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. These ULs, however, do not apply to people taking zinc under the care of a physician.

Higher intakes can cause nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, headaches, and a metallic taste in the mouth [ 29 , 32 ]. In clinical trials in children, zinc supplementation to treat diarrhea increased the risk of vomiting more than placebo [ , ].

Zinc supplements might interact with several types of medications. For example, zinc can reduce the absorption of some types of antibiotics and penicillamine, a drug used to treat rheumatoid arthritis [ , ]. Other medications, such as thiazide diuretics and certain antibiotics, can reduce zinc absorption [ , ].

More information on zinc is available in the ODS health professional fact sheet on zinc. For information on zinc and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Andrographis paniculata , also known as Chuān Xīn Lián, is an herb that is native to subtropical and Southeast Asia [ ].

Its leaves and other aerial above-ground parts are used in traditional Ayurvedic, Chinese, and Thai medicine for relieving symptoms of the common cold, influenza, and other respiratory tract infections [ ]. The active constituents of andrographis are believed to be andrographolide and related compounds, which are diterpene lactones that might have antiviral, anti-inflammatory, and immune-stimulating effects [ , , ].

Results from several clinical trials suggest that andrographis might reduce the duration of upper respiratory tract infections and the severity of symptoms. One of these trials used a common andrographis preparation called Kan Jang. The trial included 50 men and women age 18 to 50 years with the common cold who took four tablets of Kan Jang each containing 85 mg of an andrographis extract three times daily for 5 days 1, mg total daily dose or placebo within 3 days of developing cold symptoms [ ].

Participants who took Kan Jang experienced milder symptoms, recovered sooner, and took fewer days of sick leave than those who took placebo. In another clinical trial, men and women age 18 to 60 years with upper respiratory tract infections took either KalmCold containing mg of an andrographis extract twice daily or placebo for 5 days [ ].

The results showed no differences in symptom severity during days 1 to 3 of treatment. However, between days 3 and 5, participants who took KalmCold experienced milder symptoms—including cough, nasal discharge, headache, fever, and sore throat but not earache —than those who took placebo. Two systematic reviews and meta-analyses of clinical trials found that andrographis preparations had beneficial effects on symptoms and duration of the common cold.

The more recent of these analyses, published in , included 33 clinical trials including the two described above that evaluated the effects of andrographis alone or in combination with other herbs on symptoms of acute upper and lower respiratory tract infections in a total of 7, participants [ ].

Treatment protocols varied widely, but typical daily doses ranged from to 1, mg andrographis extract for 3 to 7 days; studies compared andrographis with placebo, usual care, or other herbal interventions.

The analyses showed that andrographis significantly reduced the severity of cough, sore throat, and overall symptoms. However, the authors noted that the findings should be interpreted with caution because the studies were heterogenous and many were of poor quality. Similar findings were reported from a systematic review and meta-analysis [ ].

It included six clinical trials including the two described above that administered Kan Jang or KalmCold All studies in this analysis compared andrographis with placebo, not usual care or other herbal interventions as in the meta-analysis described above. Andrographis reduced the frequency and severity of cough to a greater extent than placebo.

Three earlier systematic reviews also showed that andrographis appears to alleviate symptoms of upper respiratory tract infections [ , , ].

Although these findings suggest that andrographis might be useful to manage the symptoms and reduce the duration of upper respiratory tract infections, the evidence has several weaknesses. For example, the studies used different andrographis formulations, and many of the clinical trials were conducted by investigators affiliated with the manufacturer of Kan Jang or KalmCold [ , ].

Clinical trials have found minor adverse effects, including nausea, vomiting, vertigo, skin rashes, diarrhea, and fatigue [ , , ]. Allergic reactions might also occur [ , ]. Findings from some animal studies suggest that andrographis might adversely affect fertility, so experts recommend against its use by men and women during the preconception period and by people who are pregnant [ , , ].

According to animal and laboratory studies, andrographis might decrease blood pressure and inhibit platelet aggregation, so it could interact with antihypertensive and anticoagulant medications by enhancing their effects [ ].

