Other sleep hygiene tips include sleeping in a completely dark room or using a sleep mask, going to bed at the same time every night, and exercising regularly 3. Inadequate sleep may increase your risk of getting sick. Most adults should get at least 7 hours of sleep per night. Whole plant foods like fruits, vegetables, nuts, seeds, and legumes are rich in nutrients and antioxidants that may give you an upper hand against harmful pathogens.

The antioxidants in these foods help decrease inflammation by combatting unstable compounds called free radicals, which can cause inflammation when they build up in your body in high levels 5. Meanwhile, the fiber in plant foods feeds your gut microbiome, or the community of healthy bacteria in your gut.

A robust gut microbiome can improve your immunity and help keep harmful pathogens from entering your body via your digestive tract 6. Furthermore, fruits and vegetables are rich in nutrients like vitamin C , which may reduce the duration of the common cold 7.

Several whole plant foods contain antioxidants, fiber, and vitamin C, all of which may lower your susceptibility to illness. Although low-level inflammation is a normal response to stress or injury, chronic inflammation can suppress your immune system 8.

Olive oil, which is highly anti-inflammatory, is linked to a decreased risk of chronic diseases like heart disease and type 2 diabetes. Plus, its anti-inflammatory properties may help your body fight off harmful disease-causing bacteria and viruses 9 , Omega-3 fatty acids , such as those in salmon and chia seeds, fight inflammation as well Healthy fats like olive oil and omega-3s are highly anti-inflammatory.

Since chronic inflammation can suppress your immune system, these fats may naturally combat illnesses. Fermented foods are rich in beneficial bacteria called probiotics, which populate your digestive tract Research suggests that a flourishing network of gut bacteria can help your immune cells differentiate between normal, healthy cells and harmful invader organisms In a 3-month study in children, those who drank just 2.

In a day study in people infected with rhinovirus, those who supplemented with probiotic Bifidobacterium animalis had a stronger immune response and lower levels of the virus in their nasal mucus than a control group Gut health and immunity are deeply interconnected.

Fermented foods and probiotics may bolster your immune system by helping it identify and target harmful pathogens. Emerging research suggests that added sugars and refined carbs may contribute disproportionately to overweight and obesity 16 , According to an observational study in around 1, people, people with obesity who were administered the flu vaccine were twice as likely to still get the flu than individuals without obesity who received the vaccine Curbing your sugar intake can decrease inflammation and aid weight loss, thus reducing your risk of chronic health conditions like type 2 diabetes and heart disease 19 , Given that obesity, type 2 diabetes, and heart disease can all weaken your immune system, limiting added sugars is an important part of an immune-boosting diet 18 , 21 , This equals about 2 tablespoons 25 grams of sugar for someone on a 2,calorie diet.

Added sugars contribute significantly to obesity, type 2 diabetes, and heart disease, all of which can suppress your immune system. Lowering your sugar intake may decrease inflammation and your risk of these conditions. Although prolonged intense exercise can suppress your immune system, moderate exercise can give it a boost.

Studies indicate that even a single session of moderate exercise can boost the effectiveness of vaccines in people with compromised immune systems Examples of moderate exercise include brisk walking , steady bicycling, jogging, swimming, and light hiking.

Most people should aim for at least minutes of moderate exercise per week Moderate exercise can reduce inflammation and promote the healthy turnover of immune cells.

Jogging, biking, walking, swimming, and hiking are great options. Dehydration can cause headaches and hinder your physical performance, focus, mood, digestion, and heart and kidney function. These complications can increase your susceptibility to illness To prevent dehydration, you should drink enough fluid daily to make your urine pale yellow.

You may need more fluids if you exercise intensely, work outside, or live in a hot climate Older adults need to drink regularly even if they do not feel thirsty.

Relieving stress and anxiety is key to immune health. Long-term stress promotes inflammation, as well as imbalances in immune cell function 7 , 9. In particular, prolonged psychological stress can suppress the immune response in children Activities that may help you manage your stress include meditation , exercise, journaling, yoga, and other mindfulness practices.

