A Comprehensive Guide to Nutrition and the Immune System

Nutrition and the Immune System: Can Certain Foods Prevent Viruses and Bacterial Infections?

Before going too far, I want to answer this nutrition and the immune system questions. The answer is ‘it’s complicated,’ there is not one magic food, nutrient, or supplement that can prevent a bacterial or viral infection. There are nutrients, however, that can support your immune system. Moreover, if we become deficient or even marginally deficient in nutrients, especially nutrients involved in immune function, our immune system will not function properly.

Therefore, food does plays a crucial role in preserving our health and can directly and indirectly effect our risk of developing cold and flu viruses and bacterial infections. 

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My Background and Personal Story

When my son was in kindergarten, he came down with two common cold viruses. He quickly developed Pneumonia, which ultimately permanently damaged his lung to the point where he had to have a lobe if his lung removed. The good news is he is doing wonderful now! He is 10 years old and is now busy playing for a travel soccer team!

I Kept Tiptoeing Around Something, but Would Never Come Out and Say It Until Now…

In the past when I would talk about my son’s illness, I kept tiptoeing around something… 
I’m a dietitian, and I sometimes feel like I failed my son nutritionally. When my children were little, I couldn’t figure out how to regularly get nutritious meals on the table. I felt like I was nursing my daughter 24/7, and my son was starting to participate in so many after school activities. 

If I had been more diligent about nutrition would my son never have gotten sick?

I have since developed a strategy that made getting healthy food on the table extremely easy. You can find this strategy in The Nourishing Meal Builder.

Nutrition and the Immune System: Do we have control over the bad health outcomes, or do bad things sometimes happen no matter what we do?  

I’m comforted that the answer seems to be both. I’m comforted in the fact that my son’s illness probably had nothing to do with his diet….STUFF..JUST..HAPPENS! Yet I’m also comforted in the hope that we can do something to reduce the risk of so many conditions. I don’t want to hold onto guilt when something does goes wrong, but I also want to feel like I can do SOMETHING. I don’t want to feel completely helpless! My hope, based on science, is that there are things that we can do to prevent or at least, reduce the risk and duration of many illnesses and diseases. This evidence-based hope IS what drove me to start Mindful Vending and write The Nourishing Meal Builder.

With this in mind, I spent a year organizing the research and writing

I organized the research on…

• Mood boosting foods 
• Foods that reduce the risk of chronic disease and Alzheimer’s 
• Anti-inflammatory foods 
• Foods that help with cognitive function, focus, and attention 
• Nutrition and the Immune System including antiviral and antibacterial foods
• Foods that reduce the risk of cancer 
• Stress-relieving foods 
• Foods that help with acne 
• Foods that help with seasonal allergies… 

Just to name a few conditions!

I collected and organize day in and day out, and today I want to talk about one of these topics:

Nutrition and the Immune System

But First, Let’s Start with the BIGGIE…Hygiene

When we are talking about cold and flu prevention, we can’t skip over hygiene even if this post IS about nutrition. We can eat all the healthy foods in the world; but if we don’t practice good hygiene, we are fighting an uphill battle.  

Here are a few simple hygiene tips that have helped my family: 

1. Use handwashing or hand sanitizer after leaving EVERY store, restaurant, business, school, or doctor’s office. As soon as we get in the car, we pull out the wipes or hand sanitizer. We also wash our hands as soon as we get home. And of course, we wash our hands before we put any food in our mouth and after going to the bathroom. We even use hand sanitizer after we touch door handles, stair rails, and elevator buttons. 
2. Make a hygiene bag and take it with you everywhere. Included in my hygiene bag are wipes, hand sanitizer, and travel size Lysol cans. I spray down the movie theater seats and the tables and chairs in restaurants before we sit down. Before touching condiments in restaurants, I wipe down them down. I always wipe down grocery carts before I use them.  
3. Take our shoes off in the laundry room as soon as we enter the house, and once we are home for the night, we immediately change our clothes (and we wash our hands before and after we change clothes). 
4. We leave the kid’s bookbags in one spot away from the kitchen counters. 

These things may seem like a lot, but after a little practice you are soon in the habit. These hygiene practices will soon becomes second nature!  

Sleep and Immune Function

The next on the list is sleep. According to research, lack of sleep has a negative effect on our immune system and can make us more susceptible to catching colds and the flu (2). Lack of sleep may also slow our ability to fight our viruses after we get them as well. Studies show our T-cells, an important part of our immune function, decrease when we are sleep deprived.

So what is the take home message about sleep and the immune system? Our bodies need down time and sleep so aim for at least 6-8 hours a night. Start relaxing at least an hour before you sleep so that your body and mind are ready to sleep when it is time. Tea has been shown to decrease the stress hormone, cortisol and has a calming effect. Try drinking an cup of hot green tea before bed (3, 4). I love the Tazo tea products like this Tazo Zen Green Tea.

