Textbook on Nutrition & Dietetics for Post Basic BSc Nursing Students I Clement
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SECTION 1
1Nutrition2

Introduction to NutritionChapter 1

 
► INTRODUCTION
Food is prime necessity of life. The food we eat is digested and assimilated in the body, and used for its maintenance and growth. Food also provides energy for doing work. Man has exhibited much thought and foresight in cultivating a variety of grains, fruits, vegetables, nuts and oil seeds, and in rearing birds and animals for use as food. Nutrition deals with the way in which the human body receives, and uses all the substance or materials necessary for its growth and development and for keeping it in good condition. This begins in eating food. The food swallowed then digested as it is passed through the stomach and small intestines. During digestion, the food is broken up into simple substances. These are absorbed into bloodstream and carried to the liver, where they are either stored, or changed further or sent out to other parts of the body for use as required.
 
► DEFINITIONS
  1. Food: It is defined as anything solid, liquid or semisolid, which when ingested putting into the mouth, digested and assimilated, nourishes the body. The edible stuff that provides us with nutrients is termed as food. It is broadly classified as cereals, pulses, vegetables, fruits, milk, eggs, flesh foods, fats and sugar.
  2. Nutrients: These are defined as those chemical substances, which are supplied by food, and are needed as a source of energy and as a structural material for every cell of the body. These are constituents in food that must be supplied 4to the body in suitable amounts. They include proteins, fats, carbohydrates, minerals, water and vitamins.
  3. Nutrition status: It is defined as the extent to which a customary diet meets the body's requirement. In other words, it signifies the condition of the body after the consumption of food. The condition of individual's health is influenced by the utilization of nutrients. It can be assessed by dietary survey, anthropometry, clinical and laboratory investigations.
NUTRITION
Nutrition is the combination of processes by which the living organism receives and utilizes the materials necessary for the maintenance of its function, and for the growth and renewal of its components.
Nutrition is that condition, which permits the development and maintenance of the highest state of fitness. And also it involves is processes or activities by which the human body receives and uses all the food necessary for its growth, development, regulation and repair. It is the science of food, the nutrients and other substances therein, their action, interaction and balance in relationship to health and disease.
 
► HISTORY OF NUTRITION
Nutritional discoveries from the earliest days of history have had a positive effect on our health and well-being (Table 1.1). The word nutrition itself means “the process of nourishing or being nourished, especially the process by which a living organism assimilates food, and uses it for growth and replacement of tissues.” Nutrients are substances that are essential to life, which must be supplied by food. Today more than ever, obtaining nutritional knowledge can make a big difference in lives. Air, soil and water pollution in addition to modern farming techniques, have depleted soils of vital minerals. The widespread use of food additives, chemicals, sugar and unhealthy fats in the diets contributes to many of the degenerative diseases such as cancer, heart disease, arthritis and osteoporosis. 5Here is a brief history of the science that offers the hope of improving health naturally.
The first recorded nutritional experiment is recorded in the book of Daniel in the Bible. Daniel was among the finest young men captured by the King of Babylon when the Babylonians over ran Israel and was to serve in the King's court. He was to be fed from the King's table of fine foods and wine. Daniel objected and preferred his own choices, which included vegetables (pulses) and water. The chief steward was afraid for his head, but agreed to a trial. Daniel and his friends received his own diet for 10 days and then were compared to the King's men, as they appeared fitter and healthier. They were allowed to continue with their own foods, not defiling themselves with those of the King. The 20th century became the era of the Golden Age of Nutrition, when most of the discoveries of the nutrients took place. Stephen Babcock was instrumental in helping to open the age. Babcock, better known for the Babcock test for milk fat that bears his name and conceived the idea to feed dairy cattle feed from just one source, all corn plant or all wheat plant.
Table 1.1   Highlights of history of nutrition
Sl No
Year
Description
1.
400 BC
Hippocrates, the ‘Father of Medicine’, said to his students, “Let food be thy medicine and medicine be thy food”. He also said, “wise man should consider that health is the greatest of human blessings”.
Foods were often used as cosmetics or as medicines in the treatment of wounds. In some of the early Far Eastern Biblical writings, there were references to food and health. One story describes the treatment of eye disease, now known to be due to vitamin A deficiency, by squeezing the juice of liver onto the eye. Large amounts of vitamin A is stored in the liver.
2.
1447
James Lind, a physician in the British Navy, performed the first scientific experiment in nutrition. At that time, sailors were sent on long voyages for years and they developed scurvy (a painful, deadly bleeding disorder). Only non-perishable foods such
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6
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Sl No
Year
Description
as dried meat and breads were taken on the voyages, as fresh foods would not last. In his experiment, Lind gave some of the sailors seawater, others vinegar and the rest lime. Those given the lime were saved from scurvy. As vitamin C was not discovered until the 1930s, Lind did not know it was the vital nutrient. As a note, British sailors became known as ‘Limey’.
3.
1500
Scientist and artist Leonardo da Vinci compared the process of metabolism in the body to the burning of a candle.
4.
1770
Antoine Lavoisier, the ‘Father of Nutrition and Chemistry’ discovered the actual process by which food is metabolized. He also demonstrated where animal heat comes from. In his equation, he describes the combination of food and oxygen in the body, and the resulting giving off heat and water.
5.
1800
It was discovered that foods are composed primarily of four elements such as carbon, nitrogen, hydrogen and oxygen, and methods were developed for determining the amounts of these elements.
6.
1840
Justus Liebig of Germany, a pioneer in early plant growth studies, was the first to point out the chemical make up of carbohydrates, fats and proteins. Carbohydrates were made up of sugars, fats were made up of fatty acids and proteins were made up of amino acids.
7.
1897
Christiaan Eijkman, a Dutchman working with natives in Java, observed that some of the natives developed a disease called beriberi, which cause heart problems and paralysis. He observed that when chickens were fed the native diet of white rice, they developed the symptoms of beriberi. When he fed the chickens, unprocessed brown rice (with the outer bran intact), they did not develop the disease. Eijkman then fed the brown rice to his patients and they were cured. He discovered that food could cure disease. Nutritionists later learned that the outer rice bran contains vitamin B1, also known as thiamine.
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7
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Sl No
Year
Description
8.
1912
  1. McCollum EV, while working for the US Department of Agriculture at the University of Wisconsin, developed an approach that opened the way to the widespread discovery of nutrients. He decided to work with rats rather than large farm animals such as cows and sheep. Using this procedure, he discovered the first fat-soluble vitamin (vitamin A). He found that rats fed butter were healthier than those fed lard, as butter contains more vitamin A.
  2. Casimir Funk was the first to coin the term ‘vitamins’ as vital factors in the diet. He wrote about these unidentified substances present in food, which could prevent the diseases of scurvy, beriberi and pellagra (a disease caused by a deficiency of niacin or vitamin B3). The term vitamin is derived from the words vital and amine, because vitamins are required for life and they were originally thought to be amines—compounds derived from ammonia.
9.
1930
William Rose discovered the essential amino acids, the building blocks of protein.
10.
1940
  1. The water soluble B and C vitamins were identified.
  2. Russell Marker perfected a method of synthesizing the female hormone progesterone from a component of wild yams called diosgenin.
11.
1950 to the present
The roles of essential nutrients as a part of bodily processes have been brought to light. For example, more came to known about the role of vitamins and minerals as components of enzymes and hormones that work within the body.
12.
1968
Linus Pauling, a Nobel Prize winner in chemistry, created the term ‘orthomolecular nutrition’. Orthomolecular is literally ‘pertaining to the right molecule’. Pauling proposed that by giving the right molecules to the body in the right concentration (optimum nutrition), nutrients could be used by people to achieve better health and prolong life. Studies in the 1970s and 1980s conducted by Pauling and colleagues suggested that very large doses of vitamin C given intravenously could be
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Sl No
Year
Description
helpful in increasing the survival time and improving the quality of life of terminal cancer patients.
13.
1994–2000
Have you ever wondered, why vitamin bottle labels and nutritional websites include a phrase saying that their products and information are not intended to diagnose, cure or prevent any disease? They usually state that their health claims have not been evaluated by the Food and Drug Administration (FDA). Here is why: The Dietary Supplement Health and Education Act was approved by Congress in October of 1994 and updated in January 2000. It sets forth, what can and cannot be said about nutritional supplements without prior FDA review.
 
