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A guide to
nutrition

What are
functional foods?

Probiotics &
your health

Obesity –
an Irish epidemic

Nutrition & pregnancy

Your digestive system

The role of vitamins & minerals

Finland – a case
study in healthy
eating


Health Calculators

 


Vitamins
What are ‘water soluble’ and ‘fat soluble’ vitamins?
What is the best source of vitamins?
How much vitamins do you need in your diet?
What are minerals?
What are the more important minerals?
What if I am a vegetarian?
Is it useful to take vitamin and mineral supplements?

Vitamins
Vitamins are complex chemical substances contained mainly in food. They enable the body to break down and use the basic elements of food, proteins, carbohydrates and fats. Certain vitamins are also involved in producing blood cells, hormones, genetic material and chemicals in your nervous system. Unlike carbohydrates, proteins and fats, vitamins and minerals do not provide calories. However, they do help the body to use the energy from food.

Most vitamins cannot be made in your body, so they must be acquired from food. One exception is vitamin D, which is made in the skin when it is exposed to sunlight. Bacteria present in the gut can also make some vitamins.

What are ‘water soluble’ and ‘fat soluble’ vitamins?
Vitamins are either water soluble or fat soluble. Water soluble vitamins can be dissolved in water and are found in non-fatty, water-based food such as fruit and vegetables. Fat soluble vitamins are found in fatty foods and as their name suggests, they can be dissolved in fat.

There are 14 vitamins, which fall into two categories, fat-soluble: Vitamins A, D, E and K, and water-soluble: vitamin C, choline and the eight B vitamins: biotin, thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), folic acid/folate (B9) and cobalamin (B12).


What is the best source of vitamins?

Food is the best source of vitamins and minerals and you should get enough vitamins from your food by eating a healthy, balanced diet.


How much vitamins do you need in your diet?

Only small amounts of each vitamin are required each day by the body but it is vital to ensure the right balance of vitamins and minerals in the body. Prolonged vitamin or mineral deficiencies can cause specific diseases or conditions, while an overdose can literally poison the body.

Recommended daily allowances (RDAs) describe the average amount of each vitamin and mineral needed each day to meet the needs of the average healthy person and these can vary according to sex, age and other physical conditions such as pregnancy.

Water-soluble vitamins:
Vitamin C (ascorbic acid)

Vitamin C helps to maintain skin integrity, absorb iron from the gut and heal wounds, and is important in immune functions. Vitamin C deficiency is rare in healthy people but can affect those with illnesses such as cancer, coeliac disease and alcoholism, or those being fed intravenously. This can lead to a condition called scurvy, which causes fatigue, bleeding and poor wound healing.

Vitamin C is found in citrus fruit and juices, tomatoes, spinach, potatoes, berries, green and red peppers, and broccoli. It is easily destroyed by heat and light, so vitamin C-rich food should be stored in a cool, dark place, and prepared and cooked as quickly as possible.

Research has shown that people who eat foods high in vitamin C have lower rates of cancer and heart disease. Too much vitamin C can cause diarrhoea and kidney stones and, as it increases iron uptake, taking too much can also lead to iron overload.

Folate (vitamin B9)
Folate (folic acid), also called vitamin B9 is essential for the normal formation of the red blood cells, protein metabolism, growth and cell division.

A good supply is particularly important for women who are planning to conceive and those who are in the first three months of pregnancy, when the recommended intake is 400 micrograms a day. Folate has been shown to reduce the risk of having a baby with a neural tube defect such as spina bifida.

Folate has also been shown to work together with vitamin B6 and vitamin B12 to decrease the risk of heart attack, stroke or loss of circulation in the hands and feet.

Food sources include liver, yeast extract, citrus juices and fruits, beans, nuts, seeds, liver, dark green leafy vegetables. Folic acid is the synthetic form of folate and is found in supplements and in fortified breads, milks and cereals.

People with folate deficiency may develop a condition called megaloblastic anaemia in which the red blood cells are enlarged.

Vitamin B1 (thiamine)
Thiamine helps to break down carbohydrate, fat and alcohol. Dietary sources include fortified cereals and bread, offal, pork, nuts, and legumes (peas and beans). Large doses may cause headaches, insomnia, weakness and skin problems.

People who have a thiamine deficiency (known as beri-beri) cannot properly process carbohydrates or fat and develop a range of symptoms such as cardiac and neurological problems. It mainly affects people with chronic disease, malabsorption problems, anorexia or chronic, binge drinking alcoholics.

