Zinc: Daily Needs, Food Sources, Colds and Why High Doses Backfire

Nutrition · By the Well Kept editorial team · Published 2026-11-02

A dish of opened oysters on the half shell next to a flowered plate of lemon slices on a blue tablecloth — Shellfish, and oysters above all, are among the richest food sources of zinc.

Every autumn, zinc lozenges and "immune support" tablets appear next to the cold remedies. Zinc is genuinely essential, and most people get enough from ordinary food. The evidence on colds is weaker than the packaging suggests, and taking too much for too long causes a deficiency of another mineral, copper. Here is what the official bodies and the latest systematic review say.

What zinc does

Zinc is a trace mineral needed by a large number of enzymes. The NHS lists its main roles as making new cells and enzymes, processing the carbohydrate, fat and protein in food, and wound healing; it is also needed for normal immune function, growth and the senses of taste and smell. The body has no dedicated store of zinc to fall back on, so a regular intake from food is needed.

How much you need

Official figures differ, partly because they assume different diets:

Body	Men	Women
NHS (UK)	About 9.5 mg a day (19–64)	About 7 mg a day
US National Academies (NIH ODS)	RDA 11 mg	8 mg; pregnancy 11 mg; breastfeeding 12 mg
EFSA (EU, 2014)	9.4–16.3 mg, depending on phytate intake	7.5–12.7 mg, depending on phytate intake

The European Food Safety Authority gives a range rather than a single figure because of phytate, a compound found in wholegrains, pulses, nuts and seeds that binds zinc in the gut and reduces how much is absorbed. EFSA calculated population reference intakes for phytate intakes of 300, 600, 900 and 1,200 mg a day, a range that covers typical European diets. The more phytate-rich the diet, the higher the zinc requirement. EFSA's full set of values is listed on its dietary reference values page; how to read reference intakes explains what these different terms mean.

Food sources

The NHS lists meat, shellfish, dairy foods such as cheese, bread and cereal products such as wheatgerm as good sources. Oysters contain more zinc per serving than any other common food, and red meat and poultry provide much of the zinc in Western diets. Zinc from animal foods is generally better absorbed than zinc from plant foods, because of phytate. Some breakfast cereals are fortified with zinc.

Plant foods still contribute: pulses (beans, lentils, chickpeas), wholegrains, nuts and seeds all contain zinc. Soaking, sprouting and fermenting, as in leavened bread, reduce phytate and make the zinc easier to absorb.

Who may run low

Zinc deficiency is uncommon in healthy adults in high-income countries. The NIH Office of Dietary Supplements identifies groups more likely to have low intake or status:

people with digestive conditions that reduce absorption or increase losses, such as Crohn's disease, ulcerative colitis, chronic diarrhoea, or after some gastrointestinal surgery;
vegetarians and vegans, because of lower intake from meat and higher phytate intake. Well-planned plant-based diets can provide enough, as discussed in who may need supplements;
pregnant and breastfeeding women, whose needs are higher;
older infants who are exclusively breastfed, once the zinc in breast milk no longer covers their needs;
people with alcohol use disorder or sickle cell disease.

Signs of deficiency include loss of appetite, poor growth in children, frequent infections, slow wound healing, hair loss, diarrhoea, skin changes and changes in taste. None of these is specific to zinc, and blood zinc levels are not a reliable measure of a person's status, so a doctor will consider diet and medical history rather than a single test.

Zinc and the common cold: what the 2024 Cochrane review found

The most complete assessment so far is a Cochrane systematic review published in May 2024. It included 34 randomised, placebo-controlled trials with 8,526 participants, adults and children, using lozenges, tablets, syrups and nasal products.

Prevention: taking zinc regularly may make little or no difference to the risk of catching a cold (9 studies, 1,449 people; low-certainty evidence).
Treatment: started once a cold had begun, zinc may shorten it by about two days on average (8 studies, 972 people), but the evidence is of low certainty and the trials gave very inconsistent results. It is uncertain whether zinc makes symptoms less severe.
Side effects: when zinc was used as treatment, non-serious side effects were probably more common than with placebo, mainly an unpleasant or altered taste and stomach upset (16 studies, 2,084 people; moderate-certainty evidence).

The reviewers note that the trials used very different products and doses. Zinc gluconate lozenges, the most common form tested, were given at 45 to 276 mg a day for 4.5 to 21 days, often well above the long-term upper limits below. Most studies were funded by organisations with commercial links or did not report their funding. The review's conclusion is cautious: zinc may have little or no effect on preventing colds, may shorten colds that have started, and causes more minor side effects.

Nasal zinc deserves particular caution. In 2009, the US Food and Drug Administration warned consumers to stop using three nasal zinc cold products after reports of people losing their sense of smell, in some cases permanently. The evidence on vitamin C, the other classic cold remedy, is covered in vitamin C: colds and high doses.

Upper limits: why more is not better

Zinc and copper compete for absorption in the gut. Over weeks and months, high zinc intakes cause copper deficiency, which the NHS warns can lead to anaemia and weakening of the bones, and which can also cause neurological problems.

NHS: do not take more than 25 mg of zinc supplements a day unless advised to by a doctor.
EFSA (EU): tolerable upper intake level of 25 mg a day for adults, from all sources.
US National Academies: 40 mg a day for adults, from food, drinks and supplements combined.

Large single doses cause nausea, vomiting, stomach cramps and diarrhoea. Zinc can also reduce the absorption of some antibiotics (quinolones and tetracyclines) and other medicines, so doses usually need to be taken apart from them. The site's guide to upper limits compares zinc with the other vitamins and minerals most often taken in excess.

If you are thinking about a supplement

Check the label for the amount of elemental zinc, and add up every product you take: multivitamins, "immune" blends and lozenges often all contain zinc.
For most adults, food covers needs; a multivitamin providing roughly the reference intake is a different thing from high-dose zinc taken for weeks.
Do not use nasal zinc products.
Ask a pharmacist or doctor before using zinc if you take antibiotics or other regular medicines, are pregnant, or have a digestive condition.

In short

Adults need roughly 7–11 mg of zinc a day; EFSA's figures rise with the phytate content of the diet.
Meat, shellfish, dairy, bread and wholegrains supply most people's needs; oysters are the richest source.
A 2024 Cochrane review found zinc may make little or no difference to catching a cold and may shorten one by about two days, on low-certainty evidence and with more side effects.
Keep supplements at or below 25 mg a day unless a doctor advises otherwise; high doses cause copper deficiency.

This page is general information, not medical advice. Talk to a doctor or pharmacist before taking zinc supplements, especially if you are pregnant, take regular medicines or have a long-term health condition.

Sources

NHS, Vitamins and minerals: others (including zinc).
Nault D, Machingo TA, Shipper AG, et al. Zinc for prevention and treatment of the common cold. Cochrane Database of Systematic Reviews 2024;5:CD014914.
EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for zinc. EFSA Journal 2014;12(10):3844; EFSA, Dietary reference values topic page.
NIH Office of Dietary Supplements, Zinc: fact sheet for health professionals.
Institute of Medicine (US) Panel on Micronutrients. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academies Press, 2001.