Home Sciences

In this unit the learner should be able to:

≈ analyses the types of food nutrients.

≈ explain principles of food nutrients selection.

Key unit competency: Learners should be able to apply principles of food nutrient selection.

INTRODUCTION

When making food choices, there is need to follow guidelines, referred to as principles. We are reliably aware that food gives our bodies nourishment in multiple ways. So understanding and using nutrition to enhance wellbeing is indispensable to our day to day living.in this unit we shall fully understand the importance of food nutrients in our bodies, the sources of food and effect of excess and deficiency of such nutrients in our bodies.

From our research findings and group discussion, we shall note that food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and food contains essential nutrients. The nutrients are used to produce energy, maintain life or stimulate growth.

Food nutrients include macro and micro nutrients.

Macro nutrients are needed by the body in large quantities. They include proteins, carbohydrates and lipids while the micro nutrients are needed in small amount and they include mineral salts and vitamins.

i.   Proteins

Proteins are made of complex molecules which contain elements like oxygen, hydrogen, carbon, nitrogen and sometimes sulphur and phosphorous. The protein molecules are made up of small units called amino acids joined together like links in a chain.

There are 21 different amino acids and each has its own chemical name. Different proteins are made when different numbers and types of amino acids combine through a covalent peptide bond. Proteins are therefore known as polypeptides.

Examples of proteins are; collagen, myosin and elastin found in meat, caseinogen, lactalbumin, lactoglobulin found in milk, avalbumin, mucin and liporitellin found in eggs, glutein and gliadin in wheat, zein found in maize and hordenin found in barley.

  The 21 different amino acids found in protein are;

1.  retardation of growth especially in children.
2.  less resistance to diseases.
3.  malfunctioning of the body organs and systems.
4.  body wastage because the worn out cells and tissues are not replaced.
5.  in severe cases of protein deficiency kwashiorkor arises

1. Carbohydrates are a source of energy used as they provide glucose that is used in the brain and cells.
2. Carbohydrates are used as a ‘protein sparer’ so that proteins are used for it’s main functions rather than a source of energy because when carbohydrates are not provided in the body, the proteins available are broken down to provide energy.
3. Carbohydrates add bulk or roughage to the food which helps in digestion for example, cellulose in cassava.
4. Carbohydrates provide warmth or heat to the body.

                                        

• Essential for growth in children.Ž
• It helps in vision or eye sight.Ž
• Increases body resistance to diseases.Ž
• Necessary for healthy skin and glands.
• Helps in teeth and bones formation.Ž
• Keeps the nose and membranes moist like eyes, throat and digestive system.

                        

• Skin infection.Ž
• Retarded growth in children.
• ŽPoor resistance to infections like cough and flu.

• Soluble in fat.Ž
• Insoluble in water.
• ŽNot destroyed in ordinary cooking. Ž
• Destroyed if fat turns rancid(goes bad).

• ŽRequired for the proper formation of bones and teeth.Ž
• Helps the body to absorb minerals that is calcium and phosphate, where by after digestion these minerals are absorbed from small intestines into the blood, which takes them to the bones and teeth.

                        

• Absorption of calcium and phosphorus is reduced thus leading to weak bones and teeth.Ž
• Failure to absorb calcium and phosphorus to the blood and bones leads to rickets in children and osteomalacia in adults.

                           

• Growth in children is retarded.Ž
• Leads to dental decay.

• It is not affected by normal cooking temperatures and processes.Ž
• It does not dissolve in water.Ž
• Not destroyed by sunshine.Ž
• Soluble in fats.

• Is an effective antioxidant that protects fatty acids from damage especially in the cell membrane in the body.
• ŽIt is an antioxidant used in food industry to stop fat from becoming rancid.Ž
• Helps in normal metabolism of the body.Ž
• Very significant in fertility.

                 

• Miscarriages.Ž
• Premature births.

• ŽIt is fat soluble.Ž
• Not lost during cooking.
• ŽCannot be destroyed by sunshine.

