Immunity boosting vitamins -
The results of studies of the effects of vitamin A supplementation on risk of HIV transmission or disease outcomes in children and adults have been mixed. Two Cochrane Reviews found that vitamin A supplements improved some but not all outcomes examined in children but offered no benefit in adults with HIV infection.
A Cochrane Review included three clinical trials in a total of infants and children with HIV age 5 years or younger [ 45 ]. Another Cochrane Review examined the effects of vitamin A supplementation in four clinical trials that included a total of adults with HIV infection mostly women age 18 to 45 [ 46 ].
None of the trials was adequately powered to assess mortality or morbidity outcomes. Results were negative in another Cochrane Review [ 47 ]. It included five clinical trials conducted in sub-Saharan Africa with a total of 7, pregnant participants with HIV.
Vitamin A supplementation did not affect the risk of mother-to-child transmission of HIV. Largely because of the findings from this analysis, the WHO does not recommend vitamin A supplementation in people with HIV who are pregnant in order to reduce the risk of mother-to-child transmission of HIV [ 48 ].
Most of the findings were also negative in a systematic review of vitamin A supplementation that included 17 clinical trials, conducted mostly in sub-Saharan Africa, in a total of 12, children and adults mostly pregnant women with HIV [ 31 ].
Vitamin A dosing schedules varied widely but commonly included 1, to 3, mcg RAE 5, to 10, IU daily or one-time doses of 15, to , mcg RAE 50, to , IU at baseline or delivery. In addition, it did not affect rates of gastrointestinal and HIV symptoms. However, in one trial included in the review, vitamin A supplementation , mcg RAE [, IU] at delivery reduced the number of clinic visits for some health conditions in women with HIV postpartum and in another trial, supplementation with 15, to 60, mcg RAE 50, to , IU vitamin A depending on age five times per year reduced rates of diarrhea in children with HIV.
Supplements 1, mcg RAE [5, IU] daily plus 60, mcg RAE [, IU] at delivery also reduced the risk of preterm birth in one study in pregnant women with HIV.
Whether maternal vitamin A supplementation affects the morbidity and mortality of breastfed infants was the focus of a cross-sectional study in lactating people with HIV from sub-Saharan Africa [ 49 ]. The study included mothers, of whom took vitamin A supplements after giving birth doses and frequency not reported ; the other did not.
Vitamin A supplementation did not affect infant mortality rates or the risk of cough with difficulty breathing, diarrhea, or fever in the breastfed infants. In , measles was responsible for more than , deaths around the world, mostly in young children in low-income countries [ 50 ].
A major risk factor for severe measles is low vitamin A status [ 5 ]. Research suggests that vitamin A supplementation reduces the risk of measles in children who are at high risk of vitamin A deficiency. However, whether vitamin A supplementation reduces the risk of death from measles is less clear.
However, other studies have found no effect of vitamin A supplementation on risk of death from measles. A systematic review included six clinical trials in a total of 19, children younger than 5 years that examined the effect of vitamin A supplementation on risk of measles and five clinical trials in a total of 88, children that examined the risk of death from measles.
Most studies were conducted in low- and middle-income countries [ 40 ]. Vitamin A doses ranged from 2, mcg RAE 8, IU to 60, mcg RAE , IU , depending on age, and were administered as single doses or over weeks or months.
However, the supplements did not affect risk of death due to measles, according to the results of six clinical trials in a total of 1,, children. Again, findings were mostly negative in a systematic review of 13 clinical trials conducted in India or sub-Saharan Africa of vitamin A supplementation for measles in a total of 1,, infants and children [ 31 ].
Vitamin A supplementation did not reduce the risk of measles in healthy infants and children or mortality rates in those with measles. The supplements also had no effect on immunological responses, except for higher levels of immunoglobulin G antibodies in children taking vitamin A in one study.
However, a few trials found that vitamin A supplementation reduced the risk of a few measles-related complications, such as pneumonia, especially among children with vitamin A deficiency, and severe diarrhea. Vitamin A deficiency is associated with recurrent respiratory tract infections in children [ 33 , 51 ].
However, findings have been mixed from trials of the effects of vitamin A supplementation on the risk and severity of pneumonia and other respiratory tract infections in children [ 33 , 52 ].
