Zinc

Uses based on scientific evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare professional.

Grade*

Diarrhea (children)

Multiple studies in developing countries found that zinc supplementation in malnourished children with acute diarrhea may reduce the severity and duration of diarrhea, especially in children with low zinc levels.

A

Gastric ulcers

The healing process of gastric ulcers may be enhanced through treatment with zinc, although further studies will be needed to determine to what extent zinc may be beneficial for patients with this condition. Most studies report no or few adverse effects associated with its use.

A

Sickle cell anemia (management)

There is strong scientific evidence to suggest that zinc may help manage or reduce symptoms of sickle cell anemia. Most of these studies reported increased height, weight, immune system function, and testosterone levels and decreased numbers of crises and sickled cells following zinc treatment.

A

Zinc deficiency

Causes: Zinc deficiency is caused by inadequate intake or absorption, increased zinc excretion, or increased bodily need for zinc. Symptoms: Zinc deficiency symptoms include growth retardation, hair loss, diarrhea, delayed sexual maturation, impotence, eye and skin conditions, and loss of appetite. Additional symptoms may include weight loss, delayed wound healing, taste changes, and mental lethargy.Diagnosis: Zinc can be measured in plasma, red blood cells, white blood cells, and hair.

A

Acne vulgaris

Based on high-quality studies, topical or oral use of zinc seems to be a safe and effective treatment for acne vulgaris; however, some studies report no or negative effects of zinc. Additionally, many studies used combination treatments. Several studies have identified a positive correlation between serum zinc levels and severity of acne, while others did not, and it remains to be determined to what degree internal zinc levels may correlate with the severity of acne.

B

Attention deficit hyperactivity disorder (ADHD)

Early studies have shown a correlation between low serum free fatty acids and zinc serum levels in children with attention deficit hyperactivity disorder. Additional studies found that zinc supplements reduced hyperactive, impulsive, and impaired socialization symptoms, but did not reduce attention deficiency symptoms. Zinc supplementation may be a more effective treatment for older children with higher body mass index (BMI) scores.

B

Down's syndrome

In several studies, zinc supplements seemed to counteract hypothyroidism and slightly reduce the number of infections in children with Down syndrome. However, zinc did not seem to improve depressed immune systems. Additional human research is needed before a firm conclusion can be made.

B

Fungal infections (scalp)

Evidence from human trials suggests that zinc pyrithione shampoo may be an effective treatment for tinea versicolor fungal infections of the scalp. No side effects were noted. Additional research is needed before a strong recommendation can be made.

B

Herpes simplex virus

Low-quality studies have been conducted to assess the effects of zinc (topical or taken by mouth) on herpes type I or II. Several of these studies used combination treatments or permitted the continued use of other medications, so the exact role of zinc in those studies is unclear. However, the positive results obtained in most trials suggest that zinc may represent a safe and effective alternative treatment for herpes type I and II and should encourage further research into the topic using well-designed studies.

B

High cholesterol

Zinc may improve blood cholesterol levels in hemodialysis patients. There is some evidence that zinc may improve cholesterol ratio of HDL "good cholesterol" versus LDL "bad cholesterol," which would be considered a positive effect. Well-designed clinical trials are needed before a strong recommendation can be made.

B

Immune function

Zinc appears to be an essential trace element for the immune system, but research on the effect of zinc supplementation on immune function is scant and mostly focuses on patients with specific diseases. Zinc gluconate appears to have beneficial effects on immune cells. There are relatively few studies that examine zinc levels and the effects of zinc supplementation on the health of the elderly population. Further research is needed before a recommendation can be made.

B

Plaque/ gingivitis

A few studies have reported significant reduction in plaque accumulation following treatment with zinc rinses and dentifrices. Preliminary research suggests that zinc citrate dentifrice may reduce the severity and occurrence of supragingival calculus formation. However, more well-designed studies are needed to confirm such benefits. More research might help to determine zinc's potential efficacy in other dental applications.

B

Wilson's disease

Wilson's disease is an inherited disorder of copper metabolism characterized by a failure of the liver to excrete copper, which leads to its accumulation in the liver, brain, cornea, and kidney, with resulting chronic degenerative changes. Early research suggests that zinc treatment may be effective in the management of Wilson's disease. Relatively few cases of adverse effects have been reported, including one case report presenting a fatality; however, it is unclear whether or not the death was caused by zinc. Several studies have been conducted by the same authors, resulting in possible bias. More well-designed trials are needed to confirm these early results.

B

Alopecia (hair loss)

A few studies that examined the efficacy of zinc in treating alopecia report conflicting results. Additional information is needed before a conclusion can be made.

