Several double-blind trials indicate that zinc supplements reduce the severity of acne.^{1 , 2 , 3 , 4} In one double-blind trial,⁵ though not in another,⁶ zinc was found to be as effective as oral antibiotic therapy. Doctors sometimes suggest that people with acne take 30 mg of zinc two or three times per day for a few months, then 30 mg per day thereafter. It often takes 12 weeks before any improvement is seen. Long-term zinc supplementation requires 1–2 mg of copper per day to prevent copper deficiency.

Supplementation with zinc brings about complete remission in hereditary acrodermatitis enteropathica. Zinc supplements in the amount of 30 to 150 mg per day are used by people with this condition.⁷ People with acrodermatitis enteropathica need to be monitored by a healthcare professional to ensure that their level of zinc supplementation is adequate and that the zinc supplements are not inducing a copper deficiency.

Blood levels of the antioxidant minerals selenium and zinc were normal in one study of people with Down’s syndrome,⁸ but others have found selenium^{9 , 10} and zinc^{11 , 12 , 13} levels to be low. In some studies more than 60% of patients with Down’s syndrome had low zinc levels.^{14 , 15} A preliminary study of selenium supplementation in children with Down’s syndrome found that the antioxidant activity in the body improved; however, the implications of this finding on the long-term health of these people is unclear.¹⁶ Zinc is critical for proper immune function, and in one preliminary study the majority of patients with Down’s syndrome examined had low zinc levels and low immune cell activity. Supplementation with zinc resulted in improved immune cell activity.¹⁷ In preliminary intervention trials, improved immune cell activity was associated with reduced rates of infection in Down’s syndrome patients given supplemental zinc in the amount of 1 mg per 2.2 pounds of body weight per day.^{18 , 19} A controlled trial, however, did not find zinc, at 25 mg daily for children under 10 years of age and 50 mg for older children, to have these benefits.²⁰ Zinc has other roles in the body; preliminary data have indicated that zinc supplementation, at 1 mg per 2.2 pounds of body weight per day, improved thyroid function in Down’s syndrome patients,^{21 , 22 , 23} and increased growth rate in children with Down’s syndrome.²⁴

Zinc deficiency leads to reduced numbers of sperm and impotence in men.²⁵ The correlation between blood levels of zinc and sperm quality remains controversial. Infertile men have been reported to have lower levels of zinc in their semen, than do men with normal fertility.²⁶ Similarly, men with normal sperm density tend to have higher amounts of zinc in their semen, than do men with low sperm counts.²⁷ However, other studies have found that a high concentration of zinc in the semen is related to decreased sperm motility in infertile men.^{28, 29} A few studies have shown that oral zinc supplementation improves both sperm count^{30, 31} motility,^{32, 33} and the physical characteristics of sperm in some groups of infertile men.³⁴ For infertile men with low semen zinc levels, a preliminary trial found that zinc supplements (240 mg per day) increased sperm counts and possibly contributed to successful impregnation by 3 of the 11 men.³⁵ However, these studies all included small numbers of volunteers, and thus the impact of their conclusions is limited. In a controlled trial, 100 men with low sperm motility received either 57 mg of zinc twice daily or a placebo.³⁶ After three months, there was significant improvement in sperm quality, sperm count, sperm motility, and fertilizing capacity of the sperm. The ideal amount of supplemental zinc remains unknown, but some doctors recommend 30 mg two times per day. Long-term zinc supplementation requires 1–2 mg of copper per day to prevent copper deficiency.

Dietary zinc deficiency is common, and a lack of zinc may reduce the activity of retinol dehydrogenase, an enzyme needed to help vitamin A work in the eye. Zinc helps night blindness in people who are zinc-deficient;³⁷ therefore, many physicians suggest 15 to 30 mg of zinc per day to support healthy vision. Because long-term zinc supplementation may reduce copper levels, 1 to 2 mg of copper per day (depending on the amount of zinc used) is usually recommended for people who are supplementing with zinc for more than a few weeks.