In addition, some evidence suggests that doses of vitamin A supplementation that are higher than the WHO recommends might increase the risk of respiratory tract infections among children with normal nutritional status [ 53 ].
Effects were mixed in a meta-analysis of 15 clinical trials in a total of 3, children age not specified that examined the effects of mcg RAE 1, IU to , mcg RAE , IU vitamin A supplementation for several days or weeks on the risk of morbidity and mortality from pneumonia [ 52 ].
Vitamin A supplementation shortened the durations of hospital stays and of signs and symptoms, including fever, cough, and abnormal chest X-rays. However, it did not reduce the risk of death due to pneumonia. Other clinical trials have found that vitamin A supplements do not reduce the risk of respiratory tract infections or of death from these infections.
A Cochrane Review that included 11 clinical trials in a total of 27, children age 6 months to 5 years found that 15, mcg RAE 50, IU to 60, mcg RAE , IU , depending on age, vitamin A supplementation did not significantly affect the risk of lower respiratory tract infections [ 33 ].
In addition, vitamin A supplements did not affect the risk of death due to these infections, according to the results of nine studies in a total of 1,, children that examined this outcome. A separate Cochrane Review also found that vitamin A supplementation 7, mcg RAE [25, IU] or 15, mcg RAE [50, IU] given three times during the first 14 weeks of life did not reduce the risk of respiratory tract infections or death due to such infections in very young infants age 1 to 6 months, although the review included only one trial for each outcome [ 41 ].
Similarly, a systematic review of 16 clinical trials that combined nine trials in a meta-analysis in a total of 32, children found that vitamin A supplementation did not reduce the risk of respiratory tract infections [ 54 ]. Another meta-analysis found that taking vitamin A supplements to reduce the risk of respiratory tract infections might even be harmful in some circumstances [ 53 ].
The analysis included 26 clinical trials that examined acute or lower respiratory tract infections in a total of 50, children from birth to age 11 years. Vitamin A doses ranged from 15, mcg RAE 50, IU to , mcg RAE 1,, IU depending on age and were administered as a single dose or over days, weeks, months, or years.
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.
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.
People over 50 tend to need more of certain nutrients, including vitamin D, calcium , vitamin B6, and vitamin B However, many standard multivitamins may not contain enough vitamin C. Researchers believe that milligrams mg a day is necessary for immune health.
If a person already has a deficiency, they likely need more of that nutrient than a multivitamin contains. Although some studies suggest that supplementation with multiple immune-supporting micronutrients is beneficial, more research is needed. Currently, the strongest evidence suggests that these three micronutrients offer immune support: vitamin C, vitamin D, and zinc.
Vitamin C , or ascorbic acid, is a water-soluble vitamin known for its ability to support a strong immune system. In addition to promoting various cellular functions of the immune system, vitamin C helps the body grow and repair tissue, heal wounds, and absorb iron. Vitamin C is also an antioxidant , meaning that it fights off free radicals, which may help prevent certain cancers and heart disease.
Studies show that a vitamin C deficiency can lead to an impaired immune system and an increased risk of infection. The human body cannot make vitamin C, so it needs to come from foods or dietary supplements. The RDA for vitamin C is 90 mg for male adults and 75 milligrams for female adults.
However, many scientists believe this is not enough and recommend mg per day for maximum health benefits. While most studies show that taking vitamin C does not prevent colds in the general population, it may help reduce the symptoms and severity of a cold.
For example, one meta-analysis from found that taking extra doses of vitamin C may help reduce the duration of the common cold by up to half a day, as well as symptoms such as chest pain, a fever , and chills. Vitamin C supplementation may be even more beneficial for people who perform heavy physical activity.
Vitamin D plays a critical role in keeping the immune system strong so that the body can fight off bacterial and viral illnesses, such as a cold. Some clinical trials suggest that supplementation of international units IU , or 10 micrograms mcg , of vitamin D per day may help prevent the common cold.
Other studies show that vitamin D treatment can reduce respiratory tract infections, especially in those with a vitamin D deficiency.
Some researchers also believe that there is a link between vitamin D deficiency and an increased risk of COVID hospitalization, though there is controversy about this claim.
In some cases, it has been used to minimize the impact of socioeconomic factors for at-risk groups. Many experts believe that the current vitamin D RDA of IU 15 micrograms for people up to age 70 and IU 20 micrograms for people over 70 is not enough to support healthy immune function.