C

Anorexia nervosa

Reports of zinc's effectiveness in treating symptoms of anorexia nervosa observed in young adults are based on small, low-quality studies, but all agree on the beneficial effects of zinc. Well-designed trials with a larger number of participants are needed to confirm these results.

C

Bad breath

Chewing gum containing zinc or rinsing out the mouth with a solution containing zinc seemed to reduce bad breath (halitosis) in early studies.

C

Beta-thalassemia (hereditary disorder)

One small study noted that children with beta-thalassemia who took oral zinc supplements for 1-7 years increased in height more than those who did not take zinc. More studies are needed to confirm these findings.

C

Blood disorders (aceruloplasminemia)

Data from case reports suggest a potential role for zinc supplementation in aceruloplasminemia, a neurodegenerative disease caused by a gene mutation.

C

Boils

In one study, patients with recurrent boils (furunculosis) treated with zinc found their furuncles did not reappear. Well-designed clinical trials are needed to confirm this potential benefit.

C

Burns

Study results of zinc sulfate supplements given to burn victims to increase healing rate yield mixed results. Further research is needed before a recommendation can be made.

C

Chronic prostatitis (CP)

Early studies suggest that zinc supplements taken with antibiotics may be more effective than antibiotics alone in reducing pain, urinary symptoms, quality of life, and maximum urethra closure pressure for patients with chronic prostatitis. Further research is needed to confirm these results.

C

Closed head injuries

Early poorly designed studies indicate that zinc supplementation may enhance neurological recovery in patients with closed head injuries. Further research is needed to confirm these results.

C

Cognitive deficits (children)

Early studies indicate that daily supplementation with zinc may be of limited usefulness for improving cognition in lead-exposed schoolchildren. Further study may be warranted in this area.

C

Common cold

There are conflicting results regarding the effect of zinc formulations in treating duration and severity of common cold symptoms. Although zinc might be beneficial in the treatment of cold symptoms, more studies are needed to clarify which zinc formulations may be most effective, which rhinoviruses are affected by zinc, and if nasal sprays provide a useful alternative application route for zinc treatment. A recent study found no significant differences between zinc nasal spray and placebo.Negative results may be caused by using doses of zinc that are too low or they may be affected by the presence of compounds like citric or tartaric acid, which may reduce efficacy due to chelating of the zinc ion.

C

Crohn's disease

Early studies of zinc supplements in patients with Crohn's disease have found positive results. Well-designed clinical trials are needed to confirm these results.

C

Dandruff

Shampoo containing 1% of zinc pyrithione has been shown to reduce dandruff in some people.

C

Diabetes (type 1 and type 2)

Diabetic patients typically have significantly lower serum zinc levels compared with healthy controls. In early high-quality studies, zinc supplementation for type-2 diabetics may have beneficial effects in elevating serum zinc level and in improving glycemic control that is shown by decreasing HbA1c concentration. Further study is needed before a strong recommendation can be made.

C

Diabetic neuropathy (nerve damage)

Oral zinc supplementation may improve glycemic control and severity of peripheral neuropathy. Further research is needed before a recommendation can be made.

C

Diaper rash

Zinc may reduce the incidence of diaper rash and have a preventative effect.

C

Eczema

There are conflicting data regarding the correlation of zinc serum levels and eczema. One study noted that zinc might have caused an increase in itching after several weeks of supplementation. Additional information is needed to help clarify these results.

C

Exercise performance

Zinc may improve exercise performance in athletes with low serum zinc or zinc deficiencies. Additional evidence is needed before a recommendation can be made.

C

Gilbert's syndrome

Gilbert's syndrome is a common, often inherited disorder that affects processing by the liver of the greenish-brown pigments in bile (called bilirubin). The resulting abnormal increase of bilirubin in the bloodstream can lead to yellowing of the skin (jaundice), but the liver itself remains normal. It is more common in men than women and is named after a French gastroenterologist. Zinc sulfate supplementation seemed to decrease serum unconjugated bilirubin levels in a small study. Well-designed clinical trials are needed to confirm these results.

C

Growth (stunted infants)

Evidence suggests that supplementation with zinc plus iron (but not with zinc alone) may improve linear growth (length) of stunted infants with low hemoglobin.

C

Hepatic encephalopathy

Hepatic encephalopathy is abnormal brain function caused by passage of toxic substances from the liver to the blood. Early high-quality trials of zinc for this indication have yielded conflicting results.

