The forgotten minerals: Iodine, zinc and magnesium

We all know it’s important to get enough iron and calcium, but there are other minerals which are also important.
Published 31 July 2018 | Updated 6 June 2024

The minerals your body needs

When we think of minerals, most of us think of iron and calcium, as they’re generally considered the minerals we are most likely to be deficient in. But there are others that are equally important to our health, and because these days people tend to eat more processed foods and fewer whole foods, many of us may not be getting enough. So what are these ‘forgotten’ minerals?

1. Iodine

Why do I need iodine?

Iodine gets surprisingly little attention considering its vital role in our bodies. It helps regulate the thyroid gland and influences everything from brain development to metabolism. In 2009 the Australian population was classified by the World Health Organization as mildly iodine deficient and the Australian Health Survey found that 10 per cent of women still had an inadequate iodine intake.

How can I increase my iodine intake?

Seawater is the richest source of iodine, so anything that comes from the sea, such as fish, seafood and seaweed, is high in iodine. Iodised salt is one of the other major sources of iodine in the Australian diet and all bread sold in Australia and New Zealand (excluding organic breads) is fortified with iodine. According to the Australian Institute of Health and Welfare, this is now delivering sufficient amounts of iodine to the general population, but pregnant and breastfeeding women are still not getting enough.

How much iodine do I need?

Men and women need approximately 150 micrograms of iodine per day, which for most people can be met through iodised salt and bread, combined with two to three serves per week of fish or seafood. However, those on low-salt diets and those with higher iodine requirements, such as pregnant and breastfeeding women, may need supplements.

2. Zinc

Why do I need zinc?

The ultimate multi-tasker, zinc plays a role in our immune function, protein synthesis, wound healing, taste and smell.

How can I increase my zinc intake?

Animal products such as meat, fish, poultry and dairy are the major contributors of zinc in the Western diet but grain foods also contribute significant amounts. The Australian Health Survey found 37 per cent of men and 9 per cent of women had inadequate zinc intakes. Zinc deficiencies are more common in vegetarian and vegan diets, which are becoming increasingly popular. This is not only because meat and animal products are higher in zinc than plant-based foods, but also because compounds known as phytates, present in many vegetarian staples such as wholegrain breads, cereals and legumes, bind to zinc and reduce its absorption in the body.

How much zinc do I need?

Men need approximately 14 milligrams per day - the equivalent of one medium steak and one cup of milk. While women need approximately 8 milligrams per day - the equivalent of one small steak and one cup of milk. This requirement increases to 11 milligrams per day during pregnancy and 12 milligrams during breastfeeding. However, vegans and vegetarians who rely on grains and legumes as dietary staples may need up to 50 per cent more.

Symptoms of a zinc deficiency can include decreased immunity, skin conditions such as acne and dermatitis, poor wound healing and an impaired sense of taste and smell. Zinc supplements are generally considered safe, however, excess zinc can be harmful as it can suppress copper and iron absorption, so it’s important to only take the prescribed dose. And don’t take supplements without talking to your doctor first.

3. Magnesium

Why do I need magnesium?

Magnesium plays a crucial role in the proper functioning of every organ in our body, especially vital areas such as the heart, muscles, and kidneys. Additionally, research suggests that maintaining optimal levels of magnesium can serve as a protective measure against depression. Despite its importance, findings from the Australian Health Survey indicate that one in three people fall short in magnesium intake (37 per cent of men and 34 per cent of women). Factors such as excessive consumption of processed grains and salt, along with alcohol or coffee intake, as well as prolonged exposure to stress, can contribute to declining magnesium levels.

How can I increase my magnesium intake?

Magnesium is present in many foods, including nuts, legumes, green vegetables, meat and seafood. Wholegrains have also traditionally been an important source of magnesium, however, processing of grains substantially reduces their magnesium content.

How much magnesium do I need?

The recommended intake of magnesium is about 400 milligrams per day for men and 300 milligrams per day for women, increasing to 350 milligrams per day during pregnancy and breastfeeding. One tablespoon of pumpkin seeds provides about 100 milligrams of magnesium and one cup of cooked spinach is about 160 milligrams.

Symptoms of magnesium deficiency include fatigue, insomnia, muscle weakness, high blood pressure and poor memory. The amount of magnesium absorbed varies depending on how much your body needs, so supplements generally cause few side effects. However, excessive doses can cause gastrointestinal discomfort.

Should you take supplements? Most healthy people can easily obtain adequate amounts of magnesium from a balanced diet. However, in some cases supplements may be required due to dietary restrictions, pregnancy or illness. If you feel that you may be at risk of deficiency, make sure you speak to your doctor or a registered dietitian.