However, the evidence remains inconclusive, and finding the dosage that best supports immune function requires further research.
A zinc deficiency can weaken the immune system by impairing the formation, activation, and maturation of lymphocytes, white blood cells that are an active part of the immune system. Several studies suggest that low zinc levels can increase the risk of viral infections.
Some also show that zinc lozenges may shorten the duration of the common cold. However, identifying the best dosages for supporting immune health and treating colds will require further research.
We know that they play a key role in helping maintain a healthy balance of bacteria in the gut, and new research supports the idea that they have beneficial effects on immunity. For example, one study from — carried out, it must be noted, by a company that produces probiotics — found that probiotic use may reduce the incidence and duration of upper respiratory infections.
The authors call for more research to establish a relationship between probiotics and the immune system. Many people are taking one or a combination of supplements to prevent or treat COVID But there is not enough data to support the use of any vitamin, herb, or other supplement to treat or prevent this illness.
Only vaccines , together with strict hygiene measures , are proven to help prevent COVID For severe cases of COVID, doctors may use specific medications. Research does suggest that supplementation with vitamins and minerals can be a low-cost way to support optimal immune function. Even supplementation with vitamins C and D above the current RDAs may be beneficial to the immune system, as long as dosages stay below the recommended safety limits.
Many supplements can interact with medications and other supplements. And combining different supplements can also lead to very high amounts of certain nutrients in the body, which can have potentially severe side effects. For example, excess vitamin C is excreted in the urine and usually causes no serious side effects.
But very high amounts can cause diarrhea , abdominal pain, and nausea. Too much vitamin D — more than 4, IU or mcg — can be harmful and lead to nausea, vomiting, kidney stones , confusion, loss of appetite, and muscle weakness.
Very high levels can even lead to kidney failure, an abnormal heartbeat, and death. Vitamin D also interacts with medications, such as the weight loss pill orlistat Alli, Xenical , steroids , and cholesterol-lowering statins.
If a person has too much zinc, it can cause negative effects such as nausea, vomiting, diarrhea, and headaches. Over time, excess zinc can lead to low copper levels, decreased immunity, and lower levels of helpful cholesterol.
Zinc can also interact with other medications. Probiotics are safe for most people. However, they may worsen illnesses or cause bacterial infections in people who have very weak immune systems or are severely ill.
This can involve :. There is no evidence that mega-doses of vitamins and nutrients can boost the immune system. The best way to ensure that the immune system functions well is to have a balanced diet, get enough sleep, exercise, and take the vaccinations that are offered.
Anyone with nutrient deficiencies who is unable to have a healthy, balanced diet may find it beneficial to take a daily multivitamin. But though some research shows that getting more than the RDAs of vitamins C and D might help support immune health, confirming this requires more research.
If a person thinks they have a nutrient deficiency, they should consider speaking with a doctor about having a blood test.
This will help pinpoint any deficiencies and determine the right approach to supplementation. Before taking any supplement, a person should have a conversation with a primary care doctor who is familiar with their medical history.
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Focusing on a few Immunity boosting vitamins Inmunity will better your chances of staying Chia seed porridge. Your immune boostingg is a Immunity boosting vitamins vittamins checks boostign balances that helps fight and protect the body from disease and illness. Many products claim to give your immune system the boost it needs to keep you running at your best. But, Hansen says approach immune system supplements with caution. But, your body can only absorb so much of any vitamin in a given day. Supplements can cause side effects as well. On the other hand, there are habits you might have that Hansen says weaken your immune system, rather than boosting it. In a perfect world, we'd all have access to a balanced, nutrient-dense diet that's chock-full Boossting healthy fats, fruits, Immunity boosting vitamins, adequate Immmunity and Herbal formulas for weight loss — and Ayurvedic detox diets, shouldn't have to take additional citamins supplements in order to strengthen Immunitg immune Immunity boosting vitamins. However, not only do most of us fail to hit these daily nutrition goals, but we may have situations — like physical stress or inflammatory health issues — when we need more of certain nutrients than what we're getting from food. As an immunologist and functional medicine doctorI always say that you cannot supplement yourself out of bad health or replace a poor diet with vitamins, but you can fill in the gaps to give yourself that extra leg up. Below are the four supplements that I take every day and often recommend to my patients. Trust me: Your body will thank you.
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