C

Hepatitis C viral infection (chronic)

Early studies have shown that zinc in combination with interferon or interferon and ribavirin for hepatitis C viral infection patients did not show significant benefits, except for lower incidence of gastrointestinal side effects in one study. Further study may be warranted in this area. Recent high-quality evidence suggests that supplementation with polaprezinc in patients undergoing treatment with pegylated interferon alpha-2b and ribavirin may decrease damage to the liver cells.

C

HIV/AIDS

Patients with HIV/AIDS, especially those with low zinc levels, may benefit from zinc supplementation. Some low-quality studies cite reduction in infections, enhanced weight gain, and immune system function, including increased CD4 and CD8 cells. However, other low quality studies conflict with these findings. Further research is needed before a conclusion can be drawn.

C

Hypothyroidism

Case report data suggest zinc supplementation may improve thyroid hormone levels (particularly T3) among women with hypothyroidism.

C

Incision wounds

Although zinc is frequently thought to have beneficial effects on incision wound healing, few studies have investigated this use. Further research is needed before a firm recommendation can be made.

C

Infertility

Many studies report beneficial results of zinc supplements on infertility, as expressed in improved sperm quality and number, although this effect may depend on the cause of infertility. A minor increase in abnormal spermatozoa in subfertile males taking zinc was noted in one study. Additional information is needed before a firm conclusion can be drawn.

C

Kidney function

Early studies show potential improvement in uremic patients taking zinc supplements. Further research is needed to confirm these results. Zinc supplementation may be recommended only in the patients with proven zinc deficiency, but for all chronic renal failure patients it is questionable.

C

Kwashiorkor (malnutrition from inadequate protein intake)

Short-term zinc supplementation may increase weight gain and decrease infections, swelling, diarrhea, anorexia, and skin ulcers in children with extreme malnourishment.

C

Leg ulcers

There are conflicting findings regarding the potential benefit of zinc for healing leg ulcers. All studies, however, reported no or few adverse effects.

C

Leprosy

A few studies have examined the efficacy of zinc treatment in leprosy. Studies of zinc taken by mouth report positive results, while one study of topical zinc reports negative results. Further research is needed before a conclusion can be drawn.

C

Liver cirrhosis

People with alcoholic liver cirrhosis may be deficient in zinc. Preliminary studies suggest that zinc may benefit these patients. Further evidence is needed to confirm these findings.

C

Lower respiratory infections in children

Results from large clinical trials suggest that supplementation with zinc may reduce the incidence and severity of lower respiratory infections. Some studies suggest these effects to be only apparent in boys and not girls. A trend toward increased respiratory infections in children has been noted in one study. A recent study does not support the use of zinc supplementation in the management of acute lower respiratory infections requiring hospitalization in indigenous children living in remote areas. Due to conflicting results, further research is needed before a conclusion can be drawn. Future studies could examine whether these adult populations have a similar response.

C

Macular degeneration

Most studies examining the relationship between dietary zinc intake over many years and macular degeneration have not reported positive correlations. However, one large high-quality study, which examined the efficacy of zinc supplements in preventing loss of visual acuity, found that zinc supplements helped prevent the occurrence of age-related macular degeneration. Since study results are conflicting, additional well-designed clinical trials are needed before a recommendation can be made.

C

Malaria

Results are contradictory for the effect of zinc on malaria symptoms. Some high-quality studies suggest no effect of zinc supplementation on the severity of malaria. Other studies suggest that zinc supplementation may reduce the number of stays in hospital and death rate due to P. falciparum infection. Further well-designed trials are required to address these discrepancies.

C

Menstrual cramps

Case report data suggest a possible role for zinc supplementation in menstrual cramps. Additional study is needed to confirm these findings.

C

Muscle cramps (cirrhosis)

The results of one case series suggest that zinc supplementation may improve muscle cramps in patients with cirrhosis. Further research is needed to confirm these results.

C

Mortality

Evidence from high-quality studies found no association between zinc supplementation and mortality among children. Additional study is needed in this area.

C

Parasites

In a few studies of varying quality, patients with cutaneous leishmaniasis were injected with zinc sulfate intralesionally. One study found zinc sulfate was better than meglumine antimoniate for the first four weeks, but no statistical differences were observed after six weeks. Zinc may decrease the severity of infection and re-infection of S. mansoni, but does not seem to prevent initial infection. More research should be done in this area to examine how zinc affects the S. mansoni life cycle and whether this data can be extrapolated to other species of Schistosoma. The effects of zinc on the rate of parasitic re-infestation have been examined in children. No significant effect of zinc treatment was found. Recent high-quality study data suggest that supplementation with zinc and vitamin A may favorably alter infection rate and duration among children. Due to conflicting results in this area, more research is needed before zinc can be recommended for the treatment of parasites.