► CONCEPT OF NUTRITION
Nutrition is also known as nourishment or aliment in the form of food in order to support life. The diet of an organism refers to what they eat. Many common health problems can be prevented by having a healthy diet. Dietitians are professionals who specializes human nutrition, meal planning, preparation and so on. They are trained people to provide dietary advice for every individual in health and disease. There are seven major classifications of nutrients, they are, carbohydrates, fibers, fats, proteins, minerals, water and vitamins. These classes of nutrients are categorized as macronutrients are needed in relatively large amounts. Micronutrients are needed in smaller quantities. Macronutrients are carbohydrates, fats, fibers, water and proteins, while micronutrients are vitamins and minerals.
The macronutrients provide energy, which is measured in Joules or kilocalories and written with a capital ‘C’ to distinguish them from gram calories. Carbohydrates and proteins provide 17 kJ (4 kcal) of energy per gram, while fats provide 37 kJ (9 kcal) of energy per gram. Vitamins, minerals, fiber and water do not provide energy, but are necessary for other reasons. Other nutrients include antioxidants and photochemicals. These substances were recently discovered, which have 9been not yet recognized as vitamins or contribute to health, but they are necessary to the bodies. Photochemical may act as antioxidant, but not all of them are antioxidants.
 
► NUTRITION AND HEALTH
Health is defined by the World Health Organization (WHO) as the “state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.” To maintain good health and nutritional status, one must eat a balanced food, which contains all the nutrients in the correct proportion. The essential requisites of health would include the following:
  1. Achievement of optimal growth and development, reflecting the full expression of one's genetic potential.
  2. Maintenance of the structural integrity and functional efficiency of body tissues necessary for an active and productive use.
  3. Mental well-being.
  4. Ability to withstand the inevitable process of aging with minimal disability and functional impairment.
  5. Ability to combat diseases such as:
    1. Resisting infections (immunocompetence).
    2. Preventing the onset of degenerative diseases.
    3. Resisting the effect of environmental toxins/pollutants.
Till 3 decades, the role of nutrition in growth and development, and tissue integrity alone was clear, but now the persuasive role nutrition plays in the other dimensions of health is implicit. Hence an optimal nutritional status is an indication of good health. This recent advance has brought about a large-scale change in dietary habits and practices of the population.
 
Facts About Basic Nutrition and Health
  1. The amount and kinds of food taken affect his/her health and well-being.
  2. Eating the recommended servings of food ‘from the food guide pyramid’ will provide key nutrients and enable a 10person to meet the dietary recommendations outlined in this concept.
  3. Counting food servings is important to assuring that adequate choices are made from the pyramid.
  4. New dietary guidelines are available to help a person to plan for sound nutrition.
    The number of calories needed per day depends upon the basal metabolic rate (BMR), which in turn, depends upon factors such as age, sex, size, muscle mass, glandular function, emotional state, climate and exercise.
  5. Eating well can reduce risk of various health problems and increase quality of life.
 
Fat Dietary Recommendations
 
For Fats
  1. Excess fat in the diet, particularly saturated fat, is associated with an increased risk of disease and is inversely related to optimal health.
  2. Modified fats and fat substitutes in the diet can have varying health consequences.
  3. There are some recommendations that can be followed to assure healthy amounts of fat in the diet.
 
For Carbohydrates
  1. For optimal health, carbohydrates, especially complex carbohydrates, should be the principle source of calories in the diet.
  2. There are some recommendations that can be followed to assure healthy amounts of carbohydrate in the diet.
 
For Proteins
  1. Protein is the basic building block for the body, but dietary protein constitutes a relatively small amount of daily calorie intake.
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  2. There are some recommendations that can be followed to assure healthy amounts of protein in the diet.
 
For Vitamins
  1. Adequate vitamin intake is necessary to good health and wellness, but excessive vitamin intake is not necessary and can be harmful.
  2. There are some recommendations that can be followed to assure healthy amounts of vitamins in the diet.
 
For Minerals
  1. Adequate mineral intake is necessary for good health and wellness, but excessive mineral intake is not necessary and can be harmful.
  2. There are some recommendations that can be followed to assure healthy amounts of minerals in the diet.
 
For Water and Other Fluids
  1. Water is a critical component in the healthy diet. Beverages other than water are a part of many diets. Some beverages can have an adverse effect on good health.
  2. There are some recommendations that can be followed to assure healthy amounts of water and fluids in the diet.
 
