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Nutrition

Vitamins

Vitamins are organic compounds needed in small amounts – milligrams (mg) or micrograms (µg) – by the body for essential processes. The majority of vitamins required need to be consumed in the diet as they can’t be produced in the body.

Vitamin A is responsible for the normal structure and function of skin and the lining of the digestive system and lungs. Maintaining healthy skin/linings helps prevent invasion of bacteria and viruses into the body, which assists the body’s immune system. Vitamin A is also involved in cell differentiation, including normal cell growth and development, vision and the immune system.

There are two forms of Vitamin A, retinol which is found in animal sources and carotenoids (beta carotene) from plant sources. Beta carotene can be converted to retinol in the body.


RDI for Vitamin A (µg/day for NZ)

Men 19-70+ = 900µg/day
Men 19-70+ = 700µg/day

NB: Retinol equivalent – 6mg beta carotene = 1mg retinol

Vitamin A status depends on the adequacy of the Vitamin A stores (90% stored in the liver) and protein (carriers). If a person stops consuming foods containing Vitamin A, signs of deficiency will not appear until all of the stores are depleted.


Food sources of Vitamin A

Sources of Retinol include liver, whole milk, cheese and butter. Good sources of carotenes are milk, carrots, dark green leafy vegetables and orange coloured fruits.

The intake of carotenes is strongly related to the amount of fruit and vegetables consumed. People should be encouraged to eat brightly coloured – yellow, orange, red and green – fruits and vegetables as these are the richest in Vitamin A compounds.


Vitamin A deficiency

Vitamin A deficiency is the developing world’s major nutrition problem, but is very rarely seen in Western countries. One of the symptoms is night blindness, in which a person will lose the ability to recover promptly from a temporary blinding when a flash of bright light occurs at night or when a light goes out. In serious cases of deficiency this leads to blindness.


Vitamin A toxicity

High levels of retinol in a pregnant woman’s diet have been linked to an increase risk of birth defects. Pregnant women should avoid taking high doses of Vitamin A unless as advised by a medical professional.

Acne medicine is made from Vitamin A but is chemically very different. Vitamin A itself has no beneficial effect on acne, and therefore taking supplements for the prevention or healing of acne is of no benefit.

Vitamin B1 is also known as Thiamin – both names can be used on food packaging.

Vitamin B1 plays an important role in carbohydrate metabolism. As a component of a coenzyme it acts to release energy from carbohydrates. The amount of Vitamin B1 required in the body is related to the amount of carbohydrate that is eaten in the diet. Vitamin B1 subsequently plays a role in the nervous system, because nerves, tissues and muscles rely heavily on the energy produced from the metabolism of carbohydrates.


RDI for Vitamin B1 (mg/day for NZ)

Men 19-54 = 1.1mg/day
Men 54+ = 0.9mg/day
Women 19-54 = 0.8mg/day
Women 54+ = 0.7mg/day

In the most recent National Nutrition Survey the median intake of Vitamin B1 in New Zealanders was 1.6 mg/day for Men and 1.1mg for Women.


Food sources of Vitamin B1

Good sources of Vitamin B1 are wholegrain cereals, pork, dried peas and beans. The main dietary sources of Vitamin B1 in the New Zealand diet are bread, vegetables and milk.

Twenty five percent of Vitamin B1 is lost from foods during cooking, especially meat and vegetables. Vitamin B1 leaches into water when foods are blanched or boiled for a prolonged period. The amount of Vitamin B1 lost can be reduced by using a microwave or small amounts of water when cooking.


Vitamin B1 deficiency

Deficiency of Vitamin B1 is now very uncommon in the western world, although it can be seen in older people or people who suffer from chronic alcoholism. The disease associated with Vitamin B1 deficiency is beri-beri, a disorder of the nervous system affecting the workings of the heart and muscles. An associated condition, most commonly seen in alcoholics, is Wernicke’s disorder, which affects brain function after prolonged Vitamin B1 deficiency.

Vitamin B2 is also known as Riboflavin – both names can be used on food packaging.

Like Thiamin, Vitamin B2 plays an important role in the release of energy from protein, carbohydrate and fat. Vitamin B2 is also involved in the transport and metabolism of iron and is required for the normal structure and function of the skin. Growing infants and pregnant women have higher requirements than normal for this vitamin due to the rapid amount of growth occurring.