You may also benefit from seeing a licensed counselor or therapist, whether virtually or in person. Lowering your stress levels through meditation, yoga, exercise, and other practices can help keep your immune system functioning properly.

Thus, you should only purchase supplements that have been independently tested by third-party organizations like United States Pharmacopeia USP , NSF International, and ConsumerLab. Though some supplements may fight viral infections, none have been proven to be effective against COVID If you decide to supplement, make sure to purchase products that have been tested by a third party.

These include reducing your sugar intake, staying hydrated, working out regularly, getting adequate sleep, and managing your stress levels. Read this article in Spanish. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.

Anxiety is a common symptom of trauma. Here's why. Try this: Current government guidelines suggest adults get minutes of heart-pumping moderate aerobic exercise like brisk walking or 75 minutes of intense exercise think jogging, cycling, or swimming a week.

That can feel more manageable if you break it down. For example, you could take a brisk minute walk on your lunch break from Monday to Friday to get to minutes, or jog for less than 40 minutes a day twice a week to get to 75 minutes.

Specific foods loaded with probiotics include yogurt or fermented foods like kimchi, miso, and sauerkraut. Try this: Forget the capsules and look to the supermarket aisles. It has also been tied to higher risks for pulmonary disease and certain cancers.

Think of limiting your alcohol intake as a healthy habit that impacts your whole body — much like exercising, eating well, getting enough sleep, and reducing stress — which in turn helps boost the immune system.

David M. Goldberg , M. He is board-certified in Internal Medicine and Infectious Diseases and has a special interest in travel medicine, Lyme disease, HIV, and community-acquired infections. Find a Doctor or call Keep in touch with NewYork-Presbyterian and subscribe to our newsletter.

At A Glance Featured Expert David M. Goldberg, M. Internal Medicine, Infectious Disease. Internal Medicine.

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. Results were more positive in another trial, in which men and women mean age 53 years took one capsule of a garlic supplement dose not specified or placebo daily for 12 weeks between November and February [ ].

Participants who took garlic had fewer colds 24 among the full study population during the study than those who took placebo 65 colds.

In addition, colds lasted an average of only 1. Garlic is safely consumed worldwide as a culinary ingredient [ ], and garlic and its derivatives are generally recognized as safe, according to the U.

Food and Drug Administration FDA [ ]. The adverse effects of garlic dietary supplements are minor and include bad breath, body odor, and skin rash [ 32 , , ].

Garlic might interact with medications. For example, garlic might have anticoagulant effects, so it might interact with warfarin Coumadin and similar medications [ , , ]. However, the findings from reported case studies on this interaction are inconclusive [ ]. Garlic might also reduce blood pressure, so it might interact with antihypertensive medications [ ].

Ginseng is the common name of several species of the genus Panax , most commonly Panax ginseng also called Asian ginseng or Korean ginseng and Panax quinquefolius American ginseng [ , ].

Asian ginseng is endemic to China and Korea, whereas American ginseng is endemic to the United States and Canada [ ]. Triterpene glycosides, also known as ginsenosides, are some of the main purported active constituents of ginseng [ , ].

Although ginseng contains numerous ginsenosides, research has focused on the Rb1 ginsenoside and compound K, a bioactive substance formed when the intestinal microbiota metabolize ginsenosides [ , ].

Animal and laboratory studies suggest that ginseng stimulates B-lymphocyte proliferation and increases production of some interleukins and interferon-gamma [ ]; these cytokines affect immune activation and modulation [ 1 ].

Ginseng might also inhibit virus replication and have anti-inflammatory activity. However, whether ginseng has a clinically meaningful effect on immune function in humans is not clear [ , ]. Another botanical, eleuthero Eleutherococus senticosus , is sometimes confused with true ginseng.

