Onions: Are They Good for You, Nutrition Facts, Proven Benefits (Science Based)

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Onions: Are They Good for You, Nutrition Facts, Proven Benefits

Onion is a vegetable used in cooking and is full of healthy nutrients. Onion bulbs are extremely good for you because they contain antioxidants, vitamins, minerals, and amino acids. Consuming raw, cooked, or boiled onions can help you lose weight, boost your cardiovascular health, strengthen your immunity, and reduce inflammation.


There are many varieties of onions, all with nutritional benefits. Onion bulbs can be yellow, red, or white, and range in taste from mild and sweet to sharp and pungent. All types of onions contain antimicrobial properties. But red onions contain more antioxidants than yellow onions or white onions.

Onions are from the Allium genus that also includes vegetables such as garlic, scallions (green onions), leeks, and chives.

In this article, you will find out why onions are so good for you and how scientific research backs up claims about the health benefits of onions. At the end of the article you will find how to use onions in home remedies.

White Onion vs. Red (Purple) Onion vs. Yellow Onion

The most common type of onion used in cooking is the yellow onion. Yellow onions have white flesh and yellow skin and generally have a sharp flavor. Usually, yellow onions become sweeter and softer during the cooking process.

What is the difference between white onions and yellow onions apart from their color? Most people say that white onions have a milder and crispier flavor than yellow onions.

Red onions are sometimes referred to as purple onions and are usually eaten raw in salads. Most people prefer to eat red onions raw rather than yellow onions as they aren’t as sharp and astringent.

Red onions could be the healthiest type of onion as they contain more antioxidants.

Nutritional Value of Onion (Yellow, Red, White)

There is little difference in nutritional value comparing yellow, white, and red onions. All varieties of onion are healthy because they contain vitamins, minerals, and other beneficial micronutrients.

According to the United States Department of Agriculture, red, yellow, and white raw onions have 40 calories per 100 grams. One medium-sized onion contains nearly 2 grams of fiber which is 7% of your recommended daily intake (RDI). (1)

100 grams of onions contain 9.3 grams of carbs and around 4 grams of sugar. However, depending on the variety of onion, the sugar content of the onion could differ slightly.

One of the reasons why onions are really good for you is that they contain a number of amino acids. Amino acids are essential for metabolic processes in your body. Onions contain essential amino acids such as lysine, threonine, leucine, and phenylalanine. (2)

Red onions, white onions, and yellow onions all contain trace amounts of vitamins C and B-group vitamins, as well as minerals such as calcium, iron, manganese, and magnesium.

Scallions (or, spring onions) are sometimes referred to as green onions. The nutritional value of green onion is also quite impressive. For example, 1 large scallion (25 g) contains 52 mcg of vitamin K (65% RDI), 4.7 mg vitamin C (8% RDI), and all the essential amino acids that are in regular onions. (3)

Onions are packed with antioxidants

Regularly consuming raw or cooked onions in your diet can also help to keep you healthy and boost your body’s immune system.

Onions are a rich source of unique antioxidants and dietary flavonoids. Research has found that yellow onions contain between 270 and 1187 mg flavonoids per kilogram of fresh onion. However, red onion has even more antioxidants – between 415 and 1917 mg per kilo of red onion. (4)

Red onions also contain an antioxidant compounds called anthocyanins which have benefits in protecting against numerous diseases. In fact, anthocyanins may make up about 10% of the total flavonoid content in red onion. (4, 5)

Quercetin is another important antioxidant contained in onions. Research has shown that quercetin has antimicrobial properties and can help to lower blood pressure. (6, 7) Quercetin is also more prevalent in red onions than in yellow and white ones. (8)

Other studies have shown that the sulfur-containing compounds in onions have anticancer properties. (9)

Also, the outer layers of onion bulbs and onions skins have a higher antioxidant content than the inner portions. (9)

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It seems that red and yellow onions are healthier for you than white onions because they contain more antioxidants. (10)

Are Onions Good For You? Health Benefits of Onion

Are onions healthy? It is clear that onions, especially the red and yellow varieties, have the potential to treat many health issues. Let’s look in more detail at why eating onions is good for you.

Onions are Good for Keeping Your Heart Healthy

The rich antioxidant content in onions means that eating onions is good for your cardiovascular health.

