Enjoy a variety of foods
The enjoyment of food is one of life's pleasures. For those who have an adequate food supply, eating is about far more than survival. Eating together is an important part of daily family life and of social events, celebrations and festivals.
In addition to the enjoyment it provides, food is, of course, essential for life. Obtaining the nutrients the body needs depends on the amount and variety of food locally available. This varies widely in different parts of the world. In addition, people have their individual food tastes and eating habits. Different groups of people also have different nutritional needs (this is covered in Section 2).
All foods can be enjoyed as part of a nutritious diet. From a nutritional point of view, a particular food is neither «good» nor «bad» of itself. What matters is how well a given food complements or combines with other foods to meet a person's energy and nutrient needs. The best advice is that people should try to eat a wide variety of foods and to spread consumption over the day. This is especially important for children who cannot eat enough in only one or two meals to meet their nutrition needs. Breakfast is particularly important to provide fuel both for physical and mental activity.
Some Vital Nutrients
Food provides us with the energy we need for growth, physical activity and for basic body functions (breathing, thinking, temperature control, blood circulation and digestion). Food also supplies us with the materials to build and maintain the body and to promote resistance to disease.
These different functions are made possible by the nutrients contained in food. The types of nutrients in food are: carbohydrates, proteins, fats, vitamins, minerals and water. All foods contain one or more of these nutrients in varying amounts. Each type of nutrient serves particular functions:
Carbohydrates include sugars, starches and dietary fibre. They are the major source of food energy for most of the world's population. The sugars, or simple carbohydrates, are either monosaccharides (glucose, fructose and galactose) or disaccharides (sucrose, lactose and maltose). Starch, glycogen and dietary fibre (including cellulose, hemicellulose and pectin) are referred to as complex carbohydrates or polysaccharides.
Some complex carbohydrates cannot be digested by humans and therefore are not a significant source of dietary energy. These are referred to as dietary fibre and come primarily from the walls of plant cells. Even though it is not a significant source of energy, fibre is still a very important part of the diet. Fibre is important in keeping the digestive tract healthy and working properly.
Foods rich in carbohydrates are rice, maize, wheat and other cereals, all types of root crops such as potatoes, yams and cassava; legumes such as peas and beans; as well as many fruits and vegetables, and sugars.
More about Carbohydrates
Glucose is the most important carbohydrate. It is essential for brain function. It is also the form of carbohydrate used for energy in humans and other mammals and is often called 'blood sugar. ' Glucose is found naturally in many fruits and vegetable juices, but it commonly combines with another monosaccharide to form a disaccharide.
For example, sucrose or table sugar is a disaccharide containing one molecule of glucose and a molecule of fructose, which is the primary sugar in most fruits. Lactose is a combination of glucose and galactose and occurs only in milk, including human milk. Maltose is a combination of two glucose units and is formed during the breakdown of starch.
Following digestion and absorption, the simple carbohydrates are converted to glucose which may be used immediately for energy or converted to glycogen (the storage form of glucose in mammals which is produced in only small amounts in the muscles and the liver) or to fat.
The complex carbohydrates are many glucose molecules (often hundreds) joined together in long chains. During digestion, the starches are broken down into simple sugars which are then absorbed and utilized as any other sugar would be. When serum (blood) glucose levels fall, glycogen is also reconverted to glucose to provide a ready source of energy. This mechanism is especially important for physically active people.
Proteins are needed to build and maintain muscle, blood, skin and bones and other tissues and organs of the body. Proteins can also be used to provide energy. Proteins are made from amino acids - the primary building blocks of the body. When proteins are eaten and digested they are broken down into their amino acids which are then absorbed and used to build new tissues.
Protein is especially important for growing children. Breastmilk contains the perfect combination of amino acids for growth and mothers should be encouraged to breastfeed as long as possible. As children are weaned from the breast it is important that their staple foods are supplemented with adequate protein-rich foods.
Good sources of proteins are all types of meat, poultry, fish, beans, peas, soya beans, groundnuts, milk, cheese, yoghurt and eggs. These are often more expensive than other foods. To get the best from these foods it is important to ensure that the body's energy requirements are met from other foods. If not, the amino acids from the protein will be converted to glucose and used for energy, and will not be available for building new proteins and tissues. Eating more protein than is needed can be wasteful: excess protein will be converted to glucose and used as energy or stored in the body as fat.