Zinc is known for its ability to reduce copper absorption and has been used successfully in patients with Wilson’s disease,³⁸ with some trials lasting for years years.^{39, 40} Researchers have called zinc a “remarkably effective and nontoxic therapy for Wilson’s disease.”⁴¹ The U.S. Food and Drug Administration has approved the use of zinc to treat Wilson’s disease for maintenance therapy following drug therapy, although some scientists recommend that it be considered for initial therapy as well.⁴²

Zinc has also been used to keep normal copper levels from rising in people with Wilson’s disease who had previously been treated successfully with prescription drugs.⁴³ Zinc (50 mg taken three times per day) has been used for such maintenance therapy,⁴⁴ though some researchers have used the same amount of zinc to successfully treat people with Wilson’s disease who had not received drug therapy.⁴⁵

Zinc is so effective in lessening the body’s burden of copper that a copper deficiency was reported in someone with Wilson’s disease who took too much (480 mg per day) zinc.⁴⁶ Nonetheless, zinc may not help everyone with Wilson’s disease. Sometimes increased copper levels can occur in the liver after zinc supplementation;⁴⁷ however, leading researchers believe this increase is temporary and may not be not harmful.⁴⁸

Zinc supplementation (25 mg or 50 mg three times daily) has also been used to successfully treat pregnant women with Wilson’s disease.⁴⁹ Management of Wilson’s disease with zinc should only be undertaken with the close supervision of a doctor.

Zinc is a component of many enzymes, including some that are needed to repair wounds. Even a mild deficiency of zinc can interfere with optimal recovery from everyday tissue damage, as well as from more serious trauma.^{50, 51} One controlled trial found the healing time of a surgical wound was reduced by 43% with oral supplementation of 50 mg of zinc three times per day, in the form of zinc sulfate.⁵²

Whether oral zinc helps tissue healing when no actual zinc deficiency exists is unclear,⁵³ but doctors often recommend 30 mg of zinc per day for four to six weeks to aid in the healing of wounds. Topical zinc-containing treatments, on the other hand, have improved healing of skin wounds even when there is no deficiency.^{54 , 55} Long-term oral zinc supplementation must be accompanied by copper supplementation to prevent a zinc-induced copper deficiency. Typically, if 30 mg of zinc are taken each day, it should be accompanied by 2 mg of copper. If 60 mg of zinc are used, it should be accompanied by 3 mg of copper each day.

In a double-blind study, supplementing with zinc (23 mg three times per day for three months) decreased the severity of rosacea by about 75%, whereas no improvement occurred in the placebo group. Mild gastrointestinal upset was reported by 12% of the people taking zinc, but no other significant side effects occurred.⁵⁶ Long-term zinc supplementation should be accompanied by a copper supplement, in order to prevent zinc-induced copper deficiency.

Zinc deficiency has also been detected in people with anorexia or bulimia in most,^{57, 58} though not all,⁵⁹ studies. In addition, some of the manifestations of zinc deficiency, such as reduced appetite, taste, and smell, are similar to symptoms observed in some cases of anorexia or bulimia.⁶⁰

In an uncontrolled trial, supplementation with 45–90 mg per day of zinc resulted in weight gain in 17 out of 20 anorexics after 8–56 months.⁶¹ In a double-blind study, 35 women hospitalized with anorexia, given 14 mg of zinc per day, achieved a 10% increase in weight twice as fast as the group that received a placebo.⁶² In another report, a group of adolescent girls with anorexia, some of whom were hospitalized, was found to be consuming 7.7 mg of zinc per day in their diet—only half the recommended amount.⁶³ Providing these girls with 50 mg of zinc per day in a double-blind trial helped diminish their depression and anxiety levels, but had no significant effect on weight gain. Anyone taking zinc supplements for more than a few weeks should also supplement with 1 to 3 mg per day of copper to prevent a zinc-induced copper deficiency.

In a double-blind study, children with ADHD who received 15 mg of zinc per day for six weeks showed significantly greater behavioral improvement, compared with children who received a placebo.⁶⁴ This study was conducted in Iran, and zinc deficiency has been found to be quite common in certain parts of that country. It is not clear, therefore, to what extent the results of this study apply to children living in other countries.

Zinc deficiency has also been linked with recurrent canker sores in preliminary studies⁶⁸ and in one case report.⁶⁹ A preliminary trial found that supplementation with up to 150 mg of zinc per day reduced recurrences of canker sores by 50 to 100%; participants who were zinc deficient experienced the most consistent benefit.⁷⁰ However, a double-blind trial (that did not test people for zinc deficiency) did not find zinc supplements helpful for recurrent canker sores.⁷¹

The malabsorption that occurs in celiac disease can lead to multiple nutritional deficiencies. The most common nutritional problems in people with celiac disease include deficiencies of essential fatty acids, iron, vitamin D, vitamin K, calcium, magnesium, and folic acid.⁷² Zinc malabsorption also occurs frequently in celiac disease⁷³ and may result in zinc deficiency, even in people who are otherwise in remission.⁷⁴ People with newly diagnosed celiac disease should be assessed for nutritional deficiencies by a doctor. Celiac patients who have not yet completely recovered should supplement with a high-potency multivitamin-mineral. Some patients may require even higher amounts of some of these vitamins and minerals—an issue that should be discussed with their healthcare practitioner. Evidence of a nutrient deficiency in a celiac patient is a clear indication for supplementation with that nutrient.

