© livestock & meat commission for northern ireland 2015 micronutrients

© Livestock & Meat Commission for Northern Ireland 2015

Micronutrients

Learning objectives

Identify the sources of nutrients and explain the functions of each nutrient.

Explain the effects on health of deficiency and excess of each nutrient.

Discuss the link between vitamin C and iron, vitamin D and calcium, and factors maximising availability of calcium and iron.


Micronutrients

The body requires micronutrients in tiny amounts.

They are required for a number of important processes in the body but they do not provide energy.

There are two main groups of micronutrients:• vitamins;• minerals and trace elements.

Micronutrients are measured in milligrams (mg) and micrograms (μg) with 1mg = 0.001g and 1μg = 0.001mg.


Vitamins

Vitamins are required by the body in small amounts for a variety of essential processes.

Most vitamins cannot be synthesised by the body so need to be provided in the diet.

Vitamins are grouped into:• fat-soluble vitamins; • water-soluble vitamins.


Fat soluble vitaminsThese can be stored in the body, and include vitamins A, D, E and K.

These vitamins are not required daily as the body can build up stores in the liver and fatty tissues for future use.

These are mainly found in fatty foods and animal products.


Vitamin A

Vitamin A is required in the diet for a number of functions:

• Normal iron metabolism;

• To maintain normal skin and mucous membranes in eyes, lungs, and the digestive system;

• To maintain normal vision;

• For normal function of the immune system.


Sources of vitamin AVitamin A (retinol) can be obtained in two forms:

1. Retinol - ready-made from animal sources;2. Carotenoids (e.g. beta carotene) – from

plant sources, from which retinol can be made in the body.

The concentration of vitamin A is usually expressed as retinol equivalents (RE).

6µg of beta carotene is equivalent to 1µg of retinol.


Vitamin A

Vitamin A is found (as retinol) in liver and whole milk.

Beta-carotene provided by dark green leafy vegetables, carrots and orange coloured fruit can also be converted to retinol to provide vitamin A.

In the UK margarine must be fortified with vitamin A and D by law. Vitamins A and D are also often added voluntarily to reduced fat spreads.


Sources of vitamin A in Northern Ireland


Cereals and cereal products

Milk and milk products

Eggs and egg dishes

Fat spreads

Meat and meat products

Fish and fish dishes

Vegetables and potatoes

Fruit

Sugar, preserves and confectionary

Non-alcoholic beverages

Miscellaneous

0% 5% 10% 15% 20% 25% 30% 35%

8%

13%

5%

16%

17%

1%

29%

1%

1%

4%

5%

Sources of vitamin A in the diet of Northern Irish adults

Deficiency and excess of vitamin AA severe deficiency in vitamin A is rarely seen in the UK.

Deficiency can result in night blindness (where the eye is unable to adapt to low-level light) and ulceration of the eye which can lead to total blindness.

Conversely, a high intake of vitamin A (>1500µg of RE/day) can be toxic and result in liver and bone damage.

As excess retinol during pregnancy can lead to birth defects, pregnant women should not consume liver and liver pâté as high levels of retinol may be present.


Vitamin D

Vitamin D is needed for:

• the absorption and use of calcium and phosphorus;

• normal blood calcium levels;

• the maintenance of normal bones and teeth;

• the maintenance of normal muscle function;

• the normal function of the immune system.


Function of vitamin D

Vitamin D is a pro-hormone in the body, and can be obtained in two forms:

1. ergocalciferol (vitamin D2);2. cholecalciferol (vitamin D3) formed by

the action of sunlight.

Vitamin D is only required in very small amounts and is measured in micrograms (µg).


Vitamin D: sources

Sources include: oily fish (such as salmon, trout, mackerel, sardines, pilchards, herring, kipper), meat, eggs and fortified breakfast cereals and margarine/spreads.

For most people the main source is synthesis in the skin following exposure to sunlight during the summer months in the UK (April – October).

Did you know?The wavelength of UVB during the winter months in the UK does not support vitamin D synthesis.


Sources of vitamin D in Northern Ireland


Cereals and cereal products

Milk and milk products

Eggs and egg dishes

Fat spreads

Meat and meat products

Fish and fish dishes

Vegetables and potatoes

Miscellaneous

0% 5% 10% 15% 20% 25% 30% 35% 40%

14%

3%

13%

22%

35%

10%

1%

1%

Sources of vitamin D in the diet of Northern Irish adults

Deficiency of vitamin D

Deficiency is commonly seen in people who have darker skin, wear concealing clothing or are housebound. This is because they are less able to synthesise vitamin D from sunlight.

