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How to avoid NZ’s top dietary deficiencies

You may not know it, but there’s a good chance you are deficient in at least one essential nutrient. Georgia Rickard explains how to avoid the most common dietary deficiencies in New Zealand.

The word ‘malnourished’ often evokes images of someone who is underweight, pale and unwell. But that’s not necessarily the case. You could be missing out on vital nutrients – and be at risk of serious health consequences – but show no symptoms.

You may be eating enough (or too much), but may not be eating enough nutritious foods. Here are six of the most common nutritional deficiencies in New Zealand – and the best ways to boost your intake of each of these essential nutrients.

Are you at risk?

If you answer ‘no’ to any of these questions you could be at risk of deficiency in an essential nutrient.

  • Do you have three serves of dairy (or calcium-enriched alternative) every day?
  • Do you eat two serves of fruit and at least three serves of vegetables every day?
  • Do you eat wholegrain breads and cereal foods every day?
  • Do you eat moderate amounts (100-200g every day) of lean protein foods?
  • Do you have two to three serves of fish each week?

Vitamin D

Vitamin D helps the body absorb calcium and it is vital for healthy bones and muscles.

Adequate intake (AI)

  • Women and men (micrograms)
  • 19-50 years: 5mcg
  • 51-70 years: 10mcg
  • 71+ years: 15mcg
  • Pregnant/breastfeeding: 5mcg

How common is vitamin D deficiency?

President of the Australian and New Zealand Bone and Mineral Society Professor Rebecca Mason says “research suggests that among the general population, around one in three of us will be vitamin D deficient by the end of winter.”

Vitamin D insufficiency affects most segments in the New Zealand population including pregnant women and children. There is a higher incidence among ethnic groups such as African, Middle Eastern, Asian, Maori and Samoan people.

Those at risk

Professor Mason says those who are more susceptible to vitamin D deficiency include “older people and anyone who’s chronically ill, because they don’t get out in the sun much; people with darker skin; and Asian women, due to a cultural appreciation for pale skin.”

New evidence also suggests teens are possibly at higher risk than previously estimated because of increased computer screen time. A 2002 study in New Zealand showed that 31 per cent of children aged five to 14 whose blood was analysed indicated vitamin D deficiency. Additionally, Professor Mason says, “those of us who work indoors all day – leaving home at 8am and coming home at 6pm – and work on the weekend, aren’t in the sun much.”

How do I know if I’m deficient?

“Generally, you won’t know [you are deficient] unless you’ve got severe symptoms such as bone pain and muscle weakness [which can lead to an] increased risk of fracture,” says Professor Mason. A blood test is available so consult with your doctor if you suspect you are vitamin D deficient.

What happens if vitamin D deficiency is left unchecked?

“If you don’t get enough vitamin D, you don’t absorb calcium well so you end up taking your calcium from your bones, resulting in osteoporotic fractures,” says Professor Mason.

“There’s also a link between low vitamin D and greater risk of some cancers,” says Professor Mason, “– colon cancer, particularly – as well as increased risk of multiple sclerosis, rheumatoid arthritis and irritable bowel syndrome.” If a pregnant woman is deficient, then the baby’s bone calcium content can be low, which may lead to rickets if the deficiency is severe enough.

Boost your vitamin D intake

Even though there are some dietary sources of vitamin D available, there’s not enough in an average diet to account for more than the five to 10 per cent of what you need.

In other words, focus on getting enough sun exposure – which will vary depending on the time of year. “You need sun exposure on about 20 per cent of your body surface (ie. face, arms and hands) on most days”, says Professor Mason. In winter, go outside at lunchtime for about 25 minutes if you live in Auckland, as much as 40 minutes if you’re in Christchurch. Walk briskly and roll up your sleeves so you can get more skin exposure, and do it most days. If you’ve got darker skin, you will need three to six times longer in the sun.

“In summer, if you’ve got pale skin, you need about six to eight minutes of sun exposure, either mid-morning or mid-afternoon,” says Professor Mason. Your doctor may also recommend vitamin D supplementation, especially as you get older.


Iodine is needed to make thyroid hormones which help control metabolism, growth and development (including growth and development of the brain).

Recommended daily intake (RDI)

  • Women and men 14+ years: 150mcg
  • Pregnant: 220mcg
  • Breastfeeding: 270mcg

How common is iodine deficiency?

