the refrigerator, placing them in a dark and cool place will help them to keep for several weeks.

After I cut an onion, how long will it be good for?

Once an onion is cut, it can be stored in a sealed container. By doing this the onion will typically last 7-10 days. Onions can also be stored in the freezer.

What should I look for when purchasing an onion?

When looking for onions to purchase, look for ones that have minimal scent to them. Good onions are typically dry on the outside skin without or with minimal blemishes and dark spots.


Onions are a part of the Allium species and they include many different vegetables like garlic, shallots, and more. Their powerful nutrient profile makes them a beneficial addition to a healthy balanced diet.

With many vitamins, minerals, antioxidants, and compounds, onions may help to aid in heart health, reduce the risk of many types of cancer, and even lower inflammation in the body, helping to prevent many common diseases.

Adding onions to your diet from pickled onions to cooked, raw, and much more. See where you can start reaping the health benefits of onions in your diet today.