Stress and the Immune System

Before we get into food and the immune system, I want to talk for a moment about stress. Why? Because hygiene, sleep quality, and stress are probably the most impactful lifestyle habits when it comes to immune function. Although working hard and physically exercising your mind, body, and spirit is a good thing, too much stress can weaken the immune system. In fact, for some, chronic stress can cause activation of latent viruses (87). According to research, elevated levels of stress hormones suppresses immunity (88). For others, however, chronic stress may exaggerate the immune system responses, which can increase the risk of autoimmune disease and contribute to chronic inflammation (87). Neither is a good thing; therefore, we should find ways to decrease or cope with the stress in our lives.

How to Reduce Stress

• Say ‘no” to activities sometimes so that you can make time for what is important to you.
• Schedule time to slow down: Write in your journal, spend quiet time with God, sit outside and read a book.
• Practice mindfulness: When we focus on being in the present moment, we are not worrying about what is going on in the future or what happened in the past. You can find more mindfulness techniques in The Nourishing Meal Builder or on the blog here.
• Eat a healthy diet that includes foods that help with stress (post coming soon). Tea has been shown to decrease the stress hormone, cortisol and has a calming effect so try drinking an cup of hot green tea before bed (3, 4).
• Practice mindful eating: Sometimes life is too hectic to schedule in mindfulness activities, but we all have to eat. Eating is already something scheduled into your day. Use that eating time as an opprotunity to slow down and rest your mind, body, and spirit. Mindful breathing is about clearing your head and focusing on one thing- breathing. Mindful eating is about clearing your mind and focusing on one thing- enjoying your food. You can find more about mindful eating techniques in The Nourishing Meal Builder or on the blog here.

Okay, now that we have the crucial steps out of the way, let’s get down to nutrition and the immune system.

Nutrition and the Immune System

Food vs. Supplements

Some of the studies discussed in this post looked at the benefits of taking a nutrient in the form of a supplement. While I take an optimistic approach with food and their benefits, I am more cautious with supplements for two reasons. One, they can be expensive, and two, we can take too much and become toxic. Some supplements can negatively interact with medications. Always talk with your doctor before taking supplements. Moreover, when you are taking a supplement that is shown to “boost” your immunity, this could theoretically cause your immune system to become overactive. Overactive immune systems could possible trigger an autoimmune disease or allergies.

In the case of food, however, even if the research is preliminary and conflicting as far as a particular benefit; if the food is generally healthy, why not incorporate it in our diets? 

Nutrition and the Immune System: A Note on the Research

In this post, I tired to give you a short overview of what studies are saying. To keep the post as simple as possible and a reasonable length, I didn’t go into extensive details about each research article. Each article has their own strengths and weaknesses and some are stronger than others. Some of the strongest research will be double-blinded, controlled, randomized studies done on a large population of HUMANS. If a study doesn’t meet these standards, it doesn’t mean you throw the data out. It means that the results are interesting and indicate more research should be done on the subject. The more studies that repeat a result, the more promising the findings are.

This variety of strengths of the research, is the reason why I take an optimist view when it comes to eating healthy foods that may have a specific immune benefit and am more cautious about taking supplements.

Be Aware of Potential Bias in Others and Yourself

We are all bias. Researchers are bias and people who interpret the research are bias. I know that because of my son’s medical history, I am going to be bias towards the positive benefits of nutrients. It helps to be aware and acknowledge your bias so that you can look out for it.

One more thing..

Even if research does show a positive effect in regards to nutrition and the immune system, the effect may not be very impactful when compared to say washing your hands. This is yet another reason why we should focus on overall diet.

Promising Research

With all that being said there IS some promising research showing that certain nutrients DO have a positive effect on the immune system, especially if you were deficient or marginally deficient in the nutrient.

Antioxidants and the Immune System 

Research has shown that antioxidants significantly improve certain immune responses and are effective in the protection against infection (1, 7). Oxidative stress promotes viral growth; therefore, by reducing oxidative damage, antioxidants may have a protective role in infections caused by bacteria, viruses, and parasites (2, 6) 

Many nutrients can fall under the antioxidant category. Some of these nutrients include Vitamin A, Vitamin C, Vitamin E, Selenium, Polyphenols, Glutathione and Flavonoids (a class of polyphenol) like Quercetin. 

Below we will go into specific antioxidants; however, antioxidants seem to work best when combined with each other in a healthy diet. This may be one reason why research on specific antioxidants is sometimes conflicting. The missing component is the synergetic effects of a diet full of various antioxidants. Fruits, vegetables, nuts, and whole grains are all great sources of a variety of antioxidants. Antioxidants also seem to work best when eaten in food vs. supplements. In fact, excessive intake of isolated antioxidants can be toxic and even promote oxidative stress instead of preventing it!  

