NUTRIENTS, FOOD SOURCES AND FUNCTIONS: DISCUSSING CARBOHYDRATES, PROTEIN, FAT AND OIL
Before any serious consideration can be given to food and health, it is necessary to give you an insight into the various ways in which people have looked at food. It will also show you how you, this content will guide your readers to understand and even explain the mentioned classes of food and the role they play in the human body.
There are some basic concepts usually used in connection with nutrition that you must be familiar with. Water as a nutrient is explained because several students like you often do not understand why water can be classified as a nutrient. An explanation of the concepts will offer a better understanding of the processes and the issues that are raised as you get on.
The Different Meanings of Food
Very often people always give the definition which focuses on food being edible. There are different ways by which we can define food and these definitions will enable you to realize that food is something more than just being edible. The various definitions of food are based on physiological, psychological and sociological meanings of food.
The Physiological Meaning of Food
Usually, people define food as anything that is edible. This definition is the simplest form. There are other ways food can be defined. The common definition of food is usually based on its physiological importance. The aim of considering the other definitions is for you to realize that food is something more than just being edible.
Food can be defined as anything solid or liquid which when taken into the body, promotes growth, provides heat and energy and also provides materials that protect and regulate body processes. This is the physiological definition of food.
The food we eat has several influences on our bodies. As we study the effects of food nutrients on our bodies we are dealing with the branch of science known as physiology.
Food provides materials and energy for growth, building the body and for regulating body processes. Examples of the body processes are growth, regulation of body temperature, respiration and reproduction.
Social Meaning of Food.
The social meaning of food is related to the fact that food helps to build relationships, faster bonds and express appreciation. As families during family dinners, friends eat together or party, and business lunches are established, bonds are strengthened. During festivals and festive occasions such as and birthday parties, relationships are built. In Ghana, people offer cooked foods such as groundnut soup and chicken or cakes as gifts, and other food gifts such as eggs, yams and goats to show appreciation.
Changing work patterns and family roles have had a tremendous impact on family eating patterns. In several families in Ghana now supper time is the only time of the weekday when the whole family can eat together.
Psychological Meaning of Food
Food can also be important psychologically. It can be explained in terms of the emotional satisfaction it gives. Food can be a signal for love and affection. As a hungry child is fed, the child shows love and also feels that the one who fed him or him/her. When some individuals get stressed up or when they are worried or bored they eat a lot in order to satisfy the boredom. On the other hand, some people lose their appetite. This is why some people put on a lot of weight even when they are worried.
Hunger and Appetite
Wardlaw and Insel, (1995) refer to appetite as an external or a psychological influence that encourages us to eat food. Appetite comes in an absence of obvious hunger.
Hunger, on the other hand, is an internal or a physiological drive that makes us find and eat food. Hunger fulfils a need. It can also be said to be the body’s signal when it is short of energy and needs food.
Definition of Basic Terms Used in Nutrition
In nutrition, there are several words or concepts you need to understand. Learning them will make it easy to understand and use them in the study of nutrition.
i. A Nutritionist: Who is a Nutritionist? There are several scientists who study different aspects of science. The scientist who studies food and its effects on the body is called a Nutritionist.
ii. Nutrition. We all need food for life. The living body can only function normally if the body is supplied with materials for growth, for repair and maintenance of worn out tissues, for energy and also for the regulation of various functions of the body. Whatever the mixture of food we eat, the basic constituents are made up of simple or complex chemical substances called nutrients.
The study of these simple or complex chemical substances called nutrients, how they react and interact in the body, in relation to health after they have been taken into the body is referred to as nutrition.
iii. Nutrients. Food can be described as being composed of several chemicals substances. These substances are called nutrients. Nutrients are chemical substances in food that nourish the body by providing the body with energy, growth, repair and maintenance of the body and also regulate the needed body functions. Nutrition is related to the study of the nutrients in food and the people who eat it.
Several nutrients have been identified and they have been classified into six main classes. These are proteins, carbohydrates, fats and oils, vitamins, mineral salts and water. Nutrients are classified in various ways. The first five nutrients have further been grouped into two based on quantities needed by the body. These are those that are needed in large amounts (macro) and those needed in minute amounts (micro) but they must be present for the body to function successfully.
