Does Red Onion Have Any Health Benefits?

Health benefits of red onions
Red onions are good for you!

Red onions contain antioxidant compounds that help regulate blood pressure, and reduce your risk of type 2 diabetes, heart disease, cancer, and aging. There are also glucosinolates ( indole derivatives) that help with the sulfur compounds, which is why red onions are often used in cooking.

Glucosinolates are biological compounds with a sulfur-containing ring and tail, usually found in the plant kingdom. Glucosinolates belong to a family of compounds called isothiocyanates generated by myrosinase enzymes from breaking down glucosides that naturally occur in plants and certain vegetables such as broccoli, red onion, cabbage, cauliflower, rapeseed, mustard, and horseradish.

Glucosinolate hydrolysis products, isothiocyanate (ITC) metabolites, elicit toxic effects at the cellular level mediated through reactive oxygen species (ROS). ROS strains can be generated within cells by either endogenous or exogenous electrophilic agents such as activated peroxidases like cytochrome P450 inhibitors.

The phytochemical glucosinolates, which are found in vegetables like broccoli and horseradish, have many benefits. These benefits include cancer prevention or slowing down the growth of cancer cells for those who already have cancer.

Glucosinolates are believed to be effective at preventing cancers because they induce apoptosis (programmed death) within certain cells. For instance, these plant-based compounds target prostate tumor cells by activating a protein called p53 that leads to programmed cell death followed by autophagy where the cell self-digests its own healthy contents. By inducing apoptosis or programmed cell death within diseased cells, glucosinolate-containing vegetables might help to prevent cancers from spreading.

Red onions are commonly known for their use in salad dressings, dips, and spreads; they can also be sliced or chopped and added to any dish like spaghetti or onion soup. The juices will turn brown when cooked but stay white when raw (or if very thinly cut).

Sulfur compounds act as antioxidants in the body by reducing inflammation caused by damaging free radicals. This is proven through numerous studies on animals suggesting these anti-inflammatory properties may reduce the risk of cardiovascular disease.

Red onions generally contain many types of natural antioxidant compounds ranging from quercetin to anthocyanins; they may enhance dental health through their antibacterial properties, and they also typically lack sugar or unhealthy fat (such as lard).

Red onion has a long list of benefits. Some of them include:

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  • Improves cardiovascular health by limiting the platelet aggregation in blood vessels helping reduce the chances of heart attack or stroke.
  • Clear sinuses and relieve coughs — reduces cholesterol by 20% when eaten every day for two months.
  • Fight cancer like Giardia lamblia (an intestinal parasite) and Giardomania (a rare form disease that starts in the stomach lining) when eaten raw. Red onion extract may also help fight cancer when applied to the skin. This extract can also inhibit inflammation in cells. Skin cancer cells are much more sensitive to the extract than healthy skin cells because healthy skin metabolizes it much faster.

In January 2018, a study found that when eaten raw, red onion is effective at combating bacteria in the stomach.

In the study, investigators from Lehman College in New York divided 42 healthy volunteers into two groups. The first group ate a meal of tomato and three ounces of red onion before bedtime for five days in a row every weekday.

The second group was given plain toast instead. Not surprisingly, just one day after starting this new regimen, breath samples revealed that people who had been eating the onions were significantly less likely to have dangerous levels of Helicobacter pylori (H pylori) bacteria in their stomachs than those on toast alone.

What is red onion?

Red onion is also known as Allium cepa. Allium cepa, also known as onions, is a genus of perennial flowering plants from the amaryllis family.

Onions come in several varieties and sizes for different uses including sauteed or fried as a vegetable, red onion or Spanish onion used as a flavoring agent to cut sauces, diced onion cooked to give flavor to soups and stews. Onions have been domesticated by humans for at least 4000 years.

The carrot’s close relatives are parsley and garlic; these three vegetables share an extensive root system that creates an important dataset from which alliums can be derived. They were probably consumed even before our own species arose on this planet because their remains have been found quite literally everywhere.

Chemical composition of red onions:

Red onions are composed of varying amounts of chromium, potassium, sulfur, and phosphorus.

The flavor of red onions comes primarily from its volatile compounds which include quinones (which give it a spicy-garlicky taste), γ-glutamyl peptides (gives an initial bite), γ-aminobutyric acid (which gives them a sweet aftertaste). These compounds come from the enzyme that turns amino acids into sugars during ripening.

Red onions can range from light red to dark brown. Red onions contain at least six different pigments, including carotenoids and anthocyanins, which give them their characteristic color. Of the two types of carotenoid pigment molecules responsible for giving these onions a red color, one appears greenish-yellow when converted to alloxanthin by enzymes in the leaves or skin that are cut back when they are peeled off.

Similarly, purple grapes get their color from anthocyanins, but when digested in presence of air this molecule is modified into flavonol quercetin hydrate (a different molecule than obtained after digestion in darkness).


There are many conditions that can be exacerbated by contact or ingestion of the chemical compounds that accompany red onions, such as chemical burns to your skin and eyes.

There are many different oxidative chemicals in raw onion which can cause irritation to those who have been cut or bruised. Raw onions have been linked to pain around soft tissues and have even been shown to induce hair loss.

Some side effects of red onions are burning in the throat when eaten raw, stomach upset when eaten without adequate fluid intake, or skin irritation due to acid in the body reacting with sulfur in red onion.

Onions contain a chemical compound going by the name of quercetin. Quercetin can have a variety of side effects including headaches, allergic reactions, and abdominal upset. Quercetin is also found in apples, berries, broccoli, cherries, grapes tomatoes as well as other vegetables and fruits. However, onions contain more than five times as much quercetin as oranges or apples for example.

In worst-case scenarios, onions may lead to ringing in the ears via an allergic reaction that affects sinuses and the respiratory tract. When consumed with alcohol it could also produce a dangerous cocktail robbing a person of their senses leading to coma or death especially going over 40 grams per kilogram of your weight daily.


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