Eleuthero used to be called Siberian ginseng, but it comes from the Eleutherococcus genus of plants, not the Panax genus, and it does not contain ginsenosides [ ].

Several clinical trials have examined whether ginseng helps prevent upper respiratory tract infections, such as the common cold and influenza. Although the evidence is limited, results from these trials suggest that ginseng might help reduce the risk of developing colds and other respiratory tract infections.

However, its effects on symptom severity and duration are unclear. In one clinical trial, healthy men and women age 30 to 70 years who had not received an influenza vaccine in the previous 6 months took 1 g Panax ginseng extract three times daily or placebo for 12 weeks [ ]. Participants taking ginseng were less likely to develop an acute respiratory infection during the study period.

However, for study participants who did develop an infection, symptom duration and severity did not differ between groups. A few clinical trials have examined the effects of CVT-E COLD-fX , a patented ginseng extract that contains mg Panax quinquefolius in each capsule.

One of these trials included men and women age 18 to 65 years with a history of at least two colds during the previous year who had not received an influenza vaccine in the past 6 months [ ]. Participants took either two capsules per day of Cold-fX for a daily dose of mg ginseng or placebo for 4 months starting in November.

Participants who took ginseng developed fewer self-reported colds mean 0. In addition, ginseng reduced the total number of days with cold symptoms from a mean of A systematic review and meta-analysis of ginseng to prevent or treat acute upper respiratory tract infections included 10 clinical trials of Panax ginseng or Panax quinquefolius extracts including those described above in a total of 2, participants [ ].

The authors noted that the risk of bias was high to unclear for most trials and that the limitations of the evidence prevented them from drawing conclusions. Ginseng appears to be safe. Most of its adverse effects, including headache, sleep difficulty, and gastrointestinal symptoms, are minor [ , , ].

However, doses of more than 2. A few case reports of vaginal bleeding and mastalgia breast pain in the s and s from the use of ginseng preparations raised concerns about the safety of ginseng; as a result, some scientists concluded that ginseng has estrogenic effects [ ].

However, one of these case reports involved use of Rumanian ginseng [ ], and whether this was true ginseng is not clear.

In addition, eleuthero was often referred to, incorrectly, as ginseng at that time because it was called Siberian ginseng. So, it is unclear whether these case reports reflected the effects of true ginseng. Nevertheless, some experts caution that ginseng might not be safe for use during pregnancy [ , , ].

Ginseng might interact with many medications. For example, it might increase the risk of hypoglycemia if taken with antidiabetes medications, increase the risk of adverse effects if taken with stimulants, and reduce the effectiveness of immunosuppressants [ , ].

For information on ginseng and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID Tea Camellia sinensis is a popular beverage around the world that has several purported health benefits. Tea is usually classified into one of three types—green, black, and oolong—according to the way in which the tea leaves are processed [ ].

Green tea is made from dried and steamed tea leaves, whereas black and oolong teas are made from fermented tea leaves. Tea extracts are also available as dietary supplements. The purported health effects may vary by the type of tea as well as whether it is consumed as a beverage or dietary supplement.

Tea is one of the richest sources of catechins, which are polyphenolic flavonoids, especially epigallocatechin gallate EGCG [ , ]. A typical mL cup of brewed green tea contains 50 to mg of catechins [ ], whereas the same amount of brewed black tea contains about 14 to 88 mg of catechins [ ].

Amounts vary, however, among tea samples and by brewing time. Studies are evaluating the potential health benefits of EGCG and other catechins, including their ability to modulate the immune system and their anti-inflammatory and antimicrobial properties [ , ].

Laboratory studies suggest that catechins might also have antiviral effects against the influenza A and B viruses [ ].

Laboratory research suggests that tea and tea catechins might have antiviral activity. Researchers have therefore examined whether drinking tea or taking supplemental tea catechins affects the risk, duration, and severity of influenza or other respiratory tract infections.