After commencement of a gluten-free diet, overall nutritional status gradually improves. However, deficiencies of some nutrients may persist, even in people who are strictly avoiding gluten. For example, magnesium deficiency was found in 8 of 23 adults with celiac disease who had been following a gluten-free diet and were symptom-free. When these adults were supplemented with magnesium for two years, their bone mineral density increased significantly.⁷⁵

Zinc preparations have been shown to inhibit the replication of herpes simplex in the test tube.⁷⁶ In one study, people with recurrent herpes simplex infections applied a zinc sulfate solution daily to the sores. After healing occurred, the frequency of applications was reduced to once a week for a month, then to twice a month. During an observation period of 16 to 23 months, none of these people experienced a recurrence of their cold sores.⁷⁷

Zinc oxide, the only commercially available form of zinc for topical application, is probably ineffective as a treatment for herpes simplex.⁷⁸ Other forms of topical zinc can be obtained by prescription, through a compounding pharmacist. However, because an excessive concentration of zinc may cause skin irritation, topical zinc should be used only with the supervision of a doctor knowledgeable in its use.

Crohn’s disease often leads to malabsorption. As a result, deficiencies of many nutrients are common. For this reason, it makes sense for people with Crohn’s disease to take a high potency multivitamin-mineral supplement. In particular, deficiencies in zinc, folic acid, vitamin B12, vitamin D, and iron have been reported.^{79 , 80 , 81} Zinc, folic acid, and vitamin B12 are all needed to repair intestinal cells damaged by Crohn’s disease. Some doctors recommend 25 to 50 mg of zinc (balanced with 2 to 4 mg of copper), 800 mcg of folic acid, and 800 mcg of vitamin B12 daily. Iron status should be evaluated by a doctor before considering supplementation.

In a test tube, zinc is capable of inactivating the type of herpes virus responsible for the majority of genital herpes cases.⁸² Topical zinc may therefore help prevent outbreaks of genital herpes. One preliminary study treated people (four of whom had genital herpes) with a 4% zinc sulfate solution applied to the site of the initial outbreak.⁸³ In all cases, the pain, burning, and tingling stopped within 24 hours of beginning the topical zinc therapy. The use of lower concentrations of zinc (0.025–0.05%) has also been shown effective against oral and genital herpes outbreaks.^{84 , 85} While topical zinc has been shown to be helpful, there is no convincing evidence that oral zinc offers the same benefits.⁸⁶

Supplementation with 17 mg of zinc twice a day (in the form of a zinc complex of L-carnosine) enhanced the response to interferon therapy in patients with chronic hepatitis C, in a preliminary trial.⁸⁷ It is not known whether this benefit was due primarily to the zinc or the carnosine, or whether other forms of zinc would have the same effect.

Blood levels of both zinc⁸⁸ and selenium⁸⁹ are frequently low in people with HIV infection. Zinc supplements (45 mg per day) have been shown to reduce the number of infections in people with AIDS.⁹⁰ Zinc supplementation (12 mg per day for women, 15 mg per day for men) also slowed the decline in immune function in HIV-infected adults with low blood levels of zinc.⁹¹

Most,^{92 , 93} but not all,⁹⁴ double-blind studies have shown that elderly people have better immune function and reduced infection rates when taking a multiple vitamin-mineral formula. In one double-blind trial, supplements of 100 mcg per day of selenium and 20 mg per day of zinc, with or without additional vitamin C, vitamin E, and beta-carotene, reduced infections in elderly people, though vitamins without minerals had no effect.⁹⁵ Burn victims have also experienced fewer infections after receiving trace mineral supplements in double-blind research.⁹⁶ These studies suggest that trace minerals may be the most important micronutrients for enhancing immunity and preventing infections in the elderly.

Marginal deficiencies of zinc result in immune function impairments.⁹⁷ In a double-blind study of healthy elderly people, supplementing with 45 mg of zinc per day for one year significantly reduced the frequency of infections.⁹⁸ Some doctors recommend lower amounts of supplemental zinc for people experiencing recurrent infections, such as 25 mg per day for adults and even lower amounts for children (depending on body weight). Zinc lozenges have been found helpful in some studies for the common cold. Long-term zinc supplementation should in most cases be accompanied by a copper supplement in order to prevent zinc-induced copper deficiency.

