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Overuse of zinc supplements can lead to neurological problems and anaemia

Clinicians often misdiagnose zinc deficiency and seem to be unaware of the health risks of excess zinc, suggests an audit of clinical practice in Glasgow hospitals.

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Zinc is an essential trace element that is required in daily quantities of 5.5-9.5mg for men and 4-7mg for women. Zinc supplements are usually only available in formulations of 45 or 50mg. Excessive intake of zinc dietary supplements can disrupt copper uptake, leading to neurological problems and anaemia.

Researchers studied the case notes of 70 patients who were prescribed zinc supplements in Glasgow hospitals between 2000 and 2010. Zinc was prescribed to aid skin healing, for poor nutrition, to support alcohol withdrawal and for alopecia. Plasma concentrations of zinc, copper, C reactive protein and albumin were recorded from the laboratory database.

They found that 62% of patients were prescribed zinc at doses sufficient to cause copper deficiency. In 48% of patients, plasma zinc concentrations were low as a probable result of hypoalbuminaemia or the systemic inflammatory response rather than deficiency. Copper deficiency was only documented as a possible side effect in one patient and plasma copper was measured in only two patients. Almost one in ten patients (9%) developed unexplained anaemia and 7% developed neurological symptoms typical of copper deficiency.

The findings indicate that clinicians consider zinc ‘a safe nutrient rather than a drug carrying potential risk’, write the researchers.

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