RDI for Vitamin B2 (mg/day for NZ)

Men 19-54 = 1.7mg/day
Men 54+ = 1.7mg/day
Women 19-54 = 1.2mg/day
Women 54+ = 1.0mg/day


Food sources of Vitamin B2

Good sources of Vitamin B2 are milk, eggs, fortified breakfast cereals, yoghurt, cottage cheese and leafy green vegetables. Light destroys Vitamin B2, but it is stable to heat so ordinary cooking should not reduce the quantities present in foods.


Vitamin B2 deficiency

There is no specific deficiency disease associated with Vitamin B2. Symptoms such as dryness and cracking of the skin around the nose and mouth are signs of low Vitamin B2 status.

Vitamin B3 is also known as Niacin – both names can be used on food packaging.

Vitamin B3 is also involved in the release of energy from nutrients namely, glucose, fat and alcohol. Vitamin B3 is required for the normal structure and function of the skin and normal functioning of the nervous system.


RDI for Vitamin B3 (Niacin equivalent mg/day for NZ)

Men 19-70 = 18-20mg/day
Women 19-54 = 12-14mg/day
Women 54+ = 10-12mg/day

The term ‘Niacin equivalent’ is used as the body is capable of making Niacin from an amino acid called tryptophan.


Food sources of Vitamin B3

All protein-containing foods are sources of Vitamin B3, but especially wholegrain breads and cereals, milk, eggs, poultry, fish, and nuts.


Vitamin B3 deficiency

Deficiency of Vitamin B3 is common in countries where maize is the stable diet. Maize contains very little tryptophan and the Vitamin B3 in maize is unavailable. The condition is called pellagra and the symptoms are diarrhoea, dermatitis and dementia.


Vitamin B3 toxicity

Large doses of Vitamin B3 can be toxic and exert a drug-like effect on the nervous system, causing tingling and then severe pain. Medical professionals in some countries treat atherosclerosis using diet and large doses of Niacin in conjunction with another drug to decrease total cholesterol and increase the ‘good’ HDL cholesterol. High doses can cause liver damage so self-dosing is not advised.

Vitamin B6 is also known as Pyridoxine – both names can be used on food packaging. Vitamin B6 plays an important role in the metabolism of protein. Vitamin B6 is also involved in the metabolism and transport of iron, as well as in immune functions. In conjunction with folate and Vitamin B12, Vitamin B6 controls normal blood homocysteine, reducing the risk of cardiovascular disease. Unlike other water-soluble vitamins which cannot be stored in the body, Vitamin B6 can be stored in muscle of tissues.


RDI for Vitamin B6 (µg/day for NZ)

Men 19-54+ = 1.3-1.9µg/day
Women 19-54 = 0.9-1.4µg/day
Women 54+ = 0.8-1.1µg/day


Food sources of Vitamin B6

Beef, fish and poultry are rich sources of Vitamin B6, as well as eggs, wholegrains, green leafy vegetables and fruits.

Heat processing destroys vitamin B6, so unprocessed or lightly processed foods contain more Vitamin B6 than when cooked.


Vitamin B6 deficiency

Deficiency is usually associated with complications due to illness or side-effects of medication. The symptoms are a feeling of weakness, irritability and insomnia. In extreme cases this can lead to growth failure and impaired motor function, although this is relatively uncommon.


Vitamin B6 toxicity

Long-term high intakes from supplements can cause sensory nerve damage, leading to numb feet, loss of sensation in the hands and eventually to an inability to carry out normal everyday activities. People can recover from these toxic effects after discontinuing use of supplements.

Folate is a B vitamin that is needed for the formation of blood cells and nerve tissue. Folic acid is the synthetic form of folate which may be added to manufactured foods or taken as a vitamin supplement.


Folic Acid and Pregnancy

Requirements for folate and folic acid increase during pregnancy and breastfeeding. Women who don’t get enough folate and folic acid before and during pregnancy have a higher risk of their baby developing abnormalities known as neural tube defects (NTDs) – spina bifida and anencephaly. The neural tube is the nerve centre of the foetus and grows into the spinal cord.

Women who plan to be come pregnant, are recommended to take a folic acid tablet (800 µg) daily for at least four weeks prior to conception and for 12 weeks after conceiving to reduce the risk of NTDs. If you find out you are pregnant and haven’t been taking a folic acid tablet, start taking tablets straight away and continue until the 12th week of your pregnancy. This recommended registered tablet can be purchased at pharmacies (or at a lower cost, when prescribed by your doctor or midwife).

