Nutrition and Health
Micronutrients - Minerals
Topics
• Minerals
– iron
– calcium – sodium – iodine
MINERALS
Minerals
• Minerals are micronutrients
• Human body needs them in very small quantities
• Minerals are used in the human body to help form bones, skin and tissue and are necessary for many body functions
• Two minerals most often lacking in the diet are calcium and iron
Minerals
Minerals Functions Sources (Examples) Deficiency Reference
values for adults per day**
Iron Forms part of the red blood cell protein, haemoglobin, which carries oxygen around the body
Meat, liver, kidneys, some breakfast cereals, fortified bread, green leafy
vegetables, dried fruits, pulses
Iron-deficiency anaemia may occur, with
symptoms of dizziness, pale skin, weakness and tiredness
Men: not less than 11.4mg Women: not less than 24.5mg Calcium Important for bones and
teeth, muscle contraction, blood clotting and enzyme secretion
Milk, cheese, yoghurt, fish that is eaten with the bones (e.g. sardines), green leafy vegetables, nuts, seeds, dried fruits, oranges
Too little calcium results in stunted growth and rickets in children, muscle cramps, brittle fingernails, osteoporosis
Not less than 1,000mg
Sodium Maintains fluid balance.
Excess sodium has been associated with raised blood pressure
Table salt, salty snacks, fresh meat and poultry, processed foods,
condiments and sauces
Deficiency in sodium may cause muscle cramps, in serious cases coma and death can result
Not more than 2,000mg (i.e.
5g of salt)
Iodine Essential part of the thyroid hormones which help to regulate growth and metabolic rate
Fish, shellfish, milk and dairy products, fruits, vegetables, cereals
Iodine deficiency causes enlargement of the thyroid gland and causes goitre
Not less than 150 µg and not more than 1,000 µg
IRON
Functions of Iron
• Iron is needed to make a red-coloured protein called haemoglobin in red blood cells (which is why blood is red)
• Red blood cells in the blood carry oxygen to body cells
Sources of Iron
• The best sources of iron are found in offal such as liver and kidney
• Other good sources of iron include:
– red meat – oily fish – poultry
– green leafy vegetables such as broccoli and spinach
Types of Iron
There are two types of iron:
• Haem iron:
– more easily absorbed and used by the body
– found only in animal foods (i.e. meat, poultry, fish and seafood) – about half of the iron in animal foods is in the form of haem
iron.
• Non-haem iron:
– not so easily absorbed by the body
– plant foods, eggs, milk and dairy products have non-haem iron only
– also found in animal foods
Deficiency of Iron
• Anaemia (inadequate haemoglobin), caused by lack of iron in the diet, is one of the most common nutritional problems world-wide
• Women and children are at greatest risk of developing iron deficiency anaemia
• Vegetarians need to make sure they obtain an adequate iron supply from foods such as
cereals, pulses and vegetables
Anaemia
Shortage of iron intake
Inadequate amounts of haemoglobin are formed
Blood is unable to carry sufficient oxygen to the cells
The body becomes tired easily
Anaemia
Symptoms of anaemia include:
• tiredness, weakness, lack of energy
• a pale complexion, pale inner eyelids
• brittle fingernails
Anaemia
Prevention of
anaemia
Develop healthy eating habits
Eat plenty of iron- rich foods
Iron supplements are only recommended when iron deficiency
anaemia actually occurs. *
*Note:
If iron supplements are given to young children who have adequate iron stores, growth may be
delayed.
Iron and Other Nutrients
• Vitamin C helps the body absorb iron from foods
• Vitamin C increases the amount of non-haem iron absorbed, so foods containing iron from plant sources should be eaten with foods rich in vitamin C preferably at the same meal
CALCIUM
Functions of Calcium
• Calcium helps to form bones and teeth
• The adult body contains more than 1 kilogram of calcium, most of which is found in the
skeleton
• Calcium is also needed for blood-clotting, muscle contraction and enzyme secretion
Sources of Calcium
• Milk and dairy products such as cheese and yoghurt are important sources of calcium
• Bean curd and soya bean products are good sources of calcium in Asian diet
• Other foods that are also good sources of calcium include:
– green, leafy vegetables
– nuts, seeds and dried fruits
– fish that is eaten with the bones, such as sardines
Sources of Calcium
Pressed bean curd, spiced
Sesame seed, black
eese, Cheddar, Processed
e, canned in oil, with bone
Bean curd, firm
Almonds
Bean curd, soft
Yogurt
azil Nut, Raw Or Blanched
d flowering white cabbage
Full cream milk
same dessert/ sweet soup
Soya milk 0
200 400 600 800 1000 1200
Amount of calcium (mg) per 100 grams of edible portion
Deficiency of Calcium
• Inadequate dietary calcium will cause some calcium from the bones to move to the blood.
• Poor intake of calcium will cause less calcium deposition in the bones, and will result in a lower bone mass and a weaker
skeleton.
• Calcium deficiency can also cause rickets in children, though rickets is more commonly associated with vitamin D deficiency.
• If a pregnant woman does not have enough calcium in her
diet, calcium will be removed from her bones and transmitted to the unborn baby to enable the bones of the baby to grow.
This will weaken the woman’s bones and teeth.
Osteoporosis
• Osteoporosis is the condition of weakening
and thinning of the bones. It is more common in elderly people, especially women.
Inadequate calcium deposition in the bones Weakening and thinning of the bones
Osteoporosis
Osteoporosis
Protect against osteoporosis
A diet with a good supply of calcium, particularly during childhood and the
teenage years
Regular exercise, especially weigh-
bearing exercise
Avoidance of smoking and drinking excessive amount of alcohol
Calcium and Other Nutrients
• Vitamin D is needed, together with calcium and phosphorus, to help build and maintain strong bones and teeth
• Vitamin C helps in the absorption of calcium.
