CWeak evidence, or evidence againstMineral
The short answer
The cold evidence is genuinely mixed and dose- and form-dependent. Not worth taking daily on the off-chance.
Who this is actually for
People with a poor diet, malabsorption, or diagnosed deficiency. Some evidence for shortening a cold if started within 24 hours.
What it is legally allowed to claim
Quoted from the EU register of authorised health claims, Regulation (EU) 432/2012. A product may only make these claims if it supplies enough of the nutrient to qualify.
- Zinc contributes to normal cognitive function
- Zinc contributes to the normal function of the immune system
How much is too much
EFSA tolerable upper intake level 25 milligrams per day for adults.
Cautions and interactions
Long-term high doses cause copper deficiency. Zinc reduces absorption of some antibiotics. Lozenges can taste unpleasant and cause nausea.
Ask a pharmacist before you start anything. Interactions with prescribed medicines are the most common way supplements cause harm, and they are easy to check. Bring the actual packet, or a photo of the ingredients panel, because doses and forms vary enormously between products. Nothing here is a substitute for advice about your own situation.