Facts About Sound Eating Practices
  1. Healthy snacks can be an important part of good nutrition.
  2. Consistency (with variety) is a good general rule of nutrition.
  3. Moderation is a good general rule of nutrition.
  4. Careful selection of food choices is important for those who rely on fast foods as a significant part of their diet.
  5. There are some recommendations that can be followed concerning fast foods.
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Facts About Nutrition and Physical Performance
  1. Carbohydrate loading and carbohydrate replacement during exercise can enhance sustained aerobic performances exceeding 1 hour in length.
  2. The timing may be more important than the make up of the pre-event meal.
  3. High-protein diets advocated for active people and athletes have been questioned by leading organizations in the areas of health, physical activity and nutrition.
  4. People who are interested in enhancing physical performance are especially subject to nutrition quackery.
 
► NUTRITION—A BASIC HUMAN NEED
Nutrition is a basic human need that changes throughout the life cycle and along the health-illness continuum. The body requires food to provide energy for organ functions, body movement and work, maintain body temperature, and to provide raw materials for enzymes function, growth replacement of cells and repair. Food provides nutrition for both the body and mind. Eating has evolved from being simply a necessity; is an integral component of medical treatment. The science of nutrition encompasses the study of nutrients and how they are handled by the body, as well as the impact of human behavior and environment on the process of nourishment. Nutrients alter specific substances used by the body for growth and development, activity, reproduction, lactation, health maintenance and recovery from illness or injury. Good nutrition is a basic component of health, growth and development for maintaining health throughout the life. Proper nutrition of the nation is necessary for the nation's growth and economic development.
Nurses must understand the functions of the basic nutrients and metabolism. An understanding of the guidelines for adequate diet is essential so that nurses can teach about nutrients and answer for the questions related to diet. Nurses must be able to assist the nutrients of the diet. They must also recognize that many divergent factors influence food intake and consider 13the factors when attempting to modify food intake. The factors that influence nutrient requirements are developmental consideration, i.e. age, sex, health status, culture and religion, socioeconomic status, personal preference, medications, alcohol and drugs, etc. Nurse also must be able to identify clients at risk for nutritional problems and be aware of common nutritional conditions (Table 1.2).
The term ‘food’ refers to anything, which nourishes the body. It would obviously include solids, semisolids and liquids, which can be consumed. The food helps to sustain the body to keep it healthy. The terms ‘food’ and ‘nutrition’ are sometimes used synonymously, but it is not strictly correct. Food is defined as “what one feeds on and is a composite mixture of many nutrient substances ranging from a fraction of a gram in some cases to hundred of gram in others. The foodstuff is defined as anything, which can be used as food. Therefore, the word ‘nutrition’ is derived from the word ‘nutricus’, which means ‘to suckle at the breast’. Nutrition is defined as combination of dynamic process by which the consumed food is utilized for nourishment, structural and functional efficiency of every cell of the body.
Metabolism refers to all the biochemical reactions within the body. It consists of anabolic reactions that build substances, body tissues and catabolic reactions those breakdown substances. Food is ingested, digested and absorbed to produce the energy needed for these reactions. The energy requirement of an awake person at rest is called the ‘basal metabolic rate’. BMR is the energy needed at a person's lowest level of cellular functions. Age, body size, temperature, growth, sex, nutritional status, emotional status and good intake affect individual energy requirements beyond the BMR. When energy requirements are completely met by caloric intake in food, people maintain that activity levels without weight change. If the number of calories ingested exceeds energy needs, people gain weight. When the calories ingested fail to meet energy requirements, people lose weight.
Nutrition encompasses all of the processes involved in consuming and utilizing food for energy, maintenance and growth. 14The processes include ingestion, digestion, absorption, metabolism and excretion. Much of the discussion throughout this chapter focuses on ingestion. Because this is the process that the indicial can control and with which the nurse can assist the client. Basic information is presented about proper nutrition and the role of the nurse in assisting clients to meet their nutritional needs. Topics covered include, specific nutrients and their functions in the body; photochemicals; promoting proper nutrition factors influencing nutrition; nutritional needs during the life cycle; nutrition and health; weight management; food labeling; quality and safety; food allergies and nutrition and the nursing process.
 
► PHYSIOLOGY OF NUTRITION
Five processes are involved in the body's use of nutrients:
  1. Ingestion.
  2. Digestion.
  3. Absorption.
  4. Metabolism.
  5. Excretion.
 
Ingestion
Nutrition begins with ingestion, taking food into the digestive tract, generally through the mouth. In special circumstances, ingestion occurs directly into the stomach, through a feeding tube.
 
Digestion
Digestion refers to the mechanical and chemical processes that convert nutrients into a physically absorbable state. Mechanical digestion includes mastication (chewing), breaking food into fine particles and mixing it with enzymes in saliva and deglutition (swallowing food), the peristaltic waves and mucus secretions that move the food down the esophagus. Chemical digestion includes the digestive juices changes food into the individual nutrients that can be used by the body.15
Digestion begins in the stomach (except in the case of some starches for which digestion begins in the mouth) and is completed in the intestines. Peristalsis [rhythmic, coordinated, serial contractions of the smooth muscles of the gastrointestinal tract (GIT) forces], chyme (an acidic, semifluid paste) pass through the small and large intestines. Only carbohydrates, proteins and fats require chemical digestion to make the nutrients available or absorption.
 
Absorption
Absorption is the process, whereby the end products of digestion (i.e. individual nutrients) pass through the epithelial membranes in the small and large intestines, and into the blood or lymph systems. The nutrients are absorbed and taken to the parts of the body that need them. Most nutrients are water soluble, and can be absorbed directly through the villi (finger-like projections that line the small intestine) and into the blood. Fats, which are not water soluble are absorbed first into the lymph system and eventually enter the circulatory system (Fig. 1.1).
 
Metabolism
The conversion of nutrients into energy by the body is called metabolism. This process is the sum total of all the biological and chemical processes in the body as they relate to the use of nutrients in every body cell. Metabolism involves two processes:
  1. Anabolism.
  2. Catabolism.
 
Anabolism
Anabolism is the constructive process of metabolism, wherein new molecules are synthesized and new tissues are formed, as in growth and repair. This process requires energy.
 