Nutrition and the Immune System: Specific Antioxidants

Polyphenol Antioxidants including Catechins, Flavonoids, and Quercetin Flavonoids

Polyphenols are a group of antioxidants and include flavonoids, catechins like EGCG, and anthocyanin, to name a few. Polyphenol antioxidants have been shown to have antiviral, including anti-influenza; anti-inflammatory; neuroprotective; and antibacterial activity (6, 5, 7)  Polyphenols have been shown to decrease the severity of the common cold and decrease the number of symptoms associated with colds and the flu (22, 23 ).

Flavonoids

Flavonoids are one type of polyphenol antioxidant. According to a review, flavonoid supplements decreased upper respiratory infections by 33%, and decreased duration (sick days) by 40% (24). Although this research study looked at supplements, you can get plenty of flavonoids from a variety of foods.

Catechins

Catechins are another polyphenol antioxidant. EGCG is the most abundant catechin found in green tea. Catechins may help fight infections, and were shown to suppress viruses in vitro. One study showed an inverse association between green tea consumption and the flu. In another study, people who consumed green tea capsules had 32.1% fewer common cold symptoms and 30.6% fewer sick days compared to the control. (25) 

Quercetin

Quercetin has anti-inflammatory properties and is part of the flavonoid antioxidants group. This powerful antioxidant has also been shown to have antiviral properties as well as anticancer and antidepressant properties. In one study, mice who were given quercetin were significantly less likely to develop the flu. Eating fruits and vegetables significantly boost levels of quercetin. Quercetin has also been shown to reduce upper respiratory infection after heavy exercise. (81)

Selenium and the Immune System

Selenium deficiency has been associated with the development and growth of several viruses (3). Good sources of selenium are Brazil nuts, tuna, salmon, turkey, chicken, brown rice, mushrooms, and oatmeal.

Vitamin A and the Immune System

Vitamin A is another antioxidant that is important for the immune system(15, 16). This vitamin also protects against infection is by keeping the skin, mouth, stomach, intestines, and respiratory systems healthy (17)  In one study, vitamin A decreased morbidity and mortality associated with measles in children. 

Vitamin E and the Immune System

Vitamin E is another antioxidant that may benefit the immune system. In fact, vitamin E may have antiviral effects, especially in the elderly (6, 17). However, vitamin E is dependent on vitamin C, vitamin B3, selenium, and glutathione. So, a diet high in vitamin E cannot have optimal effects unless you are also eating foods high in these other antioxidants. (11) 

Studies have found that elderly nursing home residents who received vitamin E supplements were less likely to catch colds and other upper respiratory infections. (11) 

Moreover, when researchers looked at vitamin E levels over a 3-year period, researchers found increased plasma vitamin E correlates with a reduced number of infections. 

The effects of vitamin E supplements on the immune system are greater when someone has a vitamin E deficiency. 

Vitamin C and the Immune System

Vitamin C has been intensively studied, and although results of these studies have varied, some studies show vitamin C may have antiviral affects. (6, 8, 10, 12,) Specifically, vitamin C helps protect you from infection by supporting your immune system and stimulating the formation of antibodies (17) 

So far, it seems that taking vitamin C regularly does not prevent a cold, but when you do get a cold, ongoing vitamin C intakes may shorten the duration in the general population.  Studies have shown that if a cold lasts 10 days, then ongoing vitamin C intakes may shorten the duration to 9 days.

Yet one study showed that regular supplementation of vitamin C decreased the duration of the common cold in adults by 8% and in children by 14%. (12) It appears that you must be taking Vitamin C for an extended period of time, because taking vitamin C at the start of a cold does not seem to help.  

Vitamin C supplements seems to be most beneficial for extreme athletes. Studies show that Vitamin C supplements may prevent colds in people who are exposed to strenuous physical activity such as marathon runners. The risk of getting colds may be reduce to half in these individuals.  

Below is what a few other Vitamin C studies and reviews have said: 

In a review of 148 animal studies, vitamin C appeared to alleviate or prevent infections from bacteria, viruses, and protozoa (8) 

The general consensus is based on this review is, again, that in humans, vitamin C does not decrease the average cold incidences in the general population but does seem to half the number of colds in physically active people. (8) 

Vitamin C deficiency, however, has been associated with an increased risk of pneumonia. Three controlled trials found that vitamin C prevented pneumonia (8)  

Vitamin C supplements may be beneficial in elderly patients with pneumonia. In one study, 94 year old patients who were hospitalized with pneumonia received either vitamin C or a placebo. The vitamin C improved total respiratory scores on all severely ill patients. There were six deaths in the trial. Five deaths were in the placebo group and only one in the vitamin C group (10) Another study found when patients were given vitamin C and vitamin E, the number of days on the ventilator were significantly reduced. 

