12 Immune-Boosting Benefits of Onions

Despite their repelling smell and their tear-inducing capacity, onions are a true weapon against disease, researchers say. Pertaining to the lilly or allium vegetable family, not only do onions give a sweet-pungent flavor to any dish, but they also shower you with a lot of health benefits boosting your immune system function to help your body fight off diseases and illnesses. The high concentration of polyphenols (one of the widest categories of phytonutrients found in food, including a full range of flavonoids and vitamins) that onions have helps improve overall health and increase immunity. If consumed raw, researchers say that onions can reduce the level of bad cholesterol (LDL), thereby improving cardiac health.

Benefits of Onions

The bright green tops of onions are high in vitamin A and therefore highly recommended for a balanced diet. Onion juice is a potent anti-inflammatory agent offering instant relief in case of insect bites and several inflammatory conditions.

The chromium in onions helps regulate blood sugar levels. Quercetin is another potent compound plentifully present in this vegetable found to significantly contribute to preventing formation of carcinoma and hence reduce cancer risks. Onions can also protect the body against free radicals significantly lowering your chances of developing gastric ulcers.

12 Health Benefits of Onions

1. Onions Has Anti-Clotting Propeties and May Enhance Cell Membrane Function

Due to it’s unique composition, compelling evidence from animal studies shows that the sulfur element in onions have anti-clotting properties and can inhibit the aggregation of platelet blood cells leading to thrombus formation. Furthermore, the sulfur in onion was shown to decrease cholesterol/trygliceride levels and enhance cell membrane function in red blood cells. (1)

2. Onions May Promote Cardiovascular Health

Human studies link the onion’s therapeutic action to aid and improve cardiac functions to a healthy diet including a generous serving of this vegetable on a regular basis. Researchers suggest that the onion is a food that can help protect the heart and blood vessels if consumed alongside other flavonoid-rich vegetables and fruits.

The protective element of onions in this overall nutritional context extends over to the prevention of heart attacks. Across all these studies, participants with a higher intake of vegetables, onions in particular, showed lower risk to developing cardiovascular disease or experience a heart attack. (2)

However, given that most of the onion’s benefits in preventing cardiovascular disease were determined mainly based on dietary research including thousands of participants, and that generally, onions are consumed in combination with other veggies and fruits, it is difficult to establish the optimal dietary intake.

5. Onions May Increase Bone Density

Multiple studies have determined that onions may also increase bone density and can provide added benefits to women in the menopausal stage when decrease. (3)

Additionally, researchers associated frequent consumption of onions to a reduction of hip fracture risks in post-menopause women. In this context, ‘frequent’ means ‘daily’. However, sporadic servings of onions, such as monthly or even less, did not prove effective or beneficial compared with daily consumption, researchers suggest.

Due to the high sulfur content, onions can work miracles on our connective tissue. (4) Most of our connective tissues need sulfur to grow and develop. GAGS (glycosaminoglycans) are sulfuric components that the connective tissue needs and onions have plenty. Therefore, a diet rich in onions promotes connective tissue health.

6. Onions Have Anti-Inflammatory Properties

Although it does not enjoy the same notoriety as garlic when it comes to improving symptoms in inflammatory health conditions, such as rheumatoid arthritis or allergic airway inflammation, onions do have significant therapeutic effects.

A truly unique component found in onion bulbs, called Onionin A, was shown to hinder macrophage activity. (5) Macrophages are specialized white blood cells and are one of the key drivers of the human immune system. When an infection is detected in the body, these cells act by triggering an inflammatory response. Despite that their overall action may be good, in some cases, it may lead to undesired inflammation. What Onionin A specifically does is to keep this inflammation in check.

7. Onions are Rich in Antioxidants

The antioxidants in onions, especially the truly 5-star compound, quercetin, has amazing anti-oxidative capacities that also work as an anti-inflammatory agent. (6) By default, antioxidants impede the oxidation of fatty acids. Specifically, the lower the levels of oxidized fatty acids are in our bodies, the fewer pro-inflammatory molecules it produces and hence, the lower the risk of inflammation.