Catabolism
Catabolism is the destructive process of metabolism, wherein tissues or substances are broken into their component parts.
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zoom view
Fig. 1.1: Digestion and absorption of food at various parts of gastrointestinal tract (GIT)
This process releases energy. During metabolism, energy is also produced by the process of oxidation, which is the chemical process of combining nutrients with oxygen. The energy produced by the body is used in a number of ways such as electrical energy for brain and nerve activities, chemical energy for metabolism, mechanical energy for muscle contractions and thermal energy to keep the body warm.
Metabolic rate: It is the rate of energy utilization in the body; it is expressed in units called calories. One calorie is the amount of heat required to raise the temperature of 1 g of water by 1°C. Because of the large quantity of energy released during metabolism, the energy is expressed in kilocalories (kcal), each of which is equal to 1,000 calories.17
Basal metabolism: It is the amount of energy needed to maintain essential physiologic functions, when a person is at complete rest, i.e. the lowest level of energy expenditure. The major factor affecting basal metabolism is body composition. Lean muscle tissue has a higher metabolic rate and thus produces more energy than fat tissue. Generally, women have a lower metabolism than men, because they have a higher percentage of fat tissue; however, metabolism increases during menstruation, pregnancy and lactation. Age has also an influence, because growth periods increase metabolism. Glandular activity, especially of the thyroid gland, affects metabolism. The rate of metabolism is governed primarily by the hormones triiodothyronine (T3) and thyroxine (T4). Hypothyroid activity, a decrease in the secretion of thyroid hormones, causes a lower rate of metabolism, whereas hyperthyroid activity, an increase in the secretion of thyroid hormones, causes a higher rate of metabolism.
 
Excretion
Excretion is the process of eliminating or removing waste products from the body. Dietary fiber, indigestible materials, salts and other products such as bile and water are converted into feces, and excreted from the body as solid waste. Other excretory organs that aid the digestive system in the elimination of wastes include the kidneys, bladder, sweat glands, skin and lungs. Most liquid waste is sent through the kidneys and bladder to be excreted as urine. Some liquid waste is removed through the sweat glands of the skin as perspiration. Gaseous waste is eliminated through the lungs.
 
► IMPORTANCE OF NUTRITION IN HEALTH
Nutrition may be defined as the science of food and its relationship to health. It is concerned primarily with the part played by nutrients in body growth, development and maintenance. The word nutrient or ‘food factor’ is used for specific dietary constituents such as proteins, vitamins and minerals. Dietetics 18is the practical application of the principles of nutrition; it includes the planning of meals for the well and the sick. Good nutrition means “maintaining a nutritional status that enables us to grow well and enjoy good health.”
Nutrition deals with the way in which the human body receives, and uses all the substance or materials necessary for its growth and development, and for keeping it in good condition. This begins in eating food. The food is swallowed and then digested as it is passed through the stomach and small intestines. During digestion, the food is broken up into simple substances. These are absorbed into bloodstream and carried to the liver, where they are either stored or changed further or sent out to other parts of the body for use as required.
Some are used to supply the body with heat and energy, and others for the building and repair of the tissues, and yet others are used to control the chemical changes taking place in the body or to protect the body from diseases, finally the waste products, which cannot be used are excreted.
 
► RELATION OF NUTRITION TO HEALTH
Good nutrition is a basic component of health. The relation of nutrition to health may be seen from the following view points.
 
Growth and Development
Good nutrition is essential for the attainment of normal growth and development. Not only physical growth and development but also the intellectual development, learning and behavior are affected by malnutrition. Malnutrition during pregnancy may affect the fetus resulting in stillbirth, premature birth and ‘small-for-dates’ babies. Malnutrition during early childhood delays physical and mental growth; such children are slow in passing their milestones and are slow learners in school. Good nutrition is also essential in adult life for the maintenance of optimum health and efficiency. In short, nutrition affects human health from birth till death.19
 
Specific Deficiency
Malnutrition is directly responsible for certain specific nutritional deficiency diseases. The commonly reported ones in India are kwashiorkor, marasmus, blindness due to vitamin A deficiency, anemia, beriberi, goiter, etc. Good nutrition therefore is essential for the prevention of specific nutritional deficiency diseases and promotion of health.
 
Resistance to Infection
Malnutrition predisposes to infections like tuberculosis. It also influences the course and outcome of many of the clinical disorders. Infection, in turn, may aggravate malnutrition by affecting the food intake, absorption and metabolism.
 
Mortality and Morbidity
The indirect effects of malnutrition on the community are even more striking; a high general death rate, high-infant mortality rate, high-sickness rate and a lower expectation of life. Overnutrition, which is another form of malnutrition, is responsible for obesity, diabetes, hypertension, cardiovascular and renal disease, disorders of the liver and gallbladder. More recent reports suggest that diet perhaps plays an important role in certain types of gastrointestinal cancers. It is now quite well-accepted that diet and certain diseases are inter-related.
 
► NUTRITION RELATED HEALTH PROBLEMS
 
Diet and Nutrition
A balanced dietary intake promotes nutritional health. Genetic predisposition seems to play subsidiary role in dietary intake. Malnutrition in developing countries is essentially because of the nature of undernutrition. Inadequate dietary intake causes health problem in pregnant women, lactating mothers and growing children.20
 
Diet and Chronic Diseases
Modern epidemics of nutrition-related chronic diseases have appeared in developed countries of the world, which is attributed to the intake of ‘affluent diet’. The disease includes hypertension, coronary heart diseases, diabetes, etc. Chronic liver diseases include cirrhosis of liver, which are also prevalent in the affluent classes, are related to excessive intake of alcohol.
 
Diet and Cancer
Epidemiological studies carried out all over the world have established that nearly one third of all cancers types are directly related to one or the other dietary component. Diet rich in saturated fats is particularly linked to colon cancer and prostate cancer. Breast cancer and rectum cancer are also related to high-fat intake. Epidemiological studies have revealed that regular intake of fruits and vegetables, high in fiber content, low in saturated fats and rich in several antioxidants, vitamins namely, retinol, carotene, vitamin C and vitamin E act are potential carcinogenic agents.
 
Diet and Dental Diseases
Diet rich in sugar content predispose to dental caries. Sugar has casual association with dental caries; the association is particularly strong during childhood years with sugars that are consumed in between meals rather than with meals. High-starch diet is not cacogenic obviously because it contains complex sugars.
 