Another approach to the classification of nutrients is to look at the predominant functions they perform in the body. Thus, they are classified as energy-providers (carbohydrates and fats/oils), body-builders and repairers (proteins) and regulators of body functions (minerals and vitamins). We have provided you with a table that will serve as a summary of the nutrients
iv. Malnutrition. You have to realize that some people do not eat enough food to get the needed food nutrients or they over eat and get excess nutrients. Some people also eat adequate food but the foods are not combined adequately to provide the required amounts of each nutrient or they combine the food in such a way that they get excess amounts of one or more of the nutrients. These are all cases we can call malnutrition and in both instances, the individual is not getting good nutrition.
Malnutrition is therefore failing or poor health resulting from a long-standing dietary intake that is not sufficient to meet or is in excess of the individual’s nutritional needs. When the dietary intake of the nutrient is not sufficient the condition is called under nutrition. It results in deficiency diseases. On the other hand, if our intake of nutrients exceeds our nutritional needs, then we experience over nutrition. An example of over nutrition is obesity while kwashiokor is an example of under nutrition.
v. A Balanced Diet. It is worth noting that there is no food that contains all the required nutrients apart from human milk. Even this milk unfortunately, satisfies all the nutritional needs of the infant up to just about six months of age. After this age, all human nutritional needs can be satisfied by adding other foods or combining the diets. In order to prevent nutritional deficiencies, we have to eat “balanced” diets. Therefore, a diet that has all the classes of food in their correct proportions is called a balanced diet.
vi. Recommended Daily Allowance (RDA). This is also referred to as Recommended Daily Intake (RDI). These are standards of nutrients indicating the quantities or how much of any nutrient is needed to perform a particular function. Nutrient intake standards have been developed to help dieticians and other professionals as well as individuals who need to determine precise dietary needs of humans and even animals.
The standards were determined based on the determination of the nutrient needs by examining the relationships between nutrient intake and diseases. The various allowances will be given as each nutrient is discussed. However, an important fact is that the RDI is just a list of recommendations, not compulsory requirements. They are to be used as guides. In nutrition, there are individual differences so all of us must use the RDA to guide as we make food choices.
Physiology. Physiology can be defined briefly as the way the human body functions.
NUTRIENTS, FOOD SOURCES AND FUNCTIONS: DISCUSSING CARBOHYDRATES, PROTEIN, FAT AND OIL
CARBOHYDRATES
The focus is on the chemical substances of which food is composed. Some of these nutrients are needed in large amounts while others are needed in minute amounts. In this session we are going to deal with those needed in large amounts, often referred to as macro nutrients. Although water is also needed in large quantity in the human body, we will only consider carbohydrates, proteins, fats and oils (lipids).
A lot of our farmers plant cassava, yams and corn. Compared to the foods that contain proteins, they, are cheap and so we tend to feed our families with a lot of these foods.
Structure and Classification of Carbohydrates
Carbohydrates are a group of organic compounds and they all contain Carbon, Hydrogen and Oxygen. The simple forms of carbohydrates are called sugars. The complex ones are cellulose, glycogen and the starches. Most carbohydrates exist in plants as a mixture of both simple and complex carbohydrates. They are produced from a process called photosynthesis, combining them to together to make basic CH2O units. They then link six of these basic units to make a simple saccharide, often taking the form of a single (monosaccharide) or a double (disaccharides). There are about eight of these simple sugars but in nutrition, only glucose, fructose and galactose are important. The common formula is CnH2n On
Monosaccharides. (The general formula is C6 H12O6.)
Glucose: This is the principal monosaccharide. It is formed during photosynthesis. Glucose is a six carbon monosaccharide called hexose (6carbons). Glucose has a sweet taste but not as sweet as sucrose. It is soluble in water.
It is the building block for the complex sugars. It is found naturally in grapes and other sweet fruit, onions, unripe potatoes and honey. Whatever form of digestible carbohydrate the body takes in, it is eventually converted to glucose. Lucozade is basically made up of glucose and so it is a ready availability source of glucose. That is why convalescents and athletes often take lucozade or glucose found in tins.