Alcoholic liver cirrhosis is associated with zinc deficiency.^{99 , 100} In a double-blind trial, zinc acetate supplementation (200 mg three times daily, providing a total of 215 mg of elemental zinc per day), given to cirrhosis patients for seven days, significantly improved portal-systemic encephalopathy (PSE).¹⁰¹ A second trial achieved similar results after three months of treatment.¹⁰² People with cirrhosis sometimes have impaired taste function, and it has been suggested that zinc deficiency may be the cause of this abnormality. Although one study demonstrated that taste problems in cirrhosis are due to the disease process itself and not to zinc deficiency,¹⁰³ a double-blind trial showed that 200 mg three times per day of zinc sulfate (providing 135 mg of elemental zinc per day) for six weeks significantly improved taste function in people with alcoholic liver cirrhosis.¹⁰⁴ A doctor should supervise long-term supplementation of zinc in these amounts.

Two important enzymes in the retina that are needed for vision require zinc. In a double-blind trial, supplementation with 45 mg of zinc per day for one to two years significantly reduced the rate of visual loss in people with macular degeneration.¹⁰⁵ However, in another double-blind trial, supplementation with the same amount of zinc did not prevent vision loss among people with a particular type of macular degeneration (the exudative form).¹⁰⁶

Zinc is also needed for the repair of damaged tissue and has protected against stomach ulceration in animal studies.¹⁰⁷ In Europe, zinc combined with acexamic acid, an anti-inflammatory substance, is used as a drug in the treatment of peptic ulcers.¹⁰⁸ In a small controlled trial, high amounts of zinc accelerated the healing of gastric ulcers compared with placebo.¹⁰⁹ Some doctors suspect that such an exceptionally high intake of zinc may be unnecessary, suggesting instead that people with ulcers wishing to take zinc supplements use only 25 to 50 mg of zinc per day. Even at these lower levels, 1 to 3 mg of copper per day must be taken to avoid copper deficiency that would otherwise be induced by the zinc supplementation.

Experimental animal studies have shown that a zinc salt of the amino acid carnosine exerts significant protection against ulcer formation and promotes the healing of existing ulcers.^{110 , 111} However, because zinc by itself has been shown to be helpful against peptic ulcer, it is not known how much of the beneficial effect was due to the carnosine.^{112 , 113} Clinical studies in humans demonstrated that this compound can help eradicate H. pylori, an organism that has been linked to peptic ulcer and stomach cancer.¹¹⁴ The amount of the zinc carnosine complex used in research studies for eradication of H. pylori is 150 mg twice daily.

In a preliminary study, pregnant women who used a zinc-containing nutritional supplement in the three months before and after conception had a 36% decreased chance of having a baby with a neural tube defect, and women who had the highest dietary zinc intake (but took no vitamin supplement) had a 30% decreased risk.¹¹⁵

Deficient zinc levels have been reported in people with RA.¹¹⁶ Some trials have found that zinc reduced RA symptoms,¹¹⁷ but others have not.^{118 , 119} Some suggest that zinc might only help those who are zinc-deficient,¹²⁰ and, although there is no universally accepted test for zinc deficiency, some doctors check white-blood-cell zinc levels.

Antioxidant nutrients protect the body’s cells from oxygen-related damage. Many studies show that sickle cell anemia patients tend to have low blood levels of antioxidants, including carotenoids, vitamin A, vitamin E, and vitamin C, despite adequate intake.^{121, 122, 123, 124, 125, 126} Low blood levels of vitamin E in particular have been associated with higher numbers of diseased cells in children¹²⁷ and with greater frequency of symptoms in adults.¹²⁸ A small, preliminary trial reported a 44% decrease in the average number of diseased cells in six sickle cell anemia patients given 450 IU vitamin E per day for up to 35 weeks. This effect was maintained as long as supplementation continued.¹²⁹

In another preliminary trial, 13 patients with sickle cell anemia were given two supplement combinations for seven to eight months each. The first combination included 109 mg zinc, 153 IU vitamin E, 600 mg vitamin C, and 400 ml (about 14 ounces) of soybean oil containing 11 grams of linoleic acid and 1.5 grams of alpha linolenic acid. The second combination included 140 IU vitamin E, 600 mg vitamin C, and 20 grams of fish oil containing 6 grams of omega-3 fatty acids. Reduction in diseased cells was observed only during the administration of the first protocol. The authors concluded that zinc was the important difference between the two combinations and may be a protector of red blood cell membranes.¹³⁰