Because of its potential immune-stimulating effects, andrographis might also reduce the effectiveness of immunosuppressants [ , ]. For information on andrographis and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Echinacea, commonly known as purple coneflower, is an herb that grows in North America and Europe [ ].

Although the genus Echinacea has many species, extracts of E. purpurea , E. angustifolia , and E. pallida are the most frequently used in dietary supplements. The echinacea supplements on the market in the United States often contain extracts from multiple species and plant parts [ ].

Echinacea contains volatile terpenes, polysaccharides, polyacetylenes, alkamides, phenolic compounds, caffeic acid esters, and glycoproteins [ ]. Echinacea might have antibacterial activities, stimulate monocytes and natural killer cells, and inhibit virus binding to host cells [ 3 , ].

It might also reduce inflammation by inhibiting inflammatory cytokines [ 3 ]. Most studies of echinacea have assessed whether it helps prevent and treat the common cold and other upper respiratory illnesses, but it has also been used in traditional medicine to promote wound healing [ , ].

Results from clinical trials examining the effects of echinacea for the common cold have been mixed. Overall, studies suggest echinacea might slightly reduce the risk of developing a cold but does not shorten the duration or severity of illness. For example, one clinical trial examined the effects of echinacea on the risk of the common cold in men and women mean age 23 years [ ].

purpurea extract Echinaforce or placebo; if participants came down with a cold during the study, they increased their dose to 4, mg per day. Participants taking echinacea had fewer colds and fewer days with cold symptoms than those taking a placebo. Another clinical trial examined whether echinacea helps treat the common cold in male and female participants age 12 to 80 years who developed cold symptoms within 36 hours before enrollment [ ].

Participants took E. purpurea and E. angustifolia extracts four times a day for a combined dose of 10, mg during the first 24 hours and then 5, mg for 4 days or placebo.

Echinacea did not shorten illness duration or severity. A systematic review and meta-analysis examined the effects of echinacea E.

purpurea , E angustifolia , E. pallida , or more than one form to prevent upper respiratory tract infections or reduce the duration of illness [ ]. Nine clinical trials eight in adults and one in children were included in the prevention meta-analysis portion of this analysis, and seven all in adults were included in the duration meta-analysis, including the two trials described above [ , ].

A Cochrane Review of echinacea use for preventing and treating the common cold had similar results [ ]. The review included 24 clinical trials with a total of 4, participants.

Limited research has also examined whether echinacea is beneficial for influenza. One clinical trial found that echinacea had similar effects to oseltamivir Tamiflu , a medication used to treat influenza.

This trial included male and female participants age 12 to 70 who had had influenza symptoms for up to 48 hours [ ]. Participants took either E. The results showed no difference between E. Purpurea and oseltamivir followed by placebo in rapidity of recovery from influenza after 1 day, 5 days, or 10 days of treatment.

In addition, participants taking echinacea experienced fewer adverse events, especially nausea and vomiting. Additional research is needed to confirm this finding. Echinacea appears to be safe. In rare cases, echinacea can cause allergic reactions [ ].

The safety of echinacea during pregnancy is not known, so experts recommend against the use of echinacea supplements by people who are pregnant [ ]. Echinacea might interact with several medications. For example, echinacea might increase cytochrome P activity, thereby reducing levels of some drugs metabolized by these enzymes [ ].

In addition, echinacea might reduce the effectiveness of immunosuppressants due to its potential immunostimulatory activity [ ]. For information on echinacea and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Elderberry contains many compounds—including anthocyanins, flavonols, and phenolic acids—that might have anti-inflammatory, antiviral, antimicrobial, and immune-stimulating effects [ 3 , ].

Studies of the effects of elderberry have primarily used elderberry extracts, not the berries themselves [ ]. Components of elderberry might help prevent respiratory infections by inhibiting virus binding to host cells and by stimulating the immune system [ ].

A few clinical trials have examined the effects of elderberry on the common cold and influenza. The results from these trials have been mixed. However, overall, they suggest that elderberry might help relieve symptoms of respiratory tract infections.

One clinical trial examined whether elderberry extract helps prevent and treat the common cold [ ]. Elderberry extract did not reduce the number of participants who developed a cold.

