Zinc Explained Simply

1. What Is Zinc?

Zinc is a trace element. The body cannot produce it itself and can store it only to a limited extent. Therefore, it must be regularly taken in through food. It is found in many animal and plant foods. In addition, zinc is available as a supplement, for example in the form of salts or compounds bound to organic carriers. Zinc is administered in cases of insufficient supply. In studies, it is investigated for colds, wound healing and diarrhea in children.

2. Where Is It Found, and What Is It Made From?

Zinc occurs in soils, waters and many foods. It is especially abundant in meat, seafood, legumes and seeds. In the body, zinc is contained in many tissues and enzymes. For supply, zinc is obtained from zinc ores and bound to salts or organic carriers. Common forms are zinc sulfate, zinc gluconate, zinc citrate, zinc picolinate and zinc acetate. Zinc oxide is available for external use.

3. What Does Zinc Do? What Research Shows

Respiratory Tract Infections

In adults without zinc deficiency, zinc somewhat prevented mild respiratory infections 68. In treatment, symptoms subsided earlier, but the data are uncertain 68. In children under five years, preventive zinc reduced the frequency of pneumonia in a review 7. A larger review found no difference in lower respiratory tract infections in children 3. In regions with zinc deficiency, young children with zinc gluconate fell ill again less often 30. In children with pneumonia in the hospital, zinc shortened the hospital stay in two studies 3238. A meta-analysis (joint evaluation of many studies) found fewer deaths from pneumonia in children under five years 2. In adults with COVID-19 in the hospital, intensive care or death occurred less often with zinc acetate 37. This study was small and unblinded 37.

Common Cold

Preventively, zinc hardly changed the risk of colds in a large systematic review 4. With an existing cold, the duration was shorter with zinc 425. The certainty of these data is low. Meta-analyses of lozenges with zinc acetate or zinc gluconate found a significantly shorter duration than with placebo 161718. Two of them evaluate the same patients 1718. A study with commercially available zinc acetate lozenges, however, found no difference 34. After discontinuation, the zinc group there even recovered more slowly 34. Zinc nasal spray with zinc lozenges did not shorten colds in a placebo-controlled study 44.

Immune Function

Two joint evaluations of many studies found lower levels of the inflammatory marker C-reactive protein in the blood with zinc 2123. One concerned diabetes and prediabetes 21, the other also found lower interleukin-6 and tumor necrosis factor-alpha 23. In older nursing home residents with low serum zinc, serum zinc and the number of T cells increased with a higher zinc dose 41. The comparison was with a low zinc dose 41. In HIV patients with zinc deficiency, the activation marker soluble CD14 decreased with zinc gluconate, but other inflammatory markers did not 31. The findings mostly come from small studies in special groups and concern laboratory values.

Diarrhoea in Children

In children with acute diarrhea, zinc shortened the duration in a meta-analysis 22. More children recovered than with placebo (sham treatment), also in persistent diarrhea 22. Another review reaches the same conclusion 19. Preventive zinc reduced the frequency and severity of diarrhea in young children, mostly with low zinc levels 29. A large review of preventive administration also found somewhat fewer diarrheas 3. For mortality from diarrhea, no confirmed difference was shown 23.

Skin

People who regularly undergo blood washing (dialysis) suffered less from itching with zinc gluconate, but not less from dry skin 33. A systematic review (structured summary of all studies) sees only limited evidence that ingested zinc heals skin warts 26. This is most likely the case with zinc deficiency 26. In children with Hirschsprung disease, the skin was less often sore after surgery with zinc 39. With the cancer drug regorafenib, hand-foot skin reactions occurred less often with zinc 43. The skin studies are small and short and use different zinc forms.

Taste

In unexplained taste disorders, zinc gluconate improved taste in a randomized placebo-controlled study 40. A controlled study with zinc picolinate showed a better result in a taste test with filter paper disk method in zinc deficiency taste disorders 45. However, subjective complaints and the whole-mouth test did not improve more than with placebo 45. A second double-blind study with zinc picolinate showed the same pattern 47. A meta-analysis with various zinc salts found improvement in taste disorders more often than with control 14. The individual studies are small and use different zinc forms. It is open which form and dose help for which cause.

Wound Healing

The controlled studies (with comparison group) on wound healing tested zinc only in combinations. A skin care product with prebiotics, panthenol and zinc shortened healing time after cryotherapy 36. In pressure ulcers, polaprezinc, a zinc-carnosine complex, worked better than no treatment 46. L-carnosine alone, however, worked just as well 46. A liquid nutritional supplement with arginine, vitamin C and zinc did not reduce the number of pressure ulcers in a statistically confirmed way 42. From these mixtures, no independent effect of zinc can be derived. A review on supply during operations links low zinc levels with slower wound healing and more infections 20. Whether targeted zinc administration changes this is still open 20.

Other Investigations

Further studies tested zinc for very different questions, from metabolic values to pregnancy and infections. Meta-analyses in diabetes and prediabetes found more favorable blood sugar or blood lipid levels with zinc 911121321. One of them saw a slight increase in LDL cholesterol 13. A broader meta-analysis found no difference in LDL cholesterol, blood pressure and liver enzymes 23. These are laboratory values; whether this leads to fewer cardiovascular diseases remains to be clarified. In menstrual pain, zinc alleviated pain more than placebo in a meta-analysis 15. Mixed preparations concerned, for example, pregnancy 1 or vitamin A in tuberculosis 10; the share of zinc remains open there.

4. How Was Zinc Taken in the Studies?

The studies predominantly used oral zinc forms such as zinc sulfate, zinc gluconate, zinc citrate, zinc picolinate and zinc acetate. In part, zinc was also given under the tongue, as a nasal spray or as a lozenge. Individual investigations tested zinc oxide for external use as well as zinc-L-carnosine in mouth rinses and adhesive suspensions. Form, amount and duration of intake varied considerably between studies. This limits comparability.

5. Is Zinc Safe? Side Effects in the Studies

In the treatment of respiratory infections, mild side effects occurred more often with zinc than with placebo 468. Nausea and irritation in the mouth and nose are mentioned 68. With zinc acetate lozenges, more participants reported side effects than with placebo 34. A zinc nasal spray caused pain in the olfactory area in some participants 44. The authors warn against putting zinc into the nose because of reported loss of smell 44. Serious adverse events were not observed in several evaluations 517. In children, vomiting occurred more often with zinc than without zinc 322. Lower doses caused vomiting less often 2227. In menstrual pain, side effects did not differ in a confirmed way from placebo 15.

All details with tables and sources: full expert page on Zinc