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Role of vitamins

Key points about the role of vitamins in your diet

Vitamins are vital for good health, but needed in much smaller amounts than macro-nutrients, like carbs and fats.
They’re important for many daily bodily functions, such as cell reproduction and growth, but most importantly for the processing of energy in cells.
Most New Zealanders can meet their daily vitamin needs by eating a range of food from the 4 main food groups.
That means most people do not need to take supplements.

Happy Māori mum holds young daughter up in the air

Most vitamins are provided by food – so they are classed as ‘essential’. Vitamins are team players – they help other nutrients work better, eg, vitamin D enhances the absorption of calcium, vitamin C is needed to absorb iron and B vitamins work together in cells.

Because only vitamins A, E and B12 are stored to any significant extent in your body, a regular intake of most vitamins is important. You can easily meet your daily vitamin needs by eating a range of food from the 4 main food groups:

vegetables and fruits
grain foods
milk and milk products
a group of foods consisting of legumes, nuts, seeds, fish and other seafood, eggs, poultry and/or red meat with the fat removed.

Vitamins are divided into 2 groups: fat soluble and water soluble.

Fat-soluble vitamins include vitamins A, D, E and K. These can be stored in your fat cells for later breakdown and use when needed. For this reason, these vitamins can build up to toxic levels if you eat them in larger amounts than your body needs. In extreme cases this can cause death. This means you should only supplement with these vitamins on the advice of your healthcare provider.

You need vitamin D for strong bones, muscles and overall health. You can get it from sunlight and what you eat. If you don't get enough of it, you may get aches, cramps and pain in your muscles and your bones may become soft and break more easily.

About 5% of adults in New Zealand are deficient in vitamin D. A further 27% are below the recommended blood level of vitamin D. People with darker skin, who spend less time outside or who have health conditions that make it hard to absorb nutrients are more at risk of vitamin D deficiency.

Vitamin D supplementation is not recommended for most New Zealanders, only those who are at risk of deficiency. Read more about vitamin D and vitamin D supplementation.

Vitamin E (α-tocopherol) is an antioxidant that protects red blood cells, muscle cells, vitamin A and unsaturated fatty acids from oxidation (it destroys ‘free radicals’).

Vitamin E works together with:

the mineral selenium
a wide variety of plant foods
seafood

However, be careful as vitamin E is destroyed by cooking at high temperatures. Vitamin E deficiency is rare in humans, but can lead to:

haemolysis (the bursting of red blood cells)
anaemia
sterility (in rats)

RDI (recommended daily intake) for vitamin E:

men, 10mg
women, 7mg

Vitamin K (phylloquinone and menaquinon) is needed to make prothrombin, important for blood clotting. Vitamin K works with vitamin A to keep bones and teeth healthy.

Vitamin K can be obtained from:

our own gut bacteria
eating wholegrain cereals
leafy green veges
vege oils
liver
green tea
fortified milks such as Anlene

Deficiency can cause bleeding in newborns who lack the intestinal bacteria needed to produce vitamin K. There is currently no available RDI (recommended daily intake) for vitamin K.

Vitamin K - AI (average intake):

men, 70μg/day
women, 60μg/day

Vitamin K supplements (and foods fortified with vitamin K) can be dangerous for people taking blood thinning agents, like warfarin or aspirin, which will not work as effectively.

* RDI: Recommended Daily Intake; AI: Average Intake; UL: Upper Limit. See RDIs explained

These vitamins are also known as co-enzymes, and are needed during the breakdown of food to make energy. They are excreted by the kidney, so are not stored in the body.