Fructose is also made up of the same numbers of carbon, hydrogen and oxygen just like glucose. It is also absorbed any rapidly into the body and it is used more quickly than glucose. It is found in fruits, honey and in processed sugars and high-fructose corn syrup. It is responsible for much of the sweetness of fruits.
Galactose is usually not found free in nature in large quantities. It combines with glucose to form lactose. It is also made up of six carbons, six hydrogen and six oxygen atoms.
Once you have become familiar with the monosaccharides it becomes much easier to understand the other types of sugars.
Disaccharides : It is formed from linkages of two or more amino acids with water released. Disaccharides are also formed from two monosaccharides. The bond between the two is called a glucosidic bond. The three most common disaccharides found in nature are maltose, sucrose and lactose.
- Maltose or malt sugar consists of two glucose molecules. It is important in the sense that in the production of alcoholic beverage fermentation it is the intermediate product. It gives the sweetness and stickiness to malt extract.
- Lactose, popularly called milk sugar. It is formed from glucose and galactose. Some people’s body cannot digest lactose efficiently due to a reduction in the activity of the enzyme lactose. When lactose activity is low lactose travels unchanged into the large intestines. Intestinal bacteria then metabolize it into acids and gases, thus causing bloating, cramping and discomfort.
- Sucrose, also known as cane sugar is the form that all of us consume sugar. It is our popular sugar from cane sugar. Sucrose is formed from glucose and fructose. Plant sources: sugar cane, sugar and honey have significant amounts of sucrose, brown, white and powdered sugars are common forms of sugar sold in the shops and markets. Sucrose can encourage the activity of bacteria which live in the teeth, to cause tooth decay (dental caries). Excess of sucrose can also cause overweight.
Oligosaccharides
These are combined with the polysaccharides in some texts. They are slightly larger than the disaccharides. They are formed by a few, three or four monosaccharides. Examples are raffinose, (trisaccharide) and stachyose, (tetrasaccharides). They are mostly found in leguminous plants, such as beans, etc.
They are not easily absorbable so the bacteria in the intestines act on them to produce gases. Now you can guess why some people give the reputation to beans that they are “flatulence producers”.
Polysaccharides
These polysaccharides are found both in plants and animals. They are formed by several molecules of monosaccharides linked straight or branched chains.
Starch is the main source of energy for humans. It is usually made up of two substances. The first one is amylose which is the unbranched chain. The second part is the branched chain known amylopectin. The starches are digestible.
Dextrin. What happens when you toast bread or fry yams? You cannot see that the starch has been broken down but you can see the brown crust formed on the surface of foods. This brown crust is formed from carbohydrates called dextrin.
Glycogen. The starch that we consume is stored in the body as glycogen. People, therefore, refer to glycogen as animal starch. Its structure is a little simpler than starch but it is still composed of thousands of monosaccharide molecules. Glycogen is stored in the liver, the muscle, particularly those that are subjected to strenuous activities.
Pectin is not known to have any specific nutritional value. However, it is important in nutrition because it makes jams set. It is found in apples, plums, citrus fruits and to a lesser extent in root crops and turnips.
Cellulose
The cellulose molecule contains over 3000 monosaccharide units or more. Cellulose, on the whole contributes very little food value to the body. They are broken down by bacteria in the large intestines partially to produce maltose. For good health, we are often told to eat a lot of food with fibre and not refined sugar.
Cellulose is a type of fibre, also called roughage, important in making humans have free bowels. In most areas, vegetables and fruits have fibre. This fibre is reported to reduce cholesterol in the blood and useful in the treatment of obesity. Cellulose (fibre) is indigestible. Soluble fibre is gummy. An example is dextrin. Insoluble fibre is not digestible. Fibre forms the framework of plants.
Functions, Deficiency Diseases and Sources of Carbohydrates.Excess Carbohydrates in the Body
The body weight can be threatened if one consumes a lot of sugar with other fats and oils without exercises. You may become overweight, which in turn will lead to other problems that include diabetes and other heart diseases.
Do you think simply eating large amounts of sugar is what leads to a high level of sugar in the blood? What causes the high level of blood sugar is mostly dependent on the efficiency of the hormones. It can be a serious issue if the hormones are not able to manage sugar efficiently. Other factors such as fat intake, hereditary and stress as well as activity level must also be analyzed. It signals the condition known as diabetes.