                    

• ŽIt is fat soluble
• ŽNot lost during cookingŽ
• Cannot be destroyed by sunshine.

• ŽReleases energy from carbohydrates and fats.
• ŽPromotes growth in children and general health.Ž
• Required for the function and maintenance of the nerves.

               

• Depression, irritability.
• ŽDifficulty in concentrationŽ
• Defective memory Ž
• AnxietyŽ
• Growth retardation in children.Ž
• Muscles become weak.
• Severe deficiency leads to beriberi.Ž
• It has symptoms such as: excessive weight loss, the legs, ankle and writes drop)

• soluble in water.
• it’s lost during cooking.Ž
• it is destroyed by sunshine.

• Releases energy from fats and carbohydrates.Ž
• Works together with vitamin C to form materials which bind cells together.Ž
• Essential for normal growth.

              

• Failure to grow.Ž
• Skin lesions, skin disorder and conjunctivitis (disorder of the outer membrane of the eye).Ž
• Tongue may swell, mouth and lips become sore.

                                  

• Soluble in water.
• ŽIt is lost during cooking.Ž
• It is destroyed by sunshine.

• Helps in the release of energy from foods especially carbohydrates by oxidation.Ž
• It helps in the formation of blood hence preventing anaemia.

                        

• Dermatitis which is cracking and flaking of the skin that is exposed to sunlight.                    
  

                           

• Dementia which is loss of memory, confusion and depression.Ž
• Diarrhoea, abdominal discomfort, loss of appetite, loose and frequent stools.

Properties of vitamin B₃

• ŽSoluble in water but is resistant to heat, oxidation and alkalis.Ž
• It is the most stable vitamin in the B complex in normal cooking processes.

Vitamin B₆- pyridoxine

Functions of vitamin B₆

• ŽHelps in prevention of anaemia.Ž
• Helps in the formation of red blood cells.
• Acts as a co-enzyme factor for release of energy from foods.

Sources of foods rich in vitamin B₆

Meat, whole grain cereals, dry beans, potatoes, dark green leafy vegetable.

                   

Effects of deficiencyŽ

• Loss of energy Ž
• Pernicious anemia.

Properties of vitamin B_6Ž

• Soluble in water.Ž
• It is lost during cooking.
• ŽIt is destroyed by sunshine.

Vitamin B₉-folate

Functions of vitamin B₉

Helps in the formation of red blood cells.

• ŽEssential for normal growth.Ž
• Required in the release of energy from foods.
• ŽRequired in production of nucleic acids RNA and DNA.

Sources of food rich in vitamin B₉

Whole grain cereals, liver, dry beans, dark green leafy vegetable, meat, potatoes, okra, pulses, dairy products, oranges, bananas, fish, peas, yeast extracts and so on.

                

Effects of deficiency of vitamin B₉

Failure to grow normally.

• ŽMegaloblastic aneamia where the red blood cells become enlarged and cannot give their oxygen properly to the body cells.Ž
• A deficiency in early pregnancy may lead to a condition called spin.

Bifida in a baby which causes permanent disability.

• Poor growth.Ž
• Tongue inflammation.
• ŽLoss of appetite.
• ŽShortness of breath.
• ŽDiarrhoea.
• ŽIrritability.
• ŽForgetfulness.

Properties of vitamin B₉

Folate is soluble in water and is destroyed by prolonged cooking.

Vitamin B₁₂-cobalamine

Functions of vitamin B12

It is required in the metabolism of amino acids as well as other enzymes throughout the body.

• ŽControls genetic make-up of cells.
• ŽFormation of red blood cells.

Sources of food rich in vitamin B₁₂

Meat, poultry, shellfish, kidney, eggs, and dairy products.

Effects of deficiency of vitamin B₁₂

Deficiency causes megaloblastic aneamia where the red blood cells become enlarged and cannot give their oxygen properly to the body cells.Ž

• Loss of energy.

