Discrimination at work is linked to high blood pressure. Icy fingers and toes: Poor circulation or Raynaud's phenomenon? During the winter months, you've likely seen ads for products that claim to give your immune system a boost to help you ward off colds and the flu. But can something in a bottle, whether a vitamin formulation or probiotic, really rev up your immune system to help you stay healthy?

To understand why, you need to know a little about how the immune system works. The very idea of boosting the immune system is flawed. There is a balance between an immune system that is effective at limiting the ability of bacteria, viruses, and parasites to cause infection, and a hyperactive immune system that can cause such problems as allergies, diabetes, and other types of autoinflammatory and autoimmune disorders.

Products that claim to boost or "support" the immune system typically fall into a couple of categories: vitamin formulations and probiotics. There is some truth to the idea that vitamins can help immunity. Vitamins can help ward off disease and other health problems, but only in people who are severely malnourished, something that's not true of the average American adult, says Starnbach.

So, vitamin formulations will do little to help you stay healthy if you are healthy already. When it comes to probiotics, there is also some truth to the idea that the bacteria and organisms living in your gut may play a role in your health. Someday, scientists may very well be able to tell us how to prevent disease by modifying these various species inside our bodies, which make up what is called the microbiome.

But today, there isn't enough understanding of the complex interplay between the body and the microbiome to effectively use probiotics to improve health.

So, if you can't help your immune system by taking an over-the-counter potion or pill, what can you do to cut down on illness this winter? Differences between people who rarely get sick and those who are sick all the time may have more to do with habits than immune function, says Starnbach.

Here are some tips that might help. Clean your hands. While some germs are airborne, more often than not, illness occurs after you touch a contaminated surface, says Starnbach. Most often germs move from your hands into your eyes, nose, or mouth, so also make an effort not to touch your face.

Keep your body in top shape. Maintaining a healthy and balanced diet, exercising regularly, and getting enough sleep can help keep your body and your immune system working well.

Manage stress. Research has shown that high stress levels may impair the immune system. So whenever possible, try to be aware of your stress levels and work to lower them when they get too high. Get vaccinated. Getting vaccinated against the flu and other diseases stimulates the immune system to protect against illness.

Vaccines teach the immune system to recognize specific pathogens and prepare them to mount a defense if they are encountered. The bottom line is that aside from vaccines, there's really nothing you can take to improve your immune system, so it's probably best to avoid pills and potions that make those types of claims.

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No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician. Thanks for visiting. Don't miss your FREE gift. That doesn't mean that it's impossible that they're providing any benefit.

It just means that we haven't been able to prove the benefit. DON'T MISS: Do Americans have a vitamin D problem? Though he notes that some people have severe, medical vitamin C and vitamin D deficiencies — which can lead to swollen, bleeding gums or bone fractures — and for those individuals, vitamin supplementation is a very effective and necessary measure.

A Cochrane review of randomized controlled trials that examined the effects of taking vitamin C supplements daily on the prevention and treatment of the common cold found that taking the supplement every day didn't reduce the incidence of colds. However, "it did at least reduce the severity and duration of colds," says Dr.

John Mafi , an associate professor of medicine in the Division of General Internal Medicine and Health Services Research at the David Geffen School of Medicine at UCLA. It's not untrue that vitamin C and vitamin D actually can help to support the function of your immune system.

Vitamin D helps your body to create an antimicrobial peptide called cathelicidin, which "stops bacteria, microbes and viruses," and "[regulates] the function of your body's T-cells," Mafi says. Vitamin D supplements have a bit more evidence for their potential benefits. A systematic review of randomized controlled trials published in the British Medical Journal in found that daily intake of vitamin D supplements protected against acute respiratory infections.

Yet, there are many proven ways to strengthen your immune system outside of supplements like vitamin C and vitamin D, Ben-Aderet says. And if you really want to try vitamin C or vitamin D supplements, Ben-Aderet says: "The jury's still mostly out [on their effectiveness], and vitamin supplementation is cheap and mostly harmless.

If you decide to take vitamin C supplements, you should make sure you don't exceed 2, milligrams of vitamin C in a day, Mafi notes. Too much vitamin C can cause stomach issues like nausea and vomiting and kidney stones, according to Mayo Clinic.