The Journal of Hypertension reported that there is a link between consuming vegetables such as onions and a reduced risk of cardiovascular disease. One study found that over a 6-year period, people with type 2 diabetes had less of a risk of suffering from heart disease if they regularly consumed onions and other allium vegetables. (11)

Scientists have identified that quercetin is one of the reasons why onions are good for your cardiovascular health. (12)

Further reading: The best foods you can eat to keep your heart healthy.

Onions promote good heart health by helping to lower blood pressure

It is a good idea to eat onions every day if you have high blood pressure because onions may help to lower hypertension.

One study on the effects of onion on blood pressure found that antioxidants in onions have an anti-hypertensive effect. The research showed that onions affected enzymes and compounds that are connected with high blood pressure. (13)

Drinking onion skin tea may also help lower blood pressure if you have hypertension. A randomized double-blind trial found that onion skin extracts can also help lower blood pressure. Quercetin in onion skin has a cardio-protective effect and improves vascular health. (14)

There is also evidence to suggest that increasing your consumption of raw onion can help lower blood pressure. For example, researchers have found that the main ingredients in the Mediterranean diet (olive oil and onions) affect blood pressure by helping to lower it. (15)

Learn about other ways to lower your blood pressure without medication.

Consuming onions is good for your blood circulation because they help prevent clotting

Another reason that eating more onions is good for your heart is that onions have anticoagulant properties.

One study found that onions were better than garlic for helping to prevent blood clotting. (16) Other studies have found that a combination of raw onions and garlic help to prevent red blood cells from clumping together. (17)

Are you showing signs of poor blood circulation? Learn what to do to improve your circulation naturally and keep your cardiovascular system healthy.

Onions may reduce blood cholesterol

Onions are good for you because eating them improves your cardiovascular health because they help to lower serum cholesterol levels.

One trial involving rats found that onion affects levels of blood fat and helps to lower high cholesterol levels. Onions help to increase certain compounds that play a role in lowering levels of LDL cholesterol (the type doctors refer to as “bad” cholesterol). (18)

Clinical trials involving adults have also shown that onions have a cholesterol-lowering effect. Overweight and obese women were given between 80 and 120 g of raw red onion a day to consume. After 8 weeks, scientists noted that there was a significant decrease in total blood cholesterol. (19)

Learn about other effective ways to reduce high cholesterol naturally.

Raw Onion is Good for Weight Loss

Drinking onion skin tea regularly can help you shed extra pounds of excess body fat.

The journal Experimental and Therapeutic Medicine reported that onion peel tea prevents obesity and can suppress increase in body weight. Scientists reported that consuming foods rich in flavonoids are essential for weight management, and onions are one of the richest sources of flavonoids in the human diet. (20)

Researchers concluded that onion skin tea has the potential to treat, prevent, and manage obesity. (20)

Other studies on onion extracts have found that they help to regulate blood glucose levels and lower body weight. (21)

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To use onion skin tea for weight loss, make an infusion by steeping the skins from one onion in a cup of hot water. Drink 1 or 2 times a day to help boost the effects of your weight-loss program.

If you don’t like the taste of onion skin tea, find out how to make delicious ginger tea to help burn belly fat.

Onions Contain Antimicrobial Properties

Many of the health benefits of onions are due to the fact that they contain antimicrobial properties that kill various types of germs and bacteria.

Research published in 2016 found that onions have an antibacterial effect because they contain flavonoids and phenolic acid compounds. Researchers found that red onion, green onion, and white onion help to kill off various strains of bacteria including Methicillin-sensitive Staphylococcus aureus (MSSA). (22)

Other studies have demonstrated that onions contain anthocyanins and quercetin that have a range of health benefits including antibiotic effects. (23)

In 2018, the International Journal of Biological Macromolecules reported that onions are a functional food with antioxidant actions. Onions also contain polysaccharides that have an antimicrobial effect and potential application in the medical industry. (24)

There is also evidence to suggest that onions are effective against oral bacteria that cause gum disease. However, cooking onions seemed to lower their antibacterial activity. (25)

Onions Promote Healthy Digestion

Onions contain beneficial compounds that are good for your digestive system. In fact, consuming onions could help to prevent Clostridium difficile-related diarrhea (a bacteria that causes inflammation of the colon).