There is evidence to show poor vitamin D status across the UK population, in particular during the winter months.


Deficiency of vitamin D

In children, a lack of vitamin D causes rickets, where leg bones become weakened and bent.

In adults, a similar condition called osteomalacia is seen.

Links have also been made between poor vitamin D status and an increase in falls in elderly people, which is thought to be linked to an adverse effect on muscle.


Water soluble vitamins

Water-soluble vitamins cannot be stored in the body and are therefore required daily, i.e. B vitamins and vitamin C.


B vitamins

There are a number of B vitamins, each with a specific function in the body.

Regular intake is required as the body is unable to store water soluble vitamins.

The different types of B vitamins are:• vitamin B1 (Thiamin) • vitamin B2 (Riboflavin)• vitamin B3 (Niacin)• vitamin B6 (Pyridoxine)• vitamin B12 (Cyanocobalamin)• folate• pantothenic acid• biotin


Thiamin (vitamin B1)Functions:• The release of energy from carbohydrate;• Normal function of the nervous system and

heart.

Sources:• Wholegrains, nuts, meat, milk, fruit,

vegetables and fortified breakfast cereals.• White and brown flour in the UK are

fortified with thiamin.

Deficiency:• Rarely seen in the UK;• Causes the nervous system disease beri-

beri.


Riboflavin (vitamin B2)

Functions:• To release energy from protein,

carbohydrate and fat;• Transport and metabolism of iron in the

body;• Normal structure and function of mucous

membranes and the skin.

Sources:• Milk, eggs, rice, fortified breakfast cereals,

liver, legumes (the fruits or seeds of anything that comes in a pod, e.g. beans, peas, lentils), mushrooms and green vegetables.


Riboflavin (vitamin B2)Deficiency:• Rarely seen in the UK;• Characterised by dryness and cracking

of the skin around the mouth and nose;• Painful tongue that is red and dry

(magenta tongue).

There is evidence of low intakes and poor status in teenagers and young adults, especially teenage girls.


Niacin (vitamin B3) Functions:• The metabolism of carbohydrate to enable

energy release from food;• Normal function of the skin and mucous

membranes;• Normal functioning of the nervous system.

Sources:• Meat, wheat flour, eggs, dairy products and

yeast. In the UK, white and brown flour are fortified with niacin.


Niacin (vitamin B3)

Deficiency:• Rarely seen in the UK and other

westernised countries;• Characterised by sun-sensitive skin, known

as pellagra.


Vitamin B6

Functions:

• Metabolism of amino acids;• Breaking down glycogen;• Modification of steroid hormone action;• Formation of red blood cells and

metabolism and transport of iron;• Maintenance of normal blood

homocysteine levels (raised homocysteine is a risk factor for cardiovascular disease).


Vitamin B6

Sources:• Poultry, white fish, milk, eggs, whole

grains, soya beans and peanuts.

Deficiency:• Rare as it is widely distributed in foods and

synthesised in body’s gut flora;• May only occur as a complication of

disease of prolonged administration of certain drugs.


Vitamin B12Functions:• Normal formation of red blood cells and

the metabolism of folate;• Involved in energy production.

Sources:• Found in almost all foods of animal

origin. Meat, fish, milk, cheese, eggs, yeast extract and fortified breakfast cereals are all dietary sources.


Vitamin B12Deficiency:• Rare in younger people, only occurs among

strict vegans.• More common in older people as a result of

impaired absorption.• Deficiency results in the development of

pernicious anaemia, where red blood cells are enlarged, and peripheral neurological damage develops.


Folate/folic acid

Folic acid is the synthetic form of folate. It is used in supplements and for food fortification.

Functions:• Works together with vitamin B12 to form

healthy red blood cells;• Normal cell division;• Normal structure of the nervous system,

specifically the development of the neural tube in the embryo, as this develops into the spinal cord and skull. It is recommended that all women of childbearing age who are planning a pregnancy take a daily supplement.


Folate/folic acidSources:• Green leafy vegetables, brown rice, peas,

orange, bananas and fortified breakfast cereals are sources of folate.

Deficiency:• Deficiency results in neural tube defects in

new-borns and megaloblastic anaemia, which is characterised by the release of immature red blood cells into the blood stream.


Vitamin C

Vitamin C (ascorbic acid) can help with the absorption of iron from plant foods when consumed at the same meal.