Iodine deficiency is the number one cause of preventable intellectual disability in children, and recent studies have shown evidence of iodine deficiency re-emerging in New Zealand. On average, New Zealanders may be consuming less than 60 per cent of what is recommended.

Who’s at risk?

Every New Zealander is potentially at risk. This re-emergence appears to be due to several factors: an increased consumption of commercially prepared foods which are mostly manufactured with non-iodised salt, the declining use of iodised sanitisers in the dairy industry and less salt being added in the home in response to health messages to reduce salt intake.


The consequences of iodine deficiency are most serious for women who are pregnant, planning to fall pregnant or breastfeeding. They may not be affected by their low iodine levels, but if pregnant women don’t get enough iodine while the foetus is developing, this can cause devastating and irreversible effects to the child. These effects can include mental disabilities and problems with growth, hearing and speech.

How do I know if I’m deficient?

You are most likely at risk if you follow a low-salt diet (salt is often fortified with iodine) and/or don’t eat iodine-rich seafood or bread. As of 2009, bread sold in New Zealand is legally required to be fortified with iodine (with the exception of organic bread).

However, you often can’t tell if you are iodine deficient unless it’s quite pronounced. Moreover, the tests for checking iodine levels are not terribly reliable. Urine samples can be measured to give an indication of iodine status.

What happens if iodine deficiency is left unchecked?

Long-term deficiency can be serious – apart from the ramifications for babies born to iodine-deficient mothers, iodine deficiency can result in enlarged thyroid gland (goitre) and hypothyroidism.

Boost your intake

Iodised salt is still the most simple and effective way to get iodine into your diet. In fact, the World Health Organization (WHO) recommends all salt for human consumption should be iodised. That doesn’t mean we should eat more salt, rather it’s more that iodised salt should replace non-iodised salt wherever possible.

In addition, the Ministry of Health recommends expecting and breastfeeding mothers take a subsidised iodine-only supplement. New Zealand soils are low in iodine so locally grown produce reflect this. Foods containing iodine include low-fat milk and milk products, eggs, seafood and foods containing seaweed such as sushi.

Does gluten-free bread contain iodine?

To make sure your gluten-free bread contains iodised salt, check the pack – if it contains yeast, it’s legally classified as a bread and therefore required to use iodised salt in its preparation – unless it’s organic.


Iron helps deliver oxygen throughout the body. Iron is important for transforming food into energy, it assists in making neurotransmitters (chemical messengers in the brain), and it plays an important role in the immune system.

Recommended daily intake (RDI)

  • Girls 14-18 years: 15mg
  • Boys 14-18 years: 11mg
  • Women 19-50 years: 18mg
  • Men 19+ years and women 50+ years: 8mg
  • Pregnant: 27mg
  • Breastfeeding: 9-10mg

How common is iron deficiency?

The last National Nutrition survey found about 11 per cent of New Zealand women had low iron stores, iron deficiency or iron deficiency anaemia with a higher prevalence among Maori. A 2001 study found that 45 per cent of adolescent women were at risk of low dietary intakes and that up to 13 per cent of women aged 15-49 years had sub-optimal iron levels.

Who’s at risk?

Other high-risk groups include children – especially pre-school children (their iron requirements are quite high relative to the amount of food they eat) – older people (due to reduced absorption capabilities), vegetarians and vegans (due to eating lower amounts of readily absorbed iron), disadvantaged communities and those with chronic inflammatory conditions such as obesity.

How do I know if I’m deficient?

You may feel tired and lethargic, like you can’t pull yourself together, or you may not notice anything at all. You may be more susceptible to infections and be more sensitive to the cold or the inside of your mouth may be pale. If you are worried, see your GP for a blood test to check your iron levels.

What happens if iron deficiency is left unchecked?

If the iron deficiency becomes serious, you may experience an inability to regulate your body temperature. There may be developmental delay (such as stunted growth), impaired immune function, cognitive and intellectual impairment, and if pregnant, an increased chance of premature birth and/or an underweight baby.

Boost your intake

Animal meats such as red meat, poultry, mussels and fish which contain haem iron are the best source of iron. Non-haem iron found in vegetable sources is not easily absorbed. Combining non-haem iron sources with foods containing vitamin C helps our bodies absorb non-haem iron. Breakfast cereals, beans and lentils are also an important source of non-haem iron.

You can also help your body absorb non-haem iron by avoiding tea, coffee and red wine at meals since the tannins they contain inhibit non-haem iron absorption.


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