Download Micronutrients

MICRONUTRIENTS
Extension
LEARNING OBJECTIVES
▪ To understand the importance of micronutrients.
▪ To recognise the difference between water-soluble and fatsoluble vitamins, major minerals and trace elements.
▪ To learn the functions and sources of the micronutrients.
▪ To learn the problems caused by malnutrition.
▪ To understand some interactions between nutrients.
MICRONUTRIENTS
Micronutrients are needed in much smaller amounts than the
macronutrients.
In general vitamins are needed to regulate the maintenance
and growth of the body, and to control metabolic reactions in
cells.
Most vitamins are provided to the body through the diet,
however, the body can make vitamin D, vitamin K and niacin.
VITAMIN A (RETINOL, CAROTENE)
Vitamin A is fat-soluble vitamin needed for the normal structure
and functioning of the cells in the skin and body linings, e.g. in
the lungs.
This vitamin also helps with vision in dim light, as well a keeping
the immune system healthy.
It is found in two forms; retinol in foods from animal
sources and carotenoids (the most abundant of which
is the beta-carotene) from plant sources.
Vitamin A – retinol is found in liver and whole milk,
Vitamin A – carotenoids are found in dark green leafy
vegetables, carrots and orange coloured fruits.
TOO MUCH OR TOO LITTLE?
Deficiency leads to poor vision in dim light or night blindness.
Severe deficiency can lead to total blindness.
Vitamin A is stored in the liver and too much vitamin A can be
toxic.
Consuming too much vitamin A whilst being pregnant has been
linked to birth defects.
VITAMIN D (CHOLECALCIFEROL)
Vitamin D is needed for the absorption of calcium and phosphorous
from foods, to keep bones healthy.
Recent research also suggests that vitamin D enhances immune
function and improves muscle strength.
Vitamin D is found in the diet, but most of our vitamin D is made in
the body the action of ultra violet rays on the skin.
Vitamin D occurs naturally in some animal
products, including fish liver oils, oily fish,
egg yolk, and butter.
Cereals, margarine and low fat spreads are
also fortified with vitamin D.
TOO MUCH OR TOO LITTLE?
Deficiency of vitamin D leads to rickets and the formation of soft
bones. This causes the bones in the legs to bend. Deficiency in
adults causes Osteomalacia resulting in pain and muscular
weakness.
Vitamin D can be stored by the body. Too much vitamin D can lead
to excess levels of calcium in the blood.
Young children, housebound older adults, and people who
practice religions where their skin must be covered, may be at risk
of deficiency through lack of exposure of their skin to sunlight.
VITAMIN E (TOCOPHEROL)
Vitamin E is a group of similar molecules with common
properties and functions.
Vitamin E acts as an antioxidant and protects cells in the body
against damage.
Vitamin E is mainly found in vegetable oils, nuts,
seeds and wheat germ.
DEFICIENCY AND EXCESS OF VITAMIN E
A deficiency in this vitamin is rare because it is so widely available
in the diet.
In very rare cases neurological disabilities such as lost reflexes
have developed.
Vitamin E has a low toxicity, but in very large doses may interfere
with absorption of vitamin A.
VITAMIN K
Vitamin K is needed for normal clotting of blood and is
also required for normal bone structure.
Infants are given vitamin K at birth.
Vitamin K is also produced by the bacteria in the gut.
Vitamin K is found in green leafy vegetables e.g.
broccoli, lettuce, cabbage, spinach and meat and
dairy products.
TOO MUCH OR TOO LITTLE?
Deficiency of vitamin K is rare in
adults, but is sometimes seen in
new born babies.
THIAMIN (B1)
Thiamin is needed for the release of energy from carbohydrate. It
is also involved in the normal functioning of the nervous system
and the heart.
Thiamin is mainly found in whole grains, nuts, meat
(especially pork), fruit and vegetables and fortified
cereals.
TOO MUCH OR TOO LITTLE?
Thiamin deficiency can lead to the development of the disease
beri-beri. Symptoms include fatigue, weakness of the legs and
anorexia.
As the body excretes any excess thiamin, there is no evidence of
any toxic effects of high doses.
RIBOFLAVIN (B2)
Riboflavin is needed for the release of energy from carbohydrate,
protein and fat.
It is also involved in the transport and metabolism of iron in the
body and is needed for the normal structure and function of skin
and body linings.
