Benefits
Immune System Support
EU regulators accept that zinc contributes to normal immune function. In 50 healthy adults aged 55 to 87, 45 mg a day for 12 months lowered the number of infections versus placebo. In 231 adults with HIV and low zinc, 12 to 15 mg a day for 18 months delayed immune decline. In adults already ill with COVID-19, one trial found fewer ICU admissions and another found no shorter symptoms.
Wound Healing
Zinc plays a role in wound healing, and in older adults zinc deficiency can delay healing. That supports correcting a shortfall rather than taking extra zinc to speed healing when intake is already adequate.
Protein Synthesis and Growth
Zinc is vital for protein synthesis, DNA formation, and cell division, supporting growth and development, particularly in children and pregnant women.
Taste and Smell
Zinc is involved in the sense of taste, and zinc deficiency can interfere with both taste and smell. Correcting a deficiency is the reason to supplement here.
Lower Oxidative Stress Markers in Blood
EU regulators accept that zinc contributes to the protection of cells from oxidative stress. In 50 healthy adults aged 55 to 87, 45 mg a day for 12 months lowered blood oxidative stress markers versus placebo. A pooled analysis of 25 trials (1,428 adults) found zinc lowered malondialdehyde and raised total antioxidant capacity; glutathione did not change.
Clearer Skin
In people with inflammatory acne, 30 mg a day of zinc as gluconate improved the inflammatory score more than placebo over 8 weeks in a 66-person trial. In 332 people it succeeded in 31% versus 63% with the antibiotic minocycline. Oral zinc acne trials overall gave mixed results: about half were positive, most were of poor quality, and doses were often far above the RDA.
Helps Maintain Normal Testosterone When Zinc Is Low
Tested only in men with low zinc. In a small trial of 20 men on kidney dialysis, 50 mg zinc as zinc acetate by mouth for 6 months nearly doubled serum testosterone, with no change on placebo. In 9 older men with marginally low zinc, about 30 mg a day for 3 to 6 months raised it from 8.3 to 16.0 nmol/L, but there was no control group. Nothing here shows a rise in men whose zinc is already adequate.
Mechanism of action
Immune System Support
Zinc is needed for T-cell development and activation and for immune signaling. Laboratory work also suggests zinc can interfere with the replication of some viruses, such as rhinovirus; that is cell-level biology, not a proven effect of swallowing zinc.
Wound Healing
Zinc promotes wound healing by supporting collagen synthesis and fibroblast proliferation, acting as a cofactor for enzymes like matrix metalloproteinases that facilitate tissue remodeling and repair.
Protein Synthesis and Growth
Zinc is required for the activity of hundreds of enzymes, including those that make DNA and RNA, and it stabilizes zinc-finger proteins that control cell division.
Antioxidant Properties
In laboratory studies zinc induces metallothionein, a protein that mops up free radicals, and dampens NADPH oxidase, an enzyme that makes reactive oxygen species. Human trials show lower blood oxidative stress markers but do not show which pathway is responsible.
Hormonal Health
Zinc is a cofactor for enzymes involved in steroid hormone production. Men with moderate or severe zinc deficiency can develop low testosterone, which is why the hormone gains in trials were seen in men with low zinc.
Skin Health
Zinc is thought to act on blemish-prone skin by lowering oil production, calming inflammatory cells and acting against acne bacteria, though the exact mechanism is not fully understood.
Taste and Smell
Zinc enables taste and smell by acting as a cofactor for gustin (carbonic anhydrase VI), an enzyme essential for taste bud function and olfactory receptor signaling, ensuring sensory acuity.
Clinical trials
Randomized double-blind placebo-controlled multicenter trial of oral zinc twice daily for 15 days in adults who tested positive for COVID-19 without organ failure. (Ben Abdallah et al. 2023, Clin Infect Dis)
470 adults with COVID-19 in Tunisia (231 zinc, 239 placebo); 60% were hospitalized.
The combined outcome of death or ICU admission within 30 days was lower on zinc (OR 0.58). ICU admission was 5.2% versus 11.3%; 30-day death, 6.5% versus 9.2%, was not significantly different. Hospital stays were 3.5 days shorter and outpatient symptoms 1.9 days shorter on zinc. This was a treatment study in people with COVID-19 under medical care; zinc supplements are not a treatment for COVID-19.
Open-label randomized factorial trial: zinc gluconate 50 mg a day, vitamin C 8,000 mg a day, both, or usual care for 10 days, with no placebo arm. (Thomas et al. 2021, JAMA Netw Open)
214 outpatients with PCR-confirmed SARS-CoV-2 infection in Ohio and Florida.
The trial was stopped for low conditional power. Days to a 50% drop in symptoms were 5.9 with zinc versus 6.7 with usual care (P=0.45 across the 4 groups), and secondary outcomes did not differ.
Randomized placebo-controlled trial of 12 mg (women) or 15 mg (men) of elemental zinc a day for 18 months. (Baum et al. 2010, Clin Infect Dis)
231 adults with HIV and low plasma zinc.
Zinc cut the likelihood of immunological failure (CD4 count below 200) about 4-fold (relative rate 0.24) and more than halved diarrhea. Viral load and death rates did not differ. HIV is managed with antiretroviral medicines.
Randomized double-blind placebo-controlled trial of zinc gluconate (45 mg elemental zinc a day) for 12 months. (Prasad et al. 2007, Am J Clin Nutr)
50 healthy adults aged 55 to 87 from a senior center.
Infections were significantly less frequent on zinc than on placebo. Plasma oxidative stress markers and TNF-alpha production by blood cells were lower, and plasma zinc was higher.
Systematic review and meta-analysis of 25 clinical trials (1,428 adults) of zinc supplements and inflammation and oxidative stress markers. (Mohammadi et al. 2021, J Trace Elem Med Biol)
1,428 adults across 25 trials.
Zinc lowered malondialdehyde (by 0.78 umol/L), CRP and IL-6 and raised total antioxidant capacity. Nitric oxide and glutathione did not change significantly, and results varied between studies.
Double-blind placebo-controlled trial of zinc gluconate 200 mg a day (30 mg zinc) for 8 weeks. (Dreno et al. 1989, Acta Derm Venereol)
66 people with inflammatory acne (32 zinc, 34 placebo).
The inflammatory lesion score improved significantly more on zinc than on placebo (P<0.02). A later review of this trial reports clinician-rated improvement in 75% versus 23.5%.
Multicenter randomized double-blind trial of 30 mg zinc as gluconate or 100 mg minocycline a day for 3 months, with no placebo arm. (Dreno et al. 2001, Dermatology)
332 people with inflammatory acne.
Clinical success (more than a two-thirds drop in inflamed lesions) was 31.2% with zinc versus 63.4% with minocycline. Side effects in both groups were mostly digestive.
Double-blind placebo-controlled trial of 50 mg elemental zinc as zinc acetate a day for 6 months. (Mahajan et al. 1982, Ann Intern Med)
20 men on hemodialysis with low zinc (10 zinc, 10 placebo).
Plasma zinc, serum testosterone and sperm count rose significantly on zinc, and LH and FSH fell; none of these changed on placebo.
Multicenter randomized placebo-controlled trial of 5 mg folic acid plus 30 mg zinc a day for 6 months in male partners. (Schisterman et al. 2020, JAMA)
2,370 couples planning infertility treatment.
Live birth was 34% versus 35% on placebo, and most semen measures did not differ. Sperm DNA fragmentation rose slightly (29.7% vs 27.2%) and digestive side effects were more common with supplements.