Agriculture food and nutrition for Africa. Chapter 7 - Food, nutrients and diets. This chapter gives information on different foods, their nutrient content and their physiological role in the body, in addition to nutrient requirements and the factors affecting them. It reviews the composition of African diets and the different factors that may affect meal preparation and eating patterns. The chapter may be helpful for those wanting more detailed nutrition information. Some people concerned with agriculture and food- related nutrition issues, for example agriculturists and agricultural extension workers, may not need all of this information. Similarly, the public will not need all of the information provided here in order to prepare wholesome meals and maintain good nutritional and health status. A practical approach to healthy eating is simply to advocate consumption of a mixture of foods, focusing on a staple with added energy and protein sources and relish foods providing essential micronutrients. Food groups. Foods, like crops, can be classified and grouped in various ways. Agriculturists divide crops into field crops, plantation crops, commercial crops, horticultural crops, forage crops and grasses. Such groups usually overlap, and particular plants may appear in more than one group. In nutrition, a number of different ways of grouping foods have been tried. Food groups may be based on the major nutrient content (e. Refined white sugar, which consists of 1. Post-election SNL opens with Leonard Cohen tribute, makes political statement News. All Lyrics displayed by LyricsPlanet.com are property of their respective owners. Agrees to Underwrite . While it is possible to classify some foods according to major nutrients, most foods fall into several categories (see Table 3. The need for diversity in both production and consumption has been discussed in Chapters 4 and 5, especially in relation to household food security. Individual food security, expressed as a balanced and adequate diet, also depends on diversity. The basis of the advice often given in nutrition education for family meal planning is: . ![]() However, other factors including cost and acceptability must also be considered (see Box 5. Table 3. 8 - Nutrients in different types of foods. Food. Rich source of. Moderate source of. Cereals. Starch, fibre. Protein, B vitamins, many minerals. Starchy roots and fruits. Starch, fibre. Some minerals, vitamin C if fresh, vitamin A it yellow or orange. Beans and peas. Protein, starch, some minerals, fibre. B vitamins. Oilseeds. Hyde Park Group Food Innovation![]() Fat, protein, fibre. B vitamins, some minerals. Fats and oils. Fat. Vitamin A if orange or red. CBC Digital Archives has an extensive amount of content from Radio and Television, covering a wide range of topics. Get the latest entertainment news, celebrity interviews and pop culture pulse on movies, TV and music and more at ABCNews.com. Dark- to medium- green leaves. Vitamins A and C, folate. Protein, minerals. Orange vegetables. Vitamins A and CFibre. Orange fruits. Vitamins A and CFibre. ![]() Citrus fruits. Vitamin CFibre. Milk. Fat, protein, calcium, vitamins. Eggs. Protein, vitamins. Fat, minerals (not iron)Meat. Protein, lat. Now teaching about food groups is not believed to be the best way to help families improve their meals and prevent undernutrition, for the following reasons. Many foods belong to more than one group. Most foods are mixtures of nutrients. Cereals are in the energy food group, but they are an important source of protein and B vitamins as well as starch. Milk is usually in the bodybuilding group, although it contains as much fat as protein, and it contains calcium and several vitamins. Groundnuts are also rich in both energy and protein. People need to eat both starch and fat. Starchy foods and fatty foods are both in the energy food group, so it is not clear that people need both. A meal of one food from each group may not be balanced. The concept of the three food groups suggests that a balanced meal could be made from margarine (an energy food), cheese (a body- building food) and a banana (a protective food), or from sugar, an egg and a lemon. These would be strange meals, and they would lack several nutrients. Important problems are left out. The concept of the three food groups only addresses the mixture of foods. It does not explain about the amounts of food that people need, or about bulky weaning foods, or about feeding children often. Most women do not use the idea of the three groups. Many women know about the three food groups, but most admit that they do not regard them, because they often cannot afford to buy the foods and they do not plan meals in that way. Source: Adapted from King and Burgess, 1. The major nutrients and their functions. Eating is a natural and essential activity. When there are constraints in the food system and access to food is restricted on economic, social or cultural grounds, basic nutritional needs for energy and essential nutrients may not be satisfied. To understand human nutrition it is necessary to know the nutrient requirements and to understand the function of food and nutrients in promoting and maintaining growth, health, activity and reproduction. An understanding of nutrient functions is particularly relevant in the prevention and control of nutrient deficiency diseases and protein- energy malnutrition (PEM) (see Chapter 8). Most animal species require a number of essential dietary factors which can be classified under chemical groupings such as carbohydrates, proteins, tats, vitamins and minerals. Dietary fibre and water are sometimes added to this list. A simple classification of dietary constituents is given in Table 3. Vitamins and minerals may also be described as micronutrients. A healthy diet supplies adequate but not excessive quantities of all these nutrients. Personal requirements vary depending on individual body size, age, sex, physiological status and lifestyle. Table 3. 