The proper name of this disease is diabetes mellitus. It is caused by insufficient or ineffective function of insulin. There are two major types of diabetes. They are Type 1, Insulin dependent and Type 2, Non-insulin dependent. Type 1 diabetes is usually found in children and young adults, and so it is also called juvenile-onset diabetes. Type 2 diabetes is found in adults and also referred to as adult-onset diabetes. It occurs whenthe body is unable to make sufficient insulin and/or use the insulin it makes properly.
Often, weight-loss, diet and exercise are the only treatment needed. Consult a medical practitioner for more information if you want to know more.
There is a Recommended Daily Allowance for the carbohydrates we take into our bodies.Different people need different amounts of calories and other nutrients. Wardlaw and Insel (1995), suggest that it is important to consume, at least, 50g to 100g per day to prevent ketosis.
Alcohol
It is also composed of carbon, hydrogen and oxygen. Strictly speaking it is not an essential carbohydrate, in spite of its association with the carbohydrates and its release of energy. It is obtained through the fermentation of carbohydrates by yeasts. It is directly absorbed into all parts of the body and has an intoxicating effect on the brain, being a stimulant. Some nutritionists refer to it as non-nutritive food. It can serve as an appetizer.
Alcohol makes it rather difficult for the kidney to retain water. This deprives the body of the necessary fluid. This does not mean that no alcohol should be taken; rather, it should be taken in moderation. It is a narcotic and it is extremely harmful when taken in large amounts. Try and avoid it because it can cause more harm to the body than good.
Tests for Carbohydrates
- Iodine will turn starch to blue-black.
- When Benedict’s solution is added to any simple sugar, such as glucose, a pink red colour will be seen after a series of colour changes. Fehling’s reagent can be used and the same colour will be obtained.
iii. If the sugar is a disaccharide, then it has to be boiled with hydrochloric acid first. Find out the reason for this for the next face-face.
Summarily, Carbohydrates are the major source of energy for the body. They are comparatively cheap and easy to get in Ghana and so a lot of diets are made up predominantly of carbohydrates. There are simple and complex carbohydrates. All carbohydrates are made up of a hexose – a saccharide unit of six carbons in a chain to which hydrogen and oxygen are attached.
PROTEINS
Without protein no life can exist. This then means that no baby can be born and no plant can grow without proteins. You may wonder how the protein can be formed.
Many of us may reject food that has no oil, particularly the sauces. Formerly, among the ignorant population, a plump person is equated with beauty and wealth. In some communities, this belief is still held because people believe that the person has money to afford the luxury of a high status meal.
Structure of Proteins
Just like carbohydrates, the basic components of proteins are carbon, hydrogen and oxygen but one element that makes proteins different from carbohydrates and fats and oils is nitrogen. It can be seen from the studies of some texts that there are 22 amino acids.
These 22 amino acids can be arranged in any order to form millions of proteins found in plants and animals, both human and other animals. The amino acids are arranged in long and complex order. These can be several of these amino acids in a single protein molecule. Amino acids can be described as the building blocks. The character of the protein is determined by the way the amino acids are put together.
When two amino acids link together the product formed, the dipeptide, can then link readily with a third amino acid molecule and so on until a structure of the necessary protein is formed. These linkages or the peptide bonds make proteins be referred to as peptides.
The commonly occurring amino acids are divided into two major groups. We have essential and non-essential amino acids. Why do you think they called essential or non-essential? It is not because some are not important to the body.
The reason is that our bodies cannot produce or synthesize them. Even if some can be synthesized, the quantity is insufficient to meet the body requirement. They must therefore be eaten in our diets by a healthy, well-nourished body if all the necessary components are available. On the other hand, we can then describe the non-essential amino acids as those that can be synthesized in our bodies either from the nitrogen and carbon chains or from the essential amino acids.
Protein Quality
The best way you can ensure that you are taking in the proper quality of protein is to put the foods into categories as complete, incomplete, complementary or supplementary, according to a given criteria. They used to be categorized as first class or second class proteins.