C

Poisoning (arsenic)

Results from one study show that a combination of spirulina extract plus zinc may be useful for the treatment of chronic arsenic poisoning with melanosis and keratosis. More research is needed to confirm the effects of zinc alone.

C

Pregnancy

According to multiple reviews, there is no evidence to suggest that zinc supplementation offers benefits during pregnancy, although there is a possible reduction in labor complications and pre-term deliveries. However, results from individual studies suggest a possible benefit of zinc supplementation on blood pressure during pregnancy. Further research is needed before a conclusion can be drawn.

C

Psoriasis

There are only a few studies that examine the efficacy of zinc treatment on symptoms of psoriasis, including psoriasis induced arthritis-like symptoms. One trial noted a reduction in pain and joint swelling. Other studies do not support a role for zinc in alleviating the symptoms of psoriasis. Further, well-designed clinical trials are required to clarify these results.

C

Radiation-induced mucositis

Radiation has the potential side effect of mucositis, which is inflammation of mucous membranes inside of the mouth, nose, and throat. Two trials suggest that zinc may lower the degree of mucositis in patients on radiation. Further research is needed to confirm these results.

C

Respiratory disease (respiratory papillomatosis)

Evidence from case reports suggests a possible role for zinc supplementation as adjuvant therapy in JORRP. This area warrants further investigation.

C

Rheumatoid arthritis

Most trials do not show significant improvements in arthritis symptoms following zinc treatment. Interpretation of some data is difficult because patients in the studies were permitted to continue their previous arthritis medication and most studies used a small number of participants. Well-designed clinical trials are needed before a decision can be made.

C

Skin damage caused by incontinence

Early evidence suggests that topical zinc oxide oil may help manage perianal and buttock skin damage in incontinent patients. Further research is needed to confirm these results.

C

Stomatitis

Zinc sulfate has been studied for the treatment of recurrent aphthous stomatitis (RAS, mouth ulcer). Study results conflict and no clear conclusion can be drawn at this time.

C

Taste perception (hemodialysis, cancer)

Results from studies investigating the potential role of zinc in treating taste and smell disorders are contradictory. Recently, a large high-quality trial showed no evidence of a benefit of zinc supplementation on taste alterations among patients undergoing radiation therapy for head and neck cancer. Well-designed research is needed to determine if zinc contributes to the treatment of taste and smell disorders.

C

Tinnitus

Studies on the efficacy of zinc in treating tinnitus yield contradictory results based on subjective findings. Further research is necessary before a conclusion can be drawn.

C

Trichomoniasis

Little research is available on the efficacy of zinc for the treatment of trichomoniasis, a sexually transmitted disease (STD). One very small study suggests that a zinc sulfate douche and the prescription antibiotic metronidazole may effectively treat patients with recalcitrant trichomoniasis. However, more well-designed human studies are necessary before a firm conclusion can be drawn.

C

Viral warts

Studies have found conflicting results of the effect of zinc on viral warts. Well-conducted studies are needed to clarify these early results.

C

Celiac disease

In a very small study, oral zinc supplements did not seem to improve the clinical condition of patients with unresponsive celiac syndrome.

D

Chronic inflammatory rheumatic disease

Early studies found that zinc supplementation did not seem to benefit patients with chronic inflammatory rheumatic disease.

D

Continuous ambulatory peritoneal dialysis (CAPD)

Zinc supplementation did not improve the nutritional status in patients on CAPD based on one well-designed trial.

D

Cystic fibrosis

Zinc supplementation does not seem to affect clinical status, growth velocity, or lung function in children with cystic fibrosis.

D

Inflammatory bowel disease

Early studies have found that zinc supplementation does not seem to improve inflammatory bowel disease.

D

Pneumonia (children)

Studies have found that zinc supplementation does not seem to lessen the duration of abnormally fast breathing, hypoxia (inadequate oxygen), chest indrawing, inability to feed, lethargy, severe illness, or hospitalization in children.

D

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified health care professional

Acrodermatitis enteropathica, alcoholism, Alzheimer's disease, benign prostate hyperplasia, bladder cancer, bulimia, cancer, diabetic retinopathy, diarrhea (AIDS), encephalopathy, eye disorders (night blindness, retinol pigmentation abnormalities), hypoxia, human papilloma virus, hypogonadism, hyperprolactinemia, liver enlargement and disorders, menopause, nutritional deficiencies (consumption of dirt), pancreatitis, psychosis, Parkinson's disease, poisoning (nickel), schizophrenia, seizures, skin disorders (parakeratosis), smell disorders, spleen disorders (enlargement), tuberculosis, wound healing.