Zinc deficiency

What it is

Zinc is a trace element and a cofactor for hundreds of enzymes, including alkaline phosphatase. Deficiency is either inherited or acquired.

• Inherited: acrodermatitis enteropathica, an autosomal recessive defect of the intestinal zinc transporter (SLC39A4). It appears about 4 to 6 weeks after weaning, and earlier in a formula-fed infant. A breastfed infant can present before weaning if the mother's milk is low in zinc.
• Acquired: far commoner, and the form you will meet in adults.

Causes and risk

• Diet: little meat; a diet high in phytates (legumes, seeds, whole grains), oxalates or calcium, which bind zinc and block absorption.
• Malabsorption: Crohn disease, coeliac disease, short bowel, pancreatic insufficiency, hookworm.
• Chronic disease: liver disease, chronic kidney disease, diabetes, sickle cell disease, HIV, heart failure.
• Losses: chronic diarrhoea, burns, haemodialysis, alcohol use.
• Increased demand: pregnancy and lactation need up to twice the usual intake, and losses of up to 2 mg a day can continue for two months after delivery. Preterm infants are at risk.
• Drugs: penicillamine, diuretics, sodium valproate, angiotensin receptor blockers.

Daily requirement: 3 mg under 4 years, 5 mg at 4 to 8, 8 mg at 9 to 13, 8 to 9 mg in adult women, 11 mg in adult men, 11 to 12 mg in pregnancy and lactation.