Moderate-intensity exercise can help maintain a healthy immune system. Getting enough sleep. If you get enough sleep, it will help your body fight off sickness and help succeed at the tips mentioned above. Adults should get between hours of sleep each night.

Increasing vitamin intake. Vitamins B6, C and E are all known for their immune-boosting properties. Some foods rich in these vitamins include eggs, bell peppers, spinach and almonds. Immune System Supplements Many products claim to give your immune system the boost it needs to keep you running at your best.

What Weakens Your Immune System On the other hand, there are habits you might have that Hansen says weaken your immune system, rather than boosting it. Check out some spinach recipes here. These cultures may stimulate your immune system to help fight diseases.

Try to get plain yogurts rather than the kind that are flavored and loaded with sugar. You can sweeten plain yogurt yourself with healthy fruits and a drizzle of honey instead.

Yogurt can also be a great source of vitamin D , so try to select brands fortified with this vitamin. Clinical trials are even in the works to study its possible effects on COVID Research so far suggests that vitamin D deficiency may increase the risk for COVID19 and the severity of disease progression in people with the infection.

Experts therefore believe supplementation may protect people with a vitamin D deficiency. However, there is no evidence that vitamin D can treat a COVID19 infection. When it comes to preventing and fighting off colds, vitamin E tends to take a backseat to vitamin C.

However, this powerful antioxidant is key to a healthy immune system. Nuts, such as almonds , are packed with the vitamin and also have healthy fats. Adults only need about 15 mg of vitamin E each day. Sunflower seeds are full of nutrients, including phosphorous , magnesium , and vitamins B6 and E.

Vitamin E is important in regulating and maintaining immune system function. Other foods with high amounts of vitamin E include avocados and dark leafy greens.

Sunflower seeds are also high in selenium. Just 1 ounce contains nearly half the selenium that the average adult needs daily. A variety of studies , mostly performed on animals, have looked at its potential to combat viral infections such as swine flu H1N1.

You may know turmeric as a key ingredient in many curries. This bright yellow, bitter spice has also been used for years as an anti-inflammatory in treating both osteoarthritis and rheumatoid arthritis. Research shows that high concentrations of curcumin , which gives turmeric its distinctive color, can help decrease exercise-induced muscle damage.

Curcumin has promise as an immune booster based on findings from animal studies with antimicrobial properties. More research is needed. Both green and black teas are packed with flavonoids , a type of antioxidant. Where green tea really excels is in its levels of epigallocatechin gallate EGCG , another powerful antioxidant.

Research has suggested that EGCG may have antiviral properties that support the immune system. The fermentation process black tea goes through destroys a lot of the EGCG.

Green tea, on the other hand, is steamed and not fermented, so the EGCG is preserved. Papayas also have a digestive enzyme called papain that has anti-inflammatory effects.

Papayas have decent amounts of potassium , magnesium, and folate , all of which are beneficial to your overall health. Like papayas, kiwis are a rich source of essential nutrients, including folate, potassium, vitamin K , and vitamin C.

The soup may help lower inflammation, which could improve symptoms of a cold. Poultry, such as chicken and turkey, is high in vitamin B6.

About 3 ounces of light turkey or chicken meat contains nearly one-third of your daily recommended amount of B6. Vitamin B6 is an important player in many of the chemical reactions that happen in the body. Stock or broth made by boiling chicken bones contains gelatin , chondroitin, and other nutrients helpful for gut healing and immunity.

Too much zinc can actually inhibit immune system function. You may want to focus on eating a balanced diet with plenty of fresh foods and whole grains, engage in at least minutes of physical activity per week, get enough sleep, manage stress with deep breathing or talk therapy, avoid or quit smoking, and limit alcohol consumption.

Preliminary research suggests vitamin C may be involved in the development and function of white blood cells. Overall, vitamin A supplementation did not affect the risk, severity, or duration of acute or lower respiratory tract infections.

These tolerable upper intake levels ULs, maximum daily intake unlikely to cause adverse health effects , however, do not apply to people taking vitamin A under the care of a physician. Higher intakes can cause severe headache, blurred vision, nausea, dizziness, aching muscles, and coordination problems.

