Mineral overview

If you know minerals are micronutrients that are good for you but struggle to name more than 2 or 3, this mineral overview is for you.

In this guide you will find the following information (when applicable or available) for the main minerals:

• Forms
• Sources
• Bioavailability (i.e. the extent at which the mineral can be absorbed, utilised and stored) in percentages, along with enhancing and inhibiting factors

Calcium

Sources: dairy foods (e.g. milk, yoghurt, cheese) and in smaller amounts in fish with bones, legumes, dark green leafy vegetables (e.g. kale, spinach), certain nuts, fortified soy beverages and breakfast cereals.

Bioavailability: absorption from milk is between 20 and 40%, from vegetables is either in the same range or lower, depending on the vegetable (higher in cruciferous vegetables).

Absorption from food can be enhanced by fortification with vitamin D2 (e.g. in fortified milk), casein and whey (proteins present in milk), lactose and phosphorous.

Absorption from food is reduced by the presence of oxalate (present in spinach, cabbage, broccoli, Brussel sprouts, beetroot, rhubarb, beans, etc.) and phytate (present in seeds, nuts, grains, soy isolate, etc.).

High intakes of sodium and protein (especially sulphur-containing proteins) can increase calcium excretion, therefore negatively affecting calcium balance.

Absorption from supplements depends on the dose and whether they are taken with a meal.

Phosphorous

Sources: many foods (e.g. dairy products, beans, peas, cereals, nuts) and food additives (e.g. phosphate salts).

Bioavailability: ranges from 55 to 70%. It is estimated that bioavailability is higher from animal foods than plant foods, especially those that contain phytic acid (e.g. beans, peas, cereals, nuts).

Potassium

Sources: leafy green vegetables, tomatoes, cucumbers, zucchini, eggplant, pumpkin and root vegetables. To a lesser extent, also present in beans, peas, apples, oranges, bananas, kiwi fruit, dairy foods (milk and yoghurt) and meats. It is also added to processed foods as potassium chloride.

Bioavailability: absorption ranges from 60 to 85% and is negatively affected by the food matrix of fruits and vegetables.

Sodium

Forms: sodium chloride (a.k.a. salt) and food additives (as phosphate, bicarbonate and benzoate).

Sources: the main source is salt added to foods. In Australia, on average about 43% of the sodium comes from cereals and products based on them (this includes everything from breads to pies), about 8% from milk products and dishes, about 6% from processed meats and about 1.9% from snacks.

Magnesium

Sources: most green vegetables, legumes, peas, beans and nuts, some shellfish and spices, followed by most unrefined cereals.

Bioavailability: in general, absorption is inversely proportional to intake; e.g. from 25% at higher intakes to 75% at lower intakes.

Absorption from dark leafy greens is about 25–35%.

Absorption is inhibited by oxalate, phytic acid, certain plant components (e.g. cellulose, pectin), high fibre intake and high zinc intake.

Absorption is enhanced by protein, medium-chain triglycerides and indigestible carbohydrates.

Iron

Forms: haem only from animal sources and non-haem from both animal and plant sources.

Sources: meats, fish, poultry, wholegrain cereals, green leafy vegetables.

Bioavailability: haem iron is more bioavailable. The bioavailability from green leafy vegetables is around 12%.

Absorption depends on iron status of the individual, iron content and composition of the meal.

Absorption of non-haem iron is increased by vitamin C, lactic fermentation of vegetables and consumption of meat, fish or poultry in the same meal.

Absorption of haem and non-haem iron is reduced by phytic acid, calcium and zinc. In addition, absorption of non-haem iron is inhibited by polyphenols and plant protein.

Iodine

Forms: inorganic iodide in foods, iodine supplements and food additives (e.g. calcium iodate, potassium iodate, potassium iodide and cuprous iodide).

Sources: present in foods of marine origin (e.g. seaweed, seafood) and in low amounts in other foods; however the content varies depending on the soil and farming practices. Also present in fortified foods (e.g. iodised salt).

Iodine from foods can be lost during cooking.

Bioavailability: reduced by goitrogens (present in cruciferous vegetables) and goitrogenic cyanoglucosides (present in sweet potato and maize).

Zinc

Sources: meats, fish and poultry, followed by cereals and dairy foods.

Bioavailability: absorption depends on many chemical and biochemical factors, but in general is greater when the diet is high in animal proteins than plant-based proteins. Absorption from milk is approximately 25-30%.

Chromium

Sources: widely distributed in food; the actual content varies based on geochemical factors.

Bioavailability: absorption is increased by vitamin C and potentially resistance exercise.

Diets high in simple sugars and aerobic exercise can negatively affect chromium status by increasing urinary excretion of chromium.

Selenium

Forms: selenocysteine from animal sources, selenomethionine, selenocysteine or selenocysteine metabolites from plant sources.

Sources: seafood, poultry and eggs, followed by other meats. The content in plant sources (e.g. cereal products) depend on the soil and is low in Australia.

Bioavailability: absorption ranges between 55 and 70%.

Fluoride

Sources: foods, fluoridated and unfluoridated water, fluoridated toothpastes and some dietary supplements.

Molybdenum

Sources: plant foods (e.g. legumes, grains and nuts). The content depends on the soil.

Bioavailability: unknown.

Copper

Sources: organ meats, seafood, nuts and seeds, followed by wheat bran cereals and whole grain products.

Bioavailability: absorption depends on intake; from <20% for higher intakes to >50% at lower intakes.

Absorption can be decreased by very high intakes of zinc or iron supplements.

Manganese

Sources: cereal products, tea, vegetables.

Bioavailability: absorption is low (<5%).

References

• National Health and Medical Research Council. Nutrient Reference Values for Australia and New Zealand [Internet]. Canberra: National Health and Medical Research Council; 2006. Available from: http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/n35.pdf
• Melse-Boonstra A. Bioavailability of Micronutrients From Nutrient-Dense Whole Foods: Zooming in on Dairy, Vegetables, and Fruits. Front Nutr. 2020;7:101.

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