The Take Home Message for Vitamin C

The take home message is to make sure you are eating foods high in vitamin C as well as other antioxidants. If you are an extreme athlete, you may want to speak to your doctor about vitamin C supplements.  Vitamin C supplements may help prevent or treat infection if a person is deficient or marginally deficient in vitamin C or in extreme athletes and perhaps the elderly. (8) 

Vitamin D and the Immune System

Evidence shows that vitamin D can have a significant impact on the immune system and may offer protection against the common cold (12, 16, 110, 111). In fact, people with low vitamin D levels are more susceptible to colds, flus, and respiratory infections. Adequate vitamin D may even decrease the rate of respiratory infections from colds, flu, bronchitis, and pneumonia. Most research shows that taking vitamin D helps prevent respiratory infections in adults and children. 

Take Home Message on Vitamin D 

Ask your doctor to test you for vitamin D deficiency. If you are deficient or are borderline deficient, supplements may be helpful, especially in colder months. Make sure to include vitamin D rich foods in your diet like salmon, tuna, eggs, mushrooms exposed to UV light, and fortified foods.  

Zinc and the Immune System

Zinc is a crucial mineral in regards to the immune system. (12), 17) Zinc helps increase white blood cells to fight off infections. In fact, the body needs zinc to activate T-cells. T-cells control and regulate the immune system and attack infected or cancerous cells.  Therefore, a zinc deficiency severely impairs the immune system (82).

 According to research, the supplementation of zinc may shorten the duration of colds by 33%-40% (12, 14, 83).

 According to a review of 15 studies, colds were prevented in people who took zinc by mouth for 5 months (14). However, eating foods high in zinc is safer than taking zinc supplements for long periods of time because excessive zinc intakes could cause copper deficiency. Another review suggests that zinc lozenges and syrup is beneficial in reducing the duration and severity of the common cold in healthy people when taken within 24 hours of the onset of symptoms (84)

Take home message about Zinc 

Eating a well balance diet that includes food sources of zinc is an important first step. Good food sources of zinc include red meat (choose grass-fed), whole grains, legumes, and nuts. During cold and flu season, or at the onset of cold symptoms, you may want take zinc supplements, but always ask your doctor before adding supplements. 

I like the Airborne Elderberry because they provide a combination of immune supportive nutrients including zinc, elderberry, and vitamin C and Vitamin D.  We will discuss the elderberry research later in this post.

L-glutamine

The amino acid L-glutamine plays an important role in the immune system. In fact, the immune system can be compromised when there is inadequate amounts of glutamine in the body (112). Mice studies have found that glutamine may improve the immune systems ability to fight bacterial and viral infections (112, 113). In healthy adults Glutamine is usually abundant in the body; however, when the body is trying to heal from an infection or injury, your body may not produce enough. Since glutamine is an amino acid, the best sources of glutamine are fish, chicken, grass-fed beef, eggs, yogurt, nuts, and beans.

Nutrition and the Immune System: Let’s Recap Before Moving On

Okay so to recap, we have talked about how crucial eating a variety of antioxidants is to our immune system. Then we discussed other immune supportive nutrients like vitamin D, zinc, and L-glutamine. Now let’s talk about the role gut health plays on the immune system. 

Gut Health and the Immune System

So how important is our gut in regards to our immune system, anyway? VERY! 70% of the entire immune system tissue resides in the gut! (19 33). Studies have shown that changes in the gut microbiome can significantly affect susceptibility to disease (26, 27  28,  29, 30, 31, 32, 33). For optimal gut health, we should incorporate probiotics, prebiotics, fiber, anti-inflammatory foods, and yep, antioxidants (they showed up again) into our diets.  

Probiotics

Probiotics are “good” bacteria in our gut. We want more “good” bacteria and less “bad” bacteria in our gut. According to research, probiotics may help reduce the frequency and severity of infections and colds. (26, 27  28,  29, 30, 31, 32, 33),     

 Keep in mind, however, that different probiotics have different benefits. With that in mind, evidence suggests that Lactobacillus can modestly reduce the likelihood of the coming down with the common cold or flu (62). 

 In one study, the frequency and severity of cold symptoms were lower in the group who were receiving Lactobacillus rhamnosus compared to the control group. In another study, the common cold symptoms significantly improved in people who consumed Lactococcus lactus . 

When a lethal dose of parainfluenza virus was fed to mice, the mice taking Lactococcus lactus had a 61% survival rate while the control group had a 0% survival rate.  

Yet another study found college students who took probiotics reduced the duration and severity of colds. 

In a 2015 review, researchers looked at 12 studies (3,720 total participants) and found that people taking probiotics may have fewer and shorter upper respiratory infections. The review also noted that people who took probiotics had less of a need for antibiotics and had less absences from schools due to colds