Fish oil alone has also been studied. In a double-blind trial, supplementation with menhaden oil, in the amount of 250 mg per 2.2 pounds of body weight per day for one year, reduced the frequency of severe pain episodes by approximately 45%, compared with placebo.¹³¹ This treatment may work by correcting an imbalance between omega-3 and omega-6 fatty acids that occurs in people with sickle cell anemia.¹³²

The zinc deficiency associated with sickle cell anemia appears to play a role in various aspects of the illness. For example, preliminary research has correlated low zinc levels with poor growth in children with sickle cell anemia.¹³³ In a preliminary trial, 12 people with sickle cell anemia received 25 mg of zinc every four hours for 3 to 18 months.¹³⁴ The number of damaged red blood cells fell from 28% to 18.6%. Addition of 2 mg of copper per day did not inhibit the effect of zinc. (Zinc supplementation in the absence of copper supplementation induces a copper deficiency.) Patients with the highest number of damaged red blood cells had a marked response to zinc, but those with lower levels of damaged cells (less than 20% irreversibly sickled cells) had little or no response.

Chronic leg ulcers occur in about 75% of adults with sickle cell disease. In a controlled trial, sickle cell patients with low blood levels of zinc received 88 mg of zinc three times per day for 12 weeks.¹³⁵ Ulcer healing rate was more than three times faster in the zinc group than in the placebo group. Zinc supplementation (25 mg 3 times per day for 3 months) also decreased the number of infections in adults with sickle cell anemia.¹³⁶

Zinc plays an important role in tissue growth processes important for skin ulcer healing. One study reported that patients with pressure ulcers had lower blood levels of zinc and iron than did patients without pressure ulcers,¹³⁷ and preliminary reports suggested zinc supplements could help some types of skin ulcer.¹³⁸ Supplementation with 150 mg of zinc per day improved healing in a preliminary study of elderly patients suffering from chronic leg ulcers.¹³⁹ Double-blind trials using 135 to 150 mg of zinc daily have shown improvement¹⁴⁰ only in patients with low blood zinc levels,¹⁴¹ and no improvement in leg ulcer healing.^{142, 143} A double-blind trial of 150 mg zinc per day in people with skin ulcers due to sickle cell anemia found that the healing rate was almost three times faster in the zinc group than in the placebo group after six months.¹⁴⁴ Lastly, a preliminary study of patients with skin ulcers due to leprosy found that 50 mg of zinc per day in addition to anti-leprosy medication resulted in complete healing in most patients within 6 to 12 weeks.¹⁴⁵ Long-term zinc supplementation at these levels should be accompanied by supplements of copper and perhaps calcium, iron, and magnesium. Large amounts of zinc (over 50 mg per day) should only be taken under the supervision of a doctor.

Topically applied zinc using zinc-containing bandages has improved healing of leg ulcers in double-blind studies of both zinc-deficient¹⁴⁶ and elderly individuals.¹⁴⁷ Most controlled comparison studies have reported that these bandages are no more effective than other bandages used in the conventional treatment of skin ulcers,^{148 , 149} but one controlled trial found non-elastic zinc bandages superior to alginate dressings or zinc-containing elastic stockinettes.¹⁵⁰ Two controlled trials of zinc-containing tape for foot ulcers due to leprosy concluded that zinc tape was similarly effective, but more convenient than conventional dressings.^{151 , 152}

Zinc is a component of many enzymes, including some that are needed to repair wounds. Even a mild deficiency of zinc can interfere with optimal recovery from everyday tissue damage as well as from more serious trauma.¹⁵³ Trace minerals, such as manganese, copper, and silicon are also known to be important in the biochemistry of tissue healing.^{154, 155, 156, 157} However, there have been no controlled studies of people with sprains or strains to explore the effect of deficiency of these minerals, or of oral supplementation, on the rate of healing.