Onions contain a type of dietary fiber called oligofructose. A randomized controlled study on the effects of oligofructose on the digestive system found that it has a prebiotic effect. Consuming oligofructose helped to prevent recurring diarrhea that was associated with C. diff infections. (26)

The Journal of Nutrition reports that onions contain about 25% of oligofructose and inulin which are types of plant-based fiber. Onions are only second to wheat as being a naturally occurring source of inulin and oligofructose. (27)

If you feel your digestion isn’t working properly, there are many ways you can improve your digestive health and keep your bowels working properly.

Onions Boost Your Immune System

Eating raw vegetables like onions is good for you because they help to strengthen your immunity and help your body resist infection.

Scientific research has found that allium vegetables like onion and garlic help to improve the body’s immune system. Onion extracts help to increase white blood cell count which is an essential factor in your immune system. Scientists reported that onion (Allium cepa) has “immune boosting capabilities.” (28)

Other studies have found that antioxidants in onions such as quercetin help to improve immunity and increase cells that strengthen the immune system (cytokines). There are 25 different flavonoids in onions that all have an important role in boosting the body’s immune status. (29)

Find out about 10 steps that can boost your immunity today. You can also prepare at home this wonderful health tonic which combines some of nature’s most potent plants, including onion, and brings them together in a powerful concoction. It is 100% natural and works as an anti-bacterial, anti-viral, anti-parasitic and anti-fungal substance.

Raw Onions Have Anti-Inflammatory Properties

Consuming onions every day in your diet can also help reduce inflammatory responses in your body.

Although short-term inflammation is necessary to fight off infections, long-term inflammation can lead to chronic disease like diabetes, heart disease, and cancer.

A medical journal on immunology reported that sulfur-rich compounds in onions help to inhibit inflammation. (30)

Other studies on the anti-inflammatory effect of consuming onions have found that onions can help protect liver health when consumed as part of a healthy diet. (31)

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Did you know that onions are just one of the many foods that reduce inflammation in the body?

Onions Can Help Regulate Blood Glucose Levels

Adding more onions to your diet is good if you have diabetes because onions help to regulate blood glucose spikes after eating.

One study found that supplementing the diet with onions had a blood glucose-lowering effect. Onions extracts reduced fasting blood glucose in people with type 1 diabetes and type 2 diabetes. (32)

The results of other medical trials have found that onion extracts lower blood glucose levels after a meal. The lowering effect may be due to delaying absorption of glucose through inhibition of the enzyme sucrase in the intestinal tract. (33)

If you have type 2 diabetes, find out about other foods that can help to regulate blood glucose levels.

Onions Help to Strengthen Bones

Compounds in onions like antioxidants and flavonoids can also protect bone health and prevent the development of brittle bones later in life.

The journal Menopause reported that consuming onions can help increase bone density in perimenopausal and postmenopausal women. Reports indicate that women who frequently consume onions can lower their risk of hip fracture by more than 20%. (34)

One study found that consuming onion powder helps to inhibit breakdown of tissue in bones and prevent bone density loss. These are 2 conditions which can lead to osteoporosis. (35)

You can also prevent bone loss if you drink onion juice every day. The journal Food & Function found that people who consumed 100 ml of onion juice daily can help to increase bone mineral density. Drinking onion juice increases antioxidants and reduces the number of free radicals that can result in bone damage. (36)

Further reading: 4 natural ways to prevent osteoporosis in later life.

Red Onions Can Improve Male Prostate Health

Consuming onions has many benefits for men because flavonoids in red onions help to prevent certain prostate problems.

One trial involving rats found that red onion extracts had a protective effect against prostatic hyperplasia (enlarged prostate). (37)

Clinical trials on adult men have also found that consuming onions help protect prostate health. In fact, it has been shown that men who daily consume more than 10 grams of Allium vegetables such as onions have a significantly lower risk of prostate cancer. (38)

If you are a man, find out how to spot the first signs of prostate cancer, as early detection decreases the risk of complications of cancer.

Onions Have Anticancer Properties

Onions are an extremely rich source of beneficial antioxidants that have potential use in cancer treatments.