8. Onions May Reduce Risk of Developing Several Types of Cancer

This allium vegetable has attracted the attention of cancer researchers and studies were not late to prove that onions indeed are able to reduce risk of several types of cancer. (7) Surprisingly, unlike the research on the onion’s benefits in strengthening bone and lowering the risk of hip bone fracture, even moderate consumption of onions can help reduce risk of carcinoma formation. Nevertheless, ‘moderate’ is to read ‘once or twice a week’ or ‘five to six times weekly’, according to some studies.

Specifically, consumed in moderate amounts, onions account for lowered risk in developing colorectal, laryngeal or ovarian cancer, researchers say. In other types of cancer though, moderate intake did not show a significant decrease in risks. In these cases, including esophageal cancer and cancers of the oral cavity, daily onion servings are recommended for optimal results.

Numerous factors account for the findings of these studies. However, they all seem to carry the same message: eat as much onions as possible. A few thin slices in a salad are good, but to benefit fully, enjoy the taste, and be at ease about any risks of developing cancer, you may consider eating about half of an onion at one meal.

9. Onion May Regulate Blood Sugar Levels

Animal studies revealed the incredible potential of onions to regulate blood sugar levels. Most of these studies were conducted on rats and used either onion juice or onion extract.

Human studies have shown that due to the inulin it contains, onions can actually reduce the risk of diabetes. (8) Among the patients diagnosed with type 2 diabetes, glycemic control was improved in those who had a supplementation of inulin. Furthermore, inulin enhanced antioxidant activity and helped patients lose weight.

10. Onions May Help Prevent Ulcers

Thanks to it’s high flavonoid content, this flavory ingredient in our food can actually help fight any type of ulcer. Recent research has also proved that onions are extremely effective against H. pylori. H. pylori are bacteria living in the digestive tract. Up to 20 percent of the Americans have H.pylori dormant in their gut, but do not necessarily develop ulcers. Eating flavonoid-rich foods was shown to further reduce risks of developing the disease. (9)

11. Onions May Help Treat and Prevent Bacterial Infections

Findings in numerous studies indicate that onions can help treat and even prevent bacterial infections. (13) Its sulfur compounds and quercetin have proved effective in combatting Streptococcus mutans and Streptococcus sobrinus, both of which account for tooth decay. Onions can also work magic on gum infections, preventing the action of bacteria, such as Porphyromonas gingivalis and Prevotella intermedia.

One study even suggests that fresh onion proved particularly effective against these bacteria, while cooked onions did not have the same effect, nor did raw onions chopped and left to sit for a couple of days at room temperature.

Scientific evidence also points out that the duration of storage and the way that onions are served can impact its antibacterial efficacy. Experts advise that onions should be consumed mostly raw for best results. Extended exposure to heat (more than 10 minutes) may affect some of its properties and make this allium vegetable less effective in preventing infections.

12. Onions Promote Healthy Digestion

Onions are an important source of prebiotic inulin. This compound is responsible for supporting the gut microbiota, thereby promoting digestion. Inulin proved effective in combating obesity and type 2 diabetes. The sulfur contained in onions is accounted for reducing blood clotting and decreasing triglyceride levels, while allium and allyl disulphide can improve blood vessel stiffness due to their capacity to release nitric oxide.


Despite its numerous benefits, particular attention must be paid in the following cases:

  • Pregnancy and breastfeeding;
  • Bleeding disorders (onion is likely to increase the risk of bleeding if taken as medicine especially in the form or dietary supplements);
  • Diabetes (although proved beneficial by some studies, blood sugar level should be checked regularly when taking allium-based supplements);
  • Surgery (stop taking any onion treatment at least two weeks before surgery to prevent any bleeding risks during and after the procedure).


Onions are an extremely beneficial food to add to one’s diet for the sake of bettering health and well being. Regular consumption of onions can boost the immune function and improve overall health.

Although there is no scientific indication as to what is the optimal intake or how many onion servings a healthy diet should include, adding onions to your menu list two to three times a week will definitely pay off in the long term.

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