Riboflavin is found in milk, eggs, rice, fortified
breakfast cereals, liver, legumes, mushrooms and green
vegetables.
TOO MUCH OR TOO LITTLE?
There is no deficiency related disease, however, the tongue, lips
and skin become affected when the body is low in riboflavin.
As the body excretes any excess thiamin, there is no evidence of
any toxic effects of high doses.
NIACIN (B3)
Niacin is important for releasing energy from food, and is
important for the normal structure of the skin and body linings.
Niacin is also needed for the normal functioning of the nervous
system.
Niacin can be found in meat, wheat and maize flour,
eggs, dairy products and yeast.
TOO MUCH OR TOO LITTLE?
Deficiency of niacin can result in the disease pellagra. Symptoms
can include:
• dermatitis;
• dementia;
• diarrhoea.
Problems associated with excessive intakes are rare.
VITAMIN B12
Vitamin B12 is needed for the formation of red blood
cells and the normal functioning of the nervous system.
Vitamin B12 also helps to release energy from food.
Vitamin B12 is found exclusively in animal products,
plant products do not provide any vitamin B12.
It is found in meat, fish, cheese, eggs, yeasts
extract and fortified breakfast cereals.
DEFICIENCY OF VITAMIN B12
Deficiency of vitamin B12 can lead to pernicious anaemia.
It can also lead to some neurological problems.
Deficiency is rare, but may be a problem for people following
strict vegan or vegetarian diets.
FOLATE (FOLIC ACID)
Folate is important for the formation of healthy red blood cells.
It is also needed for the nervous system and specifically for the
development of the nervous system in unborn babies.
It can reduce the risk of neural tube defects in a fetus, e.g. spina
bifida.
Good sources of folate include green leafy
vegetables brown rice, peas, oranges, bananas and
fortified cereals.
DEFICIENCY OF FOLATE
Deficiency of folate can lead to megaloblastic anaemia. Symptoms
can include insomnia, depression and forgetfulness.
It is recommended that all women who are planning a pregnancy
take a daily supplement of folic acid. Once pregnant,
supplementation should continue for the first 12 weeks to reduce
the risk of neural tube defects.
VITAMIN C (ASCORBIC ACID)
Ascorbic acid is needed to make collagen which is required for the
normal structure and function of body tissues, such as skin,
cartilage and bones.
It also acts as an antioxidant that protects the body from damage
by free radicals.
Sources of ascorbic acid include fresh fruits, especially
citrus fruits and berries, green vegetables, peppers
and tomatoes. Ascorbic acid is also found in potatoes
(especially in new potatoes).
TOO MUCH OR TOO LITTLE?
Scurvy can result from lack of ascorbic acid. It tends to occur in
infants and the older adults.
Scurvy leads to spots on the skin, bleeding gums and loose or loss
of teeth.
Over nutrition of ascorbic acid is rare.
MINERALS
Minerals are inorganic substances needed by the body for many
different functions.
Some minerals are needed in very tiny amounts, these are known
as trace elements, such as fluoride.
CALCIUM (CA)
Calcium is important for the formation and maintenance of strong
bones and teeth, as well as the normal functioning of nervous
system and muscles.
It is also involved in blood clotting.
Milk and dairy products are the most important sources
of calcium. Other sources include bread, calcium
enriched soya products, green leafy vegetables and fish
with soft edible bones.
TOO MUCH OR TOO LITTLE?
Poor intakes of calcium can result in poor bone health which can
increase the risk of diseases such as osteoporosis later in life.
Taking high doses of calcium supplements can cause stomach
pains and diarrhoea.
IRON (FE)
Iron is needed for needed for the formation of haemoglobin in
red blood cells which transport oxygen around the body.
It is also required for energy metabolism and has an important
role in the immune system.
Haem iron is present in animal sources in the form
of haemoglobin.
Non haem iron is present in plant sources such as
beans, nuts, dried fruits, wholegrains, soya bean
flour and dark green leafy vegetables.
TOO MUCH OR TOO LITTLE?
A lack of iron will lead to anaemia. Symptoms include:
▪ feeling of tiredness;
▪ lacking in energy;
▪ general weakness;
▪ poor concentration.
Too much iron in the diet can result in constipation,
nausea and vomiting.
