Onions (Allium cepa L.) are a vegetable that belongs to the Allium genus and believed to have originated in Central Asia.
They are often said to stimulate tears, but they can do a little bit more than that.
In fact, they are a major dietary source of the antioxidants vitamin C, glutathione and quercetin, which have been linked to various health benefits, including reduced risk of coronary heart disease, Alzheimer’s disease, cancer and other major chronic diseases.
They are also an excellent source of fructans which promotes digestive health and fights pathogens and carcinogens.
Usually red, onions can come in manifold cultivars and varieties, including Tokyo long white, Utah yellow sweet Spanish, Patterson, Italian torpedo, and more.
Read on to recognize the amazing health benefits of onions and how they can keep your heart healthy.
- Good Nutritional Value
Onions are laden with beneficial nutrients and health-promoting phytochemicals. These include phenolic compounds (e.g. quercetin) which have been associated with reduced risks of cardiovascular disease, Alzheimer’s disease, diabetes, cancer and other chronic diseases (1).
They are nutrient-dense with 1 cup (128 grams) of chopped onions containing just 64 calories but delivering an array of complex vitamins and minerals.
A particularly valuable vitamin in onions is essential vitamin C (19% DV) which plays an important role in bone formation, reduces allergic reactions, protects the immune system, and more.
Vitamin C also acts as an antioxidant that protects your body from free radical damage, and thus prevents diseases induced by tissue damage, such as cancer and atherosclerosis (2).
Onions are also a reliable source of glutathione, another excellent antioxidant and chemoprotective agent which offers protection against cellular damage. This is particularly due to their organosulfur compounds and vitamin C content. Indeed, many studies have shown that vitamin C helps increase glutathione levels in the body (3).
It is true that onions are considered lower potassium food (233.6 milligrams). But given that less than 2% of Americans achieve the recommended daily value for potassium, any supplementation is welcome.
Overall, onions are rich in manifold health-promoting components, most notably flavonoids such as quercetin, vitamin C and potassium.
- Promotes Cardiovascular Health
Onions contain phytochemicals, most notably the flavonoid quercetin, and antioxidants that are effective in lowering serum cholesterol levels and reducing inflammation and —potentially— recurrent blood clots.
Quercetin is a flavonoid that is highly concentrated in onions with up to 300 mg/kg. The only vegetable with higher quercetin content is kale.
A 2007 study in 41 men and women with prehypertension and hypertension found that a dose of 730 milligrams of quercetin per day exerts favorable effects in these patients by reducing blood pressure and reduced arterial pressures by 5 mm Hg (6).
Recent findings have shown that onions may reduce cholesterol levels.
One study examined the effects of onion consumption on lipoprotein levels (total cholesterol, LDL and HDL) and triacylglycerides and reported that dietary intake of onions may be part of primary prevention measures of cardiovascular events and atherosclerosis (7).
To sum up, onions exert favorable effects on cardiovascular health and help prevent vascular dysfunction.
- Laden with Highly Beneficial Antioxidants
Antioxidants are substances that maintain body tissue and help reduce/slow down cell and tissue damage by protecting them from the effects of free radicals.
The content of antioxidants in onions can vary greatly between cultivars and varieties (e.g. shallots, pearl onions, white onions, ramps, etc.).
While dried red onions contain a 202 mg.kg-1 concentration of the flavonoid quercetin and its glycosides, yellow onions “Sweet Savannah” provides you with the highest concentration of 286.40 mg.kg-1 (8).
They contain a plethora of other phytochemicals, among which there are at least 25 dietary flavanols, including anthocyanins, luteolin and kaempferol (9).
Several sources of evidence have shown that flavonoids reduce the risk of chronic diseases, such as heart disease, diabetes, neurodegenerative disorder, cancer and cataracts.
For example, one study examined the mechanisms of action of phytochemicals in the prevention of cancer and found that dietary intake of 5-10 servings of fruits and vegetables contribute to lower risk of chronic diseases (10).
All in all, onions are rich in quercetin and anthocyanins, which are highly beneficial antioxidants that can help reduce the incidence of chronic diseases.
- May Help Prevent Cancer
Cancer is a group of related diseases which cause abnormal changes and growth of cells, often breaking away and spreading to other parts of the body (metastasis).
Onions, garlic, Rakkyo, Kurrat and leeks are cultivated alliums that belong to the Allium genus with putative cancer-preventive properties. This is particularly due to their large amounts of chemoprotective compounds.
One population-based case-control study reported that onions have a strong inverse association with pancreatic cancer. The results showed that, compared with those in the lowest quartile of specific vegetables and fruits, the risk of pancreatic cancer was 0.46 (0.33-0.63) in the case of onions (11).
Another 2019 case-control study published in the Asia Pacific Journal of Clinical Oncology examined the relationships between the consumption of allium vegetables, most notably onion and spring onion, and colorectal cancer and found that they can lower colorectal cancer risk (12).
Overall, numerous studies have linked onion consumption and fewer incidences of pancreatic cancer, colorectal cancer, breast cancer and potentially stomach cancer.
- Helps Improve Your Digestive Health
Whether you are underweight or overweight, you are prone to digestive problems.
Onions help keep your digestive system healthy and solve digestive problems.
They are an excellent source of dietary fiber, most notably fructans which is a soluble probiotic that stimulates the growth of beneficial microorganisms in the colon.
Many studies have demonstrated the overall health benefits of fructans. These include enhancing digestion and absorption, exerting antimicrobial effects against pathogens and getting rid of carcinogens and other toxins in the body.
In addition, fermented fructans produce short-chain fatty acids and metabolic products that enhance digestive health and strengthen the immune defense system (13).
So, what are you waiting for to make a gut boosting onion and vegetable soup?