Properties of vitamin B₁₂Ž

• Soluble in water.Ž
• It is lost during cooking.
• ŽIt is destroyed by exposure to sunshine

Vitamin C ascorbic acid

Functions of vitamin C

• ŽHelps in the prevention of scurvy and skin diseases.
• ŽAssists in building of strong bones and teeth.Ž
• Helps in the absorption of iron from small intestines during digestion.Ž
• Required in the production of blood and the walls of blood vessels.Ž
• Required for the building and maintenance of the skin and linings of the digestive system.
• ŽIt is required to make connective tissues which binds the body cells together thus helping in quick healing of wounds.

Sources of food rich in vitamin C

Found mainly in fresh fruits and vegetables for example, citrus fruits like oranges, tangerine, lemons, limes, strawberries and guavas, papayas, tomatoes, green vegetables, spinach, broccoli, cabbage.

  

Effects of deficiency

• Pain in muscles and joints, bleeding of gums and loss of teeth a condition called scurvy

                 

• Loss of weight, fatigue. Ž
• Connective tissue not made or well maintained.Ž
• Walls of the blood vessels weaken and break in places then blood escapes and appears as small red spots under the skin (haemorrhages).Ž
• Cuts and wounds fail to heal properly.
• ŽScar tissues may weaken and break open.
• Aneamia because iron is not absorbed properly without vitamin C.

Properties of vitamin CŽ

• It is soluble in water.Ž
• It is lost during cooking.
• ŽIt is destroyed by exposure to air and sunshine.
• ŽIt is quickly and easily destroyed by the presence of alkali such as bicarbonate of soda which causes vitamin C to be oxidised.

v. Mineral

Groups of mineral Salts

There are two groups of mineral salts:

1.  Major mineral Salts

These are mineral elements that are required in the body in relatively large amounts. They are easily absorbed and easily excreted. These include: Calcium(Ca), Phosphorus(P), Iron(Fe), Sodium(Na), Potassium(K), Chlorine(Cl),Magnesium(Mg), Sulphur(S).

2. Trace mineral elements or minor mineral elements

These mineral salts are required in the body in smaller amounts. These minerals are difficult to absorb yet are poorly excreted. Examples are: Iodine(I), Fluorine(F), Copper(Cu), Manganese(Mn), Cobalt(Co), Zinc(Zn), Nickel(Ni), Chromium(Cr), Selenium(Se).

Calcium(Ca)

Functions of calcium in the bodyŽ

• With phosphorous, it helps in the formation of strong bones and teeth.Ž
• Helps in normal clotting of blood.Ž
• Required for the correct functioning of the muscles like the heart and the nervous system.Ž
• Required for the maintenance of bones and teeth once formed.

Effects of deficiency of calcium in the bodyŽ

• Rickets in children and osteomalacia in adults.

• Poor quality teeth.Ž
• Weak bones.Ž
• Poor clotting of blood.Ž
• Muscle spasm where muscles and nerves do not function properly resulting into tetany.

Effects of excess of calcium in the body

Excess calcium(ca) leads to hypercalcemia characterised by loss of appetite, aneamia, thirst, diarrhoea, constipation and headache.

                    

Sources of foods rich in calcium

Milk, cheese, vegetables, hard water, egg shells, whole grain cereals, fish eaten with bones and green vegetables.

                     

Iron(Fe)

Functions of ironŽ

• It helps in the formation of heamoglobin the substance which gives red blood cells the colour. Heamoglobin is required for the transportation of oxygen around the body to every cell.

Effects of deficiency of iron in the bodyŽ

• Heamogoblin is not made properly so insufficient oxygen is carried to the body and this leads to fatigue, weakness and pale complexion and this is called iron deficiency.

• Aneamia.

                              

• Brittle nails.Ž
• Sore tongue.
• ŽSore throat.Ž
• General health is affected and cells cannot function properly.

Effects of excess iron in the body

Excess is stored in the body and it forms poisonous stores especially in the liver, heart and pancreas. This leads to eye threatening conditions like liver disease, heart problems and diabetes.

Sources of foods rich in iron

Liver, kidney, heart, red meat, cocoa, plain chocolate, eggs, cabbage, pumpkin, leaves, spinach (green leafy vegetables), whole grain cereals and so on.

