The absorption and excretion of calcium in the body is controlled by hormones and Vitamin D. An inadequate supply of calcium in the body is closely related to an inadequate supply of Vitamin D. A deficiency of Vitamin D causes a weakening of bones, which can lead to a disease called rickets in children or osteomalacia in adults.
When the most recent National Nutrition Survey was completed in New Zealand, the average daily intake of calcium for men was 919mg and for women 745 mg.
RDI for Calcium (mg/day for NZ)
Men Up to 70yrs = 1000mg/day
Men Over 70yrs = 1300mg/day
Women Up to 50yrs = 1000mg/day
Women Over 50 years = 1300mg/day
Food Sources of Calcium
The amount of calcium present in foods varies greatly and people can find it hard to consume enough calcium to meet the Recommended Daily Intake (RDI) requirements. The best food sources of calcium are milk, cheese, yoghurt, dairy foods, nuts, fish with bones, broccoli and dried fruit. Although dairy foods are an excellent source of calcium, butter and cream are not good sources because of the high fat content of these foods.
Some foods contain components which bind to calcium making it unavailable for absorption in the body. People on high-fibre diets should include dairy sources in their eating plans, because fibre binds to calcium and decreases absorption. For people who are unable to consume dairy foods, owing to dietary restrictions, (e.g. lactose intolerance) calcium supplement tablets may be recommended by a medical professional.
Bread and Calcium
Bread contributes 10% of the calcium in our diet. All breads supply calcium, although white bread is a better source of calcium as it does not contain the phytates present in wholegrain breads which can bind to calcium and decrease its availability. However, mixed-grain breads are now available with added calcium, for example, Molenberg Vital (contains soy, linseed and calcium) and Tip Top UP HiFibre and calcium.
The main function of iodine is to make thyroid hormones, which control metabolic processes (normal growth and development) and normal metabolic state (body temperature/metabolic rate).
The low levels of iodine present in the soil and environment in New Zealand are reflected in the low levels present in plant foods, which increases the risk that people can suffer from iodine deficiency. Symptoms of deficiency are fatigue and swelling of the thyroid gland in the neck, called goitre. Low-iodine diets can negatively impact children’s mental and physical development and make people feel tired, overweight and constipated.
In the 1920s salt was fortified with iodine as a way of tackling the goitre endemic occurring at the time.
Although today 70% of the salt used is iodised, many people have reduced their use of salt due to the risk of increased sodium intake leading to cardiovascular disease. People are eating more prepared meals or processed meals but the majority of the salt used in the food industry is not iodised. The dairy industry has moved away from using cleaners which contained iodine. Rock salt which does not contain iodine, has also become more popular.
Food sources of iodine
Although it is advisable to limit salt intake, when using salt make sure it is iodised to ensure an adequate daily intake of iodine. Include other sources of iodine in the diet, such as seafood, fish, eggs and low-fat milk products. Supplements for iodine should only be used if recommended by a health professional, as high levels of iodine can be toxic and lead to adverse health effects.
Bread and Iodine
In September 2009 it became mandatory to replace non-iodised salt with iodised salt in all breads except organic and unleavened breads in a bid to address New Zealand’s problem of mild-moderate iodine deficiency. Pizza bases, breadcrumbs, pastries, cakes, biscuits and crackers are not required to contain iodised salt. To retain consumer choice, organic and unleavened bread are also exempt from the replacement of non-iodised salt with iodised salt.
One of the reasons bread was chosen to be fortified with iodine is because it is eaten widely by New Zealanders. Replacing non-iodised salt with iodised salt in most bread is a simple and low cost way of helping to increase the iodine intake of most New Zealanders, and reduce the number of people who aren’t getting enough iodine.For bread, the food label will list the use of iodised salt in the ingredients list.
Monitoring iodine levels in the New Zealand population
The Ministry of Health and Ministry for Primary Industries (MPI) have a joint role in monitoring the effectiveness of mandatory fortification of bread with iodine. The results of the 2014/15 New Zealand Health Survey (NZHS) found that Urinary iodine levels almost doubled between 2008/09 and 2014/15 for adults overall and in all age, gender and ethnic groups.
In 2014/15 iodine status was adequate for men in all age and ethnic groups. Iodine status was adequate for women overall and women of Māori, Pacific and Asian ethnicity. However, women of European/Other ethnicity still had mild iodine deficiency.
Iron is needed for the formation of haemoglobin in red blood cells, which transports oxygen around the body. Iron is also required in myoglobin in the muscle cells and also in many cell enzymes.
Iron needs are greatest in women of child-bearing age, as iron lost through menstruation must be replaced.
