Basic Composition of Food

Every cell in our body needs a regular supply of nutrients for it to work properly.

Protein is needed for growth, maintenance and repair. It can also provide energy. When eaten, proteins are broken down into smaller units known as amino acids which are then rebuilt into the proteins of new cells.

The main sources of protein are meat, fish, eggs, milk and dairy products, pulses (peas and beans), nuts and seeds. Grains and cereals contain smaller amounts. Plant proteins contain fewer essential amino acids than animal proteins so should be eaten in combination e.g. beans on toast, lentils with rice.

Carbohydrates are the body’s main source of energy.

The simplest forms are glucose and fructose which are readily absorbed by the gut. Sucrose (table sugar) is slightly more complex and needs to be broken down into glucose.

The most complex carbohydrates are starches and cellulose which are found in grain and cereal products such as pasta, rice and bread and in starchy vegetables like potatoes.

Excess energy from carbohydrates is stored as glycogen, which can be converted into fat.

Fats are the most concentrated source of energy and can also be stored if not used up immediately. They are important in building cell membranes and hormones.

Fats are made up of saturated or unsaturated fatty acids. Saturated fats tend to be solid at room temperature and usually come from animal sources, e.g. butter, suet. Unsaturated fats tend to be liquid and come from plants, e.g. olive oil, sunflower oil (although coconut and palm oils are high in saturated fats).

A high intake of saturated fats tends to raise the blood cholesterol, which increases the risk of coronary heart disease.

Cholesterol is an oily substance found in eggs, liver, shellfish and foods that are high in saturated fats. Although we think of cholesterol as being harmful, it is an important part of all body cells and is the starting material for the manufacture of vital chemicals.

Cholesterol becomes a problem when there is too much of it. It then forms fatty deposits which clog the arteries causing heart attacks and strokes.

Food provides energy which is measured in kcal (calories) or kilojoules. One kcal is equivalent to about 4.2 kj.

Fat supplies the most energy per gram (9kcal or 37kj). Carbohydrates and protein provide 4kcal or 17kj per gram.

Everyone has a different energy requirement, depending on their size, weight, sex, age, level of activity, and basal metabolic rate (the amount of energy needed to maintain body temperature and keep the heart and other organs working).

An average man burns up about 3,000 kcal a day. A fairly active woman uses about 2,200 kcal daily. Energy requirements decrease as we age because our muscles get smaller and we become less active.

Vitamins, minerals and trace elements

These are often referred to as micronutrients because they are needed only in small amounts. Vitamins are chemicals which occur naturally in food and are essential for health. They are classified as fat-soluble or water-soluble according to whether they are found in the fatty or watery parts of food and body tissues.

Minerals are also essential for cells to work properly. Those needed in very tiny amounts are known as trace elements. The table lists the 13 essential vitamins, together with some important minerals.

Official bodies lay down some recommended intakes which are bases on wide-ranging scientific studies. In the UK, the RNI or reference nutrient intake is the amount which is enough to meet the needs of most people.

On packs of supplements you will see the letters RDA, which means recommended daily amount. These values are used in the European Union on food and supplement labels.

Why take supplements?

The amount of micronutrients needed varies from one individual to another, depending on their age, sex and environment. The RNI or RDA is just a guide to a safe and adequate intake and is not meant to be a minimum or optimum level.

Many experts believe that a varied diet, rich in fruit and vegetables, will provide the necessary vitamins and minerals. But not everyone eats a balanced diet, particularly those with hectic lifestyles. In addition, intensive farming has meant that much of our fruit and vegetables are not as rich in these important micronutrients as they were in the past.

Even if people eat the right foods, much of the vitamin content may be lost through storage or heating. Water-soluble vitamins are particularly at risk as they dissolve in the cooking water and get poured down the sink!

People should avoid taking megadoses in the belief that this will make them twice as fit. Some vitamins are dangerous if taken in large amounts (see later).

Many people like to take a multivitamin as a general health precaution. Some people believe in taking specific vitamins to prevent disease, e.g. they may find vitamin C wards off colds. There is evidence that the anti-oxidants, vitamin C, E and beta-carotene, can protect against cardiovascular disease, some cancers and other conditions linked with ageing. Beta-carotene is converted to vitamin A in the body as required and so is safer than vitamin A itself.

Anti-oxidants neutralise free radicals which are formed by chemical reactions in the body. Free radicals are needed for many normal biological processes, but large amounts can damage healthy cells. They are also found outside the body in cigarette smoke and other pollutants.

