Zinc

What it is

Zinc is a mineral with authorised EU claims: it contributes to normal immune system function, cognitive function, normal fertility and reproduction, the maintenance of normal skin, hair and nails, and normal protein synthesis.

At the counter the dose matters: the EFSA tolerable upper level for adults is 25 mg a day from diet plus supplements, and taking more than that for months can cause copper deficiency.

What it does

It is a cofactor for hundreds of enzymes:

• Deficiency is linked to more infections, poor wound healing and loss of appetite or taste.
• If the diet covers it (meat, shellfish, legumes, seeds), a supplement adds no benefit.
• The salts (gluconate, citrate, bisglycinate) have no different claims.

At the counter

When to recommend it

• A diet low in zinc or higher needs, within the daily dose
• Take it with food to avoid nausea
• Space it 2-3 h from quinolones and tetracyclines

When not to

• More than 25 mg a day for weeks or months without monitoring
• With quinolones or tetracyclines taken at the same time
• Without asking whether they already take a multivitamin that contains it

Warnings

• Important ANTIBIOTICS: zinc forms complexes with quinolones and tetracyclines and reduces their absorption; space 2-3 h.
• Caution EXCESS: more than 25 mg a day kept up can cause copper deficiency, anaemia and iron disturbance.
• Caution No health claim on colds or wound healing: do not promise that.
• Worth knowing Nasal zinc has been linked to loss of smell: do not recommend it.