Nutrition Wise

Committee on Medical Aspects of Food & Nutrition Policy

The Committee on Medical Aspects of Food and Nutrition Policy (1991)  recommended:

• Eating more starchy foods such as bread, potatoes, rice and pasta. Assuming these replace fat-containing foods, this will help to reduce the amount of fat and increase the amount of fibre in the diet. Adding fat to these foods should be avoided or kept to a minimum.
• Eating more fruit and vegetables. It has been suggested that individuals aim for at least 5 portions of different fruits and vegetables a day (excluding potatoes). As long as extra fat is not added to these foods, these changes will help to reduce fat intake, and increase intakes of fibre and important nutrients such as vitamin C.
• Choosing leaner cuts of meat and lower fat versions of dairy products will help to reduce the amount of fat, particularly saturated fatty acids in the diet. Trimming fat, choosing cooking methods that do not require added fat and eating smaller portions of high fat foods can all be helpful.

People who are overweight should lose weight by using their fat stores to provide energy and increasing their energy output. This means eating less and increasing their physical activity. They should aim to reduce their weight by no more than 1 kg a week. To do this they need to reduce their energy intake by about 1,000 kcal (4.184 MJ) a day. In this way they will lose fat rather than muscle.

A well-balanced diet is the most important requirement for healthy living. Good nutrition helps reduce our risk of getting a large number of diseases, from diabetes to heart disease.

From the point of view of activity, a recent report by the Chief Medical Officer made the following recommendations:

• Adults should participate in at least 30 minutes of at least moderate intensity activity on five or more days a week.
• This does not have to be taken all at once – 3 brisk walks each of 10 minutes duration would be equally beneficial.

Further reading

Detail

CARBOHYDRATES

The Department of Health recommends that men should not consume more than 3-4 units of alcohol/day and women not more than 2-3 units.  A standard unit is typically half a pint of beer, a small glass of wine or a single measure of spirits.

The two main types of carbohydrate are sugars and starch. Sugars and starch provide energy.  At least half the energy in our diets should come from carbohydrate, mostly as starchy carbohydrates.

FATS

Fat has many important functions as a nutrient:

• It provides more than twice as much energy as  protein or carbohydrate. However, no more than  one third of our energy intake should come from fat. Fat is needed for health but only in small amounts.
• It is a carrier for fat-soluble vitamins A, D, E and K.
• It contains the essential fatty acids (EFAs) linoleic acid (omega-6) and alpha linolenic acid (omega-3). These - and fatty acids synthesised from them - are important in the formation of cell membranes particularly in nerve tissue. At least 1.2% of energy intake should come from EFAs. Although the fatty acids EPA and DHA are synthesised in the body, they can also be obtained pre-formed from oily fish in particular and fish oil supplements. They are also present in the meat or eggs of animals fed omega 3 enriched diets.

• Use lower fat versions of dairy products.
• Use meats low in fat, e.g. chicken (without skin) and lean cuts of meat. Remove visible fat and skin where possible.
• Use less fat in cooking and use low fat spreads for bread.
• Grill and bake foods instead of frying and roasting.
• Fats/oils richer in monounsaturates (e.g. olive oil, rapeseed oil) or polyunsaturates (e.g. sunflower oil, corn oil) should be used sparingly as substitutes for saturates.

PROTEIN

• Protein is needed for growth and repair of the body.
• Protein provides energy.
• Different foods contain different amounts and combinations of amino acids (the building blocks of proteins). Vegans and vegetarians can get all the protein they need by combining different plant sources of protein, e.g. pulses and cereals.
• The amount of protein we need changes during a lifetime.

There are about twenty different amino acids commonly found in plant and animal proteins.

Structure of protein
The building blocks of protein are amino acids. Amino acids are compounds containing carbon, hydrogen, oxygen, nitrogen and, in some cases, sulphur.

There are about twenty different amino acids commonly found in plant and animal proteins. A typical protein may contain 500 or more amino acids, joined together by peptide bonds. 

