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 provider.

Key to grades

A
Strong scientific evidence for this use
B
Good scientific evidence for this use
C
Unclear scientific evidence for this use
D
Fair scientific evidence against this use (it may not work)
F
Strong scientific evidence against this use (it likely does not work)

Grading rationale

Evidence gradeCondition to which grade level applies
A

Diarrhea (children)

Studies in developing countries found that zinc may reduce the severity and duration of diarrhea in poorly nourished children, especially those with low zinc levels.
A

Stomach ulcers

The healing process of stomach ulcers may be enhanced through treatment with zinc, although more studies are needed to more clearly determine its effects. Most studies report few or no side effects associated with its use.
A

Zinc deficiency

Zinc deficiency is caused by inadequate intake or absorption, increased zinc excretion, or increased bodily need for zinc. Zinc deficiency symptoms include growth and development problems, hair loss, diarrhea, impotence, eye and skin conditions, and loss of appetite. Other symptoms may include weight loss, delayed wound healing, taste changes, and mental slowness. Zinc can be measured in plasma, red blood cells, white blood cells, and hair.
B

Acne

Zinc taken by mouth or applied to the skin seems to be a safe and effective treatment for acne. However, some results are conflicting, and many studies used combination treatments. More research on the effects of zinc alone are needed.
B

ADHD

Early studies report that zinc may benefit children with attention-deficit hyperactivity disorder (ADHD). Zinc may reduce hyperactive, impulsive, and social problems. Zinc may be more effective for older children with higher body mass index (BMI) scores. Further research is required.
B

Herpes simplex virus

Early research has looked at the use of zinc for herpes types 1 or 2. Several studies used combination treatments, so the exact role of zinc is unclear. However, most results suggest that zinc may be a safe and effective alternative treatment for herpes types 1 and 2.
B

Immune function

Zinc appears to be essential for the immune system, but research on its impact on immune function is limited. Zinc gluconate may benefit immune cells. There are few studies on zinc levels and zinc use in elderly people. Further research is needed before a conclusion can be made.
B

Sickle cell anemia (genetic disease causing irregular blood cell shape)

There is good 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 complications following zinc treatment.
B

Wilson's disease (excess copper levels)

Early research suggests that zinc treatment may be effective in the management of Wilson's disease. More studies are needed to confirm these early results. Galzin® (zinc acetate) is a U.S. Food and Drug Administration (FDA)-approved drug used to block the absorption of copper in people with Wilson's disease. It is meant to be an additional treatment to standard therapy.
C

Age-related macular degeneration (eye disease leading to vision loss)

Most studies have found a lack of positive effect of zinc on macular degeneration. However, some high-quality research has found that zinc may help prevent the disease. Since study results are conflicting, more research is needed before a conclusion can be made.
C

Appetite stimulation (in HIV-infected children)

In early research, supplementation that included zinc in HIV-infected children improved appetite. However, the effects of zinc alone cannot be determined at this time. More studies using zinc alone are needed before a conclusion may be made.
C

Bad breath

Chewing gum containing zinc or rinsing out the mouth with a solution containing zinc seemed to reduce bad breath in early studies. More research is needed before a conclusion may be made.
C

Beta-thalassemia (blood disorder causing reduced hemoglobin production)

Limited research has found that children with beta-thalassemia who took zinc supplements by mouth 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 (iron build-up in the brain and other organs)

Studies suggest a potential role for zinc supplementation in aceruloplasminemia, a blood disorder in which iron builds up in the brain. Further research is required before conclusions may be made.
C

Boils

In early research, boils in people treated with zinc did not reappear. More studies are needed to confirm this potential benefit.
C

Burns

Studies of zinc sulfate supplements given to burn victims to increase healing rate have found mixed results. Further research is needed before a conclusion can be made.
C

Cancer

Early research reports that people undergoing radiation therapy for head and neck cancers had a better outcome after taking zinc than those who did not take zinc. More high-quality research is needed to confirm these findings.
C

Canker sores

Zinc sulfate has been studied for the treatment of canker sores. However, the results are conflicting, and a clear conclusion may not be made at this time.
C

Celiac disease

Early studies suggest a lack of effect of zinc supplements for people with celiac disease that did not respond to other treatment. More research is needed in this area.
C

Chemotherapy side effects

Early research suggests that zinc may have benefits on some side effects of chemotherapy. However, further study is needed before firm conclusions can be made.
C

Closed head injuries (injuries in which the brain stays intact)

