The health benefits of onions, like lowering levels of "bad" cholesterol, maintaining a healthy gut, reducing the risk of cancer, and preventing premature aging, can be achieved by eating onions raw, or adding them to recipes for salads, preserves, teas, and soups.

The benefits from onions (Allium cepa) come from the nutrients and bioactive compounds they contain, such as fiber, quercetin, and anthocyanins, which possess prebiotic, anti-inflammatory, antidiabetic, and antioxidant properties.

The various types of onions include white onions, red onions, and yellow onions, among others. The main difference between different types of onions is the type of antioxidants they contain. Red onions, for example, are high in anthocyanins.

Health benefits

The main health benefits associated with onions include:

1. Lowering "bad" cholesterol and triglycerides

Onions contain saponins, an organic compound with antioxidant properties that can help lower levels of "bad" (LDL) cholesterol in the blood, reduce absorption of cholesterol in the gut, and increase excretion of cholesterol in the feces;

In this way, onions can help reduce the risk of cardiovascular disease, including atherosclerosis and heart attack.

Learn more about how to lower cholesterol.

2. Maintaining a healthy gut

Inulin is a type of prebiotic fiber that promotes the growth of good bacteria in the intestines, helping to maintain a healthy gut flora and good digestive function. It also helps prevent the growth of bad bacteria that can lead to illness.

The fiber found in onions also helps to regulate bowel movements and prevent constipation by increasing the volume of the feces and stimulating the natural movements of the intestines (peristalsis).

3. Preventing high blood pressure

Onions help in the prevention of high blood pressure because they contain alliin and antioxidants that can improve blood circulation by promoting relaxation of the blood vessels.

4. Lowering the risk of cancer

Antioxidants found in onions, such as quercetin, lutein, and zeaxanthin, prevent oxidative stress and inhibit growth of tumor cells, thus helping to reduce the risk of cancer.

5. Regulation of the immune system

Onions may help to regulate the immune system because they contain vitamin C and other bioactive compounds that fight viruses, bacteria, and fungi that can cause infection and inflammation in the body.

Prebiotic fiber in onions also promotes the growth of good bacteria in the gut that help strengthen the immune system by maintaining the health of the body's defense cells.

6. Prevention against premature aging

Onions are rich in anthocyanins, antioxidants that protect the skin from damage by free radicals, and can help in the prevention of premature aging.

7. Blood sugar regulation

Onions contain fiber, which slows down the absorption of carbohydrates following a meal, helping to regulate levels of glucose in the blood.

In addition, quercetin and the sulfuric compounds found in onions have antidiabetic properties that can help control blood sugar levels and decrease the risk for insulin resistance and diabetes.

8. Relief from cold and flu symptoms

Teas and syrups made from onions can help alleviate symptoms from the flu, colds, and bronchitis. Compounds found in onions have antiseptic properties and act as an expectorant, decreasing secretions, clearing phlegm, and improving cough.

How to eat

Onions can be eaten daily and consumed raw or cooked, alone or added to recipes for salads, preserves, sauces, and soups.

There is not a specific daily intake indicated to reap the benefits of onions, however if it is recommended to consume at least 5 portions (400 grams) of fruits and vegetables per day.

Onions can also be used as natural remedy in the form of a syrup or tea.

When to avoid

People with an allergy or intolerance to onions should not eat them.

Onions may also cause indigestion, heartburn, abdominal pain, and excess gas in people with irritable bowel syndrome, acid reflux, and gastritis.

Onion recipes

Some delicious recipes using onions include:

1. Onion peel tea

Ingredients:

Peels of 2 onions;
32 ounces (1 L) of water.

Instructions:

Wash the peels well. Bring water to a boil in a pot and remove from heat. Add the onion peels. Cover the pot and let steep for 5 minutes.

Strain and drink while still warm. Onion peel tea can be used to help relieve cough in cases of the flu, colds, and bronchitis.

2. Onion preserves

Ingredients:

½ cup apple cider vinegar;
1 Tbsp sugar;
1 ½ Tbsp course salt;
1 red onion.

Instructions:

Wash and peel the onion and slice it thin. Mix vinegar, sugar, and salt together in a small glass jar until the salt and sugar completely dissolve. Finally, add the onion to the mixture and place the lid on the jar. Place in the refrigerator for at least 30 minutes before consuming.

Ideally, the preserves should sit for at least 2 hours before eating and can be stored for up to 2 weeks. For best flavor, consume within the first week.

3. Salad with red onion and lemon

Ingredients:

1 large red onion;
2 lemons;
1 Tbsp sugar;
1 garlic clove;
Salt and black pepper to taste;
1 Tbsp chopped parsley;
1 Tbsp olive oil.

Instructions:

Peel the lemons by removing the rind and the white film underneath. Cut the lemons in segments and place in a salad bowl. Sprinkle the sugar over the lemon.

Next, peel the onion and slice it in thin rounds. Add to the lemon and sugar mix. Slice the garlic thin and add to the salad.

Season with salt, pepper, parsley, and olive oil and serve.

Nutrition facts

The following table contains nutritional information based on a serving size of 100 grams of onions:

Nutrients	White onion (raw)	White onion (cooked)
Calories	40	44
Protein	1.1 g	1.36 g
Total fat	0.1 g	0.19 g
Total carbohydrate	9.34 g	10.2 g
Fiber	1.7 g	1.4 g
Vitamin C	7.4 mg	5.2 mg
Potassium	146 mg	166 mg
Lutein + zeaxanthin	4 mcg	4 mcg

It is important to remember that the health benefits from eating onions can only be obtained when onions are included as one part of a diverse and well-balanced diet. A healthy diet combined with regular physical activity is necessary for overall health.