Essential and non-essential amino acids
After a protein is eaten it is broken down by digestion into amino acids, which are then absorbed and used to make other proteins in the body.

The human body is able to make some amino acids for itself. These are known as non-essential or dispensable amino acids.  However, it is not possible to do this for every amino acid, so a certain number must be supplied by the diet. They are known as the essential (or indispensable) amino acids and for the human adult there are eight: Leucine; soleucine; Valine; Threonine; Methionine; Phenylalanine; Tryptophan; and Lysine.
In children, Histidine is also considered to be an essential (indispensable) amino acid, since children are unable to make enough to meet their needs.

Animal and plant-source proteins
It is not just the amount of protein that needs to be considered – the quality of the protein is also important. If a protein contains the indispensable amino acids in the approximate proportion required by humans, it is said to have a high biological value. If it is comparatively low in one or more of the essential amino acids it is said to have a low biological value. The amino acid that is in shortest supply in relation to need is termed the limiting amino acid.

In general, proteins from animal sources have a higher biological value than proteins from plant sources, but the limiting amino acid varies. Lysine is the limiting amino acid in wheat protein, Tryptophan in maize protein, and Methionine and Cysteine in beef protein. Among the vegetable sources, soya protein is the most complete.

Complementary action of proteins
The limiting amino acid tends to be different in different proteins, so when two foods providing vegetable protein are eaten at a meal, such as a cereal (e.g. bread) and a pulse (e.g. baked beans), the amino acids of one protein may compensate for the limitations of the other, resulting in a combination of higher biological value. This is known as the complementary action of proteins. Thus if vegetarians and vegans eat a variety of vegetable proteins in combination, there is no reason why the quality of their intake of protein cannot be as good as that of a person who eats meat or other foods that contain animal protein. In the UK, most people's diets contain plenty of protein and provide more than enough of the indispensable amino acids. However, in some countries where protein intakes are low, the complementary action of proteins plays an important role in helping individuals meet their nutritional requirements.

Protein as a nutrient
Protein has many important functions as a nutrient:

• It is necessary for the growth and repair of body tissues. There is an extra requirement for growth in infants and children, and for pregnant and breast feeding women.
• It is also a source of energy. However, carbohydrate and some fat should be the main sources of dietary energy.

DIETARY FIBRE

• The term dietary fibre describes a number of different substances and categories of substances such as non-starch polysaccharides, oligosaccharides and lignin. It also includes a number of other associated plant substances such as resistant starch.
•  Dietary fibre is found mainly in cereal foods, beans, lentils, fruit and vegetables.
• Dietary fibre can not be broken down by human digestive enzymes, although micro-organisms that live in the large intestine are able to digest fibre.
• Dietary fibre promotes a number of physiological effects, such as helping to prevent constipation, and helping to lower blood cholesterol and/or glucose levels.
• In the UK most people do not eat enough fibre.

What is dietary fibre?

Dietary fibre used to be known as ‘roughage’.  It comprises the edible parts of plants that are not broken down and absorbed in the human small intestine.

Depending on the type of fibre present in food, it is partly or completely fermented, by gut bacteria in the large intestine, producing gases (carbon dioxide, methane and hydrogen) and short chain fatty acids.  Gut bacteria are essential for the health of the large bowel.  The short chain fatty acids are absorbed into the cells of the gut wall, where they can be used as fuel, or pass on into the blood stream.  After increasing the amount of fibre in the diet, some people experience symptoms such as abdominal distension, discomfort and wind.  However, the large intestine and gut bacteria usually quickly adapt to the increased intake and problems with wind usually decrease.

Dietary fibre is traditionally found in cereal foods, beans, lentils, fruit and vegetables.  The term dietary fibre also includes a type of starch known as resistant starch, which resists digestion in the human small intestine.  A number of types of resistant starch exist naturally and these are chiefly found in whole or partly-milled grains and seeds, pulses, some breakfast cereals, and cooked and cooled (retrograded) potatoes.

