Plants undergo photosynthesis and they constitute a primary resource of carbon, vitamins, minerals, protein, essential fatty acids, and utilizable energy for food production (Young and Pelett, 1994). Plants have played a significant role in maintaining the health and improving the quality of human life for thousands of years. (Mishra, 2010). They provide a major source of food and nourishment for man and animal.
Nutrition is a science of food and its relationship to health. Nutrition refers to nourishment that sustains life. The study of nutrient requirements and the diet providing these requirements is also known as ‘nutrition’ (Chutani, 2008). Pike and Brown, 1984 defined it as “the science that interprets the relationship of food to the functioning of living organism. It includes the uptake of food, liberation of energy, elimination of wastes and all the processes of synthesis essential for maintenance, growth and reproduction (Chutani, 2008). Apart from maintaining normal body functioning, nutrition is important in fighting infections and in the recuperation of an ill person. Nutrition interacts with infections in a synergistic manner, such that recurrent infections lead to a loss of body nitrogen and worsen nutritional status; the resulting malnutrition, in its turn, produces a greater susceptibility to infection (Kurpad, 2005). Aristotle (384-322 B.C.) was the first to suggest that the composition of foods in the normal diet might contribute to health.
In an 1897 literature on metabolic investigations, Atwater divided food composition into five classes; protein, fat carbohydrate, energy and water. However, today, proximate composition is the term usually used to describe six components of food namely; moisture, crude protein, crude ash, crude fibre, crude fat and carbohydrate (nitrogen free extract) which are all expressed in percentage (%) or gram per 100 grams (g/100g). The study of proximate analysis on foods was devised over a hundred years ago by two German scientists, Henneberg and Stohmann, and even though new techniques have been introduced, their system of proximate still forms the basis for the statutory declaration of the composition of foods. (Dublecz, 2011).