C Olaiya, J Adebisi
green leafy vegetables, health, nutritional potentials, phytoevaluation, south- western nigeria
C Olaiya, J Adebisi. Phytoevaluation of the nutritional values of ten green leafy vegetables in South -Western Nigeria. The Internet Journal of Nutrition and Wellness. 2009 Volume 9 Number 2.
Vegetable consumption has been associated with decreased risk of chronic diseases. In this work, ten green leafy vegetables were analysed for basic nutrients in the diet of man with a view to ascertaining their nutritional potentials. Samples of the fresh vegetables collected were separated into two and used in the wet and dry forms. Column chromatographic separation of the ethanol extract of the wet samples showed the protein, carbohydrate and fat contents. Spectrophotometric analysis of dried samples revealed the Calcium, Magnesium, Phosphorous, Iron and vitamin contents. Potassium and Sodium were determined using flame photometry. All the vegetables showed high moisture contents (75.0 – 91.5%). The highest carbohydrate and protein contents of 5.8 and 6.4g/100g respectively, were recorded in
Vegetables are important protective foods and highly beneficial for the maintenance of health and prevention of disease. Studies have repeatedly shown that increasing colon and stomach cancer correlate with low vegetable meals, and suggests that vegetables may help resist these types of cancers (Whitney
Materials and methods
Moisture, ash, fibre, fat, proteins, carbohydrate were determined using AOAC, 1990. The analysis was repeated twice and the mean of the three values recorded.
Results and Discussion
Vegetables play an important role in human nutrition, apart from the fact that we derive most of our recommended daily needs of minerals and vitamins from them, they also supply certain constituents in which other food materials are deficient. The wide variation in colour, tastes and textures of various vegetables have added an interesting touch to meals. The cultivation and consumption of green leafy vegetables cuts across different races (Schmidt, 1974) because of their nutritional and health benefits. They have been shown to reduce the risk of degenerative diseases such as cancer and cardiovascular disease. The profile of ten green leafy vegetables commonly consumed in South – Western Nigeria examined in this work is presented in Table 1. Leafy vegetables are generally not consumed alone but they are often consumed in combination with themselves and also in combination with other vegetables such as pepper, tomatoes, melon and onions. Other ingredients such as palm oil, fish or meat and seasonings used in the preparation of the vegetable meal are all contributing in one way or the other to the total nutritional value of the vegetable meal.
The results of the biochemical analysis of the vegetables for macronutrients, moisture, fibre and ash are shown in Table 2. The carbohydrate contents of the vegetables are relatively higher in comparison with their lipid contents. The least carbohydrate content of 4.0g/100g was observed in
The vegetables are generally very low in carbohydrates, fats and proteins and therefore contribute very little to the energy values of a meal. The moisture contents of the leafy vegetable studied are relatively high ranging from 75.0% in
Table 3 shows the vitamin contents of the leafy vegetables. Vitamin A is a component of rhodopsin, the visual pigment in the mammalian eye. All the leafy vegetables are rich in vitamin A but
The green leafy vegetables are good sources of minerals as shown in Table 4. The highly soluble minerals calcium (Ca), magnesium (Mg), phosphorus (P), iron (Fe), and potassium (K) help in the maintenance of acid base balance of the hydrogen ion concentration of the body tissues. They help complete the absorption of vitamins, proteins, fats and carbohydrates of the food (Islam
Phosphorus is important in the energy transfer of nucleic acids. Its value ranged from 1.83mg/100g in
The carbohydrate, protein and fat contents of these vegetables are not enough to satisfy the recommended dietary allowances (RDAs) for these macronutrients. They therefore cannot be considered a total substitute for the staple food we consume daily but rather they can be used as sources of additional organic nutrients in our daily meals. The loss or lack of these organic nutrients in the diet of man can be averagely taken care of by generous consumption of green leafy vegetables. The vegetables are however rich sources of vitamins and minerals. The relatively high value of these micronutrients in the leafy vegetables makes them a much needed cheap source of these nutrients which are missing from our commonly consumed staple foods. Their high consumption is therefore recommended because of their invaluable health benefits.