Dietary fibre may also be broadly described according to its solubility.  There are two broad types of fibre: insoluble and soluble. Oats, fruit, vegetables and pulses (beans, lentils, chickpeas) are good sources of soluble fibre.  Wholegrain cereals  and wholemeal bread are particularly good sources of insoluble fibre.It is important to eat a variety of fibre-containing foods.

Health benefits of eating fibre

Both soluble and insoluble dietary fibre can promote a number of positive physiological effects, helping to prevent constipation, lower blood cholesterol levels and control blood glucose levels. Sources of insoluble fibre can act as bulking (laxative) agents and help prevent constipation.  For fibre to have the best effect on preventing constipation, an increase in fibre intake should be accompanied by an increase in water intake.  Soluble forms of fibre eaten in large amounts can help reduce blood cholesterol levels. They can also help people with diabetes to control their blood glucose levels.

On the other hand, eating a diet low in fibre is associated with diverticulitis (where the bowel wall becomes inflamed and ultimately damaged) and bowel (colorectal) cancer. Increasing evidence points to a protective effect of eating a diet rich in dietary fibre on diverticulitis and colo-rectal cancer.   However, it is unclear whether this is always a direct effect of the fibre or whether it is because a higher fibre content is a characteristic of a healthier diet.  In other words, it may also be that people who eat plenty of fibre follow other dietary and lifestyle advice such as to eat less fat, eat plenty of fruit and vegetables, drink plenty of fluid and do more exercise.

MINERALS

• Minerals are nutrients that are needed in the body in tiny amounts.
• Minerals have many roles in the body.
• They form the architecture of bones, they are constituents of body fluids, they help enzymes to work, they help nerves to send signals.
• The amount of each mineral we need changes during our lifetime.

Some minerals are needed in larger amounts than others, e.g. calcium, phosphorus, magnesium, sodium, potassium and chloride. Others are required in smaller quantities and are sometimes called trace minerals, e.g. iron, zinc, iodine, fluoride, selenium and copper. Despite being required in smaller amounts, trace minerals are no less important than other minerals.

Eating a varied diet will help ensure an adequate supply of most minerals for healthy people. In the UK, iron and calcium intakes are gradually decreasing.

Calcium
Calcium is the main constituent of hydroxyapatite, the principal mineral in bones and teeth. Calcium also plays an essential role in intracellular signaling and is therefore necessary for nerve and muscle function. It is also involved in blood clotting.

Foods that are particularly rich in calcium are milk, cheese and other dairy products (but not butter). White and brown flour, but not wholemeal is fortified with calcium by law so bread and other products made from this are important sources of calcium in the UK diet. Calcium is most readily absorbed from milk and dairy products. It is often less available from plant foods where the calcium may be bound by phytates (found in wholegrain cereals and pulses) and oxalates (found in spinach and rhubarb) in foods, which makes the calcium unavailable for absorption from the intestine into the blood. However, absorption from some plant foods is good e.g. broccoli, although the amount present may be lower than in milk.

Peak bone mass (PBM) is reached by the age of about 30 years. After this age, some loss of calcium from bone is normal and bone mass slowly decreases. However, severe loss causes the bones to become weak, brittle and to break easily. This condition is known as osteoporosis. 

Calcium intake is important in achieving peak bone mass in early life but there are many factors that influence the rate of age-related bone loss as we get older. There is some evidence that calcium supplementation may have a small benefit in women after the menopause. Even so, it is sensible to ensure that calcium intakes are adequate at this time. In older women, the evidence for benefits of supplementation with calcium and vitamin D is stronger, and an adequate intake of calcium and vitamin D, combined with physical activity, seems to reduce fracture risk. Adequate calcium intake may also be important in other disease processes, with evidence suggesting a role for the mineral in the prevention of high blood pressure, obesity and bowel cancer; all the subject of active research.