Complete proteins contain all the essential amino acids in the needed proportions. Examples are, albumin (protein from egg white), casein (milk protein). With the exception of gelatin, animal proteins are referred to as complete or first class proteins.
Incomplete proteins are low one or more of the essential amino acids. In this group are gelatin from animals and plant proteins except soya bean protein. These are referred to as second class proteins.
Complementary proteins are two incomplete proteins that form an amino acid pattern similar to complete protein when combined. Why do people eat koko (corn dough porridge) and koose (fried bean balls). This is a combination of a grain and a legume.
Supplementary protein is a small amount of a high quality protein added to a meal of low quality protein. An example is when we add milk to koko, which is a high-carbohydrate meal.
With these in mind, how can you improve the protein quality of the following food without adding meat, fish or poultry?
- Rice and margarine?
- Bread and jam?
- Rice porridge?
Protein value can be measured using methods such as protein density, biological value (BV),net protein utilization (NPU) and protein efficiency ratio(PER). Find out in simple terms what these terms mean.
Functions, Deficiency Diseases and Sources of ProteinsExcess Intake of Proteins
Excess protein in the body is not common due to the fact that our bodies do not store proteins to any appreciable quantities. They are converted, in a process called domination, to, glucose and fat. Urea is produced in the process and excreted from the kidneys as urine. In recent times a diseases characterized by painful and swollen joints called gout has been associated with the consumption of a particular type of proteins
Recommended Daily Allowance
The Recommended Daily Allowance for adults is 0.8 g per kg of body weight. For example, for a person weighing 70 kg (156 lbs), 56 g of protein is required (Wardlaw&Insel, 1996).
Tests for Proteins
The Biuret Test is used. A liquidized protein food in a test tube with an equal volume of 2M sodium hydroxide and a drop of 0.1M copper (II) sulphate solution added will give a mauve colour, indicating that protein is present.
FATS AND OILS (LIPIDS)
Classification of Fats and Oils
Fats and oils made up of Carbon, Hydrogen and Oxygen atoms, are also built up from smaller units called fatty acids and glycerol. Lipids that are found in the human body are of three groups based on their structures, namely triglycerides, phospholipids and the steroids. According to Dupuy and Mermel (1995), more than 95% of fats in our oils and in our bodies are made up of triglycerides. They are the forms in which our bodies store surplus fat.
Classes of Fats and Oils (Lipids)
Compar groundnuts, coconut, milk, eggs, lean meat, herrings, soya beans or maize with the margarine or butter on your breakfast table or the shea butter being sold in the market. Can you point out one major difference? You can see that they all have some amount of oil of fat but the difference here is not in terms of the quantity of oil or fat. It is the fact that in groundnuts, coconut, milk, eggs, lean meat, herrings, soya beans and maize, the oil or fat is invisible.
You can explain invisible oil or fat as in an expression that is used to describe the fat that is in the substance of the food. On the other hand, the fat in the margarine or butter is visible fat. As the term implies, this type of fat is the one we easily see.
You can again compare the margarine or shea butter to coconut oil. What main difference do you observe? We all see that coconut oil is usually a liquid, while margarine and shea butter are somehow solids, when we leave them in our kitchen or rooms.
An oil is a liquid at room temperature; Fat is a solid at room temperature.
Structure of Lipids
The different types of fats and oils are referred to as Lipids. These are also made up of Carbon, Hydrogen and Oxygen. You recall that proteins are built up from amino acids. You may also recall that carbohydrates are made from several units of glucose. In the same way fats and oils are also built up from smaller units called fatty acids and glycerol. However, the structure of a lipid is more complex.
Lipids that are found in the human body are of three types based on their structures. These three groups are triglycerides, phospholipids and the steroids. According to Dupuy and Mermel (1995), more than 95% of fats in our oils and in our bodies are made up of triglycerides. They are the forms in which our bodies store surplus fat.
The three lipids types
Triglycerides: I glycerol molecule + 3 fatty acids = I fat or oil molecule
The fatty acids have between 4 to 22 long chains of carbons with hydrogen attached to them. Small amounts of oxygen can also be found. Most of the properties of various lipids in our diets can be attributed to the fatty acids. These fatty acids are also classified based on the length of the carbon chains and the degree of saturation (the position of the double bonds).
