Scientific Evidence on the Benefits of Onions Including Nutrition Facts

An onion is a vegetable used in cooking and it is full of healthy nutrients. Onion bulbs are extremely good for you and your general well-being, as they contain a plethora of vitamins, minerals, antioxidants and amino acids.

Consuming raw, cooked or boiled onions can help you in losing weight, boosting your cardiovascular health, strengthening your immunity and reducing any inflammation.

There are many varieties of onions, all of them containing 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. However, red onions contain more antioxidants than yellow or white onions.

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

In the following text, you will find out why onions are so good for you and how scientific research backs up claims about the health benefits the onions provide. At the end of the article, we will find out how to use onions in homemade recipes.

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 the nutritional value when comparing white, yellow and red onions. All of the onion varieties are healthy since 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 percent of your recommended daily intake (RDI). 100 grams of onions contain 9.3 grams of carbs and around 4 grams of sugar. However, depending on the variety of the onion, the sugar content could change slightly.

One of the reasons why onions are so good for you is that they contain a plethora 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.

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

Scallions, or spring onions, are sometimes referred to as green onions. The nutritional value of the green onion is also quite impressive. For example, 1 large scallion, about 25 grams, contains 52 mcg of vitamin K, which is 65 percent of the RDI, 4.7 mg of vitamin C, 8 percent of RDI and all the essential amino acids that can be found in regular onions.

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 an abundant source of unique antioxidants and dietary flavonoids. Research has shown that yellow onions contain between 279 and 1187 mg of flavonoids per kilogram of fresh onion. However, red onions have even more antioxidants, between 415 and 1917 mg per kilogram of red onion.

Red onions also contain an antioxidant compound called anthocyanins which have benefits in protecting against numerous diseases. In fact, anthocyanins might make up about 10 percent of the total flavonoid content in red onions.

Quercetin is also another important antioxidant contained in red onions. Research has shown that quercetin has antimicrobial properties and can help to lower the blood pressure. Quercetin is also more prevalent in red onions than in yellow and white onions. Other studies have shown that the sulfur containing compounds in onions have anticancer properties.

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

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

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 consume onions and other allium vegetables.

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

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.

Drinking onion skin tea can also help in lowering the 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.

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.

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 other study found that onions were better than garlic for helping in preventing blood clotting. Other studies have shown that a combination of raw onions and garlic help to prevent red blood cells from clumping together.

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).

Clinical trials involving adults have also shown that onions have an effect that lowers the cholesterol. Overweight and obese women were given between 80 and 120 grams of raw red onion a day to consume. After 8 weeks, scientists noted that there was a significant decrease of the total amount of cholesterol in the blood.

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 an increase in body weight. Scientists reported that consuming foods which are rich in flavonoids are essential for body weight management and onions are one of the best sources of flavonoids in the human diet.

Researchers concluded that onion skin tee has the potential to treat, prevent and manage obesity.

Other studies on onion extracts have found similar results, in that they can help to regulate the blood sugar levels in the body as well as lower the body weight.

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 it 1 or 2 times per day to help boost the effects of your weight loss program.

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).

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

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.

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.

Onions Promote Healthy Digestion

Onions contain beneficial compounds that are good for your digestive system. In fact, consuming onions could help in preventing Clostridium difficile-related diarrhea, which is a bacteria that causes inflammation of the colon.

The onions contain a type of dietary fiber called oligofructose. A randomized controlled study on the effects of oligofructose on the digestive system found out that it has a prebiotic effect. Consuming oligofructose helped to preventrecurring diarrhea that was associated with C. diff infections.

The Journal of Nutrition reports that onions contain about 25 percent of oligofructose and insulin which are types of plant based fiber. Onions are only second to wheat as being a naturally occurring source of insulin and oligofructose.

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.”

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.

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. Other studies on the anti-inflammatory effect of the onions have found that onions can help in protecting the liver health when consumed as part of a healthy diet.

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. 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.

Onions Help to Strengthen Bones

Compounds in onions such as the 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 increasing the bone density in perimenopausal and postmenopausal women. Reports indicate that women who frequently consumed onions can lower their potential risk of hip fracture by more than 20 percent.

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.

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.

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 out that red onion extracts had a protective effect against prostatic hyperplasia, or more commonly known as an enlarged prostate.

Clinical trials on adult men have also pointed to the fact that consuming onions helps in protecting prostate health. In fact, it has been shown that men who consume more than 10 grams of Allium vegetables per day, such as onions, have a significantly lower risk of prostate 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 linked with a decreased risk of developing cancer. The onion has a protective effect against stomach cancer, colorectal cancer, esophageal cancer and prostate cancer.

Although cooking onions reduces the number of antioxidants it contains, some studies have shown that cooking with crushed onions does not destroy the sulfur rich compounds that have the anticancer effects.

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.

Onion Juice Can Improve Hair Growth

Onion juice helps you in re-growing your hair and making it stronger. The onion juice improves the blood circulation and provides the hair follicles with sufficient nourishment. Onions also have an antibacterial property to them, so it helps with scalp infections that might contribute further to hair loss.

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

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

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.

According to a study which was 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.

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.

How Long Are Onions Good For

Onions should be stored in a cool and dry place where there is plenty of ventilation. You should also avoid storing fresh onion in plastic bags since they will tend to rot quicker. Instead, you should 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 correctly, the antioxidant content of the onions can actually increase. Researchers found that the total number of phenolics, antioxidants and flavonoids in onions were highest after 3 months of proper storage.

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.

According to, 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. 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 reported 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.

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

Eating too many onions per day can also cause you to have bad breath due to sulfides which are present in the vegetable. In fact, the smell of onions can also be emitted through your pores.

The sulfur content in onions can also cause you to have odorous gas. The International Foundation of Gastrointestinal diseases lists onions among the gas-causing foods that can cause smelly farts.

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 this 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 that has ever cut an onion in an enclosed room knows that it is surely going 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 risk worsening the 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 the following:

  • 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 don’t you try out a gentler method that comes from Mother Nature and it is far less expensive than that of 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 might resort to extreme measures from time to time to keep it under control. If drugstore remedies have not worked for you, why don’t you give the onion a chance to do what chemical concoctions and products 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.

Relieving Sore Throat and Cough

Using onions for treating the symptoms of the common cold is an old home remedy which is attributed to the chemical compounds such as polyphenols, flavonoids and quercetin that research has shown 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 tablespoons of 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 gently. Shallots, red and yellow onions tend to be more effective compared to white and sweet onions.

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 it with water and you are all good.

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 the cold and flu.

How to use onions in sock under your feet:

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

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