• Magnesium is essential for absorption and metabolism of calcium
SODIUM
Functions of Sodium
• Sodium is essential for normal body functions
• It helps maintain the extra-cellular fluid balance and acid-base balance in the body
• It is required for nerve transmission and muscle contraction
Sources of Sodium
• Most raw foods contain a very small amount of sodium
• Sodium is found in sodium bicarbonate which is a raising agent in baked foods such as cakes and biscuits
• The most common form of sodium in the diet is salt (sodium chloride) –salt comprises 40% sodium and 60% chloride (1g of sodium chloride
(NaCl) contains about 393mg of sodium)
• During the processing, preparation, preservation and serving of foods, salt is added
–salt is added in foods to enhance taste and flavour (e.g. enhance sweetness, mask metallic tastes)
–salt can also:
prevent microbial growth
extend product shelf life
improve the product texture (e.g. control the stickiness of doughs,
Sources of Sodium (cont’d)
• Salt is added to foods, for example:
– condiments and sauces (e.g. soya sauce, oyster sauce,
monosodium glutamate (MSG) and stock powder/cubes, salad dressing and ketchup)
– processed vegetable products (e.g. preserved leaf mustard, preserved mustard, preserved cabbage)
– processed meat products (e.g. roast pork, sausages, meat balls, preserved fish and seafood, salted eggs)
– snacks (e.g. crisps, salted nuts/seeds, preserved fruits, dried/preserved meat snacks, preserved seafood snacks) – instant foods (e.g. instant noodles, canned soup)
Deficiency of Sodium
• Sodium deficiency can be seen in people who work or take part in sports in very hot
conditions
• Chronic conditions like kidney failure or heart failure may also cause loss of sodium from the body
Deficiency of Sodium
Work or take part in sports in
very hot conditions
The body loses sodium through
sweating
Muscle cramps
Sickness and diarrhoea
The body loses too much sodium
Headache, confusion, decreased
Excess of Sodium
• Excessive sodium intake can be detrimental to health, such as increasing the risk of developing hypertension, which in turn increases the risk of coronary heart diseases and stroke
• Salt and salt-preserved food items may also increase the risk of stomach cancer
• The World Health Organization (WHO)
recommends a maximum daily sodium intake of 2,000mg, i.e. 5g of salt
Excess of Sodium
• Kidneys are responsible for regulating the
amount of sodium in the body
• Some people are more sensitive to sodium; they tend to retain sodium
more easily and may have higher risk of
developing hypertension
Low sodium level in the
body:
Kidneys conserve
sodium
High sodium level in the
body:
Excrete the excess amount
through
Excess of Sodium
Excessive sodium intake
Kidneys cannot excrete enough sodium
Sodium and fluid retention
Hypertension
Increase the risk of coronary heart disease and stroke
Ways to Reduce Dietary Intake of Sodium
Reduce dietary intake of sodium (salt)
Read nutrition labels and choose food with lower sodium
content
Change dietary habits by reducing the amount of salt or
sodium-containing seasonings added to
food
Use natural ingredients (e.g.
garlic, ginger, lemon/lime juice, parsley) to replace
seasonings and sauce
Reduce the intake of processed food
Salt Reduction in Prepackaged Foods by
Product Reformulation
IODINE
Functions of Iodine
• Iodine is needed to make thyroid hormones in the thyroid gland
• Thyroid gland is located in the neck
• Thyroid hormones control the metabolic rate of the body – the rate at which chemical
reactions take place inside the body
Sources of Iodine
• Iodine is found in seafood, such as
– saltwater fish
– seaweed (including kelp, nori) – shellfish
• Iodine is also found in milk and dairy products as well as some plant foods, depending on the iodine content of the soil where cattle are
grazed or plants are grown
Deficiency of Iodine
• The person will feel tired, lethargic (does not want to do anything) and will gain weight
• The thyroid gland in the neck will swell up to form a goitre
Deficiency of Iodine
Inadequate intake of iodine
Thyroid tries to keep up with demand for thyroid hormone production
Thyroid progressively enlarges
Development of a goitre
Symptoms of choking, and difficulty in swallowing and
Deficiency of Iodine
Prevent against
iodine deficiency
Eating foods high in iodine
Taking iodine supplement*
Introduction of iodised
salt (only in North America)
*A supplement for the most susceptible groups – pregnant and lactating women and children 7-24 months of age –
assessment is necessary
* Source: Joint Statement by the WHO and the United Nations Children’s Fund, 2007
Reaching Optimal Iodine Nutrition in Pregnant and Lactating
References
• Centre for Food Safety, Food and Environmental Hygiene Department - Nutrients Definition and Function.
• Centre for Food Safety, Food and Environmental Hygiene Department – Nutrient Information Inquiry.
• Centre for Food Safety, Food and Environmental Hygiene Department – Report of study on sodium content in local foods.
• Centre for Food Safety, Food and Environment Hygiene Department – Reduction of Dietary Sodium and Sugar.
• Centre for Food Safety, Food and Environmental Hygiene Department – Food Safety Express (for Food Trade).
• Centre for Food Safety, Food and Environmental Hygiene Department (2012) . Study on Sodium Content in Local Foods (Rep. No. 49).
• Insel, P. M., Ross, D., McMahon, K., & Bernstein, M. (2019). Discovering nutrition.
Burlington, MA: Jones & Bartlett Learning.
• Otten, J. J., Hellwig, J. P., & Meyers, L. D. (2006). Dietary reference intakes: The essential guide to nutrient requirements. Washington, D.C.: National Academies Press.