Phosphorous(P)

Functions of phosphorous in the bodyŽ

• Works with calcium to form strong bones and teeth.
• Essential for the production of energy in the body.Ž
• Acts as a buffer as it helps in neutralising of body fluids.

Effects of deficiency of phosphorous in the body

Causes bone diseases.

Effects of excess phosphorous in the body

• ŽCauses reduction in calcium absorption thus leading to the effects of calcium deficiency.Ž
• Fragile muscles(soft and weak)

Sources of food rich in phosphorous

Fish, milk, meat, cheese, eggs, spinach, cabbage, peas, whole bread, cereals.

Potassium(K), sodium(Na) and chloride(Cl)

Functions of sodium, potassium and chloride in the bodyŽ

• Regulate water content in the bodyŽ
• All these are required for the correct concentration of body fluids
• Chloride is also required for the production of hydrochloric acid in the gastric juices of the stomach which is important in digestion.

Effects of deficiency of sodium, potassium and chloride in the bodyŽ

• Mental confusion.Ž
• Weak muscles.Ž
• Lack of sodium causes exhaustion hence reduction in body fluids.Ž
• Less appetite.ŽBlood pressure.Ž
• Muscle cramps.ŽSudden death may occur.

Effects of excess of sodium, potassium and chloride in the bodyŽ

• Kidney failureŽ
• Heart failureŽ
• ShockŽ
• Weak musclesŽ
• Oedema occurs which is the accumulation of fluids around cells hence swelling of body parts.

          

Sources of food rich in sodium, potassium and chloride

Yeast products, fish, potatoes, mushrooms, liver, beef, cauliflower, all grains, common table salt, baking powder, yeast, salty fish, cheese, bacon, root vegetables.

               

Iodine(I)

Functions of IodineŽIs

• required to make the hormone thyroxine which is produced by the thyroid gland in the neck, thyroxine along with other hormones help to control the rate of metabolism in the body.

Effects of deficiency of iodineŽ

It leads to a swelling of the thyroid gland in the neck called goitre

                            

• Fall in the metabolic rate hence lack of energy.Ž
• Cretinism may arise.

Effects of excess of Iodine

High intake causes the same symptoms as iodine deficiency including goiter.

Sources of food rich in Iodine

Sea foods, milk, green vegetables especially spinach, iodised table salt, drinking water.

Fluorine(Fl)

Functions of fluorine

• ŽIt is important for strengthening teeth against decay, it combines with protective enamel coating of the teeth, making them more resistant to attack by acids produced by bacteria in the mouth.

Effects of deficiency of fluorine

Tooth decay.

Effects of excess of fluorine

Teeth become rough and brown.

Sources of food rich in fluorine

Naturally found in tea, sea water fish, sea foods and fluorinated water.

                   

iv. Water

Water with a chemical formula [H₂O] is a transparent fluid which is the major constituent of the fluids of organisms.

Water is an essential nutrient because its required in many biochemical reactions.

Functions of water in our body

1. Water helps to carry and distribute essential nutrients to cells such as minerals, vitamins and glucose.
2. Water removes waste products in the body through urine and feaces.
3. Water helps in digestion where by it enables food to be chewed, swallowed and to break it down into its smallest particles in the body.
4. Water helps to regulate body temperature where by when the temperature is higher than the body temperature the body releases heat by perspiration and when the outside temperature is lower than the body temperature, the body begins to sweat and the evaporation of water from the skin surface cools the body.
5. Water acts as a lubricant around the joints and its also a shock absorber for eyes, brain, spinal cord and the foetus through the amniotic fluid.
6. Water helps to prevent constipation.

Food sources of water.

• ŽWater is got from the food that we eat.Ž
• We get water from liquid foods and beverages like tea, coffee, soda, drinking water and juices.

Effect of water in the body.