Magnesium
Magnesium is present in all tissues including bone. It is present in all foods, but because magnesium is found in chlorophyll,  it is abundant in dark green leafy vegetables. However much of this is bound and not readily available for absorption. Grains and nuts are also rich in magnesium, providing about a quarter of total intake among UK adults. Although deficiency is rare, low intakes have been observed in some groups.

Phosphorus
Phosphorus is present in all plant and animal cells, and 80% of the phosphorus in the body is present as calcium salts in the skeleton. It is essential for bone and tooth structure, for the structure of cell membranes and for energy metabolism. It is found in many foods and is unlikely to be in short supply in UK diets.

Sodium
Sodium helps regulate body water content and electrolyte balance, and is involved in energy utilisation and nerve function. It is also required for the absorption of certain nutrients and water from the gut. Too much salt in the diet is associated with an increased risk of raised blood pressure, which is a risk factor for heart disease and stroke. A low salt diet may be used in the treatment of hypertension.

Excess sweating, e.g. due to exercise in a hot environment, may cause some sodium depletion; sodium intakes may need to increase modestly and temporarily to replenish the loss in sweat.

Most raw foods contain very small amounts of sodium chloride (salt). But salt is often added during the processing, preparation, preservation and serving of foods.

Potassium is found in body fluids and is essential for water and electrolyte balance and for the proper functioning of cells, including nerves. It is present in almost all foods but fruit (e.g. dried fruits, bananas, berry fruits), vegetables and milk are rich sources. Processed foods typically contain less than raw foods. Potassium has a beneficial blood pressure-lowering effect in people with raised blood pressure.

Low dietary potassium intakes have been observed in some groups in the UK.

Iron

Iron is found in animal and plant sources. Iron from animal sources (haem iron) is better absorbed than iron from plant sources (non-haem iron). Absorption of non-haem iron is affected by various factors in food. Phytate (in cereals and pulses), fibre, tannins (in tea) and calcium can all bind non-haem iron in the intestine, which reduces absorption. On the other hand vitamin C, present in fruit and vegetables, aids the absorption of this kind of iron when eaten at the same time. The same applies to meat, fish and poultry. Bread and many breakfast cereals are fortified  with iron in the UK, and make a valuable contribution to iron intake.

Trace Elements

Zinc
Zinc is present in many enzymes and is essential for cell division and, therefore, for growth and tissue repair, etc. In some countries, delayed puberty and small stature have been linked to zinc deficiency, though it is not certain that this is due to zinc alone. Zinc is present in many foods and is most readily absorbed from meat, which provides about a third of zinc in the UK. For cereals and pulses, zinc’s availability is limited by phytates.

Iodine
Iodine is used to make thyroid hormones. The thyroid hormones control many metabolic processes and if there is insufficient iodine in the diet, the result is lethargy and swelling of the thyroid gland in the neck to form a goitre. . Infants born of severely iodine deficient mothers may be mentally retarded (cretinism). Nowadays iodine deficiency is very rare in the UK.

The amount of iodine in plant foods such as vegetables and cereal grains is determined by the iodine level of the environment, i.e. the amount in the soil or water. The only rich sources of iodine are sea-foods, but in some countries certain foods, e.g. salt and bread, are fortified with iodine. In the UK, dairy products are an important source of iodine. Data indicates that 12% (1 in 8) young women have intakes below recommendation. This may be associated with low intakes of milk and milk products.

Fluoride
Fluoride is found in few foods but in varying quantities in water. The addition of fluoride to toothpaste is now very common and is important in those areas where the water supply is low in fluoride. It contributes to the maintenance of bone health by supporting bone mineralisation and it protects teeth against dental decay (caries). Very large amounts of fluoride can cause mottling and crumbling of teeth, and changes to the bones - a condition called fluorosis. In the UK some water supplies, where the fluoride content is low, have fluoride added in small amounts.

Selenium
Selenium is a component of some of the enzymes which protect the body against damage due to oxidation (free radical mediated damage). It is also necessary for the use of iodine in thyroid hormone production and for immune system function. Selenium deficiency has been linked with a form of heart disease (Keshan disease) in parts of China where soil levels of selenium are very low.

