HUMAN NUTRITION Flashcards
Balanced diet
This is a diet that contains all the essential nutrients in the correct proportions to maintain good health. The nutrients needed are carbohydrate, fat, protein, vitamins, minerals, fibre and water
Ingestion
The taking of substances such as food and drink into the body through the mouth
Mechanical digestion
The breakdown of food into smaller pieces without chemical change to the food molecules
Chemical digestion
The breakdown of large insoluble molecules into small soluble molecules
Absorption
The movement of small food molecules and ions through the wall of the intestine into the blood
Assimilation
The movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
Egestion
The passing out of food that has not been digested or absorbed, as faeces, through the anus
Dietary requirements
Your dietary requirements depend on your age, sex and levels of physical activity. The amount of energy needed is provided mainly by our carbohydrate and fat intake.
Generally, males use up more energy
than females, and energy demand increases until we stop growing. Someone doing physical work will use up more energy than an office worker. While children are growing, they need more protein per kilogram of body weight than adults do.
Pregnant women need
extra nutrients for the development of the fetus. Once the baby has been born, a breast-feeding mother will need more protein and minerals, e.g. calcium, in her diet to satisfy the baby’s requirements.
Effects of malnutrition Malnutrition is the result of an unbalanced diet:
• Too much food – or too much carbohydrate, fat or protein – can lead to obesity. This can lead to coronary heart disease and diabetes (which can cause blindness). • Too much animal fat in the diet results in high cholesterol levels. Cholesterol can stick to the walls of arteries, gradually blocking them. If coronary arteries become blocked, the result can be angina and coronary heart disease. • Too little food can result in starvation. Extreme slimming diets, such as those that avoid carbohydrate foods, can result in the disease anorexia nervosa. • Constipation is caused by a lack of fibre in the diet. It can lead to bowel cancer. • Vitamin and mineral deficiency diseases are all the result of malnutrition. Scurvy is caused by a lack of vitamin C.
Carbohydrate
Source of energy Rice, potato, sweet potato, cassava, bread, millet, sugary foods (e.g. cake, jam, honey
Fat/ oil (oils are liquid at room temperature but fats are solid)
Source of energy (twice as much as carbohydrate); used as insulation against heat loss, for some hormones, in cell membranes, for insulation of nerve fibres Butter, milk, cheese, egg yolk, animal fat, groundnuts (peanuts)
Protein
Growth, tissue repair, enzymes, some hormones, cell membranes, hair, nails. Can be broken down to provide energy Meat, fish, eggs, soya, groundnuts, milk, meat substitute (e.g. Quorn), cowpeas
Vitamin C
Needed to maintain healthy skin and gums Citrus fruits, blackcurrants, cabbage, tomato, guava, mango
Vitamin D
Needed to maintain hard bones. Helps in absorption of calcium from small intestine Milk, cheese, egg yolk, fish liver oil. Can be made in the skin when exposed to sunlight
Calcium
Needed to form healthy bones and teeth and for normal blood clotting Milk, cheese, fish
Fibre
This is cellulose. It adds bulk to undigested food passing through the intestines, maintaining peristalsis Vegetables, fruit, wholemeal bread Water Formation of blood, cytoplasm, as a solvent for transport of nutrients and removal of wastes (as urine). Enzymes work only in solution Drinks, fruit, vegetables
Iron
Needed for formation of haemoglobin in red blood cells Red meat, liver, kidney, eggs, green vegetables (spinach, cabbage, cocoyam, groundnut leaves), chocolate
Water
Formation of blood, cytoplasm, as a solvent for transport of nutrients and removal of wastes (as urine). Enzymes work only in solution Drinks, fruit, vegetables
Vitamins and minerals,
although needed in only small quantities, are important for maintaining good health. A shortage can result in a deficiency disease. You only need to know vitamins C and D, and the minerals calcium and iron. Fibre (roughage) is needed in much larger quantities. Do not forget that water is also a vital part of our dietary requirements.
Vitamin D and iron deficiencies
A shortage of vitamin D can lead to a deficiency disease called rickets. The symptoms are soft bones that become deformed. Sufferers may become bow legged. Exposure to moderate sunlight helps the body make vitamin D. Thus, a lack of exposure (because of climate or season or wearing clothing that acts as a barrier to sunlight) can result in the development of a deficiency. A deficiency of iron in the diet can lead to anaemia. The symptoms are constant tiredness and a lack of energy. Normally, as red blood cells in the body are broken down, the iron in the haemoglobin is recycled to make new red blood cells. However, if a woman has a heavy period (see Chapter 16) there is a lot of blood (and therefore iron) loss, which can result in anaemia.
Sometimes the balance of food in the diet
is wrong, e.g. too much carbohydrate and too little protein, such as when the bulk of the diet is starchy food, such as sweet potato or cassava. This can lead to kwashiorkor in young children. They lack protein, but other problems such as plant toxins can also play a role. The symptoms of kwashiorkor are dry skin, pot-belly, changes to hair colour, weakness and irritability.
Marasmus
Marasmus is an acute form of malnutrition. The condition is caused by a very poor diet with inadequate carbohydrate intake and a lack of protein. The symptoms are emaciation, with reduced fat and muscle tissue. The skin is thin and hangs in folds.
alimentary canal
incisor
canine
premolar
molar
structure of teeth
amylase
protease
lipase
villi