However, among participants who did develop a cold, elderberry extract reduced cold duration by about 2 days and reduced the severity of symptoms. A meta-analysis included four clinical trials including the trial described above of the effects of elderberry supplementation on upper respiratory symptoms caused by the common cold or flu in a total of participants age 5 to 59 years [ ].

The analysis showed that elderberry supplementation reduced the duration of upper respiratory symptoms, and the effect was stronger for symptoms of influenza than for those caused by the common cold.

A review included the same four trials as well as one that administered an herbal preparation containing both elderberry and Echinacea purpurea [ ]. The results showed that elderberry might help relieve symptoms of the common cold and influenza when taken close to the onset of symptoms and for up to 2 weeks.

In contrast, in a clinical trial, 87 male and female participants age 5 years and older with influenza for less than 48 hours took 15 ml 5, mg elderberry extract twice daily for ages 5 to 12 years and four times daily for ages 13 and older or placebo for 5 days [ ].

Elderberry had no effect on the duration or severity of illness. A systematic review of five clinical trials of elderberry to treat viral respiratory illnesses found beneficial effects on some, but not all, outcomes [ ].

The results showed that elderberry supplementation for 2 to 16 days might reduce the severity and duration of the common cold and the duration of flu but does not appear to reduce the risk of the common cold.

However, the authors noted that the studies were small, heterogeneous, and of poor quality. Elderberry flowers and ripe fruit appear to be safe for consumption. However, the bark, leaves, seeds, and raw or unripe fruit of S. nigra contain a cyanogenic glycoside that is potentially toxic and can cause nausea, vomiting, diarrhea, dehydration due to diuresis, and cyanide poisoning [ , , ].

The heat from cooking destroys this toxin, so cooked elderberry fruit and properly processed commercial products do not pose this safety concern [ 3 , , , , ]. Elderberry might affect insulin and glucose metabolism, so according to experts, people with diabetes should use it with caution [ ].

The safety of elderberry during pregnancy is not known, so experts recommend against the use of elderberry supplements by people who are pregnant [ , ]. Recent analyses suggest that some elderberry supplements are highly diluted or have been adulterated with a cheaper ingredient, such as black rice extract, instead of elderberry [ , ].

Due to its potential immunostimulatory activity, elderberry might reduce the effectiveness of immunosuppressant medications [ ]. For information on elderberry and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Garlic Allium sativum is a vegetable with a long history of culinary use.

Garlic is also available as a dietary supplement in softgel, capsule, tablet, and liquid forms [ ]. Researchers have studied garlic mainly to determine whether it lowers blood pressure and cholesterol levels, but it might also have antiviral properties [ 32 , ].

These properties are often attributed to two compounds in garlic—allicin and ajoen [ ]. Garlic might also have antimicrobial and antifungal activity [ ].

Some dietary supplements contain aged garlic extract, prepared from sliced garlic that is soaked in an aqueous ethanol solution for up to 20 months.

The extract is then filtered and concentrated [ , ]. Aged garlic extract contains compounds, such as lectins, fructo-oligosaccharide, and N-alpha-fructosyl arginine, that might affect immune cell function [ ].

It also contains S-allyl-L-cysteine and other compounds that might have antioxidant effects and reduce some inflammatory markers [ , ]. Only a few clinical trials have examined whether garlic supplements help prevent or treat the common cold or influenza, and results are inconclusive.

One trial included healthy men and women mean age 26 years who took 2. After 45 days, the researchers took blood samples from the participants and cultured the natural killer cells and gamma delta T cells.

The natural killer cells and gamma delta T cells from participants who took the extract had a higher proliferation rate than those from participants who took placebo.

After 90 days, the number of illnesses colds and influenza did not differ between groups, nor did the average number of symptoms per illness. However, participants who took aged garlic extract reported a smaller total number of symptoms during the study.

Check out Emergen-C recipes at EmergenC. With a variety of flavors and forms to choose from, Emergen-C dietary supplements can help you achieve your wellness goals every day in a delicious way!

Do not exceed suggested use. If you are pregnant, nursing, or taking medication, consult your doctor before use. Keep out of reach of children.