Sources of selenium include cereals, fish, eggs and brazil nuts. In the UK selenium intakes have fallen with the decline in the use of North American hard wheats (rich in the mineral) and the increased use of European cereals which are less rich. 

Copper
Copper is a constituent of many enzyme systems and the body needs copper to be able to use iron properly. It is needed for the structure of connective tissue in bone, the lungs and blood vessels. Good sources of copper include green vegetables, fish, liver and nuts, but about a third of UK intake is from cereals and cereal products. Dietary deficiency is extremely rare but copper deficiency may arise because of a genetic defect (Menke’s syndrome).

Chromium
Chromium is found in a variety of foods and it has been suggested that it may be involved in the action of insulin, the hormone which controls glucose levels in the blood. However, there is still no general agreement for the role of chromium in insulin metabolism.

Manganese
Manganese is required for bone formation and for energy metabolism. It is also a constituent of an antioxidant enzyme. It is present in plant foods such as vegetables, cereals and nuts. Tea is also a rich source.

Other trace elements
There are other minerals which are needed in tiny amounts and which appear to be essential in the diet, e.g. molybdenum, boron. Others occur in the diet, but whether they are essential is unclear, e.g. nickel, lithium, antimony, aluminium and lead.

How much of each mineral do we need?
Certain groups of people may have higher requirements for specific minerals, e.g. those suffering from certain medical conditions, those recovering from illness and some athletes. These people need to ensure they obtain adequate intakes by eating foods rich in the mineral concerned; sometimes supplements may be useful but should not replace a varied and healthy diet.

Are mineral supplements necessary?
Although most people are able to meet their requirements for minerals (and vitamins) by eating a varied diet, there are certain groups of the population who have higher than normal requirements, e.g. the sick and those taking certain drugs. Also, women with high menstrual losses, may need to take iron supplements to avoid anaemia. Supplements may be prescribed by their doctor. Iron supplements are also sometimes given to pregnant women.

Supplements (especially if taken in an unsupervised manner) may cause mineral imbalances or have other side-effects; some minerals are toxic when taken in excess.

Minerals and diseases
Iron deficiency anaemia is a common problem, often affecting women and young children throughout the world. Deficiencies of other minerals are rare in the UK and excess intakes are sometimes a concern (e.g. sodium).

VITAMINS

• Vitamins are nutrients that are needed in tiny amounts.
• Vitamins have many roles in the body.
• The body can make vitamin D in the skin when it is exposed to sunlight.
• The amount of each vitamin we need changes during a lifetime

What are vitamins?
Vitamins are complex organic substances that are needed in very small amounts for many of the essential processes carried out in the body. Most vitamins cannot be made by the body, so have to be provided by the diet. An exception is vitamin D which can be obtained by the action of sunlight on the skin. Small amounts of a B vitamin (niacin) can be made from the amino acid, tryptophan.

Vitamin deficiency diseases are rare in the UK, but still occur in some parts of the world.

Vitamins have been traditionally grouped into two categories: the fat soluble vitamin, and the water soluble vitamins. Originally, vitamins were given letters (A, B, C, etc.) but now are usually referred to by their chemical names, e.g. folate.

The fat soluble vitamins
Vitamin A (Retinol)
Vitamin A is found in two forms: as retinol in foods from animal sources, and as carotenoids in foods from plant sources, beta carotene being the most common carotenoid. Beta carotene can be converted to retinol in the body; 6mg of beta carotene is equivalent to 1mg of retinol.

Excess retinol intake can be toxic. There is evidence that high levels of retinol may increase the risk of birth defects. It is for this reason that women who are pregnant, or who might become pregnant, are advised not to take high-dose vitamin A supplements unless they are advised to do so by a health professional. Liver and liver products may contain a large amount of vitamin A, so these should also be avoided.