Diet and Skeletal Diseases
Consumption of diet, poor in calcium may predispose to osteoporosis. Alcohol intake and smoking habit are also related to osteoporosis. Osteoporosis predisposes to fracture especially in elderly people.21
 
Diet and Mental Health
Inadequate dietary intake deficient in nutrients likes iodine, nicotinic acid and iron can retard mental development or impair mental performance. Iodine deficiency can cause an extreme degree of mental impairment as seen in cretinism. Nicotinic acid deficiency can lead to dementias in extreme cases of pellagra.
 
Diet and Diet Therapy
Dietetics is the word used to describe the practical application of the principles of nutrition to the human body in health and disease. Diet therapy is the science dealing with prescription of appropriate diet to patients, which constitutes an important component of their treatment.
FOOD
 
► FUNCTIONS OF FOOD
Food is the basic necessity of man. It is a mixture of different nutrients such as carbohydrate, protein, fat, vitamins and minerals. These nutrients are essential for growth, development and maintenance of good health throughout the life. They also play a vital role in meeting the special needs of pregnant and lactating women, and patients recovering from illness.
 
Physiological Functions
 
Energy-yielding Foods
Foods rich in carbohydrates and fats are called energy-yielding foods. They provide energy to sustain the involuntary processes essential for continuance of life, to carry out various professional, household and recreational activities, and to convert food ingested into usable nutrients in the body. The energy needed is supplied by the oxidation of foods consumed. Cereals, roots and tubers, dried fruits, oil, butter and ghee are all good sources of energy.22
 
Bodybuilding Foods
Foods rich in protein are called bodybuilding foods. Milk, meat, eggs and fish are rich in proteins of high quality. Pulses and nuts are good sources of protein, but the protein is not of high quality. These foods help to maintain life, promote growth and also supply energy.
 
Protective and Regulatory Foods
Food rich in protein, minerals and vitamins are known as protective and regulatory foods. They are essential for health and regulate activities such as maintenance of body temperature, muscle contraction, control of water balance, clotting of blood, removal of waste products from the body and maintaining heartbeat. Milk, egg, liver, fruits and vegetables are protective foods.
 
Social Function
Food has always been the central part of our community, social, cultural and religious life (Table 1.2). It has been an expression of love, friendship and happiness at religious, social and family get-togethers. Food is served at many social events such as teas, breakfasts, banquets, athletic award dinners, dances and meeting of all sorts. On all these occasions, food indirectly serves as an instrument to develop social support.
 
Psychological Function
Besides other functions, food satisfies certain emotional needs also. People often find it difficult to get adjusted to unfamiliar food, although it may be nutritionally sound. Traditional habits are characterized by certain foods, which are pleasing to people of one culture and distasteful for those of another. In addition to satisfying physical and social needs, foods also satisfy certain emotional needs of human beings. These include a sense of security, love and acceptance. For example, preparation of delicious foods for family members is a token of love and affection.23
Table 1.2   Factors affecting food and nutrition
Sl No
Factors
Description
1.
Social factors
Food habits are handed over from generation to generation in the society, particularly in the developing countries. Though these factors have very little or no scientific basis, people rigidly adhere to them in many parts of India; pregnant women are not allowed to consume papayas as it is believed that papayas produce a lot of heat in the body, which in turn induce abortion.
2.
Religious factors
Many Hindus are vegetarians; Jains do not eat curd and do not eat after sunset. To eat meat, is to destroy the seed of compassion. Islamic food laws prohibit the consumption of unclean foods such as swine and animals killed in a manner that prevents their blood from being fully drained from their bodies. Jews do not eat pork and shellfish.
3.
Cultural factors
It is a custom in most of the communities in India that women and girls eat only after men and boys finish their eating. Curd and citrus fruit should not be taken by a person suffering from cold or cough.
4.
Traditional factors
The traditional cooking practices also act as a barrier in achieving a balanced diet, e.g. using polished rice, draining away the rice water and prolonged boiling of vegetables add to the great loss of nutrients. Women should take only bread and coffee for 2 days after the delivery of a child and a very small quantity of water should be given.
5.
Economical factors
Financial resources determine the type of food, depending on the availability one selects the food. People in lower income groups in India consume a combination of cereals and cheaply available green leafy vegetables, roots and tubers.
 
Relationship of Food to Main Functions
Nutrition is the process or an activity by which the human body receives and uses all the food necessary for its growth, development and functions or activities:24
  1. Food supplies heat and energy for work and play.
  2. Food supplies materials for growth and repair of the body.
  3. Food supplies materials for regulation or control of body process and for protection of the body. People are familiar with food, but in order to understand the different types of nutrients that are used in the body, it is necessary to know what substances or materials present in food. These substances are called nutrients. The nutrients present in food are proteins, fats, minerals, elements and vitamins.
An adequate diet should contain liberal amounts of protein rich and protective foods, and it should supply all the dietary essentials in the required amounts.
 
► CLASSIFICATION OF FOODS
 
Classification by Origin
  1. Foods of animal origin.
  2. Foods of vegetable origin.
 
Classification by Chemical Composition
  1. Carbohydrates.
  2. Proteins.
  3. Fats.
  4. Vitamins.
  5. Minerals.
 
Classification by Predominant Function
  1. Bodybuilding foods, e.g. milk, meat, poultry, fish, eggs, pulses, groundnuts, etc.
  2. Energy-giving foods, e.g. cereals, sugars, roots and tubers, fats and oil.
  3. Protective foods, e.g. vegetables, fruits, milk.
 
Classification by Nutritive Value
  1. Cereals and millets.
  2. Pulses (legumes).
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  3. Vegetables.
  4. Nuts and oil seeds.
  5. Fruits.
  6. Animal foods.
  7. Fats and oil.
  8. Sugar and jaggery.
  9. Condiments and spices.
  10. Miscellaneous foods.
Since the foods vary in their contents of various nutrients, they have been broadly grouped under three categories from the nutritional point of view:
  1. Energy-yielding foods.
  2. Bodybuilding foods.
  3. Protective foods.
These are briefly discussed below.
 
Energy-yielding Foods
Food rich in carbohydrates and fats are called energy-yielding foods. Cereals, roots and tubers, dried fruits, sugars and fats are included in this group. Cereals contain fair amounts of proteins, minerals and certain vitamins, and form the important sources of the above nutrients.
 