A higher dose folic acid tablet is also available for women with a higher risk of NTD pregnancy. Talk to your doctor or midwife about which folic acid tablet is best for you.


Food sources of Vitamin B9

It is found naturally in food, especially green vegetables and grains. Choose foods naturally high in folate or fortified with folic acid, such as:

  • well-washed, fresh, raw or lightly cooked vegetables
  • raw fruit, well-washed or peeled (citrus is especially high in folate)
  • bread and cereals, especially wholegrain
  • cooked dried beans and peas
  • yeast extracts
  • freshly cooked liver and kidney (no more than one serving a week)
  • folic acid-fortified breakfast cereals, bread or fruit juice.


Folic Acid and Bread

Bread manufacturers have been voluntarily increasing the range of breads that contain folic acid fortified flour. Around 46 percent of bread is currently fortified. Folic Acid Fortified Breads 2021

In July 2021, the New Zealand Government announced that they are making it mandatory for Folic acid to be added to bread making flour. The B Vitamin will not be added to organic and non-wheat flours, meaning consumers will have a choice to avoid folic acid if they wish to.

Vitamin B12 is also known as Cobalamin – both names can be used on food packaging. Vitamin B12 is important in the formation and functions of the blood and nerves. It is a critical factor in the metabolism of folate for DNA manufacture and is required during rapid cell growth.


RDI for Vitamin B12 (µg/day for NZ)

Men 19-54+ = 2µg/day
Women 19-54+ = 2µg/day


Food sources of Vitamin B12

Vitamin B12 is produced almost entirely by bacterial synthesis in the colon and small intestine. Rich sources of Vitamin B12 are meat, seafood, milk, milk products and eggs.


Vitamin B12 deficiency

Deficiency is not usually caused by a lack of Vitamin B12 in the diet but by failure of an intrinsic factor in the body which assists in the absorption of Vitamin B12. Older people are more at risk of deficiency as absorption declines with age. Symptoms are commonly megaloblastic anaemia, (enlarged red blood cells) and, less commonly, neurological abnormalities.

Vegans are also at risk of deficiency because dietary Vitamin B12 is only found in meat or meat products. Vegans may need to consider supplementation, although this should be discussed with a medical professional.

Vitamin C is important for the production of collagen, a protein found in skin, cartilage and bone, which is involved in the healing process. Vitamin C is required for the structure and functioning of the brain and the blood vessels. This Vitamin also acts as a powerful antioxidant by protecting cells from damage by oxygen.


RDI for Vitamin C (mg/day for NZ)

Men 19+ = 40mg/day
Women 19+ = 30mg/day

From the 2008/09 Nutrition Survey, the median usual daily vitamin C intake for the New Zealand population was 99 mg for both males and females. Fewer than 2.5% of New Zealanders have an inadequate intake of Vitamin C.

Smokers are recommended to consume up to an extra 80mg of Vitamin C per day, due to the stress that cigarette smoking puts on the body.

Diets containing more than 200 mg of Vitamin C per day have been associated with a lower risk of cancer. Whether this is due to Vitamin C alone or to a combination of components found in foods also containing Vitamin C is still to be established. However, no association has yet been found between a decrease in cancer risk and Vitamin C supplements.


Food sources of Vitamin C

Vitamin C present in many fruits and vegetables is unstable and easily destroyed. 50-80% of Vitamin C is lost from vegetables when boiled, so it is advisable to cook vegetables in minimal water or in the microwave. Chopping and dicing of fruit and vegetables also causes large losses of Vitamin C because it increases the surface area available.

Vitamin C cannot be manufactured or stored in the body so we need to ensure an adequate dose from our daily diet by making sensible food choices.

The principle sources of Vitamin C in the New Zealand diet are vegetables, non-alcoholic beverages and fruits. Levels of Vitamin C can vary greatly between fruits and vegetables. Some good sources of Vitamin C are strawberries, kiwi fruit, oranges, potatoes, broccoli, spinach and kumara. It is recommended that New Zealanders should eat at least five servings of vegetables and two servings of fruit every day.

Foods containing Vitamin C also assist in the absorption of non-haem iron when consumed during the same meal.


Vitamin C Supplements

Eating a diet rich in fruit and vegetables provides a substantial intake of Vitamin C per day, approximately 50-60 mg. Supplement safe limits of Vitamin C are 250-500 mg/day, but many supplements contain Vitamin C at levels above this. An individual needs to consider their everyday dietary intake of Vitamin C before adding a supplement to their daily routine. Consuming Vitamin C in excess of 500 mg per day is wasteful as it is excreted into the urine.