Retinol is found in liver, whole milk, cheese and butter. Carotenes are found in milk, carrots, dark green leafy vegetables and orange coloured fruits, e.g. mango and apricots. In the UK, the law states that margarine must be fortified with vitamin A (and vitamin D). Vitamin A is also often voluntarily added to low and reduced fat spreads, as is vitamin D. 

With the switch to lower fat dairy products and the lack of popularity of liver these days, there is evidence that retinol intakes have fallen. Carotenoid intake is largely dependent on fruit and vegetable intake and some people’s intake of these foods is low. Currently there is concern about the vitamin A intake of some groups.

Vitamin D (Cholecalciferol)
Vitamin D is found in foods in two main forms, mostly as cholecalciferol and in small amounts as ergocalciferol. Vitamin D is also made by the action of ultra violet rays on the skin and this is the most important source for the majority of people as few foods contain significant amounts of vitamin D. Deficiency of vitamin D leads to skeletal deformity in children (rickets) and to pain and bone weakness in adults (osteomalacia). In the UK, some groups of people (e.g. Asians) are at risk of vitamin D deficiency because of low vitamin D intake from food and/or inadequate exposure of skin to sunshine.

Vitamin D occurs naturally in some animal products, including oily fish, eggs, butter and meat. Margarine is fortified with vitamin D (by law) and it is added voluntarily to other fat spreads and some breakfast cereals.

The vitamin D status of subgroups of the populations has been shown to be poor. Particularly at risk are housebound or institutionalised older people who aren’t able to benefit from exposure to sunshine. However, poor status has also been found in children, emphasising the importance of balancing the need for vitamin D synthesis with the use of sun screen, which potentially blocks this process.

Vitamin E
Vitamin E is a group of compounds called tocopherols, of which alpha tocopherol is the most active. It acts as an antioxidant and is required to protect cells against oxidative damage by free radicals. The amount of vitamin E needed in the diet is related to the amount of polyunsaturated fatty acids consumed. Since vegetable oils are rich sources of both, deficiency is rare.

Vitamin K
Vitamin K is found in foods from both plant and animal sources and is also made by bacteria in the gut. Vitamin K is essential for the clotting of blood and is required for normal bone structure. Deficiency is very rare in adults, but is sometimes seen in new-born babies. To prevent this, vitamin K is normally given routinely after birth.

The Water Soluble Vitamins
Ascorbic acid (Vitamin C)
Ascorbic acid is a water soluble vitamin required for normal structure and function of connective tissue (in skin, cartilage and bone) etc. This vitamin also has anti-oxidant activities, potentially protecting cells from free radical oxidative damage. Severe deficiency leads to scurvy. This disease is characterised by bleeding gums, poor wound healing and damage to bone and other tissues. It is rarely seen in Britain today, although it may occur very occasionally in older adults.

If the body is under stress, ascorbic acid is used up more quickly. Smoking is one such stress, and smokers should ensure they eat foods and drinks containing vitamin C. Some people take very large amounts of ascorbic acid (several grams) as it has been claimed to prevent or cure the common cold, but this has not been proved.

Ascorbic acid is found almost exclusively in foods from plant sources, although fresh milk and liver contain small amounts.

Thiamin (Vitamin B1)
Thiamin is needed to release energy from carbohydrate. The amount required is related to the amount of carbohydrate eaten. It is involved in the normal function of the nervous system and the heart. Deficiency of thiamin causes beri-beri, a disorder of the nervous system, which occurs in communities where white rice is the main food eaten. A different type of thiamin deficiency affecting brain function is sometimes seen in alcoholics, where daily thiamin intake is low and absorption and utilisation of the vitamin is impaired. Thiamin is found in whole grains, nuts and meat, especially pork. In the UK, white and brown flour and many breakfast cereals are fortified with thiamin.

Riboflavin (Vitamin B2)
Riboflavin is required to release energy from protein, carbohydrate 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 mucous membranes and skin. Although there is no specific deficiency disease, low intakes lead to dryness and cracking of the skin around the mouth and nose. Excess riboflavin is excreted in the urine. Major dietary sources of riboflavin are milks, eggs, fortified breakfast cereals, liver and green vegetables. National survey data indicate that a significant number of teenagers and young women have low intakes of riboflavin.