In severe cases, cerebral spinal fluid pressure can increase, leading to drowsiness and, eventually, coma [ 55 ]. Regular consumption of high doses of preformed vitamin A from foods or supplements can cause dry skin, painful muscles and joints, fatigue, depression, and abnormal liver test results.

High intakes of preformed vitamin A can also cause congenital birth defects [ 35 ]. Unlike preformed vitamin A, beta-carotene is not known to be teratogenic or lead to reproductive toxicity.

Therefore, beta-carotene does not have an established UL [ 56 ]. Vitamin A might interact with some medications. For example, orlistat, a weight-loss medication, can decrease the absorption of vitamin A, resulting in low plasma levels in some patients [ 57 ]. In addition, synthetic retinoids derived from vitamin A that are used as oral prescription medicines, such as acitretin used to treat psoriasis, increase the risk of hypervitaminosis A when taken in combination with vitamin A supplements [ 57 ].

More information on vitamin A is available in the ODS health professional fact sheet on vitamin A. Vitamin C, also called ascorbic acid, is an essential nutrient contained in many fruits and vegetables , including citrus fruits, tomatoes, potatoes, red and green peppers, kiwifruit, broccoli, strawberries, brussels sprouts, and cantaloupe.

The RDA for vitamin C is 15 to mg for infants and children, depending on age, and 75 to mg for nonsmoking adults, including those who are pregnant or lactating; people who smoke need 35 mg more per day [ 56 ].

Vitamin C plays an important role in both innate and adaptive immunity, probably because of its antioxidant effects, antimicrobial and antiviral actions, and effects on immune system modulators [ 5 , 32 , ]. Vitamin C helps maintain epithelial integrity, enhance the differentiation and proliferation of B cells and T cells, enhance phagocytosis, normalize cytokine production, and decrease histamine levels [ 4 , 5 , 60 ].

It might also inhibit viral replication [ 13 ]. Vitamin C deficiency impairs immune function and increases susceptibility to infections [ 5 , 58 , 60 ]. People who smoke and those whose diets include a limited variety of foods such as some older adults and people with alcohol or drug use disorders are more likely than others to obtain insufficient amounts of vitamin C [ 61 , 63 ].

In addition, regular consumption of vitamin C might reduce the duration of the common cold and the severity of its symptoms, but taking vitamin C supplements only after symptom onset does not provide consistent benefits [ 5 , 59 ].

Several clinical trials have examined whether vitamin C supplementation reduces the risk of developing the common cold in the general population and those exposed to extreme physical stress. One trial included 92 runners and a control group of 92 nonrunners mostly male, age 25 years or older who took mg per day vitamin C or placebo for 21 days before a kilometer ultramarathon [ 66 ].

Among nonrunners, however, the incidence of upper respiratory tract infections was not different between supplement and placebo users. In addition, the duration of symptoms in nonrunners who took vitamin C was shorter mean 4. A Cochrane Review included 29 clinical trials including the one described above that examined the effects of vitamin C supplementation in 11, participants [ 13 ].

Most trials had participants from the general population, but five trials involved people exposed to extreme physical stress, including marathon runners, skiers, and soldiers in subarctic areas.

The authors noted that extreme physical stress generates oxidative stress, and the antioxidant action of vitamin C might help counteract this effect in people exposed to this type of physical stress [ 13 ].

Findings were positive in a systematic review and meta-analysis that included 24 clinical trials in a total of 10, adults [ 67 ]. Daily doses of vitamin C ranged from less than mg to 2, mg for 5 days to 5 years.

Some evidence suggests that vitamin C supplementation might be more effective in people with low vitamin C status [ 64 ].

For example, a clinical trial included 28 healthy, nonsmoking men age 18 to 35 years who took 1, mg vitamin C or placebo daily for 8 weeks during the peak of the cold season, January through April [ 68 ].

Some researchers believe that high-dose intravenous vitamin C which is classified as a drug in the United States might mitigate the damage caused by sepsis, but evidence from clinical trials is mixed, and some evidence suggests that this treatment may cause harm.