Carton contains individual packets. Do not use if packet seal is torn or broken. Fructose, Sugar, Maltodextrin, Citric Acid. Satisfaction Guarantee If for any reason you are not satisfied with any GSK Consumer Healthcare product, GSK Consumer Healthcare will provide you with a reimbursement within 45 days of the date of purchase.

Please contact GSK Consumer Healthcare directly for more information. Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition. This product is not intended to diagnose, treat, cure, or prevent any disease.

To report an issue with this product or seller, click here. Customer Reviews, including Product Star Ratings help customers to learn more about the product and decide whether it is the right product for them.

Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyzed reviews to verify trustworthiness. Customers like the quality and quantity of the nutritional supplement. They say it helps with flu recovery and prevention, and it really strengthens their immune system.

They also appreciate the perfect amount of vitamins and Vitamin D. However, some customers have mixed opinions on taste. AI-generated from the text of customer reviews. Customers are satisfied with the effect of the nutritional supplement on their skin.

They mention that it really strengthens their immune system, provides awesome immune support, and helps with flu recovery and prevention. This keeps her healthy - she takes it on a daily basis and it really strengthens her immune Helps strengthen my immune system.

Easy to use. Taste great! Will be buying more. Customers are satisfied with the quality of the nutritional supplement. They mention that it is a great product, good stuff, and perfect for their son. This product is perfect!

Customers like the vitamin. They say it's an immune booster and a vitamin suppliment that contains a perfect amount of vitamins and Vitamin D. Some say the nutrients seem good, but it' s not enjoyable to drink. This does a great job as acting as a immune booster and vitamin suppliment I give one packet to my son each day The nutrients seem good , but it's not enjoyable to drink.

Customers are mixed about the taste of the nutritional supplement. Some mention that it tastes great and is easy to use, while others say that the flavor was pretty weird and not enjoyable to drink.

I took this cause I had caught the cold 3 times in 1. I dunno if it worked tbh lol" Read more. Taste is fabulous! Disclaimer : While we work to ensure that product information is correct, on occasion manufacturers may alter their ingredient lists. We recommend that you do not solely rely on the information presented and that you always read labels, warnings, and directions before using or consuming a product.

For additional information about a product, please contact the manufacturer. Content on this site is for reference purposes and is not intended to substitute for advice given by a physician, pharmacist, or other licensed health-care professional.

You should not use this information as self-diagnosis or for treating a health problem or disease. Contact your health-care provider immediately if you suspect that you have a medical problem. Information and statements regarding dietary supplements have not been evaluated by the Food and Drug Administration and are not intended to diagnose, treat, cure, or prevent any disease or health condition.

com assumes no liability for inaccuracies or misstatements about products. Skip to main content. To see product details, add this item to your cart.

You can always remove it later. Quantity: 1 2 3 4 5 6 7 8 9 Quantity: 1. Add to Cart. Enhancements you chose aren't available for this seller. Details To add the following enhancements to your purchase, choose a different seller. Ships from. Sold by. This item is non-returnable This item is non-returnable.

This item is non-returnable, but if the item arrives damaged or defective, you may request a refund or replacement. Read full return policy. This item is non-returnable. Secure transaction Your transaction is secure. We work hard to protect your security and privacy.

Our payment security system encrypts your information during transmission. Learn more. Secure transaction. Customer Service. Add to List. Added to. Unable to add item to List.

Please try again. Sorry, there was a problem. There was an error retrieving your Wish Lists. List unavailable. Image Unavailable Image not available for Color:. VIDEOS ° VIEW IMAGES. Visit the Emergen-C Store. Search this page. Size: 0. Purchase options and add-ons. About this item Includes 10 single-serving packets 0.

Report an issue with this product or seller. Frequently bought together. Get it Feb 20 - Get it as soon as Wednesday, Feb Total price:. To see our price, add these items to your cart. Try again! Added to Cart. Add all 3 to Cart. Some of these items ship sooner than the others. Show details Hide details.

Choose items to buy together. Similar items that may ship from close to you. Page 1 of 1 Start over Page 1 of 1. Previous page.