Niacin
Niacin (nicotinic acid) is found in most foods, although meat is the major source in the UK diet. It can also be made by the body from the amino acid tryptophan. It is required for the release of energy from food, for the normal structure of the skin and mucous membranes and for normal functioning of the nervous system.

Deficiency results in a disease called pellagra. It may occur in communities where maize forms the staple diet. Maize contains very little tryptophan and the niacin that is present is in an unavailable form. If, however, the maize is cooked in a particular way, the niacin is released. Nicotinic acid is sometimes prescribed by doctors (as a drug) to treat excess fat in the blood. But excessive intakes can be toxic.

Vitamin B6
Vitamin B6 (comprising 3 forms – pyridoxine, pyridoxal and pyridoxamine) is essential as a cofactor in the metabolism of protein. It is also involved in iron metabolism and transport. Together with folate and vitamin B12, vitamin B6 is required for maintenance of normal blood homocysteine levels. Long term high intakes from supplements have been reported to lead to sensory nerve damage.

Vitamin B6 is found in a variety of foods: beef, fish and poultry are rich sources. It also occurs in eggs, whole-grains and some vegetables.

Vitamin B12
Vitamin B12 (cyanocobalamin) is required for normal cell division and normal blood formation and function, etc. Dietary deficiency is rare, although it is sometimes seen in vegans who obtain virtually no vitamin B12 in their diet unless it is supplemented. Deficiency is also caused by a lack of intrinsic factor - the substance needed for the absorption of vitamin B12. This leads to a type of pernicious anaemia in which red cells are enlarged (megaloblastic), and to neurological damage.

Dietary intake is exclusively from animal sources, e.g. milk, meat and eggs (and fortified foods). Although some algae and bacteria can make vitamin B12, it is probably not in a form that can be used by the body. Fortified breakfast cereals can be a useful source of this vitamin.

Folate
The term folate describes a group of derivatives of pteroyl glutamic acid. Folic acid is the synthetic form of the vitamin and the most stable. It is used in supplements and for food fortification. Various folates are found in both plant and animal foods.

Folate is essential for normal cell division and in the formation of blood cells, etc.  Together with vitamins B6 and B12, folate is involved with the maintenance of normal blood homocysteine levels. Folates are found in liver, yeast extract, orange juice and green leafy vegetables. Various foods, e.g. breakfast cereals and bread may be fortified with folic acid (the synthetic form of folate).

Deficiency of folate leads to megaloblastic anaemia and may be due to poor diet or increased requirement, e.g. in pregnancy, from drug interaction or as a result of malabsorption. There is conclusive evidence that increasing intakes of folate through supplements of folic acid, before conception and during the first twelve weeks of pregnancy, prevents the majority of neural tube defects (e.g. spina bifida) in babies. It is recommended that all women of childbearing age, and especially those planning a pregnancy and who are in the early stages of pregnancy, take a daily supplement of 400μg folic acid as it is difficult to achieve this amount of additional folate by diet alone. 

Vitamin supplements
Although most people are able to meet their requirements for vitamins by eating a varied diet, there are certain groups of the population who have higher than normal requirements, e.g. the sick, those taking certain drugs and pregnant women, such people need to ensure they eat foods rich in particular vitamins and sometimes supplements are advised. Infants and young children are recommended to have supplements of vitamins A and D for at least 2 years. Some women many require additional iron if menstrual losses are high.

LIQUIDS

• Water is the most abundant constituent of the human body and regular fluid intake is essential for our bodies to work properly.
• The amount of fluid needed varies between people and according to age, time of year, climatic conditions, diet and levels of physical activity.
• We can obtain our fluid requirements from a number of sources such as water and other drinks, as well as from the food we eat.
• Dehydration can impair physical performance, and in extreme cases can be fatal.
• The sensation of thirst is not triggered until there is a water shortage in body tissues, so it is a good idea to drink before you get thirsty. Extra attention should be given to children and the elderly who may not recognise the sensation of thirst so easily.
• Water may be described as ‘hard’ or ‘soft’ depending on the amount of dissolved calcium and magnesium it contains.