The main factor controlling absorption is the amount of iron stores in the body. Iron absorption is also controlled by the requirements of a particular individual and the amount of iron consumed. The presence of particular components in foods can enhance or inhibit the absorption of iron.
There are two types of iron sources. Haem iron is from meat, poultry and fish and is typically well absorbed. Non-haem iron is found primarily in plant based foods, iron supplements and is the type of iron used for fortification of foods, e.g. cereals. Non-haem iron is not as well absorbed
Combining non-haem iron with meats and good sources of Vitamin C improves the absorption of non-haem iron. Components which inhibit the absorption of non-haem iron are polyphenols (in tea, coffee, and particular vegetables) and phytates (in unrefined cereals, nuts and legumes.) These components bind to the iron making it harder, or impossible, for the iron to be processed and absorbed and make it unavailable for use in the body.
RDI for Iron (mg/day for NZ)
Men 19-54+ years = 7mg/day
Women 19-54 years = 12-16mg/day
Women 54+ years = 5-7mg/day
The most recent National Nutrition Survey indicated that low iron stores and iron-deficiency anaemia mainly affected women. Females aged 15–18 years had a prevalence of inadequate intake of 34.2%; those aged 31–50 years had a prevalence of 15.4%.
A lack of iron in the diet, leads to low iron stores in the body and eventually to iron-deficiency anaemia. As so much of the body’s iron is in the blood, losses are greatest whenever blood is lost. Symptoms of iron deficiency are usually a lack of energy, reduced resistance to colds and inability to concentrate. Either iron supplements or changing food choices may be required to increase iron stores and cure iron-deficiency anaemia. The use of supplements should be discussed with a health professional.
Food sources of iron
To maintain iron stores, eat plenty of iron-rich foods such as red meat, liver, fish and chicken, or if vegetarian eat plenty of iron rich plant sources, such as beans and lentils. Breakfast cereals and vegetables are important sources of iron in the New Zealand diet. To optimise iron intake, include foods rich in Vitamin C. Avoid tea and coffee at mealtimes as components of these drinks bind to iron and prevent the absorption of iron into the body.
Bread & Iron
The Bread group provided 12% of dietary iron for New Zealanders. Older males and females (71+ years) obtained more iron from Bread than males aged 15–18 years and all younger females.
Selenium is a trace mineral which works with Vitamin E to protect the body compounds from oxidation, effectively acting as an antioxidant. It is also present in the control of thyroid hormone metabolism, in reproduction and immune functions.
Food sources of selenium
New Zealand soils are low in selenium which affects the amount of this mineral in foods. Although New Zealand intakes of selenium have been lower than other western countries, it appears that our bodies have adapted to this by absorbing more selenium from the diet. There has also been an increase in the amount of foods imported from Australia and America, where the soil contains good levels of selenium.
Foods rich in selenium are fish, seafood, meat, poultry, brazil nuts, eggs and bread. The use of selenium supplements is not recommended as high intakes can be toxic and have negative health effects.
Sodium regulates body water content and electrolyte balance. During exercise, when sweating is involved, sodium regulates the requirements for water and salts. Sodium is also involved in energy use and nerve function.
Sodium is a major component of salt. 1 g of salt contains 0.4 g sodium. When reading food packaging, to convert the sodium amount listed to salt multiply by 2.5.
High sodium intake is associated with high blood pressure, which is a risk factor for cardiovascular (heart) disease, particularly stroke. The effect of sodium on blood pressure varies according to age and each individual’s blood pressure.
RDI for Sodium (mg/day for NZ)
The Ministry of Health recommends New Zealanders limit their sodium intake to 2 grams a day. New Zealanders currently consume more sodium that is necessary for good health; most of this sodium comes from processed and ready to eat meals and foods.
Individuals can restrict their sodium intake by decreasing their intake of salty foods and by not adding salt during cooking or to a meal.
Bread and sodium
Salt is added to bread to enhance the flavour and aid in its processing. In recent years, New Zealand bread producers have lowered the amount of salt added to bread to reduce the sodium levels. Bread contains on average less than 550 mg sodium per 100 g. This is equivalent to approximately 1.4 g salt per 100 g of bread.
Breads containing soy and linseed targeted at women seem to contain lower levels of sodium, for example Molenberg Vital contains only 390 mg sodium per 100 g and Burgen Soy-Lin contains 366 mg per 100 g. The Vogel’s range also has lower sodium added, in the range of 380 mg per 100 g.
Zinc is important for growth and tissue repair (wound healing), reproductive development and the immune system.
Food sources of zinc
The principle sources of zinc in the New Zealand diet are beef and veal, bread and milk. As with other minerals, the absorption of zinc is restricted by phytates, which are found in unrefined cereals, legumes and nuts.