Other anti-oxidants include selenium and zinc. Fruit and vegetables may contain other substances which protect against degenerative diseases, so it is sensible to eat plenty of these foods rather than relying on supplements.

Who may need supplements ?

People who might need supplements include:

• The elderly. As we age, our body becomes less able to absorb vitamins from foods. Older people may have poor appetites and may be less able to shop or cook for themselves. Dental problems may restrict the foods they can eat. If they are housebound, they may not be making enough vitamin D from sunlight.
• Slimmers and others restricting their food intake.
• Children who don’t eat properly either because of food fads or because they fill up on sweets and snacks between meals.
• Vegetarians and vegans. Few plant foods contain vitamin B₁₂ so supplements are necessary for people who do not eat dairy products, eggs and fish.
• Breast-feeding women not eating a varied diet (but they should not exceed the RDAs).
• Women planning to conceive should take 0.4mg folic acid daily and for the first 12 weeks of pregnancy. Other supplements are best left for the doctor to decide. Too much vitamin A (also found in fish oils) can harm the baby.
• Women with heavy periods may need iron supplements.
• There are certain times in life when calcium is particularly important. The National Osteoporosis Society recommends taking more than the official RNI to help prevent fragile bones, namely: children 7-12 years 800mg; teenagers 13-19, men, women 20-45 and those over 45 on HRT 1,000mg; pregnant and nursing women 1,200mg; pregnant and nursing teenagers and women over 45 1,500mg. The calcium in milk products is better absorbed than that in other foods. One-third of a pint of milk contains about 230mg calcium.
• Convalescents, athletes and people under stress. The body needs more vitamin C when fighting infection and it helps wound healing after an operation. Adequate intake of B vitamins is important when coping with emotional or physical stress, such as heavy exercise.
• Asians on a traditional diet may not get enough vitamin D.
• Smokers need more vitamin C than non-smokers.
• Alcoholics often have a poor diet because they drink instead of eat. They also need more B vitamins. Alcohol abuse damages the gut and may affect absorption.

Is too much harmful?

In general, water-soluble vitamins pass out of the body if you take more than you need, but high doses may cause side effects. Fat-soluble vitamins can be stored and their accumulation can be harmful.

Taking too much of one mineral can lead to a deficiency of another. Manufacturers try to balance supplements to avoid this.

Iron and some other vitamins and minerals can interfere with the absorption of prescription medicines such as antibiotics. Iron is best taken with food as it may upset the stomach.

Summary:

Avoid taking too much of a supplement as this may cause side effects.

Dietary supplements are sold as foods, not medicines, so manufacturers are not allowed to make medicinal claims for them. To make such claims, the products must undergo clinical trials and be licensed as medicines. Some supplements, such as certain brands of fish oils, have been licensed.

Fibre

Dietary fibre is plant material the body cannot digest. Although it passes out of the body and has no nutritional value, it is important in preventing constipation and other bowel disorders. It is found in wholemeal flour, wholemeal bread, pasta, brown wheat breakfast, bran based cereals, pulses, fruit and vegetables (including baked beans). Bran is the fibrous outer layer of cereal grains.

Some types of fibre, combined with a low fat diet, can reduce cholesterol levels. Foods with a high fibre content tend to be lower in calories and make you feel full, so are useful in slimming diets.

The recommended daily intake for adults is at least 18g. A bowl of whole grain cereal provides about 6g, two slices of wholemeal bread about 4g and an apple about 3g.

What is a healthy diet ?

A healthy diet means eating a variety of foods from the following groups in order to obtain the nutrients that a person requires:

• Fruit and vegetables.
• Meat, fish and vegetarian alternatives, avoiding high fat options such as pates and sausages.
• Bread, cereals and potatoes.
• Milk and dairy foods, using low fat alternatives.

In more detail:

• Half the daily energy intake should come from carbohydrates, particularly the complex carbohydrates found in bread, cereals, pasta, rice, fruit, potatoes and other vegetables. Eat two portions of potatoes, pasta or rice and four slices of bread.
• Fats should provide no more than one-third of entire energy intake, with saturated fats less than one-third of this. If you eat 2,000 calories a day, no more than 70g of fat is allowed in a day. Use low fat spreads and dairy products instead of full fat varieties. Grill, steam, bake or boil food instead of frying it and don’t add oil, butter or margarine.
• Try not to add salt to food. In some people it causes high blood pressure. A varied diet already provides as much salt as we need. Salt substitutes (based on potassium) are useful for those who find food unpalatable without added salt. High salt foods include sauces, pickles, soups, cheese, salted nuts and smoked foods.
• Eat at least five portions of vegetables or fruit (1lb/400g) a day.
• Eat fatty, sugary foods such as cakes, biscuits and pastries only occasionally and in small amounts.
• Eat at least two portions of fish a week, one of which should be oily fish.
• Consume salt-cured, salt-pickled and smoked foods in moderation as studies have linked them with some cancers.