Harvard T. Chan's School of Public Health's hub for nutrition information, The Nutrition Source , recommends a dietary allowance for adults 19 years and older of 90 milligrams for men and 75 milligrams for women. To get vitamin C, you can eat citrus fruits like oranges, grapefruit and lemons, he notes.

Certain greens like kale and broccoli also have great amounts of vitamin C. Taking "roughly to international units IUs of vitamin D per day," is a way to safely address a deficiency, Dr.

Jad Sfeir , a Mayo Clinic endocrinologist, told CNBC Make It in August of It's best to find ways to get the vitamin in your diet from foods, Sfeir said, including fortified milk, orange juice or fatty fish like salmon or mackerel.

While orange juice may seem like the ultimate vitamin C source, Simon also recommends eating the following foods to get your fill.

Vitamin D improves the function of immune cells by reducing inflammation in the body and decreasing the risk of infection, says Simon. To help maintain healthy levels, aim for at least 15 minutes of sun exposure a day, according to Harvard Health.

Foods high in vitamin D include the following. Vitamin E is another fat-soluble vitamin with powerful antioxidant properties to help support immune cell production.

Add these vitamin E foods to your plate to help boost immune health. Think of zinc as an immunity superstar. Not only does it play a major role in wound healing, but it also aids in the development of immunity cells by impacting the growth of T-cells, says Simon. You'll find zinc in many of the foods you're probably already eating like the following.

Iron is also a major component of hemoglobin the protein in red blood cells that carries oxygen from your lungs to the rest of your body , so significant bleeding can cause your iron levels to drop. Try incorporating the following high-iron foods into your diet.

Selenium acts as a powerful antioxidant that can help reduce inflammation in the body, and studies show it promotes heart health, optimizes immune functioning, and may even help prevent cancer.

While a generally balanced diet is usually suitable for your daily selenium intake, low selenium levels have been shown to reduce immune function. Stock up on some of the following selenium-rich foods. Inflammation is a sign that your body is working overtime to heal or repair itself, but copper plays a huge role in minimizing its effects by neutralizing free radicals, says Simon.

Research shows that free radicals are unstable atoms in the body that can damage cells and cause illness, but copper has antimicrobial properties to reduce their presence and ultimately calm inflammation. Maintaining healthy copper levels is a bit of a balancing act, however, because too little copper can suppress your immune function, yet too much copper can be dangerous and lead to cell death.

But no need to overcomplicate it because copper toxicity is rare, stresses Simon. Focus on a varied diet by eating some of the following. Studies have shown that probiotics promote natural antibodies in the body by boosting immune cell production and fighting off infection.

Some research even suggests that probiotics can prevent respiratory tract infections like the cold or flu and reduce urinary tract infections in women.

Foods high in probiotics include the following. 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.

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Side effects can include stomach upset, diarrhea, trouble sleeping, and skin rashes. In rare cases, echinacea might cause allergic reactions. Echinacea might reduce the effectiveness of some medications, including medications that suppress the immune system.

For information about echinacea and COVID, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID Elderberry or elder berry is the fruit of a tree that grows in North America, Europe, and parts of Africa and Asia. Elderberry might help your body fight viruses and other germs, reduce inflammation, and strengthen your immune system.

However, some studies have found that elderberry might help relieve symptoms of colds and flu and help people recover quicker. Elderberry flowers and ripe fruit appear to be safe to eat. However, the bark, leaves, seeds, and raw or unripe elderberry fruit can be poisonous and can cause nausea, vomiting, diarrhea, and dehydration.

Cooked elderberry fruit and properly manufactured supplements do not have this safety concern. Elderberry might affect insulin and blood sugar levels.

It might also reduce the effectiveness of medications that suppress the immune system. For information about elderberry and COVID, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID Garlic is a vegetable that has been used in cooking throughout history. It is also available as a dietary supplement.

Ginseng Panax ginseng or Panax quinquefolius is a plant used in traditional Chinese medicine. It might help your body fight viruses, reduce inflammation, and strengthen your immune system.

Another botanical , eleuthero Eleutherococus senticosus , has sometimes been called Siberian ginseng, but it is not related to true ginseng. Ginseng might reduce the risk of coming down with the common cold, flu, or other respiratory infections.

Ginseng appears to be safe. Side effects can include headache, trouble sleeping, and digestive upset. However, high doses more than 2. Ginseng might interact with diabetes medications, stimulants , and medications that suppress the immune system. For information about ginseng and COVID, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID Tea Camellia sinensis is a popular beverage that may have health benefits.