Vitamin C deficiency

Severe cases of Vitamin C deficiency can cause scurvy, although in today’s modern world this disease is rarely seen. The symptoms of scurvy are bleeding gums, poor wound healing and damage to bones and muscles.


Vitamin C toxicity

Too much Vitamin C can lead to migraines and diarrhoea. Individuals consuming a balanced diet receive ample Vitamin C from fruit and vegetables, which is a safer option than risking excess intakes from supplements.

Vitamin D acts as a hormone controlling the amount of calcium absorption by the intestine and works in conjunction with other minerals and compounds in a ‘bone making/maintenance team’. Vitamin D promotes bone mineralisation by making calcium and phosphorous available in the blood and then depositing the minerals in the bone as it hardens. Vitamin D increases the blood concentration of these two minerals by increasing absorption of the minerals from the gastrointestinal tract and by retention from the kidneys.


Food sources of Vitamin D

Very few foods contain significant amounts of Vitamin D. It occurs naturally in animal products, such as oily fish, eggs, butter and meat, while margarine is fortified with Vitamin D.

Vitamin D is different from other vitamins as it can be made in the body. The most significant source of Vitamin D the action of UV light on the skin. Therefore a balance is required between the use of sun block to protect the skin from sun damage while still allowing some UV rays onto the skin so as to achieve sufficient Vitamin D production. As little as 15 minutes under the sun (without sunscreen), 3 times a week enables your body to make enough Vitamin D – but you need to be sensible. Exposing your skin to the sun increases your risks of skin cancer, so don’t get sunburnt while you do it.


Vitamin D deficiency

Low levels of Vitamin D decrease bone strength. In children, deficiency of Vitamin D is called rickets and is characterised by the bones failing to calcify normally, causing growth retardation and skeletal abnormalities. In adults, particularly females, low calcium intakes and low exposure to sun can lead to osteomalacia. This involves the movement of calcium from the bones, causing loss of bone mass and fractures. This disease is closely linked with osteoporosis and calcium deficiency. Older people who are housebound or institutionalised are most at risk of Vitamin D deficiency due to lack of sunlight and may require Vitamin D supplements.

Vitamin E is the common name for a group of compounds called tocopherols, which remain together when extracted from foods. The most active form is alpha tocopherol.

The main action of Vitamin E in the body is as an antioxidant, protecting cells against oxidative damage caused by free radicals. The body’s cells must constantly deal with free radicals, which occur as by-products from foods or from the air. As an antioxidant such as polyunsaturated fats and Vitamin A, Vitamin E protects other substances from oxidation by being oxidised itself.

There is still considerable debate regarding the ability of Vitamin E to prevent heart disease. Population studies have shown an inverse relationship between Vitamin E and coronary heart attack and Vitamin E supplements have been shown to decrease the incidence of heart attacks. Vitamin E acts by controlling the clotting of platelets in the blood and also lowering the number of platelets, therefore decreasing atherosclerosis.


RDI for Vitamin E (mg/day* for NZ)

Men 19+ = 10mg/day
Women 19+ = 7mg/day

NB: *figures are alpha tocopherol equivalents.

The antioxidant benefits of Vitamin E mean there is a benefit to New Zealanders to increase their consumption of Vitamin E. The only problem with doing this via the diet is that this increases the overall fat intake.


Food sources of Vitamin E

The amount of Vitamin E in the diet is related to the amount of polyunsaturated fatty acids consumed in the diet. As vegetable oils are a rich source of both, deficiency is rare. Other food sources of Vitamin E are dark leafy green vegetables, broccoli, avocado, kiwifruit, nuts, seeds, soy beans and whole grains. Vitamin E is readily destroyed by heat processing, so highly processed and convenience foods do not contribute enough Vitamin E to ensure adequate intake.


Vitamin E deficiency/toxicity

Deficiency is extremely rare and usually only associated with diseases relating to fat malabsorption. Likewise toxicity is uncommon and does not cause health issues.

Vitamin K is made from bacteria in the gut, plays a role in blood clotting and is one of a group of vitamins and minerals which support normal bone structure.

Leafy green vegetables and milk are both good sources of Vitamin K.

Deficiency of this vitamin is very rare in adults, although it has been identified in newborn babies. To combat this, all babies born in New Zealand are injected with Vitamin K at birth.