Evidence on the potential harms of intravenous vitamin C for sepsis comes from a clinical trial in Canada, France, and New Zealand that included men and women mean age 65 years with an infection who were in the intensive care unit ICU for 24 hours or less and were treated with vasopressor medications [ 69 ].

On day 28, those treated with intravenous vitamin C had a higher risk of death or organ dysfunction than those treated with a placebo. Other trials have had mixed findings. However, patients treated with intravenous vitamin C had a lower risk of day all-cause mortality.

Two systematic reviews and meta-analyses that examined the effects of intravenous vitamin C in critically ill patients also had mixed findings [ 71 , 72 ]. In some studies, intravenous vitamin C was combined with thiamin and hydrocortisone.

Vitamin C infusion did not affect overall mortality risk. The intravenous vitamin C did not affect organ dysfunction, length of ICU stay, or risk of death 90 days to 1 year after study enrollment.

These ULs, however, do not apply to people taking vitamin C under the care of a physician. Higher vitamin C intakes can cause diarrhea, nausea, and abdominal cramps. High intakes might also cause falsely high or low readings on some blood glucose meters that are used to monitor glucose levels in people with diabetes [ ].

In people with hemochromatosis, high doses of vitamin C could exacerbate iron overload and damage body tissues [ 56 , 61 ]. The Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine recommends that people with hemochromatosis be cautious about consuming vitamin C doses above the RDA [ 56 ].

Vitamin C supplementation might interact with some medications. For example, it might reduce the effectiveness of radiation therapy and chemotherapy by protecting tumor cells from the action of these agents [ 76 ].

Vitamin C might also enhance the absorption of levothyroxine when taken at the same time [ 77 ]. More information on vitamin C is available in the ODS health professional fact sheet on vitamin C. For information on vitamin C and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Vitamin D exists in two forms: vitamin D2 and vitamin D3.

It is an essential nutrient that is naturally present in only a few foods , such as fatty fish including salmon and tuna and fish liver oils. In addition, beef liver, cheese, and egg yolks contain small amounts. Fortified foods, especially fortified milk, provide most of the vitamin D in the diets of people in the United States.

The RDA for vitamin D is 10 to 15 mcg IU to IU for children, depending on age, and 15 to 20 mcg to IU for adults, including those who are pregnant or lactating [ 78 ]. The body can also synthesize vitamin D as a result of sun exposure.

Vitamin D obtained from sun exposure, foods, and supplements is biologically inert until it undergoes two hydroxylations in the body for activation.

The first hydroxylation, which occurs in the liver, converts vitamin D to hydroxyvitamin D [25 OH D]. The second hydroxylation occurs primarily in the kidney and forms the physiologically active 1,dihydroxyvitamin D [1,25 OH 2D]. Serum concentration of 25 OH D is the main indicator of vitamin D status [ 78 ].

However, 25 OH D levels defined as deficient or adequate vary from study to study. In addition to its well-known effects on calcium absorption and bone health, vitamin D plays a role in immune function [ 5 , 58 , ].

Vitamin D appears to lower viral replication rates, suppress inflammation, and increase levels of T-regulatory cells and their activity [ 16 , 58 , ]. In addition, almost all immune cells e. These capabilities suggest that vitamin D can modulate both innate and adaptive immune responses [ 5 , 16 , , 85 , 87 , 88 ].

It also impairs macrophage function and interleukin production [ 5 ]. Dietary surveys indicate that most people in the United States consume less than recommended amounts of vitamin D [ 90 ].

Nevertheless, according to a — analysis of serum 25 OH D concentrations, most people in the United States age 1 year and older have adequate vitamin D status [ 91 ]. Sun exposure, which increases serum 25 OH D levels, is one of the reasons serum 25 OH D levels are usually higher than would be predicted on the basis of dietary vitamin D intakes alone [ 78 ].

Researchers have investigated whether higher vitamin D status can reduce the risk of seasonal infections, having observed that low vitamin D status due to less sun exposure and higher risk of upper respiratory tract infections are more common in the winter [ 87 , 92 ]. An analysis of data on the association between 25 OH D levels and recent upper respiratory tract infections in 18, participants age 12 years and older from the third National Health and Nutrition Examination Survey — suggests that lower vitamin D levels are associated with a higher risk of respiratory tract infections [ 93 ].