Bodybuilding Foods
Food rich in proteins are called bodybuilding foods. Milk, meat, fish, eggs, pulses, oil seeds and nuts, and low-fat oil seed flours are included in the group of bodybuilding foods.
 
Protective Foods
Food rich in proteins, vitamins and minerals are termed protective foods. Milk, eggs, liver, green leafy vegetables and fruits are included in this group. Protective foods are broadly classified into two groups:
  1. Food rich in vitamins, minerals and proteins of high biological value, e.g. milk, eggs and liver.
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  2. Foods rich in certain vitamins and minerals only, e.g. green leafy vegetables and fruits.
 
► FOOD GROUPS
 
Five Food Group Plans
The nutritional expert group of Indian Council of Medical Research, India suggested a five food group plan and the nutrients supplied by each food group are given in Table 1.3.
 
Basic Seven Food Groups
The seven food group plan was developed by US Department of Agriculture (USDA) in 1943. The seven groups with their nutrient contribution are given in Table 1.4.
 
► NUTRITIVE VALUE OF COMMON FOODS
Food contains nutrients in different proposition and different organoleptic properties. Hormonal substance enzymatic substance and antioxidants are present in various propositions in addition, micro and macronutrients.
 
Cereals
Cereals are rich in carbohydrate, low protein (6%–12%) low fat, poor in iron and calcium. Rice, barley, ragi, millets and wheat are some of the examples of cereals. Insulin stimulants are present in ragi and millet, firstly rich in calcium and latter they are sources of fiber. Except yellow maize and sorghum cereals are free of vitamin A (ascorbic acid). Wheat has acarbose, a chemical helpful to maintain normal blood sugar level. Richest source of iron are bajra and samai (Panicum miliare). 100 g of staple food, cereals yield 346 kcal of energy.
 
Pulses and Legumes
Pulses and legumes are generally called protein foods. They contain 22% of protein soluble and insoluble fibers.
27
Table 1.3   Five food group plans
Sl No
Food groups
Description
1.
Group I
Cereals, roots and tubers: All these foods primarily supply energy. This group includes foods such as wheat, jowar, bajra, ragi and other cereals. Tapioca, potato, sweet potato, arbi and yam come under roots and tubers. This group provides calories, proteins, iron and vitamins. These foods are cheap and are taken in large amounts by the low-income groups. This also provides thiamine and niacin.
2.
Group II
Protein giving foods: The foodstuffs in this group are primary sources of protein; though cereals also furnish proteins. Dals, grains, peas, beans, groundnuts, cashew nuts, almonds, coconut, milk, curd, buttermilk, paneer (cottage cheese), khoa, eggs, fish, mutton, chicken, pork and other flesh foods come under this group. It provides protein both from the vegetables and animal kingdom. Milk and dairy products also provide calcium and riboflavin. Meat, fish and eggs are good sources of protein, iron and niacin.
3.
Group III
Fats/oils, sugar/jaggery: All these foodstuffs supply energy. These include–vegetable oils, vanaspati oil, ghee, butter, cream, sugar and jaggery. This group constitutes about one sixth of the energy value of the diet, but does not add appreciably to the protein, mineral or vitamin levels. Butter is a good source of vitamin A.
4.
Group IV
Protective vegetables and fruits: These are rich sources of minerals and vitamins. These include green leafy vegetables, yellow or orange fruits and vegetables, and citrus fruits.
5.
Group V
Other vegetables: They provide variety in taste and texture, and furnish roughage in the diet. These include fruits stems, leaves and flowers of plants, lady's finger, brinjals, bitter gourds, cauliflower and others. They are fair sources of certain vitamins and minerals.
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Table 1.4   Basic seven food groups
Sl No
Food groups
Description
1.
Group I
Green and yellow vegetables—provide carotene, ascorbic acid and iron.
2.
Group II
Oranges, grapes, tomatoes or raw cabbage or salad greens. These give ascorbic acid (vitamin C).
3.
Group III
Potatoes, other vegetables and fruits. They are good sources of vitamins and minerals in general and fibers.
4.
Group IV
Milk and milk products are sources of calcium, phosphorus, proteins and vitamins.
5.
Group V
Meat, poultry, fish and eggs provide proteins, phosphorus, iron and vitamin B.
6.
Group VI
Bread flour and cereals provide thiamine, niacin, riboflavin, iron, carbohydrates and fiber.
7.
Group VII
Butter or fortified margarine are rich sources of fat and vitamin A.
They are rich in potassium and vitamin B, deficient in methionine, but rich in lysine. More than 40% of protein is present in soybean. It is richest source of protein among plant foods. Calorific value of pulses and legumes are ranging from 315 to 372 kcal for every 100 g. But green peas and soybean provide 93–432 kcal respectively. Source of pulses and legumes are Bengal gram, black gram, red gram, lentil, rajma, horse gram, cowpea and field bean.
 
Green Leafy Vegetables
Green leafy vegetables are low-calorie foods, having 90% moisture, high fiber, low protein, rich vitamins and minerals particularly, beta carotene and calcium. In general greens do not have protein in sufficient amount, but agathi greens contain 8% protein. Low-cost nutritious food like curry leaves have 800 mg calcium for every 100 g. Arai keerai is richest source of iron. Familiar greens like Amaranthus gangeticus are good for normal cardiac 29function, as it provides potassium. A. tristis and A. viridis green are excellent source of iron and ascorbic acid respectively. Commonly used green leafy vegetables are coriander leaves, drumstick leaves, mint, amaranth, celery, spinach and curry leaves.
 
Other Vegetables
Vegetables are known as low-caloric foods, which contain potassium, soluble fiber, vitamin B and ascorbic acid. Some types of vegetable are good source of calcium, e.g. sundakkai and field beans. Folic acid present in lady's finger and chow chow helps in malnutrition of red blood cell (RBC). Choline of pumpkin and cauliflower is vital and regulates fat metabolism.
 
Roots and Tubers
Roots and tubers are poor source of protein, but good source of carbohydrate. The beta carotene in carrot and yam, ascorbic acid in potato, magnesium in pink radish and phosphorus in Colocasia are particularly helpful to meet normal requirements of recommended dietary allowances for an individual.
 