9 - Simple classification of dietary constituents. Constituent. Use. Water. To provide body fluid and to help regulate body temperature. Carbohydrates. As fuel for energy for body heat and work. Fats. As fuel for energy and essential fatty acids. Proteins. For growth and repair. Minerals. For developing body tissues and for metabolic processes and protection. Vitamins. For metabolic processes and protection. Indigestible and unabsorbable particles including fibre. To form a vehicle for other nutrients, add bulk to the diet, provide a habitat for bacterial flora and assist proper elimination of refuse. Source: FAO, 1. 99. Nutrients as energy sources. Some nutrients are interchangeable for meeting certain of the body's needs, depending on the metabolic state of the body. Carbohydrates are often divided into starches and sugars, which are both classified as . Fats are also very concentrated sources of energy, as is clear to any fanner who includes sunflower seed, groundnut cake or soybean meal in livestock rations. Protein may also be converted into energy if the body is starved of food, but this is an inefficient use of protein. Therefore, nutritionists normally classify only starches, sugars and fats as energy foods. Fibre, especially in the form of cellulose, is not digested in the same way as other nutrients. Most fibre stays in the gut to facilitate the digestive and excretory processes and subsequently passes out of the body in the faeces. Soluble fibre, of which there is little, ferments in the large intestine and produces fatty acids and other substances which the body absorbs and uses for energy. Starchy staples. For most African populations carbohydrates supply most of the energy needed by the body. They yield 4 kcal per gram on complete oxidation. When carbohydrate is synthesized in a green plant, much of it is stored in the plant cells as cellulose, starch or sugar. Food crops, including grains, roots, tubers and plantains, are therefore the major sources of energy for most people in Africa and have the highest yield of energy per unit of land. Because the body tissues require a constant supply of glucose to fuel most metabolic reactions, the digestive process eventually converts all carbohydrates (except those that make up dietary fibre) to three simple forms of sugar: glucose, fructose and galactose. The latter two are finally converted to glucose. Carbohydrates also make an essential contribution to the effective conversion and use of other nutrients, through the energy they supply. For optimum utilization of proteins, for example, carbohydrates must be supplied simultaneously, i. Similarly, carbohydrates are necessary for normal fat metabolism. The traditional African meal pattern, i. Although such foods as cereals, roots and tubers are mainly sources of energy, they also contain other nutrients, including a significant quantity of protein, especially in the case of cereals. Cereal grains are about 1. Table 2. 2 in Chapter 5). Legumes and oilseeds also contribute energy to the diet, from their carbohydrate and oil content; they may be 2. When enough staple food is available to meet people's energy requirements, their protein requirements are also likely to be met. Conversely, protein undernutrition is usually associated with energy deficiency resulting from an insufficient overall intake of food. Dietary protein deficiency on its own is therefore fairly uncommon, except in circumstances where children are weaned on to non- cereal staples. Fats and oils. Fats and oils are concentrated forms of energy. The energy yield from the complete oxidation of fatty acids is about 9 kcal per gram, in comparison with about 4 kcal per gram for carbohydrates and proteins. In addition, fats are stored in a nearly anhydrous form; animal fats contain only a small proportion of water, while refined oils contain virtually no water. People store energy in their bodies for future use in the form of fat. Some plants, in addition to storing energy as carbohydrate, also store oil in their nuts, seeds, seed germs and fruits. In Africa, much of the fat content of traditional diets comes from plant oils such as red palm oil, groundnut oil, coconut oil and sesame oil. Whole- grain cereals also contribute oil to the diet, but much of the oil may be lost if the cereal germ is separated before milling. For example, the oil content of maize drops from 4. Fats occur in foods mainly as triglycerides, which are fatty acid esters of glycerol.
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