Test tube studies have shown that propionyl-L-carnitine (a form of L-carnitine) protects red blood cells of people with thalassemia against free radical damage.¹⁵⁸ In a preliminary study, children with beta thalassemia major who took 100 mg of L-carnitine per 2.2 pounds of body weight per day for three months had a significantly decreased need for blood transfusions.¹⁵⁹ Some studies have found people with thalassemia to be frequently deficient in folic acid, vitamin B12,¹⁶⁰ and zinc.^{161 , 162} Researchers have reported improved growth rates in zinc-deficient thalassemic children who were given zinc supplements of 22.5 to 90 mg per day, depending on age.^{163 , 164} Magnesium has been reported to be low in thalassemia patients in some,^{165 , 166} but not all,¹⁶⁷ studies. A small, preliminary study reported that oral supplements of magnesium, 7.2 mg per 2.2 pounds of body weight per day, improved some red blood cell abnormalities in thalassemia patients.¹⁶⁸

Zinc supplements have been used to treat people who had both tinnitus and hearing loss (usually age-related). Of those who had initially low blood levels of zinc, about 25% experienced an improvement in tinnitus after taking zinc (90–150 mg per day for three to six months).¹⁶⁹ Such large amounts of zinc should be monitored by a doctor. Two controlled clinical trials^{170, 171} found no benefit from zinc supplementation (66 mg per day in one double-blind trial) in people with tinnitus. However, participants in these studies were not zinc deficient. Preliminary research suggests that zinc supplementation is only helpful for tinnitus in people who are zinc deficient.¹⁷² A doctor can measure blood levels of zinc.

People with type 1 diabetes tend to be zinc deficient,¹⁷³ which may impair immune function.¹⁷⁴ Zinc supplements have lowered blood sugar levels in people with type 1 diabetes.¹⁷⁵

Some doctors are concerned about having people with type 1 diabetes supplement with zinc because of a report that zinc supplementation increased glycosylation,¹⁷⁶ generally a sign of deterioration of the condition. This trial is hard to evaluate because zinc supplementation increases the life of blood cells and such an effect artificially increases the lab test results for glycosylation. Until this issue is resolved, those with type 1 diabetes should consult a doctor before considering supplementation with zinc.

In a double-blind study, supplementation with oral zinc, in the form of zinc sulfate, for two months resulted in complete disappearance of warts in 87% of people treated, whereas none of those receiving a placebo improved.¹⁷⁹ The amount of zinc used was based on body weight, with a maximum of 135 mg per day. Similar results were seen in another double-blind study.¹⁸⁰ These large amounts of zinc should be used under the supervision of a doctor. Side effects included nausea, vomiting, and mild abdominal pain.

Exercise increases zinc losses from the human body, and severe zinc deficiency can compromise muscle function.^{181 , 182} Athletes who do not eat an optimal diet, especially those who are trying to control their weight or use fad diets while exercising strenuously, may become deficient in zinc to the extent that performance or health is compromised.^{183 , 184} One double-blind trial in women found that 135 mg per day of zinc for two weeks improved one measure of muscle strength.¹⁸⁵ Whether these women were zinc deficient was not determined in this study. A double-blind study of male athletes with low blood levels of zinc found that 20 mg per day of zinc improved the flexibility of the red blood cells during exercise, which could benefit blood flow to the muscles.¹⁸⁶ No other studies of the effects of zinc supplementation in exercising people have been done. A safe amount of zinc for long-term use is 20 to 40 mg per day along with 1 to 2 mg of copper. Higher amounts should be taken only under the supervision of a doctor.

Prostatic secretions are known to contain a high concentration of zinc; that observation suggests that zinc plays a role in normal prostate function. In one preliminary study, 19 men with benign prostatic hyperplasia took 150 mg of zinc daily for two months, and then 50 to 100 mg daily. In 74% of the men, the prostate became smaller.¹⁸⁷ Because this study did not include a control group, improvements may have been due to a placebo effect. Zinc also reduced prostatic size in an animal study but only when given by local injection.¹⁸⁸ Although the research supporting the use of zinc is weak, many doctors recommend its use. Because supplementing with large amounts of zinc (such as 30 mg per day or more) may potentially lead to copper deficiency, most doctors recommend taking 2 to 3 mg of copper per day along with zinc.

Zinc is another mineral antioxidant nutrient that the immune system requires. Zinc deficiency results in lowered immune defenses, and zinc supplementation increases immune activity in people with certain illnesses.¹⁸⁹ As with vitamin A, zinc levels have been observed to fall during the early stages of measles infection and to return to normal several days later.¹⁹⁰ There is evidence that zinc supplements are helpful in specific viral infections,^{191, 192, 193} but there are no data on the effect of zinc on childhood exanthemous infections.