In another analysis, vitamin D insufficiency and deficiency were associated with a higher mortality risk from respiratory diseases than vitamin D sufficiency during 15 years of follow-up in 9, adults age 50—75 years in Germany [ 94 ]. Results from clinicals trials have been mixed but suggest that vitamin D supplementation might modestly reduce the risk of respiratory tract infections.

For example, in a clinical trial in Japan, children age 6 to 15 years took 30 mcg 1, IU vitamin D3 or placebo daily during 4 winter months [ 95 ]. In this trial, both groups had adequate mean 25 OH D levels for bone and overall health at baseline.

Results have been mixed from systematic reviews and meta-analyses that have examined the effects of vitamin D supplementation on the risk of pneumonia and other respiratory tract infections.

Results were negative in a Cochrane Review that evaluated the use of vitamin D supplementation for preventing infections, including pneumonia, in children younger than 5 years [ 98 ]. The review included two trials that examined pneumonia incidence in a total of 3, participants; one trial was placebo controlled, and the other had a control group that received no treatment.

A systematic review and meta-analysis of vitamin D supplementation to prevent acute respiratory tract infections mostly upper respiratory tract infections had mixed findings.

This analysis included 25 clinical trials and a total of 10, participants from newborns to adults age 95 years [ 99 ]. Study durations ranged from 7 weeks to 1.

However, vitamin D supplementation was beneficial only in participants who took supplements daily or weekly, not in those who took one or more bolus doses. A subsequent systematic review and meta-analysis by the same research team that included 46 clinical trials and a total of 75, participants age 0 to 95 years found some benefits of vitamin D supplementation [ ].

Other systematic reviews and meta-analyses have also found that vitamin D supplementation helps reduce the risk of respiratory tract infections and influenza in children and adults [ ] and that vitamin D deficiency is associated with an increased risk of community-acquired pneumonia in children and adults [ ].

In addition, serum 25 OH D concentrations are inversely associated with risk and severity of acute respiratory tract infections [ ]. In contrast, a meta-analysis of 30 clinical trials in a total of 30, participants age 3 to 81 years found that vitamin D supplementation did not reduce the risk of respiratory tract infections [ ].

Mixed findings were reported in a meta-analysis of six trials in a total of 6, children and seven trials in a total of 3, adults [ 54 ].

Vitamin D supplementation did not reduce the risk of respiratory tract infections in adolescents and adults in two clinical trials whose results were published in [ , ].

In one of these trials, 34, men and women age 18 to 75 years in Norway who were not taking daily vitamin D supplements took 5 mL cod liver oil containing 10 mcg IU vitamin D3 or placebo for up to 6 months during the winter [ ].

The cod liver oil did not reduce the incidence of acute respiratory infections. The other trial involved 6, participants age 16 years or older in the United Kingdom who were not taking vitamin D supplements [ ]. Half of the participants were offered a vitamin D blood test.

The other participants were not offered vitamin D tests or supplementation, and the study did not use a placebo. Neither lower nor higher doses of vitamin D3 reduced the risk of acute respiratory tract infections.

Researchers have also examined whether vitamin D supplementation helps treat respiratory tract infections, but results suggest that it has limited, if any, benefits.

A meta-analysis included 18 clinical trials in a total of 3, participants with mean ages between 12 months and 62 years [ ]. It assessed whether one-time, daily, or occasional vitamin D doses ranging from 15 to 15, mcg IU to , IU , depending on dosing schedule, for up to 8 months helped treat respiratory infections.

Treatment outcomes differed among trials but included sputum conversion for pulmonary tuberculosis , survival rate, and no need for ICU admission. Vitamin D supplementation had some small beneficial effects on treatment outcomes, but when the authors analyzed only the 12 high-quality trials, the differences between groups in the trials were no longer statistically significant.

Inflammation and comorbidities from HIV infection may also contribute to low vitamin D levels [ ]. Low vitamin D levels could partly explain why people with HIV appear to have a higher risk of major bone fractures [ ].

