Dietary fibre (roughage)•Dietary fibre consists mainly of cellulose that isindigestible because we do not have enzymes to digestit.•Fruits and vegetable are rich in dietary fibre.•Importance of dietary fibre:a.Provides bulk to the intestinal contents.b.Stimulates peristalsis (rhythmic muscular contractionspassing along the digestive tract)•Lack of dietary fibre in the diet leads to constipation(failure to pass motions)
Water•Water is a very essential for life because 60% to 70%of our body weight is water.•We can survive for several weeks without food butwould be die in a few days without water.•Importance of water:a.Act as a solvent in which chemicals dissolveb.Acts as a transporting agent for digested food,excretory products, hormones and antibodies.c.Takes part in biochemical reactions (for example,digestion)
d. A major component of blood, body fluids,digestive juices and urine.e. Regulates body temperature byevaporation of sweat from the skin.•We require at least 1.5 litres of water daily toreplace water lost in sweat, urine faeces andexhaled air.
The Importance of a Balance Diet•Diet refers to the food we eat.•A balance diet is a diet that contains all the seven classesof food in the right amount.•The amount of food or energy that a person needsdepends on several factors:•Age – a teenager needs more food, especially proteinsthan an old man who is no longer growing.•Body size – people with bigger body sizes require moreenergy than those with smaller body sizes.•Sex – males require more energy than females becausemales have a smaller amounts of fatty tissues in theirbody. Thus, heat loss is faster in males than in females.
•Occupation – a person who does heavy workneeds much more energy than a person who isonly moderately active.
•Climate – people living in cold countries lose moreheat to their surrounding compared with those livingin the tropics. They need more energy in order tomaintain their body temperature.
•State of health – a person suffering from hyperthyroidism (over activityof the thyroid gland in the neck) requires more energy.•The amount of food eaten must balance the quantity of energy used. Ifwe eat too much, we will gain weight and become obese. If we eat toolittle, we will lose weight. Feel weak and may suffer from difficiencydiseases.
Calorific value of food•The energy content of food is indicated by its calorificor energy value.•Carbohydrates, fats and protein supply us withenergy.•The energy value of food is measured with acalorimeter.•The unit of energy in food can be measured incalories (cal) or joules (J) where 1 cal is equals 4.2 J.1 cal = 4.2 J
Class of food Energy value (kJ g⁻₁Carbohydrates 17Proteins 18Fats 39Energy value of carbohydrates,proteins and fats
Foodstuff Carbohydrates (g)Protein(g)Fat (g) Energyvalue(kJ g⁻₁Rice 78.0 7.1 1.1 1508Potato 18.9 2.0 0.1 344Bread 51.3 7.2 1.8 1029Refinedsugar100 0 0 1626Composition and energy valueper 100 g of foodstuff