Early studies indicate that zinc supplementation may enhance recovery in people with closed head injuries. Further research is needed to confirm these results.
C

Cognitive disorders (children)

Early studies indicate that daily supplementation with zinc may be of limited usefulness for improving cognition in adolescent girls and lead-exposed children. Further research may be needed in this area.
C

Cognitive function

Early studies report that zinc supplementation in people under 70 may benefit cognitive function. More studies are needed before a conclusion may be made.
C

Common cold

Available studies report conflicting results on the impact of zinc on the common cold. Overall, studies suggest that if taken when symptoms begin, zinc may help treat cold symptoms. Effects are strongest in adults. Zinc gluconate is not recommended for sore throats. Further research is needed to clarify which zinc formulas are effective for reducing symptoms. More studies are needed before a firm conclusion may be drawn.
C

Continuous ambulatory peritoneal dialysis (treatment for kidney failure)

Zinc supplementation lacked effect on the nutritional status of people receiving CAPD in early studies. Further research is needed to confirm these results.
C

Critical illness

Zinc is required for a functional immune system. In non-critically ill people, zinc supplementation has been linked to improved immune function. Further research is required in people with critical illness before conclusions may be made.
C

Cutaneous disorders (leishmaniasis)

Early studies suggest that injecting zinc sulfate into lesions in people with leishmaniasis, a parasitic disease caused by a sandfly bite, may help improve symptoms. However, results are mixed, and more research is needed in this area.
C

Cystic fibrosis (mucus build-up in the lungs)

Zinc supplementation does not seem to benefit lung function in children with cystic fibrosis. Further research is needed to confirm available study results.
C

Dandruff

Shampoo containing 1 percent zinc pyrithione has been shown to reduce dandruff in some people. More high-quality research is needed in this area.
C

Dementia

In a small study, zinc supplementation lacked an effect on mental function in adults with senile dementia. Larger, more well-designed trials are needed.
C

Diabetes

Diabetic people typically have lower zinc levels when compared with healthy people. According to early high-quality studies, zinc supplementation in type 2 diabetics may improve zinc level and blood sugar control. Further research is needed before a conclusion can be made.
C

Diabetic nerve pain

Zinc taken by mouth may improve blood sugar control and nerve pain. Further research is needed before a conclusion can be made.
C

Diaper rash

Zinc may reduce the incidence of diaper rash and have a preventive effect. More well-designed trials are needed before a conclusion may be made.
C

Down's syndrome

In several studies, zinc supplements seemed to benefit children with Down's syndrome. However, zinc seems to lack an effect on depressed immune systems. Additional research is needed before a firm conclusion can be made.
C

Dysentery (bloody diarrhea)

Zinc may benefit children with shigellosis, a bacterial infection, as an addition to standard therapy. More well-designed trials are needed before a conclusion may be made.
C

Ear infections

There are mixed results on the effects of zinc for treating ear infections. More research is needed in this area.
C

Eating disorders

Zinc may help treat symptoms of anorexia in young adults. More research is needed to confirm these results.
C

Eczema (long-term skin inflammation)

There are conflicting results on the link between zinc levels and eczema. Early study suggests that zinc may actually increase 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 conclusion can be made.
C

Gilbert's syndrome (genetic disorder that affects bile processing)

Gilbert's syndrome may lead to yellow of the skin and is more common in men. Zinc sulfate supplementation was found to have benefits in early research. Further study is needed to confirm these results.
C

Goiter (enlarged thyroid gland)

Zinc supplementation may affect thyroid hormone profiles in people with goiter. More research is needed before a conclusion may be made.
C

Growth

Studies looking at the effects of zinc on growth have found conflicting results. More research is needed in this area.
C

Gum disease

A few studies have reported a significant reduction in plaque following treatment with zinc rinses. Early research suggests that zinc citrate may reduce the severity of hardened plaque on the gums. However, more studies are needed to confirm such benefits. More research may help to determine zinc's potential effectiveness for other aspects of dental health.
C

Hair loss

Early studies on the use of zinc in treating hair loss have found conflicting results. Additional information is needed before a conclusion can be made.
C

Hepatic encephalopathy (confused thinking due to liver disorders)

Early studies looking at zinc for hepatic encephalopathy have found conflicting results.
C

High cholesterol

Zinc may improve blood cholesterol levels in people undergoing treatment for kidney disease. There is some evidence that zinc may improve the ratio of HDL ("good cholesterol") to LDL ("bad cholesterol"), which would be considered a positive effect. More research is needed before a conclusion can be made.
C