PHOSPHORUS (P)
Phosphorus is essential for the structure bones and teeth, for the
structure of cell membranes and for energy metabolism.
Phosphorus is found in red meat, dairy products, fish,
poultry, bread, rice and oats.
POTASSIUM (K)
Potassium is essential for water and electrolyte balance and
normal functioning of cells, including nerves.
Potassium is present in all foods, but found richly in fruit
(dried fruits, bananas, berry fruits), leafy green
vegetables (e.g. broccoli and spinach) meat, nuts,
seeds and pulses.
SODIUM (NA)
Sodium is needed to regulate body water content and electrolyte
balance.
Sodium is also needed for the absorption of some nutrients and
water from the gut.
Sodium is present in very small amounts in raw
foods. It is often added as salt during processing,
preparation, preservation and serving.
High salt processed foods include bacon,
cheese, yeast extract and smoked fish.
TOO MUCH OR TOO LITTLE?
Consuming too much sodium increases the risk of high blood
pressure. High blood pressure is linked with an increased risk of
heart disease and stroke.
Sodium deficiency is unlikely, but can be caused by excessive
sweating or vomiting and diarrhoea.
It is recommended that adults and children over the age of 11
years cut down on salt and consume no more than 6g per day.
FLUORIDE (F)
Fluoride is needed for the formation of strong teeth and protects against
dental decay (caries).
Fluoride is a trace element, therefore only a small amount is required for
good health.
trace element is an element in a sample that has an
average concentration of less than 100 parts per million measured in
atomic count or less than 100 micrograms per gram.
biochemistry, a trace element is a dietary mineral that is needed in very
minute quantities for the proper growth, development, and physiology
of the organism.
Fluoride can be found in drinking water and in small
amounts in tea and saltwater fish.
Some areas add fluoride to the drinking water.
Fluoride toothpastes are another important source.
TOO MUCH OR TOO LITTLE?
An excessive intake of fluoride can lead to mottling or
discolouration of teeth.
NUTRIENT INTERACTIONS
Some nutrients work together in the body completing different
functions.
For example:
• the vitamins A,C and E;
• calcium phosphorus and fluoride;
• calcium and vitamin D;
• iron and vitamin C;
• carbohydrates and B vitamins.
ANTI-OXIDANTS
Vitamins A, C and E are anti-oxidants and work together in the
body to protect cells against oxidative damage from free
radicals.
This damage to cells can increase the risk of developing
diseases such as heart disease and cancer.
CALCIUM, PHOSPHORUS AND FLUORIDE
These nutrients are involved in the mineralisation of teeth and
bones which keep them hard and strong.
Vitamin D and calcium
Vitamin D controls the amount of calcium available.
A lack of vitamin D in the body results in reduced
absorption of calcium.
IRON AND ASCORBIC ACID
Ascorbic acid aids the absorption of non haem iron (non meat
sources of iron) when eaten at the same time.
This is particularly important for people following strict vegan or
vegetarian diets.
CARBOHYDRATES AND VITAMINS B
Riboflavin and thiamin are involved in
the release of energy from
carbohydrate.
MINERALS AND EXERCISE PERFORMANCE
▪ Minerals function primarily in metabolism
as important parts of enzymes.
▪ Minerals provide structure to bones and
teeth and in synthesizing glycogen, fat,
and protein.
▪ Consuming mineral supplements above
recommended levels on an acute or
chronic basis does not benefit exercise
performance or enhance training
responsiveness.
▪ However, loss of water and the mineral
salts sodium chloride and potassium
chloride in sweat does pose an
important challenge in prolonged, hot
weather exercise.
▪ Excessive water and electrolyte loss
impairs heat tolerance and exercise
performance and can trigger heat
cramps, heat exhaustion, or heat stroke.
DEFENSE AGAINST MINERAL
LOSS IN EXERCISE:
▪ Vigorous exercise triggers a rapid and
coordinated release of the hormones
vasopressin and aldosterone and the
enzyme renin to minimize sodium and
water loss through the kidneys and sweat.
▪ An increase in sodium conservation by the
kidneys occurs even under extreme
marathon running in warm, humid weather
during which sweat output often reaches 2 L
per hour.
▪ Excessive sweating during exercise
produces losses of body water and
related minerals; these should be
replaced during and after exercise.
Sweat loss during exercise usually does
not increase mineral requirements
above recommended values.