Water is essential for our bodies to work properly.  Water (and fluid in general) has many functions in the body.
• It acts as a lubricant for joints and eyes
• It helps us swallow
• It provides the medium in which most reactions in the body occur
• It acts as a cushion for the nervous system and helps get rid of waste
• It helps to regulate body temperature.

How much water do we need?

The amount of water (and other fluids) that we need to drink each day varies from person to person, climate, activity, diet, etc. Drinking excessive amounts of water will not lead to better skin, hair and nails.  Dehydration can be very serious.  Symptoms of mild dehydration include headache and fatigue.

Health professionals recommend at least 1.5 to 2 litres (6-8 cups) of liquids a day in temperate climates. The sensation of thirst is not triggered until there is already a water deficit, so it is important to drink before you get thirsty.  Particular attention should be paid to children and the elderly who do not recognise the signals of thirst so readily. 

We can get our fluid requirements from a number of sources. It is not necessary to only drink ‘pure’ water, although this is a good choice. Other drinks like squash, fruit juices, tea and coffee contribute to our daily requirements too.  People often forget that some of our fluid requirements come from the food we eat.  Roughly a third of an adult’s daily fluid intake is supplied by what is eaten rather than what is drank.  Fruit and vegetables provide most of this additional fluid but small amounts come from bread and dairy products for example.

Caffeine

Caffeine is a mild diuretic (i.e. it increases urine output to a small extent), but drinks that contain caffeine (e.g. tea, coffee, cola) also contribute to fluid intake. You do not need to drink more water to compensate for consuming these drinks, provided you are achieving the 6-8 cups required.

Alcohol

With alcoholic drinks, the dehydrating effect can be greater. Drinking water alongside alcoholic drinks will minimise any dehydrating effects.

Water and sport

Dehydration is common amongst athletes. Water replacement is essential, before, during and after exercise, as dehydration of as little as 2% of body weight (lost as water) impairs performance. Water is suitable for replacing any lost fluid following mild or moderate exercise, but research has demonstrated that water alone is not the best solution for fluid replacement during or after vigorous or prolonged exercise. Isotonic drinks are more suitable and will replenish water and carbohydrate stores (e.g. glycogen stores in muscle).

Hard and soft water

Water naturally contains dissolved minerals such as calcium, magnesium, potassium and magnesium.  These minerals are picked up by rain water as it passes through the ground.  If water seeps through hard rocks (such as granite) or peaty soils, it does not pick up these minerals. But, if water seeps through soft rocks, such as chalk and limestone, it picks up both calcium and magnesium.  Water that contains lots of dissolved calcium and magnesium is called hard water and is recognised by the fact that it causes deposits to develop in kettles and other household equipment.  Water with low levels of these minerals is known as soft water. 

Two types of hardness of water exist: temporary and permanent hardness.  Temporary hardness is lost naturally upon boiling, whereas permanent hardness is not. On heating, temporary hardness is deposited as limescale on heating elements, and it results in the appearance of a scum on hot drinks.  People living in hard water areas sometimes use jug filters to remove this temporary hardness. In the UK, it is estimated that hard water is supplied to approximately 60% of homes  and areas of hard water are predominately found in central, eastern and southern areas of England.

There are few nutritional differences between bottled and tap water in the UK, and regulations are often tighter for tap than bottled water.

Filtering water reduces problems with limescale build-up and scum on hot drinks by decreasing the hardness of the water and  also reduces chlorine and impurities in the water, which may affect taste, but filtered water offers no special benefits in terms of nutrition.

Tap water in the UK is safe to drink. Boiled and cooled tap water is recommended when making up infant formula milk.

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