► HEALTHY FOOD SUBSTANCES
  1. Tomato: It has lycopene, which is anticancer carotenoid.
  2. Bitter gourd: It is an insulin stimulant.
  3. Cruciferous vegetables: Brussels sprouts and broccoli, which has indole resists cancer of womb.
  4. Cucumber: It is diuretic and has arginine.
  5. Green tea: It contains catechins—an antioxidant.
 
Fruits
Fruits are roughage, provide bulk to the stools. Most of the fruits are good sources of vitamins and minerals. Ascorbic acid in amla is richer than fruits such as orange, lime and grapes. 100 g of Indian gooseberry yields 600 mg vitamin C. The beta carotene a precursor of vitamin A found in mango and papaya helps to maintain good vision because of an action similar to pepsin.30
Papain relieves the symptoms of episiotomy (surgical incision of vulva during delivery). Watermelon is very meager energy yielder, whereas dried fruits provide high calories. A report by national academy of sciences found that resveratrol, a chemical known to be highly concentrated in grapes skin, acts like estrogen, a hormone known to protect against heart diseases.
 
Nuts and Oil Seeds
Nuts and oil seeds are rich in saturated fat; contain tocopherol thiamine and niacin. Almond, cashew nut, groundnut, walnut, sesame seed, linseed are some sources of nuts and oil seeds. Groundnuts contain monounsaturated fatty acid, 25% protein and 40% fat. Nutritious ball made from groundnut and jaggery in healthy food for children. Coconut meals raises hemoglobin content, as it provides approximately 70 mg iron. Most of the nuts and oil seeds are energy yielder and rich in phosphorus. Short-and medium-chain fatty acid of coconut oil is good for infant intestine.
 
Eggs
Eggs are good mixture of all nutrients except carbohydrate and fiber; supplies essential amino acids and termed as good quality proteins. Raw egg white contains antinutritional factor avidin, which is binding with biotin and makes it unavailable. Ovalbumin, ovomucoid, flavoprotein are egg white proteins. One egg yolk contains 200 g cholesterol and proteins such as lipovitellin and phosvitin. 13% fat, 170 kcal energy, 2 mg iron, 60 mg calcium, 220 mg phosphorus can be obtained from 100 g of egg. Cooked egg is better than raw egg.
 
Meat, Poultry and Fish
Beef meal is richest source of iron among meat products. Protein in the meat and meat products are superior compared to vegetable proteins. Essential amino acids and biological value are responsible to upgrade the quality. Protein value of mutton 31is less than that of chicken, but fat percentage is higher than fish and chicken. They all are moderate source of phosphorus. Common fish varieties rohu and katla have 1.4% and 2.4% of fat respectively. Cat fish is free from fat. Fatty fish are hilsa, tapsee and dried chela. Omega-3 fatty acid content of fish is helpful in preventing cardiac diseases. Consumption of cod-liver oil protects eyes from night blindness.
 
Milk and Milk Products
Milk is ideal food since infant to aged. Skimmed milk, cheese, tinned milk powder, khoa and supplementary foods are made from milk. Cow milk, buffalo milk and processed milk are widely consumed. Protein content of cow milk is higher than human milk, but buffalo milk is rich in fat. High protein and calcium content among milk products is in skimmed milk powder. This group of foods have sufficient phosphorus, thiamine, niacin, but deficit in iron and vitamins. Energy value of 100 g cow milk, buffalo milk, goat milk, human milk is 67, 117, 72 and 65 calories respectively.
 
► CALORIE
The scientific definition of a calorie is a unit of energy for heat in particular. One calorie is the amount of heat that increases the temperature of 1 kg of water by 1°C; any food may contain one or more nutrients, but carbohydrates, fats and proteins are the nutrients, which gives calories to the body. The caloric value of these nutrients and of any common foods has been determined by burning a known weight of the nutrient or food in an atmosphere of oxygen in what is known as a bomb calorimeter. The caloric values of the nutrients are given in Table 1.5.
Table 1.5   Caloric values of the nutrients
Sl No
Nutrients
Caloric values (kcal/g)
1.
Carbohydrates
4
2.
Fats
9
3.
Proteins
4
The following examples of calorie intake are based on USDA guidelines.32
A person's daily calorie intake should be based on age, gender and physical activity level. Men generally need more calories than women and active people need more calories than sedentary (inactive) people:
  1. Children aged 2 and 8: 1,000–1,400.
  2. Active women aged 14 and 30: 2,400.
  3. Sedentary women aged 14 and 30: 1,800–2,000.
  4. Active men aged 14 and 30: 2,800–3,000.
  5. Sedentary men aged 14 and 30: 2,000–2,600.
  6. Active men and women above 30: 2,200–3,000.
  7. Sedentary men and women 30: 1,800–2,200.
 
► BODY MASS INDEX (QUETELET'S INDEX)
The body mass index (BMI) is used as a reference standard for assessing the prevalence of obesity in the community:
zoom view
 Ideal body mass index:
  1. Ideal body mass index for Indian women: 19–24.
  2. Ideal body mass index for Indian man: 20–26.
Once the BMI exceeds the normal limit; the person can be termed as overweight or obese.
 
► BASAL METABOLIC RATE
Basal metabolic rate is the minimum number of calories needed to maintain vital functions, such as breathing and keeping the heart beating. It is the energy expenditure necessary to maintain basic physiologic conditions such as respiration, cardiac contraction, conduction of nerve impulses, metabolic activity such as synthesis of macromolecules under standard conditions, reabsorption of kidney, iron transport across impulse. This function occurs continuously with one's own conscious or awareness. Basal metabolic needs are surprisingly large person 33whose total energy expenditure amounts to 2,000 calories/day, spends as much as 1,200–1,400 calories to support usual metabolism.
 
Definitions
  1. Basal metabolism is the minimum amount of energy needed by the body for maintenance of life when the person is at postabsorptive state, physical and emotional rest.
  2. Basal metabolic rate is a measure of the energy required by the activities of resting tissue can be measured directly from the heat produced (using a respiration calorimeter and metabolic chamber) or indirectly from O2 intake and CO2 expenditure when the subject is at rest.
 
Normal Values
  1. Basal metabolic rate values are expressed as kcal or kJ square meter of body surface per hour.
  2. In adults, BMR for healthy males 40 kcal/h (168 kJ) and in healthy females is 37 kcal/h (155 kJ).
 
Factors Affecting BMR
There are many factors, which affect the BMR; the most common factors are given in Table 1.6.
 
