Figure 1.5: Food guide pyramid

Activity

PLAN A BALANCED DIET

1. Plan a menu consisting of balanced meals for a day considering each of the following

special people; pregnant and lactating mothers, children, the elderly, sedentary

workers and sick people.

2. In your menu, state what you would serve each special group for breakfast, lunch

and dinner.

3. Prepare a brief report.

NUTRITIONAL DEFICIENCIES AND DISORDERS IN HUMAN BEINGS

They are generally called malnutrition.

Malnutrition is the condition which results due to failure to live on a balanced diet. Or

Malnutrition is lack of proper nutrition caused by imbalance of nutrient in the body. Or

Malnutrition is a result of not having enough nutrients or excess consumption of certain

food nutrients.

Causes of Malnutrition

(i) Deficiency in one or more key nutrients. Example; eating only some of the food

requirements and ignoring others.

(ii) Not getting a balanced diet. Example; incorrect proportion of main nutrients.

(iii) Eating too much nutritional food, that is, overfeeding.

(iv) Eating too little nutritional food, that is, underfeeding.

Symptoms of Malnutrition

(i) Lack of appetite

(v) Longer healing time for wounds

(ii) Tiredness

(vi) Depression

(iii) Inability to concentrate

(iv) Always feeling unhappy

(vii) Dry skin and mouth.

Effects of Malnutrition

(i) Mental health problem

(ii) Low intake of food

(iv) Digestive disorders

(v) Lack of breast feeding.

(iii) Social and mobility problem

NUTRITIONAL DEFICIENCIES

These deficiencies arise when the body does not have sufficient supply of a particular food

or nutrient. The following are common nutritional deficiencies:

1. Kwashiorkor

Kwashiorkor is caused by deficiency of proteins in the diet. It affects young children

between 6 months to 5 years mostly after stopping to breast-feed or during weaning.

Causes of Kwashiorkor

(i) Lack of protein rich foods in the diet.

(ii) Poor feeding practices.

(iii) Poverty and its effects.

(iv) Infections such as measles, diarrhoea and other diseases.

(v) Ignorance of the parents about balanced diet.

(vi) Poor appetite to the child because of various factors. Example; emotional and

physiological factors.

Signs and Symptoms of Kwashiorkor

(i) Extremely thin arms and legs.

(ii) Retarded (poor) growth due to lack of proteins.

(iii) Protruding stomach (swollen abdomen) due to enlargement of the liver.

(iv) Swollen lower parts of limbs (Oedema). This is caused by the accumulation of body

fluids in such parts.

(v) Reddish or yellowish thin and weak hair.

(vi) The skin becomes dry and cracks easily.

(vii) Mental retardation when a child shows no interest in his/ her environment.

(viii) Loss of weight.

(ix) Short temper.

(x) Loss of appetite and usually a child develops diarrhoea.

(xi) Anaemia

(xii) The child becomes unhappy.

(xiii) Weakened body immunity.

Prevention and Treatment of Kwashiorkor

Kwashiorkor can be treated and prevented by providing a child with diet that has

adequate amounts of proteins such as fish, milk, soya beans, groundnuts and other

food nutrients.

2. Marasmus

Marasmus means starvation. This is the deficiency disease caused by lack of enough

amounts of nutrients in children.

Signs and Symptoms of Marasmus

(i) Loss of weight; the victim becomes thin.

(ii) Stunted/slow growth caused by the lack of enough food.

(iii) The child experiences a tendency of crying continuously.

(iv) The child feels hungry all the time. Example; the patient shows the tendency of

eating a lot of food when it is available.

(v) The child’s buttocks shrink due to breakdown of body tissues.

(vi) The child becomes unhappy due to hunger.

(vii) Wrinkled skin.

(viii) General body weakness.

(ix) Dry and wrinkled skin

(x) Diarrhoea

(xi) Weak muscles.

Treatment of Marasmus

Marasmus can be treated and prevented by giving the child adequate amounts of food

that contains all the nutrients in the right proportions.

3. Rickets

Rickets is a condition where by the bones of a child soften, leading to fractures and

deformities. The cause of rickets is lack of vitamin D, phosphorous and calcium.

Sign and symptoms of Rickets

(i)

Skeletal deformities such as bow legs, knock knees, an odd – shaped skull and a

deformed spine.

(ii)

A child feels bone pain

(iii) A child experiences dental problem such as weak teeth, delayed formation of teeth.

(iv) A child develops weak muscles.

(v)

Bones are easily fractured.

(vi) Slow growth

(vii) A child experiences muscle spasms and muscle cramps.