However, evidence from clinical trials is limited and mixed. Studies that found beneficial effects include a clinical trial that examined the effects of catechins and theanine an amino acid in tea on the risk of influenza in male and female health care workers age 21 years or older in Japan [ ].

However, for laboratory-confirmed influenza, the incidence of influenza did not differ between groups. A systematic review and meta-analysis also showed that tea and tea catechins had some beneficial effects on the risk of influenza and other upper respiratory tract infections, although the evidence had some limitations [ ].

The analysis included five prospective cohort studies and clinical trials that administered tea as a dietary supplement or beverage including the trial described above in a total of 1, participants. Results were also mixed in a clinical trial examining whether drinking mL of a bottled beverage containing mg of catechins for 12 weeks during the winter affected the duration and severity of upper respiratory tract infections in healthy Japanese men and women mean age Catechins reduced the duration and severity of a runny nose, nasal congestion, and headache but did not affect other symptoms, including sore throat, cough, and fever.

Drinking moderate amounts of tea is safe. Green tea extract causes mostly mild to moderate adverse effects, including nausea, constipation, abdominal discomfort, and increased blood pressure [ ].

However, some green tea extracts might cause liver damage, especially when taken on an empty stomach [ , ]. In addition, at least 50 case reports since have linked consumption of green tea extracts, primarily ethanolic extracts of green tea, with liver damage [ ].

In a systematic review of the safety of green tea products, the U. Pharmacopeia USP evaluated 75 case reports of liver damage and animal pharmacological and toxicological information [ ]. On the basis of the 35 case reports associated with supplements containing only green tea extract, the USP concluded that the consumption of green tea products definitely caused four cases of liver damage, probably or was highly likely to have caused 25 cases, and possibly caused five cases.

The USP notes that problems are more likely when green tea extract is taken on an empty stomach and, therefore, advises taking green tea extracts with food to minimize the risk of liver damage [ , ]. In addition, tea contains caffeine, which can cause sleep disturbances and feelings of nervousness, jitteriness, and shakiness [ ].

These levels do not apply to people who are pregnant and may need to limit caffeine consumption further [ ]. Tea and its constituents might interact with certain medications.

For example, green tea extract decreases plasma levels of atorvastatin, a statin medication [ ]. Glutamine is an amino acid that is present in a wide variety of foods that contain protein, including beef, fish, poultry, soy and other beans, eggs, rice, corn and other grains, and milk and other dairy products [ ].

The body also produces glutamine endogenously. In normal conditions, the body can synthesize adequate amounts of glutamine to meet metabolic needs, so glutamine is not classified as an essential amino acid [ ].

However, under extreme physiological stress, endogenous glutamine synthesis cannot keep up with metabolic need. Therefore, glutamine is classified as conditionally essential [ ].

In the immune system, glutamine is involved in lymphocyte proliferation and cytokine production as well as macrophage and neutrophil function [ ]. Low glutamine levels are associated with poor immunologic function and an increased risk of mortality in patients in the ICU [ , ].

Many patients who are critically ill or have undergone major surgery have low plasma and muscle glutamine levels [ ]. Results from some studies suggest that glutamine reduces rates of infection and mortality in critically ill patients and reduces hospital length of stay and mortality in patients with burn injuries [ , ].

Clinical studies have administered glutamine both enterally and parenterally. When administered through these routes, glutamine is classified as a drug, not a dietary supplement, in the United States.

Researchers have examined whether glutamine administration affects immune parameters and disease prognosis in critically ill patients. The evidence from these studies is limited and mixed. For example, a crossover trial examined the effects of enteral nutrition containing glutamine on immune function in moderately ill patients with systemic inflammatory response syndrome from a pulmonary infection in the ICU [ ].

Thirty patients age 30 to 92 years received enteral nutrition containing 30 g added glutamine for 2 days followed by enteral nutrition containing 30 g added calcium caseinate for 2 days or the same formulations but in reverse order. A 1-day washout period with standard enteral nutrition separated each treatment period.

