Micronutrient (Noun) ‘A chemical element or substance required in trace amounts for the normal growth and development of living organisms’.
Micro = small so micronutrients are required in minute quantities. You should recall from Chapter 3 that macro = large scale so macronutrients (protein, fat and carbohydrate) are needed in greater quantities to support a healthy function. Micronutrients consist of vitamins and minerals are essential for health but do not provide any energy.
Types of Vitamins
There are two groups of vitamins and the type of vitamin determines whether they are stored or not.
Fat Soluble Vitamins - Fat soluble vitamins are vitamins A, D, E and K. These vitamins can be stored in the body, usually in the liver, and are absorbed into the body along with fatty foods.
Water Soluble Vitamins - Water soluble vitamins are vitamin C and the B vitamin group. This group of vitamins cannot be stored and so need to be topped up regularly. Any excess of the water soluble vitamins is excreted in the urine. This group is also easily destroyed in cooking.
Vitamin C is an antioxidant which means it has a protective effect in the body and helps to protect against diseases like coronary heart disease and cancers. Other antioxidants include beta carotene and the mineral selenium but there are also other protective antioxidants found particularly in fruit and vegetables.
Vitamin C helps the body to absorb iron from foods so is particularly important in diets that do not incorporate red meat which contains iron. Vitamin C helps form collagen, the tissue framework that connects and holds cells together in all of the tissues of the body such as the muscles, heart and lungs. Vitamin C helps to maintain this connective tissue in the body. Vitamin C also has a role in enhancing the immune system and promoting the healing of wounds.
Vitamin C helps to:
- Prevent disease including cancer
- Absorb iron
- Forms collagen (tissue that hold cells together)
- Enhances the immune system
Sources: Sources of vitamin C are fruit and vegetables especially citrus fruits like oranges and soft fruits like strawberries and blackberries, tropical fruit like kiwi fruit. Fruit juices also contain vitamin C. Many vegetables contain vitamin C such as green vegetables like peas, runner beans, cabbage and broccoli, salad vegetables such as tomatoes and lettuce also provide vitamin C. Potatoes also provide vitamin C particularly if served with skins on.
Cooking vegetables (and fruit) quickly with a minimum amount of water (or steaming them) and also serving them immediately helps to retain the vitamin C plus B vitamins.
When fruit and vegetables are frozen the vitamins C (and B vitamins) are retained so these can be a useful standby for caterers especially in the winter months when fresh vegetables can be both expensive and scarce.
B Vitamin Group
The B vitamins are a group of vitamins which help the body to release energy from food as well having functions with the nervous system and also blood cell formation. Examples of B vitamins are Thiamin, Riboflavin, Niacin and Vitamin B6.
Sources: B vitamins are found in a wide variety of different foods including meat, milk, eggs, cereals and bread. Yeast extract is a particularly good source. B vitamins are also added to fortified breakfast cereals.
Two other important B vitamins are:
Folate/Folic acid - Folate is the natural form of the vitamin found in food and folic acid is the manufactured form. This vitamin is particularly important in pregnant women as it helps to prevent conditions such as spina bifida. All women who are pregnant are recommended to take a supplement of folic acid for the first 12 weeks of pregnancy. Also those who wish to become pregnant are also advised to take a supplement.
Sources in the diet are green leafy vegetables like cabbage and broccoli, whole grain bread and fortified breakfast cereals.
Vitamin B12 - B12 is another B vitamin and is needed for the formation of red blood cells. As it is found mainly in foods from animals like meat, milk, fish and eggs, vegans (who obviously do not eat any of these foods) can lack the vitamin. Vegans can have yeast extracts and fortified breakfast cereals to provide vitamin B12 within their diet. Lack of vitamin B12 can cause a form of anaemia.
Vitamin A is one of the fat soluble vitamins and required for healthy eyesight and good immune system function.
Sources: Vitamin A is found in foods which contain fat e.g. butter and margarine, oily fish, eggs, liver and full fat milk products like hard cheese. While liver is a good source of vitamin A it is not recommended during pregnancy as too much vitamin A can be harmful to the growing foetus.
The body can also make vitamin A from beta carotene, and it acts as an antioxidant and thus helps to prevent diseases like coronary heart disease. Beta Carotene is the orange red colour in fruit and vegetables like apricots, carrots, tomatoes, mangoes, sweet potatoes and also in dark green vegetables like broccoli and spinach.
Vitamin D is needed to enable the absorption of calcium from foods. Calcium is needed for strong bones and to prevent conditions like rickets in children where the bones in the legs become softened and deformed. The adult condition similar to rickets is called Osteomalacia. Vitamin D is made by the action of sunlight on the skin during the summer months in the UK. Anyone who does not go outdoors regularly such as the elderly or housebound or those who cover themselves up with different styles of dress, do not make sufficient in the skin. These groups may lack Vitamin D.
Sources: Vitamin D is found in foods such as butter, margarine, liver, oily fish, egg yolk and red meat.
This is a group of micronutrients which is needed in the body as part of structures and also for other functions.
Iron is needed for the formation of haemoglobin which is found in the red blood cells and carries oxygen from the lungs to all cells of the body. If people do not take enough iron in their diet this can result in an iron deficiency called anaemia (symptoms include tiredness, lethargy, breathlessness and poor wound healing).
Some groups are at particular risk including older people, toddlers, those who do not eat meat and women of childbearing age are particularly at risk. Women need more iron than men due to the monthly blood loss during the childbearing years.
