A number of minerals (or trace elements) are essential requirements for well-being. Only very small quantities of minerals are needed (generally less than 100ug/day), but any deficiency can have a profound effect on health.


Selenium is a natural component of many of the body’s enzymes, including the antioxidant defense enzymes. High levels of selenium are found in meat, tuna and eggs. Plants grown in selenium-rich soil (some regions in some countries) contain increased levels of selenium, especially wheat germ, nuts (particularly Brazil nuts), turnips, garlic and oranges.

Although most adults have sufficient selenium for their metabolic functions, supplementation (even in non-deficient people) has been shown to increase natural antioxidant activity and boost immunity and thyroid function. In clinical studies, selenium supplements have been shown to reduce the risk of some cancers and improve overall survival.


Iodine is an essential trace mineral that is important for the function of the thyroid gland, which regulates the body’s metabolic rate. Most of the iodine we get from our diet comes from the sea (fish or seaweed) or iodized table salt. If we don’t eat any seafood or salt, it is easy to fall below the RDI. Too little iodine can lead to fatigue, cognitive decline, depression, weight gain or increased size of the thyroid as it tries to compensate. Iodine deficiency may also contribute to an increased risk of breast cancer. Most multivitamins contain at least 200ug of iodine.


Chromium is an important factor in the regulation of sugar and fat metabolism.  Levels are highest in meat, whole grain products, fruit and vegetables, especially brassica such as broccoli. As with iron, absorption of chromium is assisted by Vitamin C. Deficiency is rare since most adults get their RDI from a normal diet. However, high sugar levels, regular exercise, stress and aging can all increase chromium losses, which need to be offset by increased chromium intake.

The impact of deficiency on health and aging is controversial. It has been suggested that chromium supplements may promote weight loss, enhance energy and lower lipid and sugar levels in the blood, although none of these claims are proven.

Last Reviewed 02/Mar/2014

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Dr Merlin Thomas

Professor Merlin Thomas is Professor of Medicine at Melbourne’s Monash University, based in the Department of Diabetes. He is both a physician and a scientist. Merlin has a broader interest in all aspects of preventive medicine and ageing. He has published over 270 articles in many of the worlds’ leading medical journals

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