The fatty acids can be short chains if the carbon chains are from four to six. Medium chains contain 14 – 20 carbons. They are considered long chains if there are more than 20 carbons in the chains. The importance of the length is that the short-chains are partially soluble and more digestible in the digestive system. Examples are the fats in milk and milk products.
Saturation: Most of the carbon atoms, except those at the left and the right ends of the chain, are bonded to four atoms.
H = Hydrogen C = Carbon O = Oxygen.
why are carbons are said to be saturated? The reason is that they are holding the maximum number of hydrogen and/or oxygen.
In some cases something happens making two neighboring atoms in a fatty acid to lose one hydrogen atom each. When you do not have something you need in class, you sometimes share with a friend. This is exactly what happens in the case of the bonds in the lipids.
The two carbons share the remaining ones by forming a double bond between them to get the required maximum hydrogen atoms. The fatty acid formed is then called unsaturated fatty acid. H – C = C – H
If the double bond in the chain is only one, then the fatty acid is monounsaturated.
If the fatty acid has two or more double bonds, then it is referred to as polyunsaturated. We have fatty acids that have three and four double bonds.
It is interesting to know the saturation of some of our local fats and oils. Coconut oil, palm kernel oil, cocoa butter, palm oil, etc. are described as saturated. Olive oil, most margarines and groundnut oil have monounsaturated fatty acids. Most soft oils such as margarine, soyabean oil, corn oil and sunflower oil have polyunsaturated fatty acids.
Some amino acids are referred to as essential and some non-essential. The same reason is given to fatty acids. Some fatty acids can be non essential fatty acids. Those fatty acids that cannot be produced in the body and must be provided in the diet and are termed ‘essential fatty acids’ (EFA)
Phospholipids
A phospholipid has a glycerol, two fatty acids and a phosphorus group replacing the third fatty acid.
1 glycerol + 2 fatty acids + 1 phosphorus group = a phospholipid
Phosphorus is present in vegetable oils, animal fats, blood and in egg yolk. Small quantities can be found in crude soya bean oil and maize oil. Their main function is to keep fat mixtures from breaking up and separating.
Sterols: You need to know more about sterols because they are very important in nutrition and in physiology. Vitamin D is derived from sterols. Cholesterol is another sterol but it can be produced in the body. Progesterone and testosterone are sex hormones although they are not important nutritionally.
Cholesterol: Our bodies need cholesterol but the amount should be within required limits otherwise the body may have problems.
Avocad, groundnuts, coconut, milk, eggs, lean meat, herrings, soya beans, or maize, as compared to margarine or butter, shea or cocoa butter. have a major difference between them.
It can be observed that they all have some amount of fat or oil but the difference here is not in terms of the quantity of oil or fat. It is the fact that in groundnuts, coconut, milk, eggs, lean meat, herrings, soya beans and maize, the oil or fat is invisible. The term invisible oil or fat is an expression that is used to describe the fat that is in the substance or the flesh of the food.
However, the fat in the margarine or butter is visible fat. As the term implies, this type of fat is the one we easily see.
Fats and oils may also be classified according to the sources from which they are obtained. The two sources are those from plant or vegetable and those from animals. Corn, nuts and pulses (palm, coconuts, groundnuts, soya bean), avocado, shea butter, and margarine are from plant but they are often referred to as vegetable fats and oils.
There are also other plant sources such as cotton, sun flower, olive, cocoa, etc. On the other hand, butter (milk fat), lard (pig fat) tallow (goat fat), and fish oils (cod liver oil) are from animal origin. A detailed classification has already been dealt with at the introduction section.
The saturation of some of fats and oils are important in nutrition. The fat or oils may be designated either as saturated or unsaturated. A fat or oil is said to be saturated when the carbons are said to be saturated, i.e. they are holding the maximum number of hydrogen and/or oxygen atoms. Coconut oil, palm kernel oil, cocoa butter, palm oil, etc. are described as saturated.
The unsaturated fat or oil may be mono or polyunsaturated. If the double bond in the chain is only one, then the fatty acid is monounsaturated. If the fatty acid has two or more double bonds, then it is referred to as polyunsaturated.