Vitamin D deficiency might also increase HIV infection severity [ ]. Observational studies show associations between low vitamin D status and increased risk of pulmonary tuberculosis and mortality in people with HIV [ ].

In addition, low levels of vitamin D in pregnant people with HIV are associated with poor fetal and infant growth [ ]. Results from clinical trials, however, have not shown that vitamin D supplementation improves outcomes in people with HIV [ , ].

Vitamin D3 supplementation did not affect rates of mortality or pulmonary tuberculosis. Moreover, vitamin D3 supplementation did not affect secondary outcomes, including risk of HIV progression, viral suppression, comorbidities nausea, vomiting, cough, fever, or diarrhea , changes in body weight, or depression [ ].

Another clinical trial in Tanzania examined the effects of vitamin D3 supplementation during pregnancy and lactation in 2, people with HIV [ ]. Vitamin D3 supplementation did not affect the risk of maternal HIV progression or death. The results also showed no difference in the risk of small-for-gestational-age birth or of infant stunting at 1 year.

Daily intakes of up to 25— mcg 1, IU—4, IU vitamin D, depending on age, in foods and dietary supplements are safe for infants and children, and up to mcg 4, IU is safe for adults, including those who are pregnant or lactating [ 78 ].

These ULs, however, do not apply to people taking vitamin D under the care of a physician. Higher intakes usually from supplements can lead to nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, excessive urination and thirst, and kidney stones.

In extreme cases, vitamin D toxicity causes renal failure, calcification of soft tissues throughout the body including in coronary vessels and heart valves , cardiac arrhythmias, and even death [ ].

Several types of medications might interact with vitamin D. For example, orlistat, statins, and steroids can reduce vitamin D levels [ , ]. In addition, taking vitamin D supplements with thiazide diuretics might lead to hypercalcemia [ ]. More information on vitamin D is available in the ODS health professional fact sheet on vitamin D.

For information on vitamin D and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Vitamin E, also called alpha-tocopherol, is an essential nutrient that is present in several foods , including nuts, seeds, vegetable oils, and green leafy vegetables.

The RDA for vitamin E is 4 to 15 mg for infants and children, depending on age, and 15 to 19 mg for adults, including those who are pregnant or lactating [ 56 ]. Vitamin E is an antioxidant that plays an important role in immune function by helping maintain cell membrane integrity and epithelial barriers and by enhancing antibody production, lymphocyte proliferation, and natural killer cell activity [ 4 , 5 , 15 , 17 , 25 , 58 , 79 , ].

Vitamin E also limits inflammation by inhibiting the production of proinflammatory cytokines [ ]. Human and animal studies suggest that vitamin E deficiency impairs humoral and cell-mediated immunity, is associated with reduced natural killer cell activity, and increases susceptibility to infections [ 5 , , ].

Frank vitamin E deficiency is rare, except in people with intestinal malabsorption disorders [ 56 , 79 ]. Research on the ability of vitamin E to improve immune function tends to use supplemental vitamin E rather than simply ensuring that study participants achieve adequate vitamin E status because it is thought that higher doses may be needed to achieve beneficial effects [ ].

However, study findings have been mixed. However, vitamin E supplementation did not affect the risk of death from pneumonia within 30 days of the initial hospitalization. A few clinical trials that have examined the effects of vitamin E supplementation on respiratory tract infections in infants and young children or in older adults suggest that vitamin E offers limited benefits and might even increase symptom severity.

A clinical trial in a low-income urban area in India examined the effects of mg alpha-tocopherol and mg ascorbic acid twice daily or placebo for 5 days in infants and young children age 2 to 35 months who were hospitalized with severe acute lower respiratory tract infections and receiving standard care [ ].

Supplementation did not affect the time required to recover from illness. Another clinical trial in which healthy men and women age 60 years or older took one of four different treatments daily for about 15 months identified no benefits and, in fact, found potential risks of vitamin E supplementation to prevent respiratory tract infections.

All but one of the participants had adequate vitamin E concentrations at the start of the study. The vitamin E supplements did not affect the incidence of acute respiratory tract infections throughout the trial.