Sources: Food sources of iron include liver, red meat like beef, lamb and pork, dark coloured fish like salmon, there is some iron in eggs, chicken, poultry, pulses, bread, dark green vegetables and dried fruit. Meat and offal contain iron in the haem form which is easily absorbed while non-haem form iron from vegetables and cereals is poorly absorbed. As discussed vitamin C aids absorption of iron.
Tannins from tea can bind with iron in foods and for this reason are not recommended to be taken by children as it may compromise the iron intake.
Children who are having a vegan or vegetarian diet need to have the diet carefully balanced with adequate iron from pulses and vegetables as well as specially produced alternatives to meat.
Calcium is needed for bone health and as already described vitamin D is needed for the absorption from foods. The hard substance in bones is called calcium phosphate. The calcium in bones is being gradually replaced over time.
Calcium is also needed in children for the development of teeth. Most of the skeleton develops during the teenage years so adequate calcium during this period is particularly important. Calcium is also required for the growth of the foetus during pregnancy plus the production of breast milk after the birth of the baby. For toddlers and preschool children calcium is extremely important for bone development.
Lack of calcium contributes to rickets in children and bone problems like osteomalacia in adults. Osteomalacia is a condition where the bones become brittle and weakened and people can easily suffer a fracture when they fall. The condition particularly affects older women. While rickets was common in the 1930s in children it is now being seen again in the UK. Rickets is being seen in toddlers due to a lack of vitamin D which is needed for the body to absorb calcium. Some children lack vitamin D if they are not exposed to sunlight if they do not go outdoors much, wear clothes that cover most of their body or have a sun-block applied over the whole body.
Symptoms of rickets include bone pain plus bowed legs in toddlers (see Links & Resources).
Sources: Calcium is found in milk and products made from milk, e.g. cheese and yoghurt. Fish like salmon and pilchards where the small bones are eaten provides calcium. Calcium is also found in some breads and cereals as well as dark green vegetables.
Zinc is needed for fertility and the immune system which helps with the resistance to infections. Zinc also helps with healing and taste sensitivity. Zinc is particularly required during the teenage years for the development of fertility. Men need more zinc than women as it is required to produce sperm.
Sources: Zinc is found in liver, red meat like beef, pork and lamb, fish like salmon, eggs, chicken, turkey, pulses and nuts.
Sodium and potassium
Sodium and potassium are both known as electrolytes and are called this as they carry minute electrical charges. Both sodium and potassium are needed for the nervous system and also for the muscles to function properly by contracting and relaxing.
The electrolytes are also required for maintaining the fluid balance in the body. Too much sodium (and hence salt which is correctly called sodium chloride) is associated with high blood pressure (hypertension). High blood pressure is linked with coronary heart disease and also strokes.
Adults are recommended not to eat more than 6g of salt per day.
Younger children require less salt as their kidneys are less mature and thus cannot cope with a high level:
- 4-6 year olds are recommended to have no more than 3g of salt a day (1.2g sodium)
- 7-10 year olds are recommended to have no more than 5g of salt per day (2g sodium)
- 11 year olds and over are recommended to have no more than 6g of salt per day (2.4g sodium)
Sources: Sodium is found in table salt (sodium chloride) and foods that contain it which are usually processed foods such as ready meals, cheese, savory snacks such as potato crisps, sausages, ham and bacon. Potassium is found in fruit particularly bananas. It is also found in fruit juices, vegetables and potatoes and coffee.
Salt should be limited by not including many processed foods and avoiding salty snacks. Use homemade rather than manufactured soups, sauces, gravies and stocks. Some manufactured items use monosodium glutamate which also contains salt and which acts as a flavour enhancer. Avoid adding salt in cooking and do not use an excess of salty ingredients like stock cubes and soya sauce. Look at food label of products like breads, biscuits, crackers, beans and other items and choose items which are lower in salt.
Flavour foods with herbs and spices rather than salty rubs and marinades.
This table shows examples of foods that provide a good source of iron and zinc:
|Haem Iron||Non-Haem Iron||Zinc|
|Beef and lamb||Fortified breakfast cereals||Fortified breakfast cereals|
|Pork||Bread (especially wholemeal)||Whole grain breads|
|Dark poultry meat e.g. chicken legs and thighs||Pulses e.g. chickpeas, soya beans, baked beans and lentils||Red kidney beans, green and red lentils and chickpeas|
|Kidney and liver||Green vegetables e.g. spinach, broccoli and spring greens||Lean meat, dark poultry meat, canned oily fish, eggs, tofu and peanuts|
|Oily fish e.g. salmon, sardines and pilchards||Dried fruits e.g. apricots and raisins||Whole and semi-skimmed milk, cheese and yoghurts|
Menu ideas to include good sources of micronutrients (check portion sizes):
- Orange, kiwi, grapefruit salad (vitamin C)
- Steamed runner beans side dish (vitamin C)
- Chopped banana (potassium)
- Homemade stock (sodium)
- Salmon and broccoli pasta (zinc , Vitamin A and iron)
- Pilchards on toast (calcium and Omega 3)
By the end of this chapter you should have developed the following understanding and insights:
- An understanding of the role vitamins and minerals play in the function of the human body
- An understanding of the function of various vital vitamin groups
- An understanding of the function of various vital mineral groups
- An awareness of menu considerations for inclusion of vitamins and minerals