Vegetables are important accompaniments for the main course of meal, which is by and large a carbohydrate-based food (wheat, rice or millets). It not only makes the meal more palatable, but also wholesome with its diverse color, smell and taste. More importantly it facilitates the easy movement of food through the bowel, better absorption by the body and till the elimination. Besides hunger satiation, it helps to maintain the health by providing the essential micronutrients and prevent lifestyle disorders.
As a nutritious food, it provides the vitamins, minerals and phyto-chemicals which are required in small quantities for physiological processes and metabolic activities. They are cheap sources of beta-carotene, vitamin-B complex, folic acid, vitamin C, vitamin E, etc. They are rich in minerals like iron, calcium, magnesium, phosphorus, etc., and dietary fibres. It has now been proved that minerals are better absorbed by the body in presence of several other factors of plant matrix, than as mineral supplements. It also provides small amounts of carbohydrates and proteins. Vegetables are important as protective foods as their consumption prevents many diseases. They are important sources of antioxidants and phytochemicals. Each vegetable has been found to have certain specific phyto-chemical which besides being a free radical scavenger, is also inhibitor of certain conditions responsible for disease development.
Among the vegetables, tubers like cassava, potato and sweet potato being highly rich in carbohydrates, served as staples for several countries for very long time, in the history. For the same reason, there are a variety of food products based on these tubers. Others like carrot, radish, beetroot, and turnip in root vegetables, onion and garlic among bulbous crops; tomato, brinjal (egg plant), okra and capsicum among fruit vegetables serve as sources of phytochemicals (carotenoids, anthcyanins, lycopene, betalain, capsicum, bassiniloids, etc.). Beans, peas, cowpea, and other leguminous vegetables are important sources of proteins and leafy vegetables (greens) contribute to the much-needed minerals, vitamins and fibre (roughages) in the diet. Allicin and diallyl disulphide found in onion and garlic control blood cholesterol besides being anti-bacterial. The diphenylamine in onion is effective against diabetes. The ‘Charantin’ found in bitter gourd have hypoglycaemic activity. Diosgenin in yams are used for manufacture of contraceptive drugs. Cole crops like cabbage, cauliflower, Brussel sprouts and sprouting broccoli have anti-carcinogenic properties mainly due to hydrolysed glucosinolate derived isothiocynates and indoles. Similarly, health benefits and curative properties of many indigenous and exotic vegetables have been mentioned in several classical texts of India and China.