OTHER SUPPLEMENTS

Garlic

Garlic has anti-oxidant properties. Its beneficial effects on cholesterol levels, blood clotting and blood pressure make it useful in preventing cardiovascular disease. It may also help prevent coughs and colds. The advantage of supplements over natural garlic is that they are odourless.

GLA products

Evening primrose oil, borage (starflower) oil and blackcurrant seed oil are rich sources of the essential fatty acid gamma-linolenic acid. GLA helps to regulate a wide variety of cell functions.

GLA is produced naturally in the body from linolenic acid obtained in food. If this mechanism breaks down for any reason, supplements can correct the imbalance, although it is difficult to know when someone might benefit.

Two evening primrose oil products have been licensed as prescription only medicines for eczema and breast pain.

Nausea and headache are the most common side effects.

These supplements should be avoided in epilepsy.

Fish oils

Oily fish such as sardines, salmon, herring and mackerel contain two long chain fatty acids – EPA and DHA – known as omega-e fatty acids. Research has shown that these compounds can make the blood less likely to clot and they reduce the amount of triglyceride (a type of fat) in the blood. Fish oils may therefore reduce the risk of heart attack or stroke.

Many people prefer to take supplements instead of eating oily fish every week.

The main benefits of cod liver oil come from its vitamin A and D content. It is believed to help dry skin and to give some protection against coughs and colds. Some products are licensed to ease stiff joints.

Cod liver oil contains some EPA and DHA and supplements may be fortified with these fatty acids.

SLIMMING

Excess weight puts a strain on the body and increases the risk of diseases such as heart attack, diabetes and arthritis. We put on weight when we don’t use up all the energy that our food provides. The only way to shed it is to eat less or burn more calories by being more active.

Eating sensibly to lose weight.

EXERCISE

Regular exercise helps you look and feel better. It makes muscles and bones stronger, increases stamina and brings a sense of well-being which helps you relax, sleep better and feel more able to tackle problems. It makes the heart more efficient and helps prevent high cholesterol levels and high blood pressure. As we get older it keeps joints flexible, so it is never too late to start.

Infrequent bouts of intense activity are of a little long-term benefit. Changes in daily routine, such as walking instead of driving or using stairs instead of lifts, is better than a weekly burst on the squash court. To be physically fit you need to do vigorous exercise three times a week or moderate exercise five times a week.

Walking is easy to incorporate into a daily routine and can be done at any age. A two mile walk, taking about 30 minutes, at least three times a week is a reasonable aim. Swimming is excellent all-round exercise, good for suppleness, strength and stamina.

Fast walking, jogging, cycling and dancing improve stamina and increase the efficiency of the heart, lungs and circulation.

People who are not used to exercising should build up gradually and those with medical conditions such as heart disease or diabetes should seek their doctor’s advice.

ALCOHOL

Alcohol is wrongly thought to be a stimulant because it makes people chatty and outgoing. But in fact it is a depressant which makes us feel lively because it dampens our inhibitions. This depressant effect impairs our ability to concentrate and carry out complex activities such as driving.

Recent research has shown that a drink now and again can be good for you. But heavy drinking can lead to health and social problems. The immediate effects of excess alcohol are well known; in the long term it can lead to liver damage, raised blood pressure, digestive problems and cancer of the mouth and oesophagus.

CAFFEINE

Caffeine is a mild stimulant found in tea, coffee, cocoa and cola drinks. Small amounts improve alertness and concentration, but too much causes headache, nervousness, insomnia, tremors and diarrhoea.

People who regularly drink large amounts of tea and coffee may become dependent and suffer from lethargy, irritability, headache and anxiety when deprived of caffeine.

It is best to limit daily intake to 600mg. As a general guide, a 150ml cup of ground coffee contains about 80-90mg, instant coffee 60mg and decaffeinated 3mg. A cup of tea or a can of cola contains about 40mg.

People needing a temporary "pick-me-up" may benefit from caffeine supplements on sale in the pharmacy. Caffeine is also included in some tonics and analgesics, so customers should be warned to restrict their tea and coffee intake while using them.

Your pharmacy may be able to offer coffee substitutes or herbal teas for people seeking alternatives.