FOOD
What is food?
Food is anything liquid, semi-solid or solid which contains nutrients and energy and when taken or eaten nourishes the body. Food contains important substances which provide energy to move, think, work, run our body systems, keep us healthy, help to boost our immune system and protect us from infections. When we eat or take food, our bodies absorb useful nutrients into the blood and they are transported to areas where they are needed or stored. The food we eat or take is used for growth, maintenance and body functions. Classification of foods according to their functions.
Classification of Foods Based on Their Functions in the Body
a) Energyzing foods (“GO” foods)
Foods rich in carbohydrates and fats are called energy-giving foods or “GO” foods. They provide energy to the body and are essential for physical activity and basic functioning of the body. Foods like cereals, roots, tubers, starchy fruits and vegetables oils, milk, butter and ghee are good sources of energy.
b) Fitness foods (“GROW” foods)
Foods rich in protein are called body-building foods or “GROW” foods. These foods help to maintain life and promote growth, repair worn out and damaged body tissues. “GROW” foods come from animal and plant sources. Milk, meat, eggs and fish are good sources of animal proteins while legumes and nuts are good sources of plant protein. Animal protein sources are considered to be of high quality compared to plant sources, apart from soybeans.
c) Protective (“GLOW” foods)
Foods rich in minerals and vitamins are known as protective or “GLOW” foods. They are essential for promoting body immunity and regulatory functions. Fruits and vegetables are the main sources of “GLOW” foods. Fortified foods, including iodized salt, are also good sources of “GLOW” foods.
1. Basic classification of foods according to their groups
Nutrients Found in Food
Nutrients are substances contained in food that nourish the body. They are required by the body to maintain general health and physiological functions, for example: provision of energy, building the body mass, keeping the body warm, boosting immunity and regulating the various body functions that help someone to live.
Major nutrients in human nutrition
Nutrients in food are divided into three major categories: macronutrients, micronutrients and water.
1) Macronutrient
These are required in large amounts:
⦁ Carbohydrates
⦁ Proteins
⦁ Fats/oils
⦁ Vitamins
⦁ Minerals
Carbohydrates
These are the primary source of energy in most diets. They include starches, fibre and sugars. Sweet foods such as sugar, jam, cakes and sugary drinks are sources of carbohydrates but should be consumed minimally because they do not provide any other nutrients and may increase risk of overweight.
Carbohydrate requirements
Carbohydrate requirements vary according to age, sex, physical activity level and physiological status. The recommended daily carbohydrate intake should provide about 45% to 65% of the total body energy/calorie requirements of 2000–3000 kilocalories (kcal). One gram of carbohydrates provides 4 kilocalories.
Proteins
Proteins are body-building foods and are required for growth and development, maintenance and repair of tissues, production of metabolic and digestive enzymes, and formation of certain hormones and all cells and tissues.
Protein requirements
Intake of protein each day is about 1 gram per kilogram of body weight. Example: if a person is 60 kilograms, he will require 60 grams of protein each day. This is equivalent to one egg or a piece of meat about the size of an egg. However, children, teenagers, and pregnant and lactating mothers require more protein as indicated below:
⦁ Children: 30–50 g (half a palm of meat)
⦁ Teenagers: 60–75 g (a palm of meat)
⦁ Adults: 60–70 g (a palm of meat)
⦁ Pregnant and lactating mothers: 90 g (one and a half palm of meat)
Fats and oils
Lipids are derived from both animal and plant sources.Fats are rich in energy, build body cells, support brain development of infants, help body processes, and facilitate the absorption and use of fat-soluble vitamins A, D, E, and K. The major component of lipids is glycerol and fatty acids. According to chemical properties, fatty acids can be divided into saturated and unsaturated fatty acids. Generally lipids containing saturated fatty acids are solid at room temperature and include animal fats (butter, lard, tallow, ghee) and tropical oils (palm,coconut, palm kernel). Saturated fats increase the risk of heart disease. Those containing unsaturated fatty acids are liquid at room temperature. These include monounsaturated and polyunsaturated fats and are found in vegetable oils such as sunflower, corn, soybean, canola and olive oils. Replacing saturated fats with unsaturated fats lowers risk of heart disease.
Fat, Lipid, and Oil Intake Requirements
Fat provides high amounts of energy to the body; 1 g of fat produces over 9 kcals. Daily intake of fats/oils should not exceed 30% of total kilocalories. Saturated fat increases the risk of heart disease. Replacing saturated fat with unsaturated fat lowers risk of heart disease. Intake of saturated fats should be 10% or less of the total fat intake per day. Cholesterol intake should not exceed 300 mg.
Sources of fats/lipids/oils
⦁ Animal sources include meat, suet, bacon, oil fish, cheese, butter, lard, milk, and egg yolk.
⦁ Plant sources include groundnuts, soya, cocoa, sim-sim, maize, avocado, margarine, wheat germ, corn, sunflower, and palm oil.
Dietary fibre
This is a form of complex carbohydrate that is part of the nondigestible portion of the food. Dietary fibre increases the body’s sense of satisfaction thus preventing overeating. Diets high in fibre protect against constipation. Fibre can slow the body’s absorption of sugar and cholesterol protecting the body from diseases of the heart and diabetes. Dietary fibre adds bulk to the faeces. In addition, dietary fibre slows down the breakdown of starch.
Sources of dietary fibre
⦁ Whole grains of cereals, for example: oats, millet, and maize bran.
⦁ Vegetables, for example: dodo, nakati, malakwang, cabbage, and pumpkin leaves.
⦁ Legumes such as beans, peas, and pigeon peas, among others.
⦁ Fruits such as mangoes, oranges, and pineapples, among others.
