Common onion, botanically called Allium cepa (Fam. Amaryllidaceae), is a vegetable that is cultivated and consumed across the world. It is called albasa in Hausa, yabasi in Igbo and alubosa in Yoruba. Though it is a temperate crop, it can be grown under a wide range of climatic conditions (temperate, tropical, and subtropical).
Onions are nutrient-dense, meaning that they low in calories but high in vitamins and minerals. This vegetable contains vitamin C, the B vitamins, including folate and pyridoxine, and potassium. Onions contain flavonoids like quercetin, anthocyanins, fisetin and onionin; carbohydrate, protein and fibre.
Onions can be enjoyed either raw or cooked. It may be added to food while cooking, boiled, fried or dried. It may also be taken as a juice or applied topically as a paste.
Pharmacological actions and medicinal uses
Research shows that eating onions may reduce heart risk factors, such as high blood pressure, elevated triglyceride levels and inflammation. Studies show that onion consumption is associated with improved bone density. Onions have been shown to inhibit the growth of potentially harmful bacteria like E. coli, H. pylori and S. aureus.
Onions are rich sources of prebiotics, which help boost digestive health, improve bacterial balance in the gut and benefit the immune system. Chewing raw onions improves oral health. They help eliminate bacteria that can lead to tooth decay and gum issues.
Onions, when combined with garlic, are known to be effective antidepressants, painkillers, anticoagulants, and anti-inflammatory. The anti-inflammatory properties of onions can also help soothe respiratory ailments like asthma. A mixture of onion juice and honey is said to be effective as a cure for fever, coughs, common cold, catarrh and allergies. A small piece of onion, kept under the nostrils and inhaled, helps to stop or slow down a nose bleed.
Substituting onions for high-calorie foods may contribute to weight loss indirectly. As a result of some elements and phytochemicals, onions have been shown to reduce blood sugar, decrease tumour development and slow the spread of ovarian and lung cancer in test-tube studies. Onions contains compounds that are said to reduce the risk of glaucoma, macular degeneration and cataracts. They are also effective in the management of conjunctivitis.
Onions are one of the herbal medicines used for managing sexual impotence and erectile dysfunction; taking onion juice with honey is known to increase fertility in men. As a result of its antimicrobial and anti-inflammatory qualities of onion is said to be used in the treatment of acne and pimples, to soothe stings and bug bites, to get rid of moles, treat hair dandruff and enhance hair growth.
Although onion is used in treating several gastrointestinal disorders, excess consumption may cause gastric irritation, vomiting, nausea, and burning. Uncontrolled intake of onion can lead to heartburn, especially in pregnant and nursing mothers. Onion often leaves a bad breath after its consumption due to its strong aroma.
An estimated 105 billion pounds of onions are grown across the world every year. According to the Food and Agricultural Organisation (FAO), Nigeria cultivated 996,519 metric tons of dry onions and 248,072 of green onions in 2017. A 50kg bag of onions, which was sold at an average of N14,000 in September, 2019 sold for N38,000 in November, 2019 – indicating a 171 per cent rise in price. With proper care against diseases, proper storage and good road network, onions can enrich individuals, communities and Nigeria through its cultivation, sales and processing.
Pharm. Ngozika Okoye
MSc, MPH, FPCPharm (Nigeria Natural Medicine Development Agency)