The onion is a root vegetable that seems to have evolved along with the human race. At first, it was used for more than food. Prehistoric people are thought to have anointed their skin with onion juice to keep predators away. It wasn’t long before people discovered that the onion, though tear-inducing, was good to eat. Then, they discovered onion health benefits. For example, American colonials fed roasted onions to people who suffered from everything from diabetes to baldness. This article explores onion health benefits with the nutritional value and main uses of onions.

Onion Health Benefits

Onion health benefits are at least partially bestowed by the chemicals that make them pungent. These are compounds that contain sulfur, including diallyl sulfides and sulfoxides. Onions are also rich in health-giving flavonoid polyphenols, including quercetin.

Cardiovascular Benefits

Studies hint that onions support the cardiovascular system by keeping blood platelets from clotting in unhealthy ways. Blood clots in arteries can lead to strokes or heart attacks. Onion’s sulfur compounds lower levels of cholesterol and triglycerides and support the healthy functioning of red blood cell membranes. The cardiovascular benefits of onion work better when they are combined with other vegetables and fruits rich in flavonoids.

Bone Health

Other onion health benefits are the increase in bone density and support of connective tissue. Increased bone density is especially helpful in women who have undergone menopause and are at risk of losing bone density, which can lead to fractures. However, nutritionists claim that this protection works only if the woman eats an onion every day.

Anti-inflammatory Effects

Onions ease the intensity of inflammatory disorders. Scientists believe that this happens because of a sulfur molecule called Onionin A, which is found in the bulb of the plant. This molecule inhibits white blood cells that cause inflammatory responses. Though these responses are important to help the body fight off pathogens and heal from injuries, too much inflammation is undesirable.

Anti-Cancer Effects

Eating onions can lower the risk of some cancers. Unlike the support of healthy bone density, a person doesn’t have to eat an onion every day to benefit from this. A person only has to eat onions one to two times a week to lower their risk of ovarian, laryngeal and colon and rectal cancers. However, if a person wants to lower their risk of oral and esophageal cancers, then they’ll need to eat onions every day.

Blood Sugar Control and Others

Other onion health benefits may include blood sugar control. Onions may also have properties that fight the bacteria that cause tooth decay. This benefit is strongest when you eat fresh, raw onion.

Nutritional Value of Onion

Onion is abundant in several necessary minerals and vitamins. Among the nutrients found in onion are:


Biotin is one of the B-complex vitamins. It’s a type of enzyme that helps to break down and synthesize fatty acids and helps the body use protein and other B vitamins. One cup of onions provides 27 percent of the daily value, or DV of biotin.


Onions also provide 16 percent of the DV of manganese, copper and vitamin B6. Manganese is a trace mineral that helps to activate several enzymes and helps the body use biotin, thiamine and vitamin C. It also helps synthesize cholesterol and fatty acids.


Copper is also necessary in small amounts. It helps the body make hemoglobin and red blood cells and is found in enzymes that both break down and build bodily tissues. It helps the body metabolize protein and is necessary for healing.

Vitamin B6

Vitamin B6, or pyridoxine is necessary for the body to absorb vitamin B12. It is also necessary for the production of magnesium and hydrochloric acid, which helps the stomach break down food. In addition, vitamin B6 helps the body use carbohydrates, proteins and fats. It is also necessary for the production of red blood cells and antibodies.

Vitamin C

Onions are also a good source of vitamin C. Vitamin C is an antioxidant that protects the cells in the body from free radical oxygen molecules, which damage other molecules, including DNA, by ripping electrons from them. But Vitamin C’s main job is to help maintain collagen, a springy protein that’s necessary for the connective tissue that supports the structures of the body.


Onions also provide about 12 percent DV of fiber, which aids in the health of the lower gastrointestinal tract and help lower levels of “bad” LDL cholesterol and support higher levels of “good” HDL cholesterol.

Red Onion Versus Yellow Onion

A lot of people wonder what the differences are between red onions and yellow onions in terms of benefits and nutritional value. This may come as a surprise, but even though red and yellow onions look so different, when it comes to nutrition, they’re not so different actually.

Red and yellow onions containt more or less the same amount of vitamin C and calcium. They’re also very low on the glycemic index. There are some differences in the amount of antioxidants they contain. Red onions seem to have a higher amount than yellow in general. Red onions also tend to have less sugar than yellow onions. You can tell this from the fact that yellow onions tend to be sweeter. However, the difference in amount of sugar is relatively small.

Both red and yellow onions contain a similar amount of sulfur coumpounds. However, red onions have more flavanoids than yellow onions, which makes them better blood thinners than yellow onions.

If you’re wondering whether to go for red or yellow onions for a specific recipe, these are just some of the things to consider. You should think about texture. Red onions tend to a little bit more tough when raw. When cooked, they take longer to soften, unlike yellow onions. Red onions also tend to have a more intense flavor than yellow onions. And this all depends a lot on just sheer luck. Older onions will be tougher and more flavorful than younger onions. So, you may find yourselves choosing a yellow onion over a red onion for its milder taste and getting a much more powerful taste than if you would have chosen a younger red onion.

However, as a rule of thumb, the basic take away is that red onions are more pungent than yellow. If a recipe calls for a specific type of onion, and you’re not sure which type to go for, it’s best to stick to the recipe. Otherwise, it all comes down to taste and preferences. When it comes to onion health benefits, whether they are red or yellow, it doesn’t really matter all that much.

And while we’re on the topic, you can also take a look at the health benefits of scallions.


Uses of Onionsliced onion

There are few world cuisines that do not use onions. They are the foundation of many types of meals, even desserts. The French are renown for their onion soup. Onion and its close relative the scallion are aromatics in Asian stir fry. Chefs around the world use onions to make:

  • Pickled onions
  • Tarts
  • Onion marmalade
  • Slaw
  • Onion breads and cakes

Onions are baked, fried, stewed and roasted. Leek, another onion relative, is added to vinaigrettes and custards. Here is a simple onion recipe from the Piedmont in Italy:

Pearl Onions Ivrea Style


  • 1 1/2 pounds of pearl onions
  • 2 to 3 tbs. of best olive oil
  • 4 tbs. butter
  • 1 bay leaf
  • 1/2 cup chicken stock
  • 2/3 cup dry white wine
  • Salt to taste


Peel the onions carefully, and blanch them in boiling water for a minute or two.
Heat the olive and butter in a skillet, then add the onions and the rest of the ingredients save the wine.

Cook gently until the onions are golden and soft, then add the wine and continue until the liquid’s reduced by half. Serve hot. Serves six people.


Used for thousands of years, especially but not exclusively as a food, onion is rich in nutrients and has surprising health benefits. Moreover, onions are inexpensive to buy and quite easy to grow.

Do you know of any other health benefits onions have that we didn’t mention? Have you tried any of the recipes in our article? Let us know in the comments!

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