Prevention of Rickets

(i)

Rickets is prevented by increasing the amount of vitamin D, phosphates and

calcium in diet.

(ii)

Ensuring exposure to sufficient amounts of sunlight.

(iii) Providing the child with enough milk, sardines and green vegetables.

NUTRITIONAL DISORDERS

They are conditions that occur when a person’s dietary intake does not contain right

amount of nutrients for healthy functioning of the body.

1. Obesity (Overweight)

Obesity is a nutritional disorder characterized by excess body fat leading to overweight.

It results from eating large amounts of carbohydrates and fats and not exercising

enough.

Causes of Obesity:

(i) Excessive intake of foods rich in sugars and fats.

(ii) Lack of body physical exercises.

(iii) Overeating

(iv) Frequent eating

(v) Inactivity

(vi) Genetic makeup. Some people have genes that affect how foods are processed in the

body.

Signs and Symptoms of Obesity

(i) The body becomes extremely big with hanging stomach.

(ii) Increase of body weight (overweight).

Effects of Obesity:

(i) Shortness of breath and snoring.

(ii) It may lead into heart disease and stroke.

(iii) It may cause high blood pressure.

(iv) It may result into diabetes mellitus.

(v) It leads into breast, colon and prostate cancer.

(vi) It may cause arthritis due to the excess wear and tear of the extra weight put on

the spine, hips and knees.

(vii) It may lead into formation of Gallstones.

Prevention of Obesity

(i) Eating properly and practicing regular physical exercises.

(ii) Avoid eating too much fatty foods (especially animal fats) such as butter, fatty meat,

chips, margarine, sausage.

(iii) Avoid eating too much carbohydrates (sugary foods) such as sweets, cakes and

chocolates.

BODY MASS INDEX (BMI)

Body Mass Index (BMI) is the approximate measure of whether someone is over-weight or

under-weight, calculated by dividing a person’s weight in kilograms (Kg) by his or her

height squared in meters (m). It is recommended for use in children and adolescents.

퐵표푑푦 푚푎푠푠 (퐾푔)

퐵푀퐼 =

(푃푒푟푠표푛^′푠 ℎ푒푖푔ℎ푡)²

BMI gives the relationship between the estimated body fat and the risks of certain disease

or conditions. The world health organization (WHO) recommends the normal level of BMI

to be in the range of 18.5-25.4.

ퟐ

⁄

Body Condition

BMI (푲품 풎 )

Below 18.5

18.5 to 25.4

25.5 to 29.4

29.5 to 34.9

35.0 to 39.9

40 and above

Underweight

Normal weight

Overweight or pre-obese

Class 1 obesity

Class 2 obesity

Class 3 obesity (Extreme or severe obesity)

퐵표푑푦 푚푎푠푠 (퐾푔)

(푃푒푟푠표푛^′푠 ℎ푒푖푔ℎ푡)²

62퐾푔

(1.68)²

퐵푀퐼 =

=

2

⁄

퐵푀퐼 = 21.97 퐾푔 푚

2. Anorexia Nervosa and Bulimia Nervosa

(a) Anorexia nervosa is also called slimmer’s disease or self-starvation syndrome. It is

a nutritional disorder that occurs when a person intentionally refuses to eat enough

food to become slim, leading to a severe loss of body mass.

Symptoms of Anorexia Nervosa

(i)

Muscle wasting (including weakening of heart muscle).

(ii) Excessive loss of body mass.

(iii) Extreme fear of being fat.

(iv) Distorted body image or feeling fat even when one is very thin.

(v) Loss of body protein which result into severe loss of weight.

(vi) Decrease of heart beat.

(vii) Reduction in the size of uterus.

(b) Bulimia nervosa is nutritional disorder which involves excessive eating followed by

an attempt to remove food from the body. This attempt could involve self- induced

vomiting, fasting, excessive exercising or taking drugs that stimulate, emptying of

the bowels or excessive urination.

Anorexia Nervosa and Bulimia nervosa largely affect women (adolescent girls). They refuse

to eat or eat very little food (especially carbohydrate and fats) every day to prevent

overweight or obesity and maintain beauty (English figure).

Causes of Anorexia Nervosa and Bulimia nervosa

(i)

Depression. A person who is depressed may lose interest in food or try to cope with

emotional pain by controlling eating. This can lead to unhealthy eating behaviours.

(ii) Low self-esteem on body image. A person feels unhappy or insecure about his

or her body, this forces a person towards developing eating disorders.

(iii) Bottled-up emotions. Holding emotions inside such as sadness, anger or stress

can create emotional pressure leading to harmful eating habits.