Functions:• Normal structure and function of

connective tissues such as skin, cartilage and bones;

• Normal structure and function of blood vessels and neurological function;

• Increases the absorption of iron from plant sources in the gut.


Vitamin C

Sources:• Fresh fruits especially citrus fruits and

berries, green vegetables, peppers, tomatoes and potatoes.

Deficiency:• Severe deficiency leads to scurvy, and

is associated with fatigue, weakness, aching joints and muscles. Other symptoms of scurvy are characterised by bleeding gums and poor wound healing.


Minerals

The body requires minerals in small amounts for a number of different functions.

Each mineral is required in different amounts.

Some are required in larger amounts, while others are required in very small amounts and are known as ‘trace elements’.

There are a number of different minerals, however we are going to focus on the following:• Sodium;• Calcium;• Iron.


Sodium

Sodium is a component of salt, also known as sodium chloride (NaCl).To convert sodium to salt, multiply by 2.5:Amount of salt = Amount of sodium x 2.5

Functions:• Regulating body water content and

electrolyte balance;• The absorption of certain nutrients and

water from the gut.

Sodium levels are under homeostatic control, regulated by the kidneys.When supply is excessive, sodium is excreted in urine.


Sodium

Sources:Most raw foods contain sodium chloride (NaCl) in small amounts, yet salt is commonly added to food during processing, preparation and serving.

Deficiency:As intakes of sodium are considered to be too high in Northern Ireland, deficiency is unlikely to occur, however losses can occur in some circumstances:• Excess sweating• Diarrhoea• Renal failure

What ways can you think of to reduce salt when preparing and cooking food?


Calcium

The body contains more calcium than any other mineral in the body. The skeleton contains about 99% of the body’s calcium with approximately 1kg present in adult bones.

Function:• Develop and maintain healthy bones and

teeth;• Normal muscle contraction (including the

heart);• Normal blood clotting.• Calcium levels in the blood are carefully

regulated by hormones such as vitamin D to keep it within narrow limits.


Calcium

Function

If calcium intake is too low, calcium is withdrawn from bones to maintain blood levels.

This means a diet low in calcium can lead to low bone density which, over time, can lead to osteoporosis.

Osteoporosis is characterised by weak and brittle bones.

Low calcium intakes are often seen in teenage girls


CalciumSources:• Dairy products, bread as most bread flour

(except wholemeal) is fortified with calcium by law in the UK, green leafy vegetables such as broccoli, cabbage, fortified soya products, fish eaten with the bones e.g. sardines, tinned salmon.

Deficiency:• Reflected in bone density not low blood

levels, as bone acts as a reservoir in times of need;

• Insufficient calcium in bones can be a result of an inadequate supply of vitamin D, as it is essential for the absorption of vitamin D;

• In children this can result in rickets, and osteomalacia in adults. © Livestock & Meat Commission for Northern Ireland 2015

Calcium

Absorption:• Calcium absorption is influenced by a

number of factors.• Inhibitory factors include phytates (e.g. in

wholegrain cereals, pulses) and oxalate (e.g. in spinach, beetroot).

• Promoting factors include vitamin D, lactose and dietary protein.


Iron

Functions:• Formation of haemoglobin in red blood

cells;• Binding of oxygen and transporting around

the body;• Function of the immune system;• Normal energy metabolism;• Metabolism of drugs and foreign

substances that need to be removed from the body.


Iron

Sources:• Dietary iron is found in two forms:

• Haem iron (from animal sources);• Non-haem iron (from plant sources).

• Haem iron (from animals) is the most bioavailable form of easily absorbed form of iron, but the most common form of iron in our diet is from plants (non-haem iron).

• Non-haem iron can be found in cereals, vegetables, pulses, beans, nuts and fruit.


Iron

Absorption of non-haem iron is affected by phytates (found in plant seeds), fibre, tannins and calcium, by binding non-haem iron in the intestine, reducing absorption.

Vitamin C aids the absorption of non-haem iron when eaten at the same time.

What foods can you think of which contain vitamin C?


Iron

Deficiency:• A lack of dietary iron depletes the body’s

iron stores and can eventually lead to iron deficiency anaemia.

• Teenage girls and women of childbearing age need more iron than males of the same age.

• The average iron intake of teenage girls is 57% of the Recommended Nutrient Intake.

• Intakes are also low in a large proportion of young women.

Did you know?More than 2 billion people worldwide suffer from iron deficiency anaemia, making it the most common nutritional deficiency.


© livestock & meat commission for northern ireland 2015 micronutrients

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