Zinc

What It Does

Zinc sits at the active site of carbonic anhydrase, alkaline phosphatase, and copper-zinc superoxide dismutase, and it holds zinc-finger proteins in the shape they need to bind DNA. It is required for T-cell development, wound healing, taste, and spermatogenesis. Deficiency causes growth failure in children, hypogonadism, hair loss, diarrhea, poor wound healing, and impaired immunity.

The clinical evidence is narrow. Zinc lozenges started within a day of cold symptoms shortened colds by about a third in a meta-analysis of seven trials, with acetate and gluconate performing similarly (Hemilä 2017). The trials were small and the effect depends on lozenge formulation. In the AREDS trial, 80 mg zinc combined with antioxidants reduced progression to advanced age-related macular degeneration in people with intermediate disease; the formula included 2 mg copper specifically to prevent zinc-induced copper deficiency (AREDS 2001). Zinc for acne, testosterone, or general immunity in people who are not deficient has weak support.

The copper problem is mechanistic. Zinc induces metallothionein in intestinal cells, which binds copper more tightly than zinc and carries it out of the body when those cells are shed. The result is low serum copper and ceruloplasmin, anemia, neutropenia, and a myelopathy that resembles B12 deficiency. Willis described three cases first recognized on bone marrow examination, where the findings can be mistaken for myelodysplastic syndrome (Willis 2005). Heavy use of zinc-containing denture cream caused the same syndrome with serious neurologic disease (Nations 2008). Neurologic damage may not fully reverse after copper is restored.

People at higher risk of low zinc status include vegetarians (phytate binds zinc; needs may run 50% higher), people with Crohn's disease, short bowel, or chronic diarrhea, heavy alcohol users, and people with sickle cell disease.

Forms and Bioavailability

Absorption ratings are broad tiers. Head-to-head human trials rarely support a finer ranking among well-absorbed forms.

Labels column: number of labels named as zinc products that list this form. A product can list more than one form, and some labels do not state a form at all.

In a direct comparison, zinc citrate and zinc gluconate were absorbed equally (about 61%) and zinc oxide less well (about 50%), with some subjects absorbing oxide poorly (Wegmüller 2014). Picolinate's reputation rests on a 1987 crossover study in 15 people that found higher hair, urine, and red cell zinc with picolinate but no difference in plasma zinc (Barrie 1987). It has not been replicated with modern methods.

Elemental content differs widely: gluconate is about 14% zinc, picolinate 21%, citrate and acetate about 30%, oxide 80%. A label that states 50 mg of zinc gluconate delivers about 7 mg of zinc.

Typical Dosing

Supplements commonly provide 15-30 mg of elemental zinc. Long-term intake above the UL can cause copper deficiency.

Food sources: oysters, beef, crab, lobster, pork, fortified breakfast cereals, pumpkin seeds.

What to Look For

Read the elemental zinc line on the panel, then add up every source: multivitamin, standalone zinc, cold lozenges, and any "immune" product. Most people taking zinc need 8-15 mg a day on top of diet, not 50.

For use longer than a few weeks above about 25 mg, take 1-2 mg of copper as well, or choose a product that includes it. Zinc on an empty stomach often causes nausea; taking it with food helps and costs little absorption unless the meal is high in phytate.

For cold lozenges, the formulation matters more than the salt. Citric acid, tartaric acid, and glycine bind zinc and keep it from being released in the mouth. Use them only for the few days of a cold.

Red flags: intranasal zinc products, which have caused permanent loss of smell; 50 mg tablets marketed for daily long-term use; and "immune" blends that hide the zinc dose.

Products on Titrate

26,145 of the 214,745 labels in the NIH Dietary Supplement Label Database list zinc as an active ingredient (13,224 on market). 1,857 are sold as zinc products by name.

Top on-market labels, ranked by label completeness and simplicity:

1. Zinc 25 mg Emerald Labs · 25 mg as glycinate
2. Europen Elderberry + PureWay-C + Zinc Emerald Labs · 10 mg as glycinate
3. Europen Elderberry + PureWay-C + Zinc Emerald Labs · 10 mg as glycinate
4. Magnesium with Zinc and Vitamin D3 KAPPA NUTRITION · 11 mg as bisglycinate
5. Zinc Defense Pure TheraPro Rx · 15 mg

Open supplement search

Zinc does not have its own search category yet. Each product above links to its full label in the NIH database.

Related Tools

• Zinc/Copper Ratio
• Supplement Timing Optimizer
• Zinc Citrate vs Zinc Picolinate
• Zinc Acetate vs Zinc Gluconate
• Zinc Bisglycinate vs Zinc Citrate
• Zinc Bisglycinate vs Zinc Picolinate
• Zinc Citrate vs Zinc Gluconate
• Zinc Citrate vs Zinc Oxide
• Zinc Gluconate vs Zinc Picolinate
• Zinc Oxide vs Zinc Picolinate
• All zinc form comparisons
• All supplement guides

References

NIH Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals.

Barrie SA, et al. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions. 1987;21(1-2):223-228.

Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol. 2001;119(10):1417-1436.

Willis MS, et al. Zinc-induced copper deficiency: a report of three cases initially recognized on bone marrow examination. Am J Clin Pathol. 2005;123(1):125-131.

Nations SP, et al. Denture cream: an unusual source of excess zinc, leading to hypocupremia and neurologic disease. Neurology. 2008;71(9):639-643.

Wegmüller R, et al. Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr. 2014;144(2):132-136.

Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. 2017;8(5):2054270417694291.