► ENERGY
Energy is defined as the capacity for doing work. It is the heat produced in the body, which is utilized for performing the involuntary and voluntary activities, to maintain body temperature to synthesize new body constituents.
 
Basal Metabolic Rate
A number of processes go on in the body without any conscious effort, even when subject is at complete rest and no physical work is done. These include involuntary processes, such as the beating of heart, the circulation of blood, etc.
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Table 1.6   Factors affecting basal metabolic rate (BMR)
Sl No
Factors
Description
1.
Surface area of the body
The larger the surface area of the body in relation to its bulk, the greater is the heat lost by radiation.
2.
Sex
The basal metabolic rate is higher per square meter of body surface area in men than in women. According to western standards the requirements are:
  1. 40 cal/m2/h for men.
  2. 37 cal/m2/h for women.
3.
Age
Growing children and adolescent have high BMRs in relation to their weight than adults.
4.
Diseases
Some diseases, especially of thyroid gland, may raise or lower the BMRs. A rise of body temperature of 1°F is found to increase BMRs by about 7%.
5.
Nutritional status
The BMR is lower in starvation and undernourishment, as compared to well-fed state. Under prolonged or chronic undernutrition, the BMR is decreased.
6.
Stress
Psychological stress and tension caused by worry or stress will increase the BMR.
7.
Environmental factors
In cold climate, the BMR is increased and in tropical climate, the BMR proportionally low.
8.
Drugs
Smoking (nicotine), coffee (caffeine) increases the BMR, whereas, beta blockers tend to decrease energy expenditure.
These activities are called basal metabolic processes. The energy used for carrying out these activities is known as the BMR. The basal energy need constitute more than half of the total energy need, for most of the people.
 
Unit of Energy
The energy value of food is expressed in terms of kilocalories (kcal or C). A kilocalorie is defined as the amount of heat required to raise the temperature of 1 kg of water by 10°C. In 35the metric system, the international unit, which is kilojoules, is used instead of kilocalories. One kilojoule energy is expended when 1 kg of mass is moved by 1 meter using a force of a Newton:
  • 1 Calorie = 4.184 Joule (J)
  • 1 kcal or C = 4.184 kilojoules (kJ)
  • 1,000 kcal or C = 4.184 Megajoule (MJ)
  • 1 kJ = 0.239 kcal
  • 1 MJ = 239 kcal.
 
Factors Influencing the Total Energy Requirement
Among factors, which influences energy needs are age, sex, body size, climate, secretion of endocrine glands, status of health, altered physiological activity.
 
Age
During the growth period, the BMR is high. Therefore during infancy, the energy need per kilogram of body weight is higher than during adulthood. Energy requirement also decline progressively after early adulthood due to steady decline in BMR thereafter. The basal metabolism during rapid growth is at a high level. The younger the individuals the higher, the basal metabolism since, much energy are stored for growth. The period at which the basal metabolism reaches its highest level is between the ages of 1 and 2 years. A gradual decline occurs between the age of 2 and 5 years, with a more rapid decline until adult age is reached.
 
Sex
The BMR is higher in adolescent boys and adult males as compared to adolescent girls and adult females though it is not due to direct influence of sex differences, but are due to the differences in body composition. Males have a greater amount of muscles and glandular tissues, which is metabolically more active whereas, females have greater adipose tissues, which is 36metabolically less active. Hence, energy requirement of males is higher than of females.
 
Body Size
Body size will have an important effect on energy needs, because a larger body has a greater amount of muscles and glandular tissue to maintain, thus requiring higher energy allowances. Heat is continuously lost through the skin by radiation. Since the heat loss is proportional to the skin surface, the basal heat production is directly proportional to the surface area. A tall thin individual has a greater surface area than an individual of the same weight who is short and fat, and the former will therefore, have a higher BMR.
 
Climate
Climate is known that the BMR is lower in tropics then in temperate zones. Hence the energy cost of work is slightly higher when the temperature falls below 140°C. However, it is felt that there is no need to make any adjustment for temperature in India.
 
Secretion of Endocrine Glands
The thyroid gland, in particular, exerts a marked influence on the energy requirement. If it is overactive (hyperthyroidism), the BMR will increase; if the activity of the gland decreases (hypothyroidism), the BMR will be reduced. Thereby, increasing or decreasing energy requirement accordingly.
 
Status of Health
During the periods of fever as well as malnutrition, the BMR of an individual is affected. Illness involving an elevation of body temperature markedly increases the basal heat production thus increasing the BMR, hence increased energy requirement.37
 
Altered Physiological States
During pregnancy and lactation, the energy needs are increased because of an elevated BMR. In pregnancy this additional energy is needed to support the growth of fetus and maternal tissues. During lactation energy is required for synthesis of milk.
 
Effect of Food
A certain amount of work is expended in the digestion of food, its absorption, transfer to the tissues and utilization. The increased heat production as a result of the ingestion of food is known as the specific dynamic action of the food. Protein, when eaten alone has been shown to increase the metabolic rate by 30%. On the basis of the mixed diets, which are usually consumed, the specific dynamic action of food is approximately 10% of the energy requirement.
 
Extent of Physical Activity
Any kind of physical activity increases the energy expenditure above the basal energy need. Energy for the performance of all types of physical activities ranks next to basal metabolism in amount of energy expended. Sleep causes a reduction of about 10% in the BMR depending on the number of hours spent in sleeping and its manner, i.e. restless/peaceful.
The energy need is determined by the nature and duration of physical activity. Sedentary work such as includes office work, bookkeeping, typing, teaching, etc. calls for lesser energy than moderate work (more active and strenuous occupations) such as nursing, homemaking or gardening. A still greater amount of energy is required by those individuals who are involved in heavy work (hard manual laborer) such as ditch digging, shifting freight, etc. Energy needs vary with age, occupation and physiological state.38
 
► CONCLUSION
Nutrition is essential for growth and development, health and well-being. Eating a healthy diet contribute to preventing future illness and improves quality and length of life. Nutritional status is the state of health as determined by the dietary habits. There are several ways of assessing nutritional status, including anthropometric (i.e. physical body measurement), food intake and biochemical measurement. Proper nutrition is a powerful good: people who are well-nourished are more likely to be healthy, productive and able to learn. Good nutrition benefits families, their communities and the world as a whole. Undernutrition is by the same logic, devastating. It blunts the intellect, saps the productivity of everyone it touches and perpetuates poverty.