Moreover, participants who took the vitamin E supplement had longer durations of illness, more severe symptoms including fever and activity restrictions , and greater numbers of symptoms than those who did not take vitamin E. Results were also negative in a similar trial in adults age 65 or older living in nursing homes to determine whether daily supplementation with IU vitamin E 91 mg, as dl -alpha-tocopherol for 1 year reduced the risk of upper or lower respiratory tract infections [ ].

Vitamin E supplementation did not affect the incidence of upper or lower respiratory tract infections or the total durations of the infections. Vitamin E supplementation for a median of 6. Among the 5, participants who smoked more than 19 cigarettes per day or did not exercise, however, vitamin E supplementation did not affect the risk of pneumonia.

All intake levels of vitamin E found naturally in foods are considered safe. These ULs, however, do not apply to people taking vitamin E under the care of a physician. Vitamin E supplementation might interact with certain medications, including anticoagulant and antiplatelet medications.

It might also reduce the effectiveness of radiation therapy and chemotherapy by protecting tumor cells from the action of these agents [ 76 , , ]. More information on vitamin E is available in the ODS health professional fact sheet on vitamin E.

For information on vitamin E and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Selenium is an essential mineral contained in many foods , including Brazil nuts, seafood, meat, poultry, eggs, and dairy products as well as bread, cereals, and other grain products.

The RDA for selenium is 15 to 70 mcg for infants and children, depending on age, and 55 to 70 mcg for adults, including those who are pregnant or lactating [ 56 ].

Human and animal studies suggest that selenium helps support both the innate and adaptive immune systems through its role in T-cell maturation and function and in natural killer cell activity [ 2 , 25 , 58 , ].

It may also reduce the risk of infections [ 2 , 15 , 25 , 58 , ]. As a component of enzymes that have antioxidant activities, selenium might help reduce the systemic inflammatory response that can lead to ARDS and organ failure [ 27 , 58 , , ].

Low selenium status in humans has been associated with lower natural killer cell activity, increased risk of some bacterial infections, and increased virulence of certain viruses, including hepatitis B and C [ 2 , 5 , 10 , 15 , 27 , , , ].

However, evidence is conflicting whether selenium supplementation enhances immunity against pathogens in humans [ ]. Studies have also examined whether intravenous selenium which is classified as a drug in the United States benefits adults with sepsis; those who are critically ill and requiring mechanical ventilation; adults who are undergoing elective major surgery; or those who are critically ill from burns, head injury, brain hemorrhage, or stroke [ , , ].

The results of these studies provide no clear evidence of benefit. Selenium status varies by geographic region because of differences in the amounts of selenium in soil and in local foods consumed [ 56 , ].

Selenium deficiency is very rare in the United States and Canada, but low selenium status is common in some areas of the world, such as parts of Europe and China [ , ]. In children and adults with HIV, selenium deficiency is associated with a higher risk of morbidity and mortality [ ].

However, studies that examined whether micronutrient supplementation, including selenium, affects risk of HIV transmission or disease outcomes in children and adults have had mixed results.

An observational study in Thailand did not identify associations between selenium status in children with HIV and treatment outcomes [ ]. This study included boys and girls with HIV median age 7.

Baseline selenium levels all of which were adequate showed no associations with ART treatment outcomes. Clinical trials have found limited beneficial effects of selenium supplementation on immune function in people with HIV. Selenium supplementation provided no benefits in another trial that randomized men and women with HIV mean age Two Cochrane Reviews also concluded that selenium supplements offer little, if any, benefit for people with HIV.

The authors found that evidence was insufficient to determine whether supplementation with selenium alone is beneficial.

Researchers have also examined whether blood selenium levels or selenium supplementation affect pregnancy outcomes in people with HIV. Findings from these studies suggest that low blood selenium levels are associated with a higher risk of preterm delivery and that selenium supplementation might reduce the risk of preterm delivery but has mixed effects on other outcomes.