More about Proteins
There are about 20 different amino acids used by the human body. These can be joined together in a wide variety of combinations to make different proteins. Most of these amino acids can be made by the body from carbohydrates and other amino acids. However, nine amino acids cannot be made by the body and must be present in the food we eat. These nine are called «essential», amino acids. If adequate amounts of each of these essential amino acids are not present in the diet, then the body will not be able to make all the protein it needs, nor use effectively all of the proteins which have been eaten.
Different types of protein in the foods we eat have different amounts of the amino acids required by the human body. Proteins from animals, that is the protein found in meat, milk, fish and eggs, have the most of the essential amino acids. The proteins found in food from plants usually have lesser amounts of one or more of these amino acids. However, by eating a combination of different types of foods it is possible to get all the amino acids one needs. This is especially important for vegetarian populations. For example, eating legumes or pulses (beans, peas, lentils) with cereals (rice, maize, wheat, sorghum) will provide a balanced mix of amino acids. Also, small amounts of milk, yoghurt, nuts, seeds, meat or fish eaten along with the staple food can provide an adequate source of amino acids to meet the body's protein needs.
Dietary fat includes cooking fats, oils and butter and ghee and is also a natural component of meats, milk, eggs, nuts and other vegetable foods.
Fats are an essential part of a nutritious diet. They are a concentrated form of energy and are the form in which much of the energy reserve of animals and some seeds is stored. In addition to serving as an energy source, fats (also known as lipids) are essential components of cell membranes and are needed for the absorption and use of some vitamins. Fat also makes meals more tasty and satisfying.
Fats and oils provide more than twice the amount of food energy as carbohydrates and proteins. Adding fat in the form of oil to the food of young children is a particularly good way to increase their energy intake. This is important since often children are not able to eat enough «bulky» foods to meet their energy needs. Young children should receive between 30%-40% of their calories from fat.
Depending on their activity levels and dietary patterns, adults should receive between 15% and 35% of their calories from fat. Generally. people are advised to avoid excessive intakes of saturated fats (less than 10% of energy intake) to reduce their risk of heart disease.
Foods rich in fats are oils, some meat and meat products, Iard, butter, ghee and some other milk products margarine, some types of fish, nuts and soya beans.
More about Fats and Oils
The term «dietary fats and oils» most commonly refers to triglycerides. These are the most abundant of the compounds also known as lipids. Phospholipids and sterois are other types of lipids, but about 95% of what we eat are the triglycerides.
Dietary fats and oils Include the triglycerides you can see, for example the fat in meek buffer, ghee, lard and processed oils, as well as those that cannot be seen, such as that in milk, nuts, seeds and other vegetable sources (olives, avocadoes, palm fruit). Generally, fats are solid or semi-solid when cool (room temperature) and oils are liquid.
Chemically triglycerides are composed of three fatty acids bonded to a glycerol molecule. Fatty acids are chains of carbon atoms with hydrogen atoms attached and an acid group (COIH) at one end. The length of the carbon chains varies from two to over twenty.
If two hydrogens are attached to each carbon (three on the terminal carbon atom), the fatty acid is said to be «saturated». If some of the carton atoms have only one hydrogen attached, the fatty acid is «unsaturated».
Depending on the number of unsaturated carbon atoms, the fatty acid Is said to be either monounsaturated or polyunsaturated. (See Fig. 1.2 below)
In general, the more saturated fatty acids there are in a tryglyceride the more solid It is at room temperatures. Beef fat is highly saturated, chicken fat less so, and moat oils from plants (for example, olive oil, peanut oil, sunflower oil) have a high proportion of unsaturated fatty acids.
Cholesterol is an essential component of all cells in the body and it serves a number of Important functions. Most of the cholesterol in the body is manufactured in the liver, but some Is made by other cells and some come, from the food we eat. Cholesterol is transported in the blood in various forms and excessive levels of some types of cholesterol can Increase the risk of high blood-pressure, heart disease and stroke.
Several factors, Including diet, Influence how much and what type of cholesterol is produced and circulated in the body. High Intakes of saturated kits can lead to particular problems, so It is generally recommended that not more than 10% of daily energy Intake should come from saturated fats.
The Structure of Fatty Acid Chains - Figure 1.2
Vitamins and Minerals
Vitamins and minerals are called micronutrients. They are needed in much smaller amounts than protein, fat and carbohydrate but are essential for good nutrition. They help the body work properly and stay healthy. Some minerals also make up part of many of the body's tissues, for example, calcium and fluoride are found in bones and teeth and iron is found in the blood.