Vitamin B2 (riboflavin)
Your body needs vitamin B2 to extract energy from fat, protein and carbohydrate in food. It is found in dairy products, meat, fish, asparagus, broccoli, poultry and spinach.

Riboflavin deficiency can cause skin disorders, especially in and around the mouth. There is no evidence that riboflavin has toxic effects on the body or that large doses do any good.

Vitamin B6 (pyridoxine)
Pyridoxine is essential for breaking down protein and metabolising haemoglobin (the oxygen carrying red pigment in your blood). It is also essential for energy production and normal brain function.

Bacteria in the gut make pyridoxine, some of which is absorbed through your gut wall. Food sources include poultry, fish, pork, eggs, offal, soybeans, oats, whole-grain products, nuts, seeds and bananas.

Pyridoxine deficiency is rare in healthy people but can cause skin problems, especially in and around the mouth, and neurological problems. High daily doses of vitamin B6 can cause nerve damage.

Vitamin B12 (cyanocobalamin)
Vitamin B12 is involved in the production of red blood cells, in cell metabolism and in nerve function. Foods derived from animals (including meat, fish, shellfish, poultry, eggs and dairy products) and some fortified breakfast cereals are a good source of vitamin B12.

The stomach produces a substance that enables the body to use vitamin B12. However, some people cannot absorb vitamin B12 properly and are at risk of developing pernicious anaemia. Strict vegetarians and vegans may also need to take supplements to make up for any deficiencies in their diets.

Niacin
Niacin is involved in fat metabolism and helps maintain the condition of your skin. It can reduce certain types of fat in your blood, including lowering low-density lipoprotein (LDL) cholesterol (the ‘bad’ cholesterol) and triglycerides. It also raises high-density lipoprotein (HDL) cholesterol (the ‘good’ cholesterol).

Food sources include lean meats, poultry, fish, organ meats, brewer’s yeast, peanuts and peanut butter. Cereals provide moderate amounts. Niacin can also be made in your body. Niacin deficiency is rare and very large doses can cause liver problems.

Pantothenic acid and biotin
Pantothenic acid and biotin are involved in fat and carbohydrate metabolism, and are found in foods derived from animal sources, including dairy products and in certain cereals and pulses. There are no recommended intakes and they are not known to be toxic.

Fat soluble vitamins:
Vitamin A (retinol)
Vitamin A is a fat-soluble vitamin needed for healthy vision, bone growth, reproduction and the immune system. Deficiency is rare in the Western world, but inadequate amounts of vitamin A can cause vision impairment, especially at night.

Vitamin A is manufactured in your body from substances called beta-carotenes, which are found in dark green, orange and yellow vegetables, such as spinach, carrots, broccoli, cantaloupe, mangos, apricots, vegetable soup and tomato juice.
It is also found in meat and dairy products such as liver, beef, chicken, whole milk and eggs.

Large doses are toxic and can lead to liver and bone damage, and birth defects. Excess vitamin A stored in the body may reduce bone mineral density, which could result in osteoporosis and may increase the risks of birth defects and liver abnormalities.

Vitamin D (calciferol)
Vitamin D controls the absorption of calcium and phosphorus, which are essential for bone growth and development. Deficiency is rare but children who don’t get enough vitamin D can develop rickets and adults can develop a condition known as osteomalacia, which leads to weak, soft bones.

Sources of vitamin D include fatty fish such as pilchards, sardines and tuna, liver, egg yolks, and fortified foods such as margarine, some breakfast cereals and vitamin D-fortified milk. Vitamin D can also be made when the skin is exposed to sunlight.

Studies have shown that people who supplement their diets with a combination of vitamin D and calcium slow down bone loss and reduce the number of fractures they develop. Those who don’t drink milk, have dark skin, rarely go outside or are at risk of osteoporosis should consider taking a vitamin D supplement.

The prolonged excessive intake of vitamin D leads to nausea, headache, excessive urination, high blood pressure, deposits of calcium in soft tissues and kidney damage.

Vitamin E (tocopherol)
Vitamin E protects red blood cells and is important in reproduction. It also acts as an antioxidant, preventing cell damage by neutralising so-called ‘free radicals’ — molecules believed to be associated with aging and certain diseases.

Vitamin E is also important in maintaining the structure of lipids (fats) in your body and any structures such as membranes surrounding cells that are rich in lipids. Dietary sources of vitamin E include vegetable oils, vegetables, cereals, wheat germ, whole-grain products, avocados and nuts.

