Home Economics / Home Management · Lesson 5

Nutrients, digestion, food tests, effect of heat and special nutritional needs

JAMBWAECNECO

What the syllabus asks

JAMB: Feeding the family (classes of food and nutrients; scientific study of nutrients; effect of heat on nutrients; special nutritional needs of infants, toddlers, adolescents, adults, pregnant and lactating women, the aged, convalescents, invalids, vegetarians). JAMB Home Economics C1 (food and nutrition, digestive system, special groups) and C6 (scientific methods). Also foundation for WAEC Foods…

WAEC: Feeding the family (classes of food and nutrients; scientific study of nutrients; effect of heat on nutrients; special nutritional needs of infants, toddlers, adolescents, adults, pregnant and lactating women, the aged, convalescents, invalids, vegetarians). JAMB Home Economics C1 (food and nutrition, digestive system, special groups) and C6 (scientific methods). Also foundation for WAEC Foods…

NECO: Feeding the family (classes of food and nutrients; scientific study of nutrients; effect of heat on nutrients; special nutritional needs of infants, toddlers, adolescents, adults, pregnant and lactating women, the aged, convalescents, invalids, vegetarians). JAMB Home Economics C1 (food and nutrition, digestive system, special groups) and C6 (scientific methods). Also foundation for WAEC Foods…

What you will learn

Define food, nutrition, nutrients, balanced diet and malnutrition.
State the classification, functions, sources and deficiency of each nutrient.
Calculate energy values of meals.
Describe digestion and absorption of carbohydrates, proteins and fats.
Describe simple food tests.
Explain the effect of heat on nutrients and how to conserve them.
Explain special nutritional needs of different groups.

Key points

Six nutrient classes plus fibre; macronutrients and micronutrients.
Carbohydrates: energy; mono-, di-, polysaccharides.
Proteins: growth and repair; HBV vs LBV; complementation.
Fats: concentrated energy, carry vitamins A, D, E, K.
Vitamins: A (vision), D (bones), K (clotting), B1 (beriberi), C (scurvy).
Minerals: calcium (bones), iron (anaemia), iodine (goitre).
Water: about 60% of body weight; prevent dehydration.
Digestion: amylase, pepsin, bile, trypsin, lipase, maltase; absorption in villi.
Food tests: iodine, Benedict, Biuret, grease spot.
Heat: coagulation, gelatinisation, dextrinisation, caramelisation, vitamin loss.
Special needs: infants to aged, pregnant, lactating, sick, vegetarians.

Start here: Food, nutrition and nutrients

Food is any substance which, when eaten, digested and absorbed, provides the body with energy, materials for growth and repair, and substances that regulate body processes. Nutrition is the whole process by which the body takes in food and uses it: ingestion, digestion, absorption, assimilation and excretion of waste. Nutrients are the chemical substances in food that perform these functions.

Classifying nutrients

Macronutrients are needed in large amounts: carbohydrates, proteins, fats and oils (and water).
Micronutrients are needed in small amounts: vitamins and minerals.
Energy-giving: carbohydrates and fats (and proteins when in excess).
Body-building: proteins (and minerals like calcium for bones).
Protective/regulatory: vitamins, minerals and water.

Dietary fibre (roughage) is not digested but aids bowel movement and prevents constipation. Sources: vegetables, fruits, whole grains, beans, unpolished rice, garri.

Key terms

Diet: the food a person usually eats.
Balanced diet: a diet containing all the nutrients in the right proportions for the person’s age, sex, activity and condition.
Malnutrition: a condition caused by eating too little, too much or the wrong balance of nutrients. It includes undernutrition (kwashiorkor, marasmus, deficiencies) and overnutrition (obesity).
Metabolism: chemical processes in the body that build up (anabolism) and break down (catabolism) substances.

Food groups (Nigerian examples)

Cereals and grains: rice, maize, millet, sorghum (guinea corn), wheat.
Starchy roots and plantains: yam, cassava (garri, fufu, lafun), cocoyam, potatoes, plantain.
Legumes and oily seeds: beans, soya, groundnut, melon (egusi), bambara nut.
Fruits and vegetables: oranges, mango, pawpaw, ugu, spinach (efo), okra, tomatoes.
Animal products: meat, fish, eggs, milk, snails, crayfish.
Fats and oils: palm oil, groundnut oil, butter, shea butter.

Factors affecting good nutrition

Income, food prices, availability and season, knowledge of nutrition, food habits and taboos, religion, family size, health, storage facilities and cooking methods.

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Practice questions

1. Fat supplies about how many kilocalories per gram?

Show answer

A: 9
Carbohydrate and protein give 4 kcal/g.

2. A meal with 60 g carbohydrate, 12 g protein and 15 g fat supplies

339 kcal
87 kcal
783 kcal
423 kcal

Show answer

D: 423 kcal
240 + 48 + 135.

3. 1 kilocalorie equals

0.24 kilojoules
9 kilojoules
4.184 kilojoules
1,000 kilojoules

Show answer

C: 4.184 kilojoules
Standard conversion.

4. Night blindness is caused by lack of

iodine
vitamin A
vitamin C
vitamin D

Show answer

B: vitamin A
Red palm oil is a rich source.

5. Scurvy results from deficiency of

vitamin C
vitamin B1
vitamin K
calcium

Show answer

A: vitamin C
Bleeding gums and slow healing.

Key words

Nutrient: Chemical substance in food used by the body.
Balanced diet: All nutrients in correct proportions.
Malnutrition: Imbalance of nutrient intake.
Polysaccharide: Complex carbohydrate such as starch.
Amino acid: Building unit of protein.
HBV protein: Contains all essential amino acids.
Complementation: Combining proteins to supply missing amino acids.
Kwashiorkor: Protein deficiency disease in children.
Marasmus: Severe energy and protein deficiency.
Saturated fat: Fat mostly solid at room temperature.
Smoke point: Temperature at which oil smokes.
Rancidity: Spoilage of fats.

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