MICRONUTRIENTS

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LEARNING OBJECTIVES▪ To understand the importance of micronutrients.

▪ To recognise the difference between water-soluble and fat-soluble 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.

MICRONUTRIENTSMicronutrients 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.