A review of studies on onion and garlic intake and their role in reducing the risk of cancer found that Allium vegetables have an anticancer effect. High consumption of onions is associated with decreased risk of developing cancer. Onion has a protective effect against stomach cancer, colorectal cancer, esophageal cancer, and prostate cancer. (39)

Although cooking onions reduces the number of antioxidants, some studies have shown that cooking with crushed onions doesn’t destroy the sulfur-rich compounds that have an anticancer effect. (39)

More research still has to be done to find out how much onion to consume daily to help reduce your risk of cancer. Scientists also still have to research how other nutrients affect the cancer-protective effect of onions.

Find out about other foods you can add to your diet that can help prevent cancer developing.

Onion Juice Can Improve Hair Growth

Onion juice can help you re-grow your hair and make it stronger. The onion juice improves blood circulation and provides the hair follicles with sufficient nourishment. Onion also has anti-bacterial properties, so it helps with scalp infections that might contribute to hair loss.

In 2002, the Journal of Dermatology published a small study that looked into the use of onion juice for alopecia areata (an autoimmune disease that presents with patchy hair loss).

Participants who applied onion juice twice daily for two months experienced much better hair re-growth rates compared to those who only used tap water. In the study, hair regrowth was observed in 87% of patients treated with onion juice. Men had better success with the treatment than did women. (43)

You can find detailed information on how to make onion rinse for hair growth and frequently asked questions in my article “How To Make Onion Juice For Hair Growth & Strong Hair“.

Onion Kills Intestinal Parasites

The sulfur compounds in onions are anti-parasitic. Onion juice is very effective for intestinal worms, especially tapeworm and thread worms.

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According to a study published in the journal Parasitology Research, onion extract was effective in reducing the number of parasites in animals. In the study, ground onion was added to coconut flakes and food. The result was that all signs of parasites were nearly eliminated in stool samples. (44).

To use onion as part of a parasite cleanse, squeeze the juice from an onion so that you have about 2 teaspoons. Mix the onion juice with some raw plain yogurt and consume daily. Continue the parasite cleanse with onions for 2-3 weeks to be sure that you completely get rid of parasites and intestinal worms.

You can also consume other foods and herbs that naturally kill intestinal parasites.

How Long Are Onions Good For?

Onions should be stored in a cool, dry place where there is plenty of ventilation. You should also avoid storing fresh onions in plastic bags as they will tend to rot quicker. Instead, store them in a mesh bag or a loosely covered paper to allow for air circulation.

Whole onions when properly stored, can last for 2 to 3 months in the refrigerator.

The Journal of Food and Drug Analysis reported that, if stored properly, the antioxidant content of onions increases. Researchers found that the total phenolics, antioxidants, and flavonoids in onions were highest after 3 months of storage. (40)

Daily Recommended Intake of Onions

Doctors on Webmd say that at this time there is not enough scientific information to determine an appropriate range of doses for onion. (45)

According to Drugs.com, clinical trials are lacking to provide dosage recommendations. However average daily doses of 50 g of fresh onion, 50 g of fresh onion juice, or 20 g of dried onion have been suggested. (46) 50 gram of fresh onion equals to about 1/3 cup of chopped onion.

Side Effects of Eating Onions

Onions are a delicious and tasty vegetable, and chopping, crushing, or slicing the onion root or bulb will add flavor and improve the taste of any meal. Eating an onion a day certainly isn’t bad for you and also comes with many health benefits.

Doctors from WebMD report that some adverse effects of onions could be contact dermatitis if onion juice irritates the skin. Some people experience stomach pain after ingesting cooked or raw onions. (41)

Of course, it’s not uncommon for onions to make you cry while you are chopping them.

Eating too many onions a day could also cause you to have bad breath due to sulfides in the vegetable. (42) In fact, the smell of onions can also be emitted through your pores.

The sulfur content in onions may also cause odorous gas. The International Foundation for Gastrointestinal Disorders lists onions among gas-causing foods that may cause smelly farts. (42)

How to Use Onions in Home Remedies

Hard science has shown many benefits of onions, but there are “old wives’ tales” and anecdotes passed on through the generations that sing even more praises of these delicious root vegetable.

In spite of being pure hearsay and not being backed by scientific research, many people swear by the following folk remedies. Why not give them a try and see for yourself?