Micronutrients are the nutrients used by the body in smaller amounts and include vitamins and minerals.
Vitamins
Vitamins are organic compounds and are imperative for certain metabolic functions in the body. The major two categories of vitamins are:
a) Fat-Soluble Vitamins
Fat-soluble vitamins are deposited into the body, and their absorption requires fat through the diet. These include vitamins A, D, E, and K, which play important roles in the following functions:
⦁ Vitamin A: Very important for the eyes.
⦁ Vitamin D: Essential for building bones.
⦁ Vitamin K: Helpful in muscular action and blood flow.
⦁ Vitamin E: Protects cells and assists in enzyme synthesis and nutrient assimilation.
Dietary sources of fat-soluble vitamins include carrots, tomatoes, liver, offal, kidneys, gizzards, hearts, milk, dairy products, and leafy vegetables.
b) Water-Soluble Vitamins
Water-soluble vitamins do not accumulate in the body and must be supplied regularly. This category includes vitamin C (ascorbic acid) and the B complex vitamins (B1-B12 and folate). These vitamins facilitate energy release, help in utilizing macronutrients, and contribute to red blood cell synthesis.
Common dietary sources of water-soluble vitamins include fruits, dark green leafy vegetables, whole grains, and nuts. Many are also found in meat, fish, poultry, and fortified cereals. Citrus fruits are particularly rich in vitamin C, known for enhancing iron absorption from plant-based foods.
Vitamins requirements
⦁ Water-soluble vitamins are not stored in the body and must be consumed daily.
⦁ Fat-soluble vitamins are stored in the liver and may not have to be
taken daily, excessive intake of these vitamins is toxic (refer to Annex 1 for RDAs).
Minerals
Minerals are required for the normal functioning of body processes, including growth, development, water balance and neurological processes.
Minerals of public health importance
⦁ Iron is an essential component of blood and helps transfer oxygen to various body tissues. Dietary sources include red meat, fish, poultry (easily absorbed), legumes, leafy green vegetables (less easily absorbed, but absorption increases if eaten with animal source iron or vitamin C).
⦁ Calcium is a key component of bones and teeth and is needed for a strong skeleton and important in blood clotting. The major source of calcium in the world is milk and milk products. Other sources include fish eaten with bones (silver fish—mukene, haplochromis species—nkeje) and dark green vegetables (plant sources are not well absorbed).
⦁ Iodine is important for thyroid function and for mental development of children. The most important dietary source is iodized salt.
⦁ Zinc enhances and strengthens the immune system, helps wound healing, facilitates digestion and is an important component of skeletal muscle. Dietary sources include beef, seafood, liver, nuts, beans and whole grains.
⦁ Other minerals involved in various body functions are chromium, copper, fluoride, magnesium, manganese, molybdenum, nickel, potassium, phosphorus, sodium and selenium.
Mineral requirements
Minerals that are required by the body in relatively large amounts such as calcium, iron, phosphorus, potassium, sulphur, chlorine, sodium and magnesium require deliberate efforts to be supplied them through increased food production, consumption and supplementation. Most trace mineral elements such as iodine copper, manganese, fluorine, cobalt, nickel, zinc, chromium and selenium are supplied by a wide variety of foods and the body is unlikely to be deficient in them when one consumes a balanced diet.
Water
Maintains the fluid balance, cell turgidity, media for all biochemical reactions in the body, solvent for certain nutrients, used in removing excreta and keeps some parts of the body moist. Water is essential for life because it forms part of the body cells and fluids, such as blood and digestive juices.
Water requirements
Drink water everyday especially in hot weather when much is lost through sweating to avoid dehydration. A minimum of 2–3 Litres per day is recommended for an adult person. All drinks such as tea, coffee, fruit juice count towards there commended daily total of at least 8 cups a day (for an adult). Children should drink all the time as they need.
The body requires water for many functions:
⦁ To transport nutrients around the body.
⦁ To make blood, saliva, tears and sweat.
⦁ To enable body processes such as digestion.
⦁ To keep the mouth and lungs moist, and to keep the skin moist and cool.
⦁ To produce breast milk, which is also a source of water.
Extra water is needed:
⦁ During illness when a raised temperature results in increased sweating. If vomiting or diarrhoea has occurred, both of which can cause dehydration especially in babies.
⦁ In lactation when extra water is required for milk production. After intensive activity such as sport.
NUTRITION
Nutrition is the process of providing or obtaining the food necessary for health and growth. It broadly encompasses all actions necessary for obtaining, handling, preparing, serving, eating and utilization of food by the body. When individuals or communities do not feed appropriately they face a possibility of becoming malnourished and can face serious health problems. Extension workers should promote good nutrition in the community.
What is nutrition?
Good nutrition refers to a state when the food we eat is able to provide the recommended amounts of nutrients for the body to perform all its physiological activities. It is dependent on one’s age, physiological status, physical activity level and sex. Good nutrition is important throughout the life cycle; right from pre-conception, conception, pregnancy, infancy, childhood, adolescence and adulthood. Good nutrition makes an individual healthy, more productive and improves the quality of life.
Good nutrition means:
⦁ Eating the right food.
⦁ At the right time.
⦁ The right amounts (quality and quantity) to ensure a balance diet and should be prepared in the correct way and right place.
Final Statement
A deeper understanding of the basic elements of food and nutrition is related to overall health and well-being. A diet that consists of balanced carbohydrates, proteins, and fats provides energy, growth, and repair, along with micronutrients, vitamins, and minerals to support essential metabolic functions. Proper nutrition enables the body to function optimally, supports physical and mental performance, and minimizes the risk of chronic diseases. Long-term health and a better quality of life can be assured by including a wide range of nutrient-dense foods in everyday meals.