HIV/AIDS

People with HIV/AIDS, especially those with low zinc levels, may benefit from zinc supplementation. Early studies found fewer infections, weight gain, and enhanced immune function. However, findings are conflicting. Further research is needed before a conclusion can be made.
C

Hyperprolactinemia (high levels of prolactin in the blood)

Early research did not report a benefit of zinc in people with high prolactin levels. Further research is required before conclusions may be drawn.
C

Hypothyroidism (reduced thyroid function)

Early research suggests that zinc supplementation may improve thyroid hormone levels in women with reduced thyroid function. More studies are needed before a conclusion may be made.
C

Incision wounds

Although zinc is frequently thought to have positive effects on incision wound healing, few studies have looked at this use. Further research is needed before a conclusion can be made.
C

Infant development / neonatal care

Clinical trial results suggest a lack of positive benefit from zinc on the mental and physical development of infants. More studies on zinc therapy alone are needed before a conclusion may be made.
C

Infections (children)

Zinc may decrease incidence of infection, although this may depend on the type of infection. More research is needed in this area.
C

Infertility

Many studies report benefits of zinc supplements on infertility, although this effect may depend on the cause of infertility. More information is needed before a firm conclusion can be drawn.
C

Inflammatory bowel disease

Studies of zinc supplementation for inflammatory bowel disease have had mixed results. Some research reports positive effects for people with Crohn's disease, while others found a lack of improvement. More research is needed to confirm these results.
C

Kidney function

Early studies show potential improvement in people with kidney dysfunction taking zinc supplements. Zinc supplementation may be suggested only in people with proven zinc deficiency, but for all people with chronic kidney failure, it is questionable. Further research is needed to confirm available study results.
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. More research is needed in this area.
C

Leg ulcers

There are conflicting findings regarding the potential benefit of zinc for healing leg ulcers. All studies, however, reported a lack of or few adverse effects. The healing process of leg ulcers may be enhanced through treatment with zinc, although further studies are needed to determine to which extent zinc may benefit people with leg ulcers.
C

Leprosy (disease that causes sores and nerve damage)

A few studies have examined the use of zinc for leprosy. Studies of zinc taken by mouth have reported positive results, while other research on zinc applied to the skin has reported negative results. Further research is needed before a conclusion can be made.
C

Liver damage

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

Liver inflammation (long-term)

Early studies have shown that zinc in combination with interferon, or interferon and ribavirin, for hepatitis C viral infection lacked significant benefits. Further research may be needed in this area. Recent high-quality evidence suggests that supplementation with polaprezinc may decrease damage to liver cells.
C

Lower respiratory infections in children

Studies suggest that supplementation with zinc may reduce lower respiratory infections in children. Some studies suggest that these effects are apparent only in boys and not girls. Due to conflicting results, further research is needed before a conclusion can be made. Future studies could examine whether adult populations have a similar response.
C

Malaria

Results are conflicting for the effect of zinc on malaria symptoms. Some high-quality studies suggest a lack of effect of zinc supplementation on the severity of malaria. Other studies suggest that zinc supplementation may reduce the number of stays in the hospital and the death rate. Further research is needed.
C

Malnutrition

Zinc has been studied for its effects in malnutrition with mixed results on weight gain. Some research found that zinc supplementation may help prevent diarrhea, pneumonia, and stunting, with conflicting effects on growth.
C

Menstrual cramps

Early research suggests a possible role for zinc supplementation in menstrual cramps. Additional research is needed to confirm these findings.
C

Mood disorders

Zinc supplementation may improve mood states in young women. More research is needed before a conclusion may be made.
C

Mouth and throat inflammation

Zinc sulfate may help improve symptoms of inflammation in the mouth and throat. Further study is required in this area.
C

Mouth sores (caused by radiation)

Radiation may cause the side effect of inflammation inside the mouth, nose, and throat. Research suggests that zinc may lower the degree of inflammation in people undergoing radiation. Further research is needed to confirm these results.
C

Mortality reduction

Evidence from available studies found a lack of association between zinc supplementation and the risk of death among children. Additional research is needed in this area.
C

Muscle cramps (people with liver scarring)

Zinc supplementation may improve muscle cramps in people with liver scarring. Further research is needed to confirm available study results.
C

Parasites

Zinc sulfate injected into the lesions has been found to benefit people with leishmaniasis. Zinc may decrease the severity of parasite infection and reinfection, but seems to lack effect on initial infection. More research is needed to examine how zinc affects parasite life cycles. Recent high-quality studies have found that zinc and vitamin A may reduce infection rate and duration in children. Due to conflicting results, more research is needed before zinc can be recommended for the treatment of parasites.
C