Too much water intake that is more than the kidney can get rid of in the urine causes too much water to collect in the body thus causing an imbalauce between water and sodium in blood and thus will result in:Ž

• Liver diseasesŽ
• Kidney problemsŽ
• Congestive heart failure.
• ŽSyndrome of inappropriate anti-diuretic hormone(SIADH)

Effects of deficiency of water in the body

Deficiency of water in the body leads to dehydration of the body and this is seen through:

• ŽDecreased sweating.
• ŽProducing less urine.
• ŽThirst or drying of the throat.
• Dry mouth.Ž
• Dry skin.Ž
• Getting headache.
  

        

• Fainting.Ž
• Fall in blood pressure and results in shock.Ž
• Severe damage to many internal organs like kidney, liver and brain.

Principles of food nutrient selection

The principles of food nutrient selection vary widely from individual to individual and they are according to:

1. Growth or age of a person

Whereby young children require more energy for their size than adults as they are growing rapidly and tend to be very active most of the time. With increasing age, the need for energy decreases partly due to a slowing down of the body and also due to reduced physical activity.

2. Physical activity level or occupation

The amount of energy people use depends on their occupation or physical activities so the less active one is the less energy required whereas the more active one is, the more energy required by that person. Physical activities are as follows:

Sedentary life style; these include office workers, drivers, pilots, clergy, type setters, shop attendants, book writers or authors, lawyers, doctors, architects and so on.

Active lifestyle: People living an active lifestyle include; industrial workers, railway workers, plumbers, bus conductors, builder’s, labourers, farmers, army recruits, forestry workers, miners.

               

3. Pregnancy and state of body

During pregnancy, extra nutrients are required for the growth of the baby and the adjustment of the mother’s body to pregnancy, during lactation, extra energy is required for the production of milk.

During illness, the metabolism of the body may be raised at times due to the illness or fever, but at other times may be lowered due to the reduction in physical activity.

4. Adequate balance

To select food, it should be well-balanced that is containing all food nutrients in right quantities which are; carbohydrates, proteins, fat, minerals and vitamins, this enables normal growth and good health of every individual.

              

5. Caloric control

It is very important for groups of people living with diabetes, high blood pressure and the obese, these need to eat food with very little sugars and fat to avoid worsening their health conditions.

6. Vegetarian diets

This type of diet must be carefully planned, ensure it is well-balanced and use of creativity and skill avoids a dull monotonous diet. Vegetables, pulses, cereals, nuts, eggs, milk and its products are used to ensure the vegetarian acquires a well-balanced and nutritious meal.

7. Abilities and skills of the food prepare that is; does he /she know how to prepare food? Does he /she have skills for roasting or steaming and so on.

8. Time that available for preparing food for example is there time for long slow cooking like steaming or stewing? Or the food preparer has no time but can use quick cooking methods like frying.

9. Foods that are available or that are in season: buy and plan for foods in season because they are cheaper and fresh, have a budget to avoid impulse buying.

10. Money available to spend on food: money for buying food should be evenly distributed over the all foods needed, the amount of money available influence what one will buy and eat but make sure you choose foods in season because they are cheap and at their best.

11. The number of people who are going to eat and their age will also influence the amount and type of food that you are going to cook and the way you are going to present it.

12. Individual dietary requirements of individuals like planning for children, adolescents, pregnant mothers, elderly people, invalids and convalescents, be aware of the foods to be avoided for religious or dietary reasons like avoiding salt, sugar and meat for vegetarians.

13. Consider the resources available like the cooking facilities and storage facilities for example is there an oven to do the baking? Do you have a refrigerator to keep fresh perishable foods like fish and meat?

14. Occasion. The occasion the meal is being prepared for has to be considered, everyday meal will differ from those served on special occasions like birthday parties, family treats, graduation parties and anniversaries, these may involve additional expenses and extra time for meal preparation.

15. Ensure that texture and flavour is varied and the colours of food are also well varied so that the meal is tempting and you do not have to convince people to eat. This will reduce on monotony16. Individual tastes: any pronounced dislike of food can retard the flow of digestive juices or impair digestion so plan foods that are a favourite to those who are going to eat.