Some studies suggest that it might prevent or slow progression of heart disease or diabetes. Studies also suggest that vitamin E may slow the progression of Parkinson’s disease, help prevent prostate cancer and enhance immunity in older adults but more research is needed.

Deficiency of Vitamin E in humans is rare, occurring only in premature babies and in people who can’t absorb it properly from the diet. At high doses, vitamin E can cause side effects that can include bleeding, especially for people on blood-thinning medications, and gastrointestinal problems.


Vitamin K (phylloquinone, menaquinone and menadione)
Vitamin K is involved in blood clotting and dark green, leafy vegetables, pork, liver and other meats are the main source in the diet. In addition, bacteria in your gut can make vitamin K, which is absorbed into your blood.

Deficiency is rare except in newborn babies and people who have diseases affecting vitamin absorption or metabolism. A deficiency will lead to bruising and excessive bleeding.


What are minerals?
Minerals are chemical elements that are involved in various processes in your body. They help to regulate cell function and to serve as building blocks for your cells and organs. A varied diet should supply all the minerals you need. Unlike vitamins, minerals do not deteriorate during storage or cooking. Major minerals – those needed in larger amounts – include calcium, phosphorus, magnesium, sodium, potassium and chloride. In addition, your body needs smaller amounts of chromium, copper, fluoride, iodine, iron, manganese, molybdenum, selenium and zinc for normal growth and health.

Calcium
Calcium is a mineral important for the development of strong teeth and bones and for healthy muscle and nerve function. Food sources include milk, cheese, yogurt, goat’s milk, fortified soya milk, mineral water, ice cream, tinned fish, calcium-fortified tofu, calcium-fortified juices and cereals; and broccoli. Dairy products such as milk and yogurt are regarded as the best sources of calcium.

Research has shown that, taken regularly, calcium supplements help prevent osteoporosis, by reducing bone loss. Osteoporosis is a bone thinning disease, which most often affects either the wrist, spine or hip, especially in women.

Osteoporosis was traditionally seen as a disease of old age, with as many as one in two women fracturing a bone by the age of 70. But in recent times the age profile of those with low bone density has changed. Today many women in their 20s and 30s are at serious risk of osteoporosis. It is estimated that in Ireland, one in four women and one in 20 men will suffer a fracture due to osteoporosis by the age of 60.

How much calcium do people need?
• Children up to 10 years (boys and girls): 800mg calcium a day.
• Teenagers aged 11-17 years (boys and girls): 1200mg calcium a day.
• Adults (men and women): 800mg calcium a day.
• During pregnancy and lactation: 1200mg calcium a day.

More than one third of Irish women do not consume enough calcium, according to recent research. Often such women restrict their intake of nutritious foods such as milk and meat, in the mistaken belief that they are fattening, and this may have a detrimental effect on their health.

However, studies have shown that women who drink more milk do not have higher body weights. In fact, women who drink more milk have also been found to consume more nutritious diets and drinking more milk is associated with higher intakes of calcium, iron and fibre. There is also emerging evidence that women who drink more milk may benefit from a component in milk called CLA (conjugated linoleic acid), which is believed to reduce the risk of breast cancer.

Which foods are rich in calcium?
Each of the following foods provide 200mg of calcium and will help you devise a calcium-rich diet which suits your age:
• A glass of milk (whole, low fat or skimmed milk)
• Half a glass of fortified milk (with added calcium). This is a useful choice
  if you do not drink a lot of milk each day
• 1oz (28g) of cheddar cheese (matchbox size). An average cheese sandwich is made with 2oz of cheese
• 3 scoops of ice cream
• 40g tinned sardines (softened bones contain the calcium)
• 250g tinned salmon (softened bones contain the calcium)
• 8 thin slices (210g) of white bread.

Calcium is not destroyed during cooking. Here are some calcium rich ideas for you to consider; cheesy omelette, quiche, tofu and bean salad, broccoli and cheese sauce, baked potato and grated cheese, toasted cheese sandwich, salmon sandwich, bread and butter pudding, summer pudding and ice cream, hot chocolate, a smoothie or a milkshake.

What about calcium supplements?
When calcium supplements are recommended by a doctor they are necessary but in most cases, it is far more preferable to eat calcium rich foods than to take a supplement.

How do I maintain bone strength as I get older?
The calcium requirements for an older person are the same as for a person in their 20s but they also need vitamin D as they get older because the body’s ability to make it declines with age. The best sources of vitamin D are oily fish and liver. There is also a good range of foods which are fortified with vitamin D such as some fat spreads, some milks, yoghurts and breakfast cereals.