Glutamine administration resulted in higher lymphocyte counts than calcium caseinate administration, suggesting enhanced immune function, but did not affect interleukin levels.

Results from clinical trials in patients with critical illness have also been mixed. One trial in the United Kingdom included 84 men and women mean age 65 to 66 years in the ICU [ ]. Patients received a standard parenteral formulation with or without 25 g added glutamine per day. Treatment duration was not specified, but administration continued until death or as long as clinically required.

Patients who received the formulation with added glutamine had a lower risk of death during the subsequent 6 months than those who received the standard formulation. In another clinical trial in Scotland, critically ill men and women mean age 63 to 65 years in the ICU received one of four parenteral treatments daily: standard formulation, standard formulation containing Glutamine did not affect the risk of new infections during the 14 days after randomization or mortality rates in the ICU or during the subsequent 6 months.

It also had no effect on ICU or hospital length of stay, need for antibiotics, or rates of organ failure. Findings from a Cochrane Review suggest that glutamine may have beneficial effects on some but not all outcomes in patients who have critical illness or are recovering from major surgery.

This review examined the effects of glutamine administration on various outcomes, including rates of infection and mortality, in adults who were critically ill or had undergone major surgery, such as abdominal or thoracic surgery [ ].

It included 53 clinical trials including the two described above in a total of 4, participants that administered glutamine enterally or parenterally. It also reduced the length of hospital stay by about 3. However, glutamine did not affect mortality rates, and it prolonged ICU stays by about 0.

The authors of a review that examined the effects of micronutrient supplementation, including glutamine, in adults with conditions or infections similar to COVID concluded that evidence from human studies is very limited and that baseline nutrient status may affect study results [ ]. Oral, enteral, and parenteral glutamine administration is considered safe [ , , ].

Reported side effects are mainly gastrointestinal and include nausea, bloating, belching, pain, and flatulence [ ]. Other research suggests that oral doses up to 0. Children age 4 to 18 years tolerate doses of 0. The Food and Nutrition Board has not established a UL for glutamine [ ].

The board notes that very few, if any, adverse effects have been reported from glutamine administration. N-acetylcysteine NAC is a derivative of the amino acid cysteine.

NAC is an antioxidant that has mucolytic activity, so it helps reduce respiratory mucus levels [ ]. NAC might improve immune system function and suppress viral replication [ , , ].

NAC also appears to decrease levels of interleukin-6 and have other anti-inflammatory effects [ , , ]. Much of the research on NAC has used an inhaled, liquid form of this compound.

This form—which is classified as a drug in the United States, not a dietary supplement—is approved by FDA as a mucolytic agent and for decreasing respiratory secretion viscosity [ ].

NAC administered orally or intravenously also has FDA approval as a drug to treat acetaminophen poisoning [ , ]. Products containing NAC are also sold as dietary supplements [ ]. In addition to its direct effects in the body, NAC raises intracellular levels of glutathione, which is a tripeptide of glutamine, cysteine, and glycine [ , , , , ].

Laboratory and animal studies suggest that glutathione has antioxidant activity and appears to have antiviral and antimicrobial effects and enhance natural killer cell and neutrophil activity [ , , , ].

Glutathione may also have anti-inflammatory effects via altered cytokine expression [ , , ]. Adequate glutathione levels are needed for optimal innate and adaptive immune system function, including proper T-cell activation and differentiation [ , , ].

Most research indicates that oral glutathione supplementation does not raise intracellular glutathione levels because glutathione is hydrolyzed in the gastrointestinal tract [ ]. As a result, NAC is often used in research studies because of its effects on intracellular glutathione levels.

HIV infection appears to increase production of free radicals and deplete levels of free glutathione [ ]. Therefore, people with HIV may have decreased intracellular levels of glutathione, which could increase their susceptibility to infectious diseases, such as tuberculosis [ ]. Low glutathione levels have been associated with shorter survival in people with HIV [ ], and NAC supplementation increases blood and T-cell levels of glutathione [ ].