The malabsorption produced by CF may adversely affect mineral absorption as well. Blood concentrations of zinc were low in a group of children with CF.¹⁹⁴ One child with CF was reported to have a severe generalized dermatitis that resolved upon correction of zinc and fatty acid deficiencies by using a formula containing zinc (about 3 mg per day) and medium chain triglycerides (amount not reported).^[REF] In a double-blind trial, supplementation with 30 mg of zinc per day for one year significantly decreased the number of days that children with CF needed antibiotics to treat respiratory infections. The beneficial effect of zinc was more pronounced in children who had low or low–normal plasma zinc levels than in those who had higher levels.¹⁹⁵

People with DH frequently have mild malabsorption (difficulty absorbing certain nutrients) associated with low stomach acid (hypochlorhydria) and inflammation of the stomach lining (atrophic gastritis).¹⁹⁶ Mild malabsorption may result in anemia¹⁹⁷ and nutritional deficiencies of iron, folic acid,^{198 , 199} vitamin B12,^{200 , 201} and zinc.^{202 , 203 , 204} More severe malabsorption may result in loss of bone mass.²⁰⁵ Additional subtle deficiencies of vitamins and minerals are possible, but have not been investigated. Therefore, some doctors recommend people with DH have their nutritional status checked regularly with laboratory studies. These doctors may also recommend multivitamin-mineral supplements and, to correct the low stomach acid, supplemental betaine HCl (a source of hydrochloric acid).

Zinc supplements have also been reported to increase immune function.^{206, 207} As a result, some doctors recommend zinc supplements for people with recurrent ear infections, suggesting 25 mg per day for adults and lower amounts for children. For example, a 30-pound child might be given 5 mg of zinc per day while suffering from OM. Nonetheless, zinc supplementation has not been studied in people with ear infections.

Zinc and vitamin A, nutrients that aid in healing, are commonly used to help people with peptic ulcers. For example, the ulcers of people taking 50 mg of zinc three times per day healed three times faster than those of people who took placebo.²⁰⁸ Since some types of gastritis can progress to peptic ulcer, it is possible that taking it may be useful. Nevertheless, the research does not yet show that zinc specifically helps people with gastritis. The amount of zinc used in this study is very high compared with what most people take (15–40 mg per day). Even at these lower levels, it is necessary to take 1–3 mg of copper per day to avoid a zinc-induced copper deficiency.

Zinc supplementation (20 mg per day) was reported to reduce the incidence of GH in one double-blind trial studying a group of low-income Hispanic pregnant women who were not zinc deficient.²⁰⁹

When iodine deficiency is present, other nutrient levels become important in the development of goiter. Deficiencies of zinc²¹⁰ and manganese²¹¹ can both contribute to iodine-deficiency goiter; however, an animal study found that manganese excess can also be goitrogenic.²¹² It has been suggested that selenium deficiency may contribute to goiter.²¹³ However, when selenium supplements were given to people deficient in both iodine and selenium, thyroid dysfunction was aggravated, and it has been suggested that selenium deficiency may provide some protection when there is iodine deficiency.^{214 , 215} A study of the effects of selenium supplementation at 100 mcg daily in women without selenium deficiency but with slightly low iodine intake found no effect on thyroid function.²¹⁶ The authors concluded that selenium supplementation seems to be safe in people with only iodine deficiency but not in people with combined selenium and iodine deficiencies. In those cases, iodine supplementation has been shown to be most useful.²¹⁷ No studies have been done to evaluate the usefulness of supplementation with zinc or manganese to prevent or treat goiter.

Research has shown that supplementing with chromium (200 mcg per day)²¹⁸ or magnesium (340 mg per day)²¹⁹ can prevent blood sugar levels from falling excessively in people with hypoglycemia. Niacinamide (vitamin B3) has also been found to be helpful for hypoglycemic people.²²⁰ Other nutrients, including vitamin C, vitamin E, zinc, copper, manganese, and vitamin B6, may help control blood sugar levels in diabetics.²²¹ Since there are similarities in the way the body regulates high and low blood sugar levels, these nutrients might be helpful for hypoglycemia as well, although the amounts needed for that purpose are not known.

Laboratory animals with severe, experimentally induced zinc deficiency developed hypothyroidism, whereas moderate zinc deficiency did not affect thyroid function.²²² In a small study of healthy people, thyroid hormone (thyroxine) levels tended to be lower in those with lower blood levels of zinc. In people with low zinc, supplementing with zinc increased thyroxine levels.²²³ One case has been reported of a woman with severe zinc deficiency (caused by the combination of alcoholism and malabsorption) who developed hypothyroidism that was corrected by supplementing with zinc.²²⁴ Although the typical Western diet is marginally low in zinc,²²⁵ additional research is needed to determine whether zinc supplementation would be effective for preventing or correcting hypothyroidism.