Iron is a major component of red blood cells and is necessary to keep all of the body's cells working properly. Iron deficiency anaemia is the most widespread nutritional problem in the world. It can be very serious in children and women of childbearing age, especially during pregnancy, but it also affects men and older women. It leads to lethargy (low work capacity), learning difficulties, poor growth and development, and increased morbidity (illness) and maternal mortality, especially at delivery.
The best sources of iron are meat, fish, poultry, liver and other organ meats. Iron is also found in legumes, dark-green leafy vegetables and dried fruits, but this iron is not absorbed as well by the body as is the iron from animal products. Increasing the intake of Vitamin C along with the vegetable sources of iron can help more of the iron to be absorbed and utilized.
Vitamin A is needed for building and maintaining healthy tissues throughout the body, particularly eyes, skin, bones and tissues of the respiratory and digestive tracts. It is also very important for effective functioning of the immune system. Vitamin A deficiency can lead to poor night vision (night blindness), severe eye lesions and in severe cases permanent blindness. This occurs mainly in undernourished children, especially those with measles and other infections. Vitamin A deficiency can also lead to increased illness and death from infections.
Vitamin A is found naturally only in foods of animal origin, notably breast-milk, liver, eggs and many dairy products. However, many dark coloured fruits and vegetables contain pigments, called carotenes, that the body can convert to vitamin A. Foods rich in carotene include red palm oil, dark green vegetables, carrots, deep yellow and orange sweet potatoes, mangoes and papaya.
Thiamin, riboflavin, niacin, B6, folate, pantothenic acid, B12 and biotin belong to what is sometimes called the vitamin B complex. The B-vitamins are necessary for converting carbohydrates, fat and protein into energy and for using them to build and repair the body's tissues. Deficiencies of these vitamins can lead to serious effects including muscular weakness, paralysis, mental confusion, nervous system disorders, digestive problems, cracked and scaly skin, severe anaemia and heart failure.
Folate (folio acid, folacin) is needed to make healthy blood cells and its lack is a common cause of anaemia among women and young children. Folate deficiency during pregnancy can lead to birth defects.
Adequate daily intake of the B-vitamins is important. Food rich in B-vitamins are dark green vegetables, groundnuts, beans, peas, cereals, meat, fish and eggs.
Vitamin C is needed to increase absorption of dietary iron, to make collagen (connective tissue) which binds the body's cells together, and to serve as an antioxidant. Prolonged vitamin C deficiency can lead to scurvy. The signs of scurvy are bleeding gums and sore, swollen joints and it can lead to death.
Most fruits, especially citrus and guava, and many vegetables, including potatoes, are good sources of vitamin C. Eating fresh fruit and vegetables is important for both adults and children.
Vitamin D is particularly important in the use of calcium by the body. Vitamin D is found in fish oils, eggs and milk, and is also produced by the body when the skin is exposed to sunlight. Lack of vitamin D can lead to rickets, a disease which causes soft and deformed bones in young children.
Calcium and phosphorus are important to body maintenance and to having strong healthy bones and teeth. Milk and dairy products are excellent sources of calcium and phosphorus.
Iodine is important for proper growth and development. Lack of iodine in the diet can cause goitre (swollen thyroid gland) and mental retardation. Iodine is found in seafood and in foods grown on iodine-rich soils. In areas where soils are low in iodine steps should be taken to add iodine to the diet, usually through iodized salt.
Fortified Foods: Vitamins and minerals can also be added to some foods to replace nutrients lost in processing or to enhance their overall nutrient content. Foods with added vitamins and minerals are called fortified foods. For example, iodine is frequently added to salt to produce iodized salt. In many countries bread, flour and other cereal products are commonly fortified with B-vitamins and iron, and vitamins A and D are often added to processed milk and dairy products and to some vegetable-oil products.
Water is needed for many functions in the body: to make cells and body fluids, for chemical reactions to occur and to make urine which carries waste from the body. It is essential to maintain an adequate intake of clean water to replace the water lost by the body, especially in hot weather and during physical activity. People may also become dehydrated (suffer excessive loss of water) when they have diarrhoea, vomiting and fever.
Applying this information at the local level
For a greater understanding of how this information applies at the local level the following might be examined:
What are the types of food locally available?
What nutrients do these provide?
How and when are these foods mostly eaten?
How can these foods be better used or combined to Improve the local diet?
What foods are eaten on special occasions?
What are the main local nutrient deficiencies/excesses ?
How could they be prevented?
How does this picture compare with other countries?