Onions are part of the plant family Allium, which also includes chives, garlic, and leeks. These vegetables have pungent flavor characteristics and certain medicinal properties.
The size , shape, color and flavor of the onions vary. The most popular varieties of onions are red, yellow , and white. The taste of these vegetables can range from sweet and juicy to sharp, spicy, and pungent, sometimes depending on the growing and consuming season.
Allium vegetables have been grown by farmers for centuries. According to the United Nations Food and Agriculture Organization China is the biggest producer of onions worldwide.
It is common knowledge that chopping onions causes watery eyes. Yet onions may also bring possible health benefits. This may include reducing the risk of multiple cancer types, improving mood, and maintaining healthy skin and hair.
We address the possible benefits of onions in this article, their nutritional value, and how to incorporate more of them in the diet.
Researchers have extensively looked at allium vegetables in relation to cancer , especially stomach and colorectal cancers.
A research published in the Asia Pacific Journal of Clinical Oncology in 2019 compared 833 people with colorectal cancer to 833 people without the disease.
The researchers found that among those who frequently consumed allium vegetables, such as onions, the incidence of colorectal cancer was 79 percent lower.
Experts don’t fully understand the exact mechanism by which certain onion compounds inhibit cancer. Many speculate that onions inhibit tumor growth and mutation of a cells.
At least 13.11 percent of an adult’s recommended daily intake of vitamin C is also provided by one cup of chopped onions. As an antioxidant, this vitamin helps counter free radical compounds that have cancer-related ties.
One 2015 analysis found a general association between increased allium vegetable consumption and a reduced risk of cancer, especially stomach and gastrointestinal cancers.
The authors note that the onions contain compounds called organosulfurs, some of which suppressed tumor growth aspects. They do conclude, however, that not all organosulfurs have antioxidant properties.
Further research is needed to confirm which onion compounds have cancer-protective effects.
The review has also highlighted research gaps to date. The authors suggested that onions and other allium vegetables are not isolated to prevent cancer but work in tandem with other factors in the lifestyle to reduce risk.
They also advised that while research has revealed some associations between allium vegetable consumption and a reduced risk of cancer, it is not yet clear how much a person needs to eat to get the full benefit.
Skin and hair
As a good source of vitamin C, onions may support the building and maintenance of collagen.
Collagen provides structure to skin and hair.
Blood pressure moderation
A 2019 study showed that when the researchers extracted and administered it as a supplement, quercetin, a compound in the skin of onions, had ties to a lower blood pressure.
However, the research did not investigate the potential effects of consuming onion as part of the diet on the blood pressure, rather than taking quercetin in alternative form.
Onions are a food that is dense in vitamins and minerals, meaning that they are high in vitamins , minerals and antioxidants while low in calories.
One cup of chopped onion provides:
- 64 calories
- 14.9 grams (g) of carbohydrate
- 0.16 g of fat
- 0 g of cholesterol
- 2.72 g of fiber
- 6.78 g of sugar
- 1.76 g of protein
According to the recommended daily allowance (RDA), and adequate intake (AI) values from the American Dietary Guidelines, onions are a good source of the following nutrients:
|Nutrient||Percentage of daily requirement in adults|
|Vitamin C (RDA)||13.11% for males and 15.73% for females|
|Vitamin B-6 (RDA)||11.29–14.77%, depending on age|
|Manganese (AI)||8.96% for males and 11.44% for females|
Onions also contain small amounts of:
- the antioxidants quercetin and sulfur
Onions pose little risk to those people who eat them.
Some people may however have an onion allergy or intolerance. Anyone who has a reaction after eating them should certainly seek medical attention.
Read more on food allergy symptoms here.
Why does chopping onions cause tears?
Onions have a reputation for making people weep while cutting or chopping. This response occurs due to the presence of a gas called syn-Propanethial-S-oxide.
This chemical is a compound liquid that acts as a lachrymatory agent, that is, it causes the eyes to tear or sting.
The National Onion Association suggests chilling an onion for 30 minutes, and then cutting off its top to reduce tears during chopping. The individual should then peel the outer layer of the onion and leave the root intact, since this part has the highest lachrymatory agent concentration.
Despite the tears they can produce, onions can be a healthy addition to any eating plan. The overall eating pattern of a person, however, is most important in preventing disease and in good health.
When peeling people should look for those that are dry and firm with little to no scent when selecting onions.
Including onion in a dish is a great way to boost your flavor without adding calories , fat or sodium.
For many kitchens onions are a staple and complement most dishes. People can use raw chopped onion in a sandwich filling or as a topping for salad. This vegetable makes a delicious addition to salsas and dips, too.
Healthful recipes that include onions as a primary ingredient include:
- Pickled onions
- Spanish potato and onion omelet
- Dairy-free onion dip
Also, when people saute, roast, grill or caramelize them, they taste great.
While onions make a great addition to a balanced, nutritious diet, humans should eat a variety of foods rather than focusing on individual options.
Are the spring onions as nutritious as regular onions?
They are similar in nutritional content but spring onions contain more plant-derived antioxidants than bulb onions as the plant’s leafy green part is larger.
There are also B vitamins and other minerals in spring onions, including copper , iron, manganese, and calcium. The leafy green part of the plant is, however, a good source of folic acid.
Nevertheless, since people prefer to use spring onions as condiments, and in smaller quantities than bulb onions, the intake of nutrient is generally lower. Miho Hatanaka, RDN, LD
Answers represent our medical experts’ opinions. All material is purely informational and medical advice should not be considered.