Tea extracts are also available as dietary supplements. Green, black, and oolong tea leaves are processed in different ways. Green tea is made from dried and steamed tea leaves, and black and oolong teas are made from fermented tea leaves.

Tea, especially green tea, has high amounts of substances called catechins. Catechins might help fight viruses and other germs. Some studies have found that tea and tea catechins might reduce the risk of coming down with upper respiratory infections.

They might also reduce the length and severity of some symptoms but not other symptoms. Tea is safe to drink. Side effects of green tea extract can include nausea, constipation , stomach discomfort, and increased blood pressure. Some green tea extracts might damage your liver, especially if you take them on an empty stomach.

Tea also contains caffeine, which can disturb your sleep and cause nervousness, jitteriness, and shakiness. Tea might interact with atorvastatin a cholesterol-lowering drug and stimulants, such as bitter orange or ephedrine.

Glutamine is an amino acid found in many foods including beef, fish, poultry, dried beans, eggs, rice, grains, and dairy products. Your body makes enough glutamine to meet your needs, except under rare conditions for example, if you are critically ill in an intensive care unit [ICU] or have had major surgery.

Some studies in hospitalized patients who were critically ill or had undergone major surgery found that glutamine given as an IV or tube feeding reduced the risk of getting an infection, but it did not reduce the risk of death. Glutamine is considered safe. Side effects can include nausea, bloating, burping, pain, gas, and vomiting.

These side effects are more likely to occur with higher doses of glutamine. N-acetylcysteine NAC is similar to cysteine, an amino acid. It acts as an antioxidant and helps reduce mucus in the respiratory tract.

NAC raises levels in your body of a substance called glutathione, which also acts as an antioxidant. NAC and glutathione might also help your body fight viruses and other germs, reduce inflammation, and strengthen your immune system.

People with HIV may have low levels of glutathione, which might increase the risk of certain diseases including tuberculosis. However, there is very little research on NAC supplements in people with HIV.

NAC appears to be safe. Side effects can include nausea, vomiting, stomach pain, diarrhea, indigestion, and heartburn. NAC might interact with blood thinners and blood pressure medications. Taking NAC with nitroglycerine used to treat chest pain might cause low blood pressure and severe headaches.

For information about NAC and COVID, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID Omega-3s are types of fats, including alpha linolenic acid ALA , eicosapentaenoic acid EPA , and docosahexaenoic acid DHA.

ALA is found mainly in plant oils, such as flaxseed, soybean , and canola oils. EPA and DHA are found mainly in fatty fish and fish oils. Omega-3s are important for healthy cell membranes and proper function of the heart, lungs, brain, immune system, and endocrine system.

The recommended amount of omega-3s for infants is 0. EPA and DHA do not have individual recommendations. Omega-3s might help your body fight viruses and other germs, reduce inflammation, and strengthen your immune system. Acute respiratory distress syndrome ARDS is a serious lung condition that can lead to death.

In people who do recover, ARDS often causes long-term physical and mental health problems. Researchers have studied whether giving omega-3s as an IV or tube feeding is helpful for people with ARDS, but results from these studies are not clear. The immune system continues to develop in babies after birth, and their immune cells contain the omega-3s EPA and DHA.

A study in school-age children found that children who consumed milk with added EPA and DHA had fewer upper respiratory infections than those who did not consume omega-3s.

In another study, however, using an infant formula containing DHA and another fatty acid had no effect on the risk of respiratory infections in infants. Omega-3s are considered safe. Side effects can include a bad taste in the mouth, bad breath, heartburn, nausea, digestive discomfort, diarrhea, headache, and smelly sweat.

Omega-3s might interact with blood thinners, blood pressure medications, and medications that suppress the immune system. More information about omega-3s is available in the ODS consumer fact sheet on omega-3 fatty acids.

For information about omega-3s and COVID, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID Probiotics are live microorganisms bacteria and yeasts that provide health benefits. They are naturally present in certain fermented foods, added to some food products, and available as dietary supplements.

Probiotics act mostly in the stomach and intestines. They might improve immune function and help fight viruses. Acute infectious diarrhea in infants and children causes loose or liquid stools and three or more bowel movements within 24 hours.