Vitamin	Role	Source	Deficiency/Toxicity	RDI/AI/UL*
Vitamin B1(thiamin)	Works with other B group vitamins in breakdown of carbohydrates to make energy - mostly in muscles, brain, liver and kidneys.	Meat (especially pork), fish, wholegrain cereals and bread, fortified breakfast cereals, pulses (dried beans and lentils), nuts and yeast extract. Fortified breakfast cereals and bread mixes. 25% lost in cooking.	Mild: headache, tiredness, loss of appetite and muscle weakness. In most populations, deficiency doesn't occur, with exceptions found in chronic alcoholism, some older people, and those with chronic diseases involving vomiting, diarrhoea and anorexia.	RDI: Men, 1.2mg.Women, 1.1mg.UL: None estimated.
Vitamin B2 (riboflavin)	Works with other B vitamins helping with protein and carbohydrate use in cells. Helps with absorption of minerals iron, zinc and calcium.	Liver, dairy products, eggs, cereals and green vegetables. Easily destroyed by light.	Very rare: inflammation and breakdown of skin (particularly lips and corners of mouth), swollen tongue, eye irritation.	RDI: Males 1.3mg men 19-70 years, 1.6mg over 70 years, 1.1mg.Females, 19-70 and 1.3mg women >70.UL: Cannot be estimated
Vitamin B3(niacin, nicotinic acid)	Used in cells for energy transfer and to repair DNA.	Wide variety of foods: beef, pork, liver, beans, yeast extracts, eggs, wholegrain cereals, cow’s milk. Human milk contains more niacin than cow’s milk.	Deficiency very rare in New Zealand: fatigue, inflammation of the nerves and skin.	RDI: Men,16mg.Women, 14mg.UL: 35mg/day.
Vitamin B6 (pyridoxine)	Regulation of mental function and mood, and a role in the breakdown of homocysteine.	Found in most foods.	Deficiency: anaemia, irritability, convulsions, inflammation of nerves. Toxicity: in large amounts, this vitamin is toxic to sensory nerve cells.	RDI: Males, 19-64 years,1.3-1.9mg.Females, 19-54 years, 0.9-1.4mg, > 54 years, 0.8-1.1mg.
Vitamin B12 (cyaocobalamin)	Essential for the manufacture of DNA and normal blood and brain function.	All foods of animal origin: meat, especially liver, fish and seafood, eggs, and milk products. Soy milk is often fortified with vitamin B12.	Deficiency affects nearly all body tissues, particularly those containing rapidly dividing cells in times of growth. Most serious affect is pernicious anaemia and degeneration of the nervous system.	RDI: Adults 2.0µg
NB: Vitamin B12 is made only by certain bacteria found in the gut, and is contained only in foods of animal origin. This has implications for vegans. In addition, vitamin B12 can only be absorbed in the presence of ‘intrinsic factor’, a protein secreted by the stomach, which has implications mainly for the elderly and those who have undergone gastric surgery. These people may need regular replacement vitamin B12.
Folic acid(folate)	Formation of chromosomes and red blood cells, promotes normal digestion. Has been shown to prevent neural tube defects, like spina bifida, in babies, and thought to play role in reduction of chronic disease risk, from cardiovascular disease and dementia to bone fractures, cancers and DNA damage.	Good sources of folate come from: liver, yeast extract, some fortified breakfast cereals, pulses, wholegrain cereals, nuts, some fruits, asparagus and dark green leafy vegetables.*	Deficiency can cause some types of anaemia. Low daily intake in women trying to conceive and who are pregnant is linked to neural tube defects and other malformations in babies.	RDI: Men and women, 400µg.Pregnant women: 600µg per day dietary intake. plus a supplement.**Breastfeeding women: 500µg
Folate requirements can be affected by nutrient interactions, smoking, certain drugs and your genetic make-up. Intakes of folate in Australian and New Zealand populations are currently significantly below the recommended intakes, with median intakes of about 300μg/day for men and 230μg/day for women. The main sources are cereals, cereal products and dishes based on cereals (about 27%) and vegetables and legumes (about 29%). Fruit provides about 8–10%. Some orange juice are fortified with folate. From September 2009, all bread-making flour in New Zealand was to be fortified with folic acid, but this decision has now been put on the back burner for 3 years. *Maximum protection against neural tube defects is reached when a women is consuming high levels of folic acid as supplements, in the month preceding conception and in the first trimester. In New Zealand, daily 400µg folate supplements, in addition to a folate-rich diet, are recommended to women one month before conception and right up to their 12th week of pregnancy.
Pantothenic acid	Part of the body’s co-enzyme system, a key molecule in carbohydrate and fat metabolism, and essential to almost all forms of life.	Widely distributed in food: chicken, beef, potatoes, oat-based cereals, tomatoes, liver, kidney, egg yolks and whole grains are major sources.	Deficicency not seen in people who eat ‘real’ food, only in those fed synthetic diets; symptoms include irritability, restlessness, fatigue, apathy, malaise, sleep disturbance, nausea, vomiting and cramping, numbness, staggering gait, hypoglycaemia, increased insulin sensitivity.	AI: Men 6mg/day.Women, 4mg/dayUL: Not yet be determined.
Biotin	Fat metabolism.	Many foods, especially in egg yolk and liver.	Deficiency rare, but can be caused by over-consumption of raw egg white (protein combines with biotin and makes it unavailable). Can also occur when solely intravenously fed. Symptoms include dermatitis, conjunctivitis, alopecia,central nervous system abnormalities, including developmental delay in infants. Some people have a gene that makes them need more biotin than others.	AI: Men, 30µg/day.Women, 25µg/day.UL: None set.
Vitamin C (ascorbic acid or ascorbate)	Essential vitamin: helps make bone, neurotransmitters, collagen, teeth, cartilage, connective fibres. Maintains resistance to infection, frees iron to make haemoglobin. An antioxidant thought to be important in anti-cancer and anti-ageing processes. Aids the absorption of iron and copper.	Fresh and frozen fruit (not dried) and vegetables, particularly soft and citrus fruits. Those rich in vitamin C include: potatoes, broccoli, spinach, kumara, sprouts, strawberries, kiwifruit, oranges and melon, blackcurrants and guava*.		RDI: Men and women 45mg.In the UK, smokers’ RDI is 80mg or greater.UL: Not yet set, but the Nutrient Reference Values for Australia and New Zealand suggest 1000 mg/day is a prudent limit.
The Australian bush food terminalia ferdinandiana* is the richest source. Many manufactured foods, especially juices and cordials, contain vitamin C as an antioxidant to prolong shelf life.Vitamin C is susceptible to destruction by food heating and processing – damaged by cutting and bruising and leaching into cooking water. Microwaving and steaming is best way to preserve vitamin C in your cooked food. Vitamin C content can also be affected by season, transport, shelf life, storage time and chlorination of water.