Clearing irritant from the eye

Anyone who has ever cut an onion in an enclosed room knows that it’s sure to make you cry unless you jump through hoops to prevent the acrid sulfur emanating from the cut onion from reaching your eye, such as putting on fans or submerging them in cold milk or water.

This can be an annoyance, but it can also come in handy if you have debris or other irritant caught in your eye. In this case instead of rubbing your eye and risking worsening your condition:

  • Cut an onion in half.
  • Take half the onion and hold it directly below the irritated eye—careful not to touch!
  • Let the tears flow and help to clear the debris from the eye.

Treating vomiting

Gobbling down an onion may be the last thing you want to do when you’re feeling nauseated. However, if you feel like you’re going to vomit or have been vomiting, onions may be able to help. Try this:

  • Grate and strain the liquid from one whole white onion.
  • Brew a mug of peppermint tea.
  • Measure out two teaspoons of onion juice and drink it down.
  • After five minutes, drink the mug of tea.
  • Repeat this process until vomiting stops and nausea ebbs away.

Onions for wart removal

With so many wart removal cures available over-the-counter that contain strong acids or freezing implements that can harm healthy skin around the wart and cause painful irritation, why not try for a gentler method that comes from nature—and is far less expensive than the pricey chemical alternatives.

  • Cut a sliver of onion flesh just the same size as the wart.
  • Place the onion onto the wart and secure in place with a small bandage.
  • Change the onion piece and bandage daily.
  • Within days, the wart will be gone.

Another option is to use apple cider vinegar for wart removal.

Onions for removing earwax and earache

If you have an excess buildup of earwax or suffer from earache, you may resort to extreme measures from time to time to keep it under control. If drugstore remedies haven’t worked for you, why not give an onion a chance to do what chemical concoctions have failed to do? Here is how to use an onion for removing earwax:

  • Carve up an onion, reserving the innermost core.
  • Cut the core of the onion into an ear-canal sized plug, making sure it is long enough to grip easily.
  • Place the onion core into your ear and leave it in place overnight.
  • When you awaken, remove the onion piece and cleanse the ear. Your wax will come right out!

Another option is to use this homemade garlic mullein oil for ear infection treatment.

Relieving sore throat and cough

Using onions for treating the symptoms of common cold is an old home remedy which is attributed to the chemical compounds such as polyphenols, flavonoids and quercetin that research shows to have potential anti-inflammatory, antiviral and antioxidant properties.

You can use onions make this easy and effective homemade syrup to relieve sore throat and cough that contains only 3 ingredients:

4 tbsp. quality honey (Manuka honey is the best honey)
1 onion, chopped
3 cm fresh ginger, grated

  • Pour the honey into a bowl and add the chopped onion and grated ginger.
  • Leave the mixture overnight or at least for 6 hours. During this time the active ingredients in the onions and ginger will be released and absorbed in the honey.
  • Take a teaspoon of the natural dry cough remedy (you can remove the onion and ginger) every couple of hours to help clear the mucus and soothe your irritated throat.

Relieving wisdom teeth pain

Chewing on onion is another tested home remedy. If chewing proves to be too painful for you, place a slice of onion on the sore area. Alternatively, you can extract some onion juice and dab it on. Shallots, red and yellow onions tend to be more effective compared to white and sweet onions. There are also other home remedies to get rid of wisdom tooth pain that you can try at home.

Onion relieves mosquito bites

Onion slices are a commonly used method for reducing the swelling and itching of mosquito bites. Simply place a fresh slice of onion on the affected area for a few minutes until the itching subsides. Then rinse with water. Or you can try other natural ways to relieve mosquito bites.

Onion on feet or in sock for detox, cold and flu

Despite the lack of scientific evidence, there is anecdotal evidence about the effectiveness of putting onions on your feet to detox your body and to get rid of flu and cold.

How to use onions in sock under your feet:

  1. Slice an onion into a few thick slices about ½ inch thick.
  2. Place in a pair of tight-fitting socks.
  3. Put the onion in the socks, making sure the onions are tight against the bottom of your feet.
  4. Leave for a few hours to draw toxins from your body and to get rid of cold or flu.

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6 Responses to Onions: Are They Good for You, Nutrition Facts, Proven Benefits (Science Based)

  1. Pattie says:

    I love onions but they give me a lot of gas..

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