Iron
Iron is a mineral that is an essential part of blood and muscle. It is important for the transport of oxygen around the body in the blood. There are two types of iron found in the diet, heme iron and non-heme iron.

Heme iron is found in meat, seafood and poultry and is normally absorbed quite well by the body. Non-heme iron is not absorbed as well and is found in iron-fortified cereals, wholegrains, beans, peas and dark green leafy vegetables, such as spinach.

Non-heme iron is better absorbed when consumed with vitamin C-rich food, such as citrus fruit. Because absorption of non-heme iron is lower, vegetarians may need higher amounts of dietary iron.

Meat, when eaten at the same meal as fruit, vegetables, nuts and cereals can also help to increase the absorption of iron.

Liver is a good source of iron, but pregnant women should NOT eat liver because of its high vitamin A content.

What happens when there is too little iron in your diet?
Iron deficiency is the most common nutritional deficiency in the world. Too little iron in your diet leads to too few red blood cells, which affects the body’s ability to carry oxygen.

This condition is called iron deficiency anaemia and can affect can affect the growth and development of infants and people with conditions that cause internal bleeding, such as ulcers or intestinal diseases. Anaemia is a reduction in the part of the blood that carries oxygen, which is called haemoglobin. Symptoms include excessive tiredness, pale skin and poor resistance to infection.

Anaemia can also affect women of childbearing age, who lose blood and hence, iron, during their periods. For this reason, women aged between 12 and 50 years need more iron than men. The recommended daily allowance (RDA) for women aged 18-64 is 14mg compared to 10mg per day for men of the same age. However, recent research has shown that Irish women in this age group are not getting enough iron.

To achieve your RDA, you should consume iron in its most absorbable form. One of the best sources of easily absorbed iron is lean, red meat (beef, pork or lamb). This should be eaten three to four times a week. The iron in red meat can be absorbed up to seven times more easily than iron in fruit, vegetables, nuts and cereals.

Iron supplements can cause side effects such as nausea, vomiting, constipation, diarrhoea, dark-coloured stools and abdominal pain. It can help to take the supplement in divided doses or with food to avoid these symptoms. Liquid iron can stain your teeth.

What are the best sources of iron?
The best source of iron is from meat, chicken and fish. Iron is also available in cereals, eggs, vegetables and beans, however it is not as easily absorbed into the body as the iron from meat, chicken and fish.

How can I boost my intake of iron?
• Drink a glass of orange/grapefruit juice with your breakfast cereal.
  This will help to increase the absorption from the cereal
• Add a slice of lean beef, pork or lamb to a salad or salad sandwich.
  The meat will add iron to the snack and will also help to increase your
  absorption of iron from both the salad and bread
• If you are having sausages and rashers for your breakfast, add some black pudding and   a tomato
• As a snack, have pate on wholemeal bread
• Add raisins and dried apricots to beef, pork or lamb curries

What if I am a vegetarian?
If you are a vegetarian (or a vegan), you should consult a doctor or dietitian about your diet. If you are planning to raise you child as a vegetarian or vegan, you should be aware that such children are at greater risk of suffering from iron deficiency.

It is essential that you get enough iron in your diet. Since you are cutting out the food that is recognised as being the best source of easily absorbed iron, ie. red meat, you have to seek alternative sources.

Is it useful to take vitamin and mineral supplements?
Generally, supplements are unnecessary if you eat a healthy balanced diet. The benefits of taking vitamin and mineral supplements are uncertain and further research is needed to determine whether taking nutrients in pill form provides the same benefit.

Sometimes, however, a supplement may be necessary, especially during times of illness when the appetite is not as good as usual; for children who are fussy eaters or failing to thrive; for people over 65; postmenopausal women; those on a very low-calorie diet; smokers; people who drink alcohol excessively; pregnant women or women trying to become pregnant; people on a special diet; and those who can't absorb nutrients properly.

RDAs should be observed to avoid overdosing. Overdosing on fat-soluble vitamins can lead to toxic levels that can cause damage to the body. Overdosing on water-soluble vitamins, however, will have little effect as they will merely be excreted in the urine.

For more information about Irish eating habits, you can visit the website www.iuna.net to read the findings of the recent North South Ireland Food Consumption Survey.

 



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Welcome | A guide to nutrition | What are functional foods? | Probiotics & your health
Obesity – an Irish epidemic | Nutrition & pregnancy | Your digestive system
The role of vitamins & minerals | Finland – a case study in healthy eating
Health Calculators