Not only does it add extra flavour to your dish, but also serves as a source of many health promoting nutrients.
Onion, also known as ‘BULB ONION’ is a very important spice which usefulness cannot be under-estimated. It’s the most widely cultivated species of its genus ‘Allium’. This plant can either be a biennial or a perennial plant, but it’s usually treated as an annual and harvested in its first growing season.

Scientific Blassification
Kingdom: Plantea
Class: Angiosperm
Order: Asparagales
Family: Amaryllidaceae
Subfamily: Allioideae
Genus: Allium
Species: A. cepa
Binomial name: Allium cepa

Nutrients readily available in a bulb of onion include:
1. Carbohydrates
Sugars
Dietary fibers
2. Vitamins
Thiamin (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Vitamin B6
Folate (B9)
Ascorbic acid (Vitamin C)
3. Fat
4. Protein
5. Minerals: Calcium, Iron, Magnesium, Manganese, Phosphorus, Potassium, Zinc.
6. Other constituents: Water, Fluoride.

Health Benefits
Onions are rich in Vitamin C, sulphuric compounds, flavonoids and other phytochemicals. But emphasis would be laid on its flavonoid constituents.
Onions contain a high ratio of polyphenols, a compound that plays an important role in both protection and reduction in the progression of diabetes, cancer, neurodegerative and cardiovascular diseases. They contain more polyphenols than even garlic or leeks, and are one of the best sources of a polyphenol called flavonoids, especially QUERCETIN.
Quercetin is a flavonoid with very powerful antioxidant and anti-inflammatory properties that help fight chronic diseases like heart disease and cancer.

Some of the major functions of quercetin include:
1. Reduces the risk of atherosclerosis
2. Helps to prevent death as a result of heart diseases
3. Reduces blood pressure
4. Inhabits the growth of cancer cells from breast, colon, prostate, ovarian and lung tumors.

Other health benefits include:

It prevents inflammatory process associated with asthma, reduces symptoms associated with diabetes, improves bone health and diminishes replication of HIV. It also lowers the risk of having cataract and antibacterial and antifungal.

When removing the outer skin of an onion, be careful to remove as little as possible. This is because the outer layers are thought to be the most nutritious, having the highest amounts of flavonoid content.
Onions release a gas called Lachrymatory factor (L.F), which causes eye irritation and subsequent tearing (shedding of tears). This might make it impossible to peel off the outer flesh as little as possible, but there is a trick that my help to accomplish this.
Eye irritation can be avoided by cutting onions under running water or submerged in a basin of water. Leaving the root end intact also reduces irritation as the onion base has a higher concentration of sulphur compounds than the rest of the bulb.

Refrigerating the onions before use reduces the enzyme reaction rate and using a fan can blow the gas away from the eyes. And the more often you chop onions, the less you experience eye irritation.

Storage
Onions are better stored at room temperature, optimally in a single layer, in mesh bags in a dry, cool, dark and well ventilated environment. With this storage method, onions have a shelf life of 2-4 weeks.

Onions will absorb moisture from vegetables when placed close to each other, and this may cause them to easily decay. If onions are refrigerated, they have a shelf life of around one month. Any cut pieces of onion are best tightly wrapped, stored away from other produce, and use within 2-3 days.

Never mind the tears they bring on, onions lavish you with health benefits while adding oodles of taste to your food.

Note: An Onion a day may help keep the doctor away!

Written by: Omoyeni Oluwasegunfunmi José for Hub201.com

Source: http://www.hub201.com/onion-a-spice-to-food-and-health/