However, clinical research on the effects of NAC supplementation on the immune system in humans is very limited. In one clinical trial, researchers examined the effects of oral to 6, mg NAC, depending on plasma glutamine levels, every other day for 7 months or placebo in 37 men and women with HIV who were taking ART [ ].

An accompanying clinical trial described in the same publication evaluated the same treatment in 29 men and women with HIV who were not taking ART.

In addition, NAC supplementation had inconsistent effects on viral load. As an FDA-approved drug, the safety profile of NAC has been evaluated [ ]. The American College of Chest Physicians and the Canadian Thoracic Society note that NAC has a low risk of adverse effects [ ].

Reported side effects of oral NAC include nausea, vomiting, abdominal pain, diarrhea, indigestion, and epigastric discomfort [ , ]. No safety concerns have been reported for products labeled as dietary supplements that contain NAC.

NAC might have anticoagulant effects and reduce blood pressure, so it could have additive effects if taken with anticoagulants and antihypertensive medications [ ]. The combination of NAC and nitroglycerine, used to treat angina, can cause hypotension and severe headaches [ , ].

For information on NAC and COVID, please see the ODS health professional fact sheet, Dietary Supplements in the Time of COVID For example, in one study published in in Nature and Science of Sleep , researchers found disrupted sleep caused serious health ramifications, including:.

Also, don't assume you can just catch up on sleep after a night or two of staying up late or tossing and turning.

Remember, your body is busy at rest, and it's designed to sleep when the sun goes down. According to the National Sleep Foundation, adults between 18—64 need seven to nine hours of sleep per night. Also, older adults need seven to eight hours, and children and adolescents require even more sleep. Aim for the right amount for your age group, and be as consistent as possible.

Turning in and waking up at roughly the same time every day is healthier than an all-over-the-place sleep schedule. Unchecked stress, anxiety, worry, and panic pack have many negative health effects. And suppressing the immune system is one of them, said Dr. Prolonged stress also drives up levels of the hormones cortisol and adrenaline.

Eventually, too much of those hormones can inflict damage on the body. You can take small steps to help chill and unwind, including:. Excessive social media usage might increase your stress and anxiety. Still, screen time watching a movie you love or a binge session of your favorite TV show can help take your mind off things.

When it comes to keeping your immune system strong, proper handwashing is one of the most important things. But if you can't get to soap and water, hand sanitizer is the next best thing.

Plain old soap and water are all you need. It's important to scrub up for at least 20 seconds—the length of singing "Happy Birthday" twice. Per the CDC, that's the minimum time needed to significantly reduce the number of microorganisms on your skin.

But no matter how good your handwashing skills are, they won't help prevent infection unless you know when to scrub up.

In other words, that includes after using the restroom, sneezing, or coughing. Also, wash your hands before you prepare food, after caring for a sick loved one, treating a wound, or touching any publicly used door handles, knobs, switches, or surfaces, added Dr.

And if your hands are prone to dry skin, the right moisturizer can help. If you don't have access to soap and water, hand sanitizer can help kill most microorganisms. Just be sure to take a peek at the alcohol percentage first. Alcohol is the active ingredient working to kill viruses and bacteria.

You may be unable to avoid viruses and bacteria that spread the common cold and flu entirely. But you can avoid them as best you can by strengthening your immune system. Focusing on nutrition, hygiene, and other health habits is the key to doing so. These simple immune-boosting habits can help you steer clear of some infections.

Others can supercharge your immune system, so you can get better quickly if you get sick. Dietary supplements are minimally regulated by the FDA and may or may not be suitable for you.

The effects of supplements vary from person to person and depend on many variables, including type, dosage, frequency of use, and interactions with current medications. Please speak with your healthcare provider or pharmacist before starting any supplements.

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EXCLI J. American Psychological Association. Show me the science. Use limited data to select advertising. Create profiles for personalised advertising.

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