Vegetables: Sources of important nutrients in diet - Nigerian Tribune

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Vegetables are the most readily available sources of important proteins, vitamins, minerals and essential amino acids, in the diet. Toyin Akinola reports.

Vegetables are herbaceous plants which are grown for food in Nigeria and other parts of the world. They are the fresh and edible portions of herbaceous plants, which may be the root, stem, leaves, fruit or a combination of these parts depending on one’s knowledge of them and their availability. They may be eaten raw or cooked depending on the type, but most often they are cooked.

Dr Oluwaseun Aluko, a general practitioner, Teju Specialist Hospital, Ring Road, Ibadan said  vegetables are sources of important nutrients in diets; their colours, shape, texture and flavour appeal to man’s senses. Research has shown that vegetables are important and highly beneficial for the maintenance of health and prevention of diseases.

They contain valuable food ingredients which can be successfully utilised to build up and repair the body. They are valuable in maintaining the alkaline reserve of the body.

Dr Nafiu Taiwo, a general medical practitioner, Ibadan Central Hospital, Ososami, Ibadan, said green leafy vegetables contain a lot of vitamins and micro-nutrient which are essential for body metabolism. They are valued for their high carbohydrate, vitamins and mineral contents.

Vegetables are the cheapest and most readily available sources of important proteins, vitamins, minerals and essential amino acids.

The daily allowances of these excellent nutrients are very important and are essential ingredient of the diet, required for normal metabolic activities of the body tissue. They are constituent of bone, teeth, blood, muscles, hair and nerve cells.  

Vegetables, like fruits, are low in fat but contain good amounts of vitamins and minerals. All the green vegetables are rich sources of calcium, magnesium, potassium, iron and vitamin A.

Vitamin A enhances good vision, helps in tissue repair especially for a growing child; vitamin B, vitamin C and vitamin D helps in the development of bones and improves blood formation;  vitamin E; enhances fertility especially in women and for prevention of certain cardiovascular diseases, and vitamin K, as stated by Dr.Aluko.

The American dietetic association journal states that a diet rich in vegetables contains beneficial antioxidants that helps reduce the risk of cancer, stroke, and heart diseases because it develops the body’s capacity by boosting its immunity.

Scientific studies have shown that low calorie but nutrient rich foods helps the body stay fit and disease free. Many vegetables are very low in calories, such as celery which is even as less than 10 calorie per 100 g. Also the body spends considerable amount of energy during digestion of foods, which is known as BMR (Basal metabolism rate), so when vegetable is added in the diet, there is more loss in weight than weight gained.

Worowo (seneciobiafrae), a traditional vegetable grown and consumed in the  western  part of Nigeria, is considered for its high medicinal value. The juice extracted from the leaves are wholly applied to fresh wounds or cuts in the rural community. The high edible mucilaginous fibre, leaves and stem of the vegetable are used to treat indigestion or as laxative and as purgative (Fowomola and Akindahunsi, 2005).

Dr Aluko said worowo is a good source of roughages that helps to ease digestion, and prevents constipation. It also contains appreciable amount of nutrients, which could be consumed for normal growth. Vegetable is an important source of mineral, like sodium, potassium, chlorine, calcium, phosphorus, magnesium, iodine, iron and copper, and they contribute fibre to the diet, which helps in the easy digestion of food and quick absorption of food material across the intestinal wall, prevents constipation and to maintain the volume of water necessary for the life processes stated Dr.Taiwo.

They help to draw chemical substances into and out of the cells and keep the blood and tissue fluid from becoming either too acidic or alkalinic. Minerals play an important role in body functions and are present in every human cell. Minerals found in vegetables include boron which prevents tumours and cysts; calcium which ensures strong bones; chlorine, a natural disinfectant;and  chromium, which enhances glucose tolerance.

Others are copper, which converts iron into haemoglobin; fluorine which is important for healthy teeth; iodine which is required to prevent goitre; iron, which is required for purification of  the blood and magnesium, the alcoholics balm.

In addition, there is manganese which is required for growing years; molybdenum for general well-being; phosphorus, a body energiser;  potassium, which helps to prevent acidosis; selenium, a woman’s friend; silicon, the beauty mineral; sodium, known to be indispensable for life; sulphur, meant for glowing hair and skin;  vanadium for healthy heart and zinc for faster healing. These are found in trace and adequate quantity in green leafy vegetables.

Vegetables contain soluble as well as insoluble dietary fibre that absorbs excess water in the colon and retain good amount of moisture in the faecal matter, thereby helping its easy passage out of the body, thus helpful in conditions like chronic constipation and rectal fissures.

 In Nigeria as in other tropical countries of Africa where the daily diet is dominated by starchy staple foods, vegetables are very low in calories. Vegetables are either major or minor based on the intake level. Nutritionists advise that fresh vegetables be eaten at least between five and  seven servings every day.

Dr Taiwo advice that vegetables be consumed in adequate amounts and it should not be eaten as a main meal. Vegetable nutrition has widely drawn the attention of fitness- conscious individuals as well as food scientists alike, because of its proven health benefits,  its high magnesium content and low glycaemic index. Green leafy vegetables are also valuable for persons with type 2 diabetes.

An increase of one serving/day of green leafy vegetables was associated with a nine per cent lower risk of diabetes. Carotenoids found in dark-green leafy vegetables are concentrated in the eye lens and macular region of the retina, and plays a protective role in the eye, they protect against cataract.

The 2009 edition of the African Journal of Biotechnology  said the potassium content of leafy vegetables is good in the control of diuretic and hypertensive complications, because it lowers arterial blood pressure and the fibre content of vegetables contribute to the feeling of satisfaction and prevents constipation, and age-related macular degeneration, the major cause of blindness in the elderly.

The risk of hip fracture in middle-aged women was decreased 45 per cent for one or more servings/day of green, leafy vegetables compared to fewer servings.

After purchase of vegetables, they must be washed immediately, especially green leafy vegetables, rinsed in salt water for a few minutes and gently swish in cool water till satisfied with cleanliness, to ensure that they are free from dust, sand, and any residual chemical sprays. If storage is needed, then they should be placed in plastic wrappings or in zip pouches in order to preserve nutrition for short periods until they are ready for use.

It is, however advisable to always buy small quantities of vegetables that should last a day or two. There is no point eating unfit greens, buy that feature freshness, bright in colour and flavour vegetables. Care should be taking in looking for blemishes, spots, fungal mould and signs of insecticide spray on the vegetables.