(iv) The need to fit contemporary standards of beauty. Modern society promotes

very slim or perfect body shapes through media, celebrities and social networks.

Many people especially girls are force themselves to match these unrealistic beauty

standards leading them to extreme dieting.

Effects of Anorexia Nervosa and Bulimia nervosa

(i)

Heart problems due to weak cardiac muscles or an imbalance of mineral salts.

(ii) They contribute to impaired mental function because the brain lacks adequate

amount of glucose.

(iii) Dehydration.

(iv) They cause serious damage to the gum and erosion of the teeth because during

vomiting, the acid present in the stomach come into contact with the teeth and

gums.

(v) Anaemia

(vi) Stomach ulcers

(vii) Abdominal cramping and inflammation of the gut.

(viii) Irregular or absent menstrual periods.

(ix) Dry skin.

Prevention of Anorexia Nervosa and Bulimia nervosa

Anorexia Nervosa and Bulimia nervosa can be prevented by;

(i)

Resolving the underlying psychological problems.

(ii) Seeing a medical practitioner who can prescribe a way of getting back one’s healthy.

(iii) Adhering to the necessary lifestyle and dietary changes.

Factors that Cause Malnutrition in Tanzania

In developing countries like Tanzania, malnutrition cases are caused by a number of

factors such as;

(i)

Poverty. Most of the communities and people in Tanzania are running a shortage

of money to meet their food demands. As a result, they depend on only some types

of food substance that is cheaper at lowest prices.

(ii)

Ignorance. Most of the people in Tanzania are ignorant. They don’t know the

importance of balanced diet in mothers and growing children’s health. They usually

eat unbalanced diet. e.g. taking eggs to the market and leaving expectant mothers

starving.

(iii) Tribal Customs and Taboos. Certain tribal customs prevent children and women

from eating certain types of foods. e.g. in some societies pregnant women are not

allowed to eat eggs.

(iv) Religious Taboos. Certain religions prohibit certain types of food due to religious

beliefs. e.g. Muslims are not allowed to eat pork.

(v)

Drinking Behaviour. Spending too much money on alcoholic drinks instead of

buying food for the family, may lead to malnutrition.

Method That Can Eradicate Malnutrition in Tanzania

Changing or stopping the drinking behaviour so that the money saved can be used

to buy food for the family.

(i)

(ii)

Luxuries should be controlled so that the family income could be used for buying

the expensive protein for their children.

(iii) Education, that is, educate people on the importance of balanced diet.

(iv) Elimination of taboos and practices which deny expectant/lactating mothers and

children the food nutrients they acquire. Example; eggs, liver, kidneys and heart.

FOOD TEST

Food test is a process used to determine which nutrients are present in a food substance.

Food test is also defined as the investigation or test done to identify the presence or

absence of certain nutrient in a given food sample either in solution or solid state. The

major food substances tested for are carbohydrates (starch, reducing sugar and non-

reducing sugar), lipids and proteins.

When carrying out food test, consider the following; the food to be tested, the test reagent

used, the procedure to be followed, the appropriate colour change observed and the

inference/conclusion.

Food Type

1. STARCH

Reagent Used

Iodine solution

Reagent Colour

Brown

2. REDUCING SUGAR

Benedict’s/Fehling’s

solution

Blue

Benedict’s/Fehling’s

solution

Blue

3. NONREDUCING SUGAR

Hydrochloric acid (HCl)

Colourless

Sodium hydroxide (NaOH) Colourless

Copper sulphate

Sodium hydroxide

Sudan III

Blue

4. PROTEIN

5. LIPIDS

Colourless

Red

1. TEST FOR STARCH

This is a carbohydrate made by the condensation of many glucose molecules. Starch

occurs naturally in foods like potato, cassava, maize, rice and wheat.

Food Sample

Procedure

Observation

Inference

Tested

▪

Place 2 ml of food Blue-black (Dark Blue) Starch

sample in a clean and colour is observed.

present.

Starch is

absent

Starch

dry test tube.

The mixture retains the

colour of iodine.

Then add 3 drops of

iodine solution.

PROPERTIES OF STARCH

They are tasteless, that is, they are not sweet.

(i)

(ii) They are insoluble in water.

(iii) They coagulate when boiled in water.

(iv) When mixed with iodine solution, starch changes colour to blue black.

2. TEST FOR REDUCING AND NON-REDUCING SUGARS

(a) Reducing sugar can reduce copper II ion (퐶푢²⁺) which is blue to copper (I) ion (퐶푢⁺)

which is orange or brick red. During reduction process, the colour of Benedict’s

solution changes from blue, to green, to yellow and finally to orange or brick red

depending on the concentration of reducing sugar. If it is high, the colour changes

reaches to brick red but if it is low it can end up to the intermediate colours that

have been mentioned. Examples of reducing sugar; glucose, fructose, galactose,

maltose and lactose. Food sources of reducing sugar are onions and carrots.