Most,^{226 , 227} but not all,²²⁸ double-blind studies have shown that elderly people have better immune function and reduced infection rates when taking a multiple vitamin-mineral formula. In one double-blind trial, supplements of 100 mcg per day of selenium and 20 mg per day of zinc, with or without additional vitamin C, vitamin E, and beta-carotene, reduced infections in elderly people, though vitamins without minerals had no effect.²²⁹ Burn victims have also experienced fewer infections after receiving trace mineral supplements in double-blind research.²³⁰ These studies suggest that trace minerals may be the most important micronutrients for enhancing immunity and preventing infections in the elderly.

Zinc supplements have been reported to increase immune function.^{231, 232} This effect may be especially important in the elderly according to double-blind studies.^{233, 234} Some doctors recommend zinc supplements for people with recurrent infections, suggesting 25 mg per day for adults and lower amounts for children (depending on body weight). However, too much zinc (300 mg per day) has been reported to impair immune function.²³⁵

While zinc lozenges have been shown to be effective for reducing the symptoms and duration of the common cold in some controlled studies, it is not clear whether this effect is due to an enhancement of immune function or to the direct effect of zinc on the viruses themselves.²³⁶

Preliminary studies have reported that low zinc intake is associated with several of the risk factors common in IRS,²³⁷ and a low blood level of zinc is associated with insulin resistance in overweight people.²³⁸ However, people with IRS have not specifically been studied to determine whether they are zinc deficient or whether zinc supplements are helpful for them.

Another group of doctors has reported good results using a combination of zinc, manganese, and vitamin B6 for people with Osgood-Schlatter disease; however, the amounts of these supplements were not mentioned in the report.²³⁹ Most physicians would consider reasonable daily amounts of these nutrients for adolescents to be 15 mg of zinc, 5 to 10 mg of manganese, and 25 mg of vitamin B6. Larger amounts might be used with medical supervision.

One trial studying postmenopausal women combined hormone replacement therapy with magnesium (600 mg per day), calcium (500 mg per day), vitamin C, B vitamins, vitamin D, zinc, copper, manganese, boron, and other nutrients for an eight- to nine-month period.²⁴⁰ In addition, participants were told to avoid processed foods, limit protein intake, emphasize vegetable over animal protein, and limit consumption of salt, sugar, alcohol, coffee, tea, chocolate, and tobacco. Bone density increased a remarkable 11%, compared to only 0.7% in women receiving hormone replacement alone.

Levels of zinc in both blood and bone have been reported to be low in people with osteoporosis,²⁴¹ and urinary loss of zinc has been reported to be high.²⁴² In one trial, men consuming only 10 mg of zinc per day from food had almost twice the risk of osteoporotic fractures compared with those eating significantly higher levels of zinc in their diets.²⁴³ Whether zinc supplementation protects against bone loss has not yet been proven, though in one trial, supplementation with several minerals including zinc and calcium was more effective than calcium by itself.²⁴⁴ Many doctors recommend that people with osteoporosis, as well as those trying to protect themselves from this disease, supplement with 10 to 30 mg of zinc per day.

Zinc is a mineral nutrient important for proper immune system function and wound healing.²⁴⁵ One study found most surgery patients recovering at home had low dietary intakes of zinc.²⁴⁶ Low blood levels of zinc have been reported in patients after lung surgery.^{247, 248} In one study this deficiency lasted for up to seven days after surgery and was associated with higher risk of pneumonia,²⁴⁹ while another study found an association between post-operative zinc deficiency and fatigue.²⁵⁰ Poor post-operative wound healing is also more common in people with zinc deficiency.²⁵¹ Zinc supplements given to patients before surgery prevented zinc deficiency in one study, but the effect of these supplements on post-surgical health was not evaluated.²⁵²

In healthy men, prostatic secretions contain a significant amount of zinc, which has antibacterial activity and is a key factor in the natural resistance of the male urinary tract infection.^{259 , 260} In CBP^{261 , 262 , 263 , 264} and NBP²⁶⁵ these zinc levels are significantly reduced; however, it is not clear whether this indicates a predisposition to, or is the result of, prostatic infection.^{266 , 267} Zinc supplements increased semen levels of zinc in men with NBP in one study,²⁶⁸but not in another.²⁶⁹ While zinc supplements have been associated with improvement of benign prostatic hyperplasia (BPH), according to one preliminary report,²⁷⁰ no research has examined their effectiveness for prostatitis. Nonetheless, many doctors of natural medicine recommend zinc for this condition.