Plant oils are mostly polyunsaturated, while animal fats and oils are mostly monounsaturated. There are a few exceptions, such as avocado. There are some fatty acids that have three and four double bonds. Olive oil, most margarines and groundnut oil have monounsaturated fatty acids. Most soft oils such as margarine, soyabean oil, corn oil and sunflower oil have polyunsaturated fatty acids.
Dietary fats and oils can also be classified as essential and non-essential. Those fats that are essential have fatty acids that cannot be produced in the body and must be provided in the diet and are termed ‘essential fatty acids’ (EFA). The non essential fatty acids can be produced in the body from the food items that are eaten. Fats and oils are generally not soluble in water. The shapes of fats can be changed when pressure is applied and they are also affected by heat.
The body has sterols and they are very important in nutrition and in physiology. Vitamin D and cholesterol are derived from sterols. Cholesterol can be produced in the body. Our bodies need cholesterol but the amount should be within required limits otherwise the body may have problems.
Uses of Fats and Oils in the Diet and in the Body
Fats and oils have several essential uses in the diet of as well as in the body humans.
Uses in the Diet
In the diet, they are used as in the following ways:
- They impart flavor and appearance of food.
- They improve texture as they moisten the food.
- They can be used as shortening agents.
- Serve as vehicle for fat-soluble vitamins A, D, E and K.
- They have high satiety value, which means they are long satisfying.
Uses in the Body
- Fats and oils supply the most concentrated source of heat and energy.
- They form part of a structural component of the body.
- They are stored in the adipose tissues under the skin and around the organs, thus they insulate the body from temperature changes, since they are not good heat conductors (Temperature regulation).
- They protect vital organs from shock mechanical injury.
- They protect the skin from excessive dehydration.
- Act as protein-sparers, since they spare proteins from being used for the provision of energy.
Health Implications of Fats and Oils
As human beings, it is not common to be deficient in fats and oils. However, when they occur the skin becomes dry and flaky and poor eyesight. This results mainly from the absence of vitamin A that is often found in fats and oils.
Intake of excess fat is known to result in overweight and obesity, cardiovascular diseases, hypertension, some types of cancers and arteriosclerosis (the hardening of the arteries). Obesity comes with its associated problems, the two most important being high-blood pressure (hypertension) and arteriosclerosis. Some cultures used to admire plump people, mainly because they are ignorant of the associated health problems that go with excessive weight.
There is the need to know that fat intake should be reduced drastically and fats and oils that contain the polyunsaturated fatty acids should be selected. Lowered intake of saturated fats, particularly animal fats and exercises prevent the diseases. Cholesterol is known to increase the blockage of the arteries.
Overweight should be prevented because the extra weight puts a strain on the heart, the blood circulation and the joints. It can also result in diabetes, gall stones and complications during pregnancy. As we read on carbohydrates, some cultures admire plump people. They are ignorant of the associated health problems that go with excessive weight.
There is no RDA for fat. What we need to know is that we should drastically reduce our fat intake and we must select fats and oils that contain the polyunsaturated fatty acids. As human beings, it is not common to be deficient in fats and oils. However, when they occur the skin becomes dry and flaky. Poor eyesight.
Sources of Fats and Oils
Visible fats: butter, palm oil, salad oils, etc
Invisible fats: coconut, groundnuts, bacon, avocado, etc. Cereals have oils in the germ.
Effects of Heat on Fats and Oils
Fats are stable to moderate heat, but they melt and turn to oil at temperatures around 300 to 400C. Continued heating makes the oil thinner in consistency. A sizzling sound is produced in the process. As the temperature is raised, the colour darkens. At very high temperatures, as the oil is heated further, it develops a blue haze or smoke.
This is called ‘the smoking point’ and each o;i has its smoking point. The oil decomposes forming acrolein, which has an unpleasant smell. It irritates the throat, causing coughing. After this, further heating ignites the oil and it burns rapidly. There is a breakdown of the oil into carbon, hydrogen and oxygen.
Test for Fats and Oils
For fats and oils, ethyl alcohol is added to the food to be tested (2 drops of oil to 5 cm3) and thoroughly shaken to dissolve the fat. The solution is then poured into another test tube containing a little water. A cloudy white emulsion indicates the presence of fat.