Zinc is essential for growth, metabolism, detoxification and healing. Yet 75% of Australians don’t receive their RDI of zinc. This is more of a problem because, unlike iron, we do not store zinc in our bodies, so we need a daily fix to maintain our levels.

The best sources are seafood (oysters, crab, lobster), meat and poultry.  Many cereals and other products are fortified with zinc. Although whole grains, legumes and nuts contain lesser amounts of zinc, fiber in plants may partially inhibit zinc absorption, so strict vegetarians need to take twice as much zinc in a vegetarian diet. Other groups at high risk of low zinc levels include alcoholics and those with digestive diseases.

Low levels of zinc can lead to lethargy, delayed healing of wounds and increased susceptibility to infection. Zinc concentrations are correlated with sperm-count, with the lowest zinc concentrations found in infertile men. When zinc levels are low, our sense of taste and smell may also be impaired. This principle is utilized in the simple zinc taste test in which a dilute solution of zinc sulphate is used to test our sense of taste. If an immediate, strong and unpleasant taste is experienced, then our levels are OK. But if the response is not immediate or we don’t taste anything it could indicate low zinc levels.

Zinc is widely used in multivitamins, as well as over-the-counter preparations that reduce the duration and severity of cold symptoms. These are fine to maintain our levels. However, correcting deficiency may take a higher dose than can be provided by ordinary supplements, due to zinc blockade (where low zinc levels impair the absorption of all minerals).

The effect of zinc supplements on aging is unclear, although some studies suggest that supplements may reduce the risk of oesophageal cancer and age-related damage to the retina.


Magnesium is a key regulator of the body, supporting the function of muscles, bones, the immune system, brain and heart. Like calcium, the body tries to keep magnesium levels constant, storing any excess in the bone, from where it can be released if dietary intake is inadequate. And this is often the case. Two out of every three adults do not reach the RDI, through diets low in the best sources of magnesium including green leafy vegetables, legumes, nuts and whole grains.

Low levels of magnesium can lead to weakness and lethargy, cramps and low mood. There is some suggestion that magnesium supplements can reduce the risk of diabetes, hypertension, heart disease and osteoporosis in those at increased risk of these conditions. Magnesium can also be a potent (e.g. milk of magnesia). Good supplements containing chelates won’t have this effect.

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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