For example, a cross-sectional study in Nigeria of pregnant individuals age 15—49 years with HIV found that those with a selenium deficiency defined as blood selenium less than 0. In a clinical trial in Nigeria, researchers examined whether selenium supplementation affects pregnancy outcomes and disease progression in 90 pregnant individuals mean age These ULs, however, do not apply to people taking selenium under the care of a physician.

Higher intakes of selenium can cause a garlic odor in the breath and a metallic taste in the mouth as well as hair and nail loss or brittleness [ 56 ].

Other signs and symptoms of excess selenium intakes include nausea, diarrhea, skin rashes, mottled teeth, fatigue, irritability, and nervous system abnormalities. Cisplatin, a chemotherapy agent used to treat ovarian, bladder, lung, and other cancers, can reduce selenium levels in hair, plasma, and serum [ , ].

The evidence from studies examining whether selenium supplementation helps reduce the side effects of cisplatin and other chemotherapy agents is uncertain [ , ]. More information on selenium is available in the ODS health professional fact sheet on selenium. For information on selenium and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Zinc is an essential nutrient contained in a wide variety of foods , including oysters, crab, lobster, beef, pork, poultry, beans, nuts, whole grains, and dairy products.

The RDA for zinc is 2—13 mg for infants and children, depending on age, and 8—12 mg for adults, including those who are pregnant or lactating [ 29 ]. Zinc is involved in numerous aspects of cellular metabolism. It is necessary for the catalytic activity of approximately enzymes and it plays a role in many body processes, including both the innate and adaptive immune systems [ 2 , 5 , 29 , 58 , ].

Zinc also has antiviral and anti-inflammatory properties, and it helps maintain the integrity of tissue barriers, such as the respiratory epithelia [ 5 , 58 , 83 , ].

Zinc deficiency adversely affects immune function by impairing the formation, activation, and maturation of lymphocytes.

In addition, zinc deficiency decreases ratios of helper to suppressor T cells, production of interleukin-2, and activity of natural killer cells and cytotoxic T cells [ 2 , 4 , 5 , 27 , , , ].

Furthermore, zinc deficiency is associated with elevated levels of proinflammatory mediators [ ]. These effects on immune response probably increase susceptibility to infections [ ] and inflammatory diseases, especially those affecting the lungs [ ].

Studies have found associations between low zinc status and higher risk of viral infections [ 79 ], and people with zinc deficiency have a higher risk of diarrhea and respiratory diseases [ 2 ]. Poor zinc status is also common among people with HIV or hepatitis C and is a risk factor for pneumonia in older adults [ 27 , 58 , , , ].

Some research suggests that zinc supplementation increases the number of T cells in the blood of older adults living in nursing homes [ ].

population might obtain marginal amounts of zinc [ ]. Older adults are among the groups most likely to have low intakes. Researchers have hypothesized that zinc could reduce the severity and duration of cold symptoms by directly inhibiting rhinovirus binding and replication in the nasal mucosa and suppressing inflammation [ , ].

In studies of the effects of zinc supplements on the common cold, zinc is usually administered in a lozenge or syrup that temporarily sticks to the mouth and throat, placing the zinc in contact with the rhinovirus in those areas. The results from clinical trials that have examined the effects of supplemental zinc on the common cold have been inconsistent.

Overall, however, supplemental zinc in lozenge or syrup form appears to reduce the duration, but not the severity, of signs and symptoms of the common cold when taken shortly after a person develops a cold [ ].

In one clinical trial that found beneficial effects of zinc on the common cold, 50 adults took a zinc acetate lozenge In comparison with placebo, the zinc lozenges reduced the duration of colds by 3 days and the severity of cold symptoms cough, nasal discharge, and muscle aches [ ].

Results were more mixed in another clinical trial in which adults with experimentally induced colds took lozenges containing zinc gluconate Illnesses lasted 1 day less with the zinc gluconate lozenges than with the placebo, but the lozenges had no effect on symptom severity.

Furthermore, the 5. In a second trial described in the same report, neither zinc gluconate nor zinc acetate lozenges affected the duration or severity of cold symptoms in comparison with placebo in adults with colds [ ].

