Minerals · 5 min read ·

Zinc: for colds, only briefly

Zinc is essential for many enzymes, and supplements promise strong immunity. What summaries of studies show — and where the upper limit is.

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In a nutshell

1How much zinc

EFSA recommendation 9.4–16.3 mg EFSA: the recommended zinc intake depends on dietary phytate, because phytate reduces zinc absorption. It is 9.4–16.3 mg a day for men and 7.5–12.7 mg for women, depending on how much phytate they eat.1
Upper level 25 mg The tolerable upper intake level for zinc is 25 mg a day for adults, including pregnant and breastfeeding women.2

The forms of zinc in supplements are covered below under Forms and absorption, and all minerals in the article Bioavailability.

2Colds

Moderate evidence — Cochrane 34 studies A review of 34 trials with 8,526 people: zinc taken to prevent colds probably did not reduce the risk. When treating a cold already under way, it may have shortened it by about 2 days; but certainty is low and people had more non-serious side effects.3
Weak evidence −33% A summary of 7 trials with 575 people: zinc lozenges at doses above 75 mg a day shortened colds by 33% on average. Doses above 100 mg a day were not more effective.4

The doses used in cold studies far exceed the 25 mg upper level; they were taken only briefly, for 4.5 to 21 days.2,3

3Forms and absorption

Weak evidence — a small study 61% / 50% In a study of 15 adults, about 61% of zinc was absorbed from zinc citrate and gluconate (10 mg of zinc on an empty stomach), but only 50% from zinc oxide, which does not dissolve in water.5

Phytate from whole grains, pulses and nuts reduces the absorption of zinc from food — which is why EFSA recommends more zinc for people who eat a lot of it.1

In the EU, supplements may contain zinc as acetate, citrate, gluconate, bisglycinate, picolinate, sulphate or oxide, among other forms.6

Weak evidence — case reports 37 cases High doses of zinc over a long time push copper out of the body: in a review of 37 reported cases they led to anaemia and nerve damage. More in the article Copper.7

What to take from this

Sources

Written on , based on studies available at that date. Newer research may change the conclusions.

  1. EFSA (2017). Dietary Reference Values for nutrients: Summary report. EFSA Supporting Publications 14(12):e15121. doi.org/10.2903/sp.efsa.2017.e15121
  2. EFSA (2025). Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Nutrition. efsa.europa.eu
  3. Nault D. et al. (2024). Zinc for prevention and treatment of the common cold. Cochrane Database Syst Rev 5:CD014914. doi.org/10.1002/14651858.CD014914.pub2
  4. Hemilä H. (2017). Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open 8:2054270417694291. doi.org/10.1177/2054270417694291
  5. Wegmüller R. et al. (2014). Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr 144:132–136. doi.org/10.3945/jn.113.181487
  6. Directive 2002/46/EC on food supplements, Annex II — forms of vitamins and minerals permitted in supplements (consolidated version 26 Nov 2025). eur-lex.europa.eu
  7. Dutta A. et al. (2026). Zinc-induced hematologic toxicities: a systematic review of descriptive studies. Biol Trace Elem Res 204:6628–6642. doi.org/10.1007/s12011-026-05136-z

This is general information and does not replace a doctor. Food supplements are not medicines; buy them from trusted sellers and talk to a doctor if you are ill or take medicines.