Man must eat to survive for the continuity of the human race. The foods for human consumption are of both plant and animal origin. Cereals, legumes, roots, tubers, suckers, oils, nuts, fruits and vegetables are plant foods. Meat, milk, eggs and oils are animal products. Both plant and animal foods contain nutrients. Oxford Medical Dictionary (2003) defines nutrients as substances that must be consumed as part of the diet to provide energy, protein for growth or substances that regulate growth or energy production. Carbohydrate, proteins, fats, vitamins, minerals and water are the existing six nutrients.
It is known that too much or too little of these nutrients have adverse effects on health. The source of these nutrients equally determines how healthy one is. A typical example is in the case of fats. Animal fat contains about 40-60% of fat as saturated fatty acids. Plant oils contain mostly unsaturated fatty acids ranging from 73 to 94% of total fat (Wardlaw & Kessel, 2002). Plant oil is the most beneficial to health. Current studies showed that plant nutrients are not inferior to animal nutrients as it was earlier thought. In addition, plants contain other non-nutritive dietary components that are beneficial to health. These components are called phytochemicals. “Phyto” because they are only found in plant based foods (Pamplona-Roger, 2005). The present study concentrated on nutrient and phytochemical levels of five cultivated and wild vegetables.
Vegetables are generally herbaceous (non-woody) plants that are cultivated in farms, collected from forest trees, market and home gardens as well as kitchen gardens for home use. Usually, all the botanical parts of the plants (leaves, buds or flowers, calyxes, fruits, stalk, roots are consumed) (Pamplona-Roger, 2005). This study laid emphasis on green leafy vegetables.
History shows that vegetables were used for a number of purposes. Many in the past consumed these vegetables without knowing all they contain. Scent leaf was used and is still being used to stop diarrhoea. How and what stops diarrhoea in scent leaf is still a puzzle to many. The foods our ancestors consumed consisted of carbohydrates, starchy vegetables, leafy vegetables and little or no animal products. There were not much occurrences of various chronic diseases such as morbid obesity, cancer, heart and renal failure three to four decades ago as they are now. The juvenile and paediatric cases of these diseases are on the increase. The cause of their increase is due to migration/changes in lifestyle and food habits (Ene-Obong, 2008). The very sharp shift from traditional diets as well as the advent of exotic diseases appears to suggest a serious warning. These warnings call for urgent increases in consumption of preventive and curative substances inherent in plant based food, especially vegetables.
Chemically, green leafy vegetables are composed of water; 90 to 95%, minerals e.g. phosphorus, potassium, calcium, iron, vitamins, fibre, proteins, chlorophyll and most recently discovered- phytochemicals (Pamplona-Roger, 2005). Indigenous traditional foods are on the verge of extinction. The younger generation is ignorant of them as such; consume less of these vegetables (Ene-Obong, 2008). As most of these traditional foods are on the verge of extinction, so are the vegetables, condiments and spices used in their preparation. Some of the wild forest vegetables might have been used by a particular community in the past. Based on these serious observations associated with less consumption of indigenous foods and increases in many chronic ailments, it is imperative to study the nutrient and phytochemical potentials of some cultivated and wild vegetables.
1.1 Statement of problem
The increase in the consumption of western diets and neglect of our traditional foods has precipitated a corresponding increase in ill-health due to diet related non-communicable diseases. These diseases are of various forms; cancer, kidney and liver diseases, diabetes and many more. Prevention of these diseases based on new incidences of these diseases is imperative. This is because these diseases are of increasing public health concern. Extensive studies are ongoing to address these public health threats both for the cure of already existing cases and prevention of new cases. One hopes that the results of these studies will provide baseline information as to their causes and treatment.
However, some of the information based on the results of recent studies point to the type of foods consumed by people. Currently, nutrients from plant based foods have promising solution (Ene-Obong, 2008). Vegetable based foods are advocated because of their high content of non-nutritive dietary components that are safer and more beneficial to man. Some of these vegetables contain antioxidants and phytochemicals. Sadly, in Nigeria, little attention is paid to fruits and vegetables. Statistics from World Bank (1991) showed that at the National level, an average household expenditure on household staples was highest on fish (N140.84) followed by meat products (N81.54). The least weekly expenditure was on fruits (N13.12) followed by weekly expenditure on green leafy vegetables (N20.88).
Vegetables are the most affordable dietary sources of vitamins, trace elements and other bioactive compounds that offer the only practical and sustainable way to ensure that micronutrients are supplied through the diet (Odo, 2007). It is imperative to study more vegetables for their nutrient and photochemical potentials. The investigation of these vegetables would be of immense benefit to the society.
1.2 Objective of the study
The general objective of the study were to determine the effect of drying methods on the nutrient and phytochemical properties of some cultivated and wild leafy vegetables.
The specific objectives of the study are to;
- determine nutrient, and phytochemical content of these vegetables
- sun, shade dry and pulverize these vegetables to determine the nutrient content of their flours.
- determine the nutrient and phytochemical potentials of these vegetables on dry weight basis.
- Significance of the study
The results of this study would be a promising and useful tool to home makers on the increasing need to produce both cultivated and wild forest vegetable and consume them, especially the children and younger adults. Increase consumption of these vegetables might be the solution to the cases of micronutrient deficiencies world wide and some chronic and deadly diseases such as cancers and other diseases and their complications, particularly in developing countries, Nigeria inclusive.