Poisoning (arsenic)

A combination of spirulina extract plus zinc may be useful for the treatment of arsenic poisoning. More research is needed to confirm the effects of zinc alone.
C

Pregnancy

Evidence is lacking to suggest that zinc offers benefits during pregnancy, although there is a possible reduction in labor complications and early deliveries. However, other results suggest a possible benefit of zinc on blood pressure during pregnancy. Further research is needed before a conclusion can be made.
C

Problems with blood sugar metabolism

Zinc supplementation may improve blood sugar tolerance in people with liver scarring. More research is needed before a conclusion may be made.
C

Prostate inflammation (long-term)

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 pressure in people with long-term prostate inflammation. Further research is needed to confirm these results.
C

Psoriasis (long-term skin redness and irritation)

There are only a few studies that examined zinc treatment on symptoms of psoriasis. Although some evidence shows a reduction in pain and joint swelling, other studies found a lack of effect. Further research is needed to clarify these results.
C

Respiratory disease (tumor growth in air passages)

Evidence suggests a possible role for zinc supplementation as an additional therapy for the treatment of tumor growth in the air passages. Further investigation is needed.
C

Respiratory tract infections (upper)

Studies on the effects on zinc on upper respiratory tract infections have produced mixed results. More studies are needed before a conclusion may be made.
C

Rheumatic diseases (long-term pain or inflammation in joints and muscles)

Early studies found that zinc supplementation lacked benefit in people with rheumatic disease. Further research is needed before a conclusion can be made.
C

Rheumatoid arthritis

Most trials did not show significant improvements in arthritis symptoms following zinc treatment. More studies are needed before a conclusion can be made.
C

Ringing in the ears

Studies on the effectiveness of zinc in treating ringing of the ears have found conflicting results. Further research is necessary before a conclusion can be made.
C

Sexual disorders

Several studies have been conducted in men on long-term kidney disease treatment who have sexual disorders. However, the results are conflicting. More studies are needed before a conclusion may be made.
C

Skin damage caused by incontinence (urine leakage)

Early evidence suggests that applying zinc oxide oil to the skin may help manage skin damage in people with urine leakage. Further research is needed to confirm these results.
C

Stress

Zinc may help reduce stress in the elderly. More trials are needed before a conclusion may be made.
C

Taste disturbances

Results from studies investigating the potential role of zinc in treating taste and smell disorders are conflicting. More research is needed to determine if zinc contributes to the treatment of taste and smell disorders.
C

Taste perception (hemodialysis, cancer)

Results from studies investigating the potential role of zinc in treating taste and smell disorders in people with cancer or kidney disease are mixed. Recent studies showed a lack of benefit of zinc supplementation on taste changes in people undergoing radiation therapy for head and neck cancer. Well-designed research is needed in this area.
C

Tinea versicolor (fungal skin infection)

Zinc pyrithione shampoo may be an effective treatment for tinea versicolor. Side effects were not noted in available research. Additional research is needed before a conclusion may be made.
C

Ulcers (foot ulcers)

Zinc hyaluronate may help heal foot ulcers in people with diabetes. More studies are needed before a conclusion may be made.
C

Vaginitis (inflammation of the vagina)

Little research is available on the use of zinc for the treatment of trichomoniasis, a sexually transmitted disease (STD) causing inflammation of the vagina. A zinc sulfate douche and the prescription antibiotic metronidazole may help treat people with this condition. However, more research is needed before a firm conclusion can be made.
C

Viral warts

Early research suggests that zinc sulfate may be effective for viral warts. More studies are needed to clarify early study results.

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 healthcare provider.

Aging (frailty), alcoholism, anti-inflammatory, antioxidant, antiseptic (skin), asthma, birth control, bone diseases, bowel disorders (short bowel syndrome), cleansing (douching), clogged arteries, diabetic eye disease, energy (children), enlarged prostate, eye disorders, human papilloma virus (HPV), Huntington's disease, hyperglycemia (high blood sugar levels), hypoxia (lack of oxygen), menopause, mental disorders, osteoarthritis, pancreatitis (pancreas inflammation), Parkinson's disease, poisoning (nickel), postpartum depression, schizophrenia, seizures, skin disorders, spleen disorders, toxicity, tuberculosis, wound healing (general wounds).

This evidence-based monograph was prepared by The Natural Standard Research Collaboration

www.naturalstandard.com