(b) Non-reducing sugar such as sucrose cannot reduce copper II ions (퐶푢²⁺) to copper

(I) ions (퐶푢⁺). Therefore, it cannot be tested directly by Benedict’s solution.

▪

It is first converted to reducing sugar by using hydrochloric acid (HCl) in a

process called hydrolysis. The acid mixture is heated and left to cool.

HCl

C₁₂H₂₂O₁₁+ H₂O

C₆H₁₂O₆+ C₆H₁₂O₆

Glucose + Fructose

Sucrose

+ Water

▪

The acidic mixture is the neutralized by using sodium hydroxide (NaOH) or

sodium bicarbonate (푁푎퐻퐶푂₃) for the Benedict’s solution to work properly.

Food sources containing non-reducing sugar is sugarcane.

Food

Procedures

Observation

Inference

Tested

▪

Place 2mls of a food sample solution

into a clean and dry test tube.

The

colour Reducing

changed from blue sugar

Reducing

sugar

Then,

add an equal

volume of to green, yellow, present

orange and finally

to brick-red.

Benedict’s solution and heat gently

to boil.

▪

Place 2mls of a food sample into a The

colour Non-

clean and dry test tube.

Then, add 2mls

changed from blue reducing

of

dilute to green, yellow, Sugar

hydrochloric acid to the solution orange and finally present

and boil for 3 minutes to hydrolyze to brick-red.

the sugar.

Non-

reducing

Sugar

▪

Leave the solution to cool, and then

add 2mls of sodium hydroxide

solution

or

sodium

hydrogen

carbonate to neutralize the acid.

Add 2mls of Benedict’s solution,

then heat again to boil.

3. TEST FOR PROTEIN

The main sources of protein are chicken, fish, soya beans, fish, beans, milk, beef and

eggs.

Properties of Proteins

(i)

They are insoluble in water.

(ii) They coagulate on heating, the process called denaturation.

(iii) They react with sodium hydroxide (NaOH) and copper sulphate (퐶푢푆푂₄) to produce

a violet or purple colour. This is called the Biuret test.

(iv) The Biuret test can be used to identify a protein substance and confirm its

presence.

Food Sample

Protein

Procedures

Observation

Inference

Protein

▪

Put 2ml of food sample containing Colour of solution

protein solution in a clean and dry changes to purple present

test tube. or violet

Add 2ml

▪

of

dilute

Sodium

hydroxide solution and mix.

Then add 2 drops of 1% of Copper

(II) sulphate solution and shake

(No heating is required).

4. TEST FOR LIPIDS

Lipids (fats and oils) are found in groundnut, coconut, sunflower seed, margarine,

castor seed and butter.

Properties of Lipids

(i)

Fats are insoluble in water

(ii)

When oil is shaken with water, the oil breaks down into droplets which disperse

in water.

(iii) Fats and oils dissolve in organic solvents such as alcohol.

(iv) When water is added to fat or oil that has dissolved in organic solvents, a white

milky suspension is formed. This is called emulsion.

(v)

When fat is rubbed against paper, the paper become translucent.

(vi) In a mixture of water and oil, oil takes up Sudan III dye to form a red layer or ring

on top, leaving the water clear.

(vii) Oils react with osmic acid and stain black.

Food sample Procedure

Observation

Inference

Sudan III test

A red stained oil Lipids

Lipid (fat or

▪

Put 2 ml of food sample containing layer separates present.

lipid solution in a clean and dry test on the surface

oil)

tube.

of solution.

▪

Add 3 drops of Sudan III solution

and shake vigorously.

Then allow the mixture to settle for

1 minute.

Grease spot test

A

permanent

Lipids

▪

Rub a drop of the sample on to a

piece of paper.

translucent

present.

spot

to paper.

on

the

Allow

time

for

any

water

evaporate.

Warm gently in order to speed up the

process or reaction

Lipids becomes Lipids

finely

and

divided present

is

Emulsification test

dispersed

Put 2 ml of absolute ethanol in a water

clean and dry test tube, and then add shaken

in

when

with

▪

2 ml of lipid.

water it forms a

cloudy white

▪

Shake vigorously to dissolve the

lipids.

suspension

Then add equal volume of cold water.

(emulsification).

Individual Work

✓

In your Exercise Book, perform the revision exercise 1. Answer ALL questions.