A systematic review and meta-analysis found that zinc appears to reduce the duration of the common cold but has mixed effects on the severity of signs and symptoms [ ]. It included 28 clinical trials including the three described above with a total of 5, participants mostly adults younger than 65 years who had a community-acquired viral respiratory tract infection or were inoculated with a rhinovirus.

Most trials provided zinc in the form of zinc acetate or gluconate lozenges with total daily zinc doses of 45 to mg for up to 2 weeks, but some trials used nasal sprays or gels. In participants who used products containing zinc, symptoms resolved an average of 2 days earlier than in those who took a placebo.

Zinc also reduced the severity of symptoms on the third day of illness. However, average daily symptom severity did not differ between those who were and were not treated with zinc supplements.

In addition, zinc did not affect the risk of developing a cold after rhinovirus inoculation. Other recent systematic reviews and meta-analyses have also found that zinc shortens the duration of the signs and symptoms of colds but does not reduce the risk of colds [ 54 , 67 , ].

Poor zinc status is associated with greater susceptibility to pneumonia, more severe disease, and higher mortality risk in children [ ]. Several clinical trials have examined the effects of zinc supplementation on the incidence of pneumonia and as an adjunctive treatment for pneumonia. However, most research suggests that the adjunctive use of zinc supplements to treat pneumonia in children does not affect mortality or time to recovery.

A systematic review and meta-analysis included 11 clinical trials in children age 2 to 60 months with mostly severe pneumonia in low- and middle-income countries [ ]. Another meta-analysis of six placebo-controlled trials that included 2, children age 2 to 60 months found that zinc supplementation reduced mortality rates from severe pneumonia but not rates of treatment failure or changes in antibiotic therapy [ ].

Diarrhea is associated with high mortality rates among children in low-income countries, where it causes about , deaths annually [ , ].

Zinc supplementation may benefit children with acute diarrhea, especially in low-income countries, where zinc deficiency is common. Clinical trials show that zinc supplementation helps shorten the duration of diarrhea in children in low-income countries. A Cochrane Review included 33 trials that compared the effects of zinc supplementation with those of placebo in 10, children age 1 month to 5 years who had acute or persistent diarrhea [ ].

Most studies were conducted in Asian countries that had high rates of zinc deficiency. Zinc was administered in the form of zinc acetate, zinc gluconate, or zinc sulphate. In addition, evidence that the authors deemed to have high certainty showed that zinc supplementation reduces the duration of diarrhea in children with signs of malnutrition by about a day.

In children younger than 6 months, however, zinc supplementation did not affect mean duration of diarrhea or persistence of diarrhea for 7 days. A systematic review and meta-analysis had similar findings. It examined the use of zinc alone or in combination with other treatments for acute diarrhea and gastroenteritis in studies in 32, children, mostly from low- and middle-income countries [ ].

Analyses showed that zinc alone or in combination reduced the duration of diarrhea by about ¾ to 1½ days. The authors concluded that zinc was one of the most effective interventions of those examined, especially when it was combined with Saccharomyces boulardii a probiotic or smectite a natural clay that contains minerals , for reducing the duration of acute diarrhea and gastroenteritis in children.

The WHO and UNICEF recommend supplementation with 20 mg zinc per day, or 10 mg for infants younger than 6 months, for 10 to 14 days to treat acute childhood diarrhea [ ].

However, most trials of zinc supplementation for diarrhea have been conducted in low-income countries [ ]. In well-nourished children, zinc supplements might have only a marginal effect on diarrhea duration.

HIV infection reduces the absorption and metabolism of zinc from foods [ ]. In addition, people with HIV often have diarrhea, which can result in excessive losses of zinc.

For these reasons, people with HIV often have low plasma or serum zinc levels. Several clinical trials have found some beneficial effects of zinc supplementation to manage the morbidity and mortality associated with HIV infection. However, findings were less positive in two Cochrane Reviews and another trial not included in either Cochrane Review that assessed the potential benefits of supplementation with micronutrients, including zinc, or placebo in various populations with HIV.

However, zinc supplementation did not affect viral load or mortality rates in this second trial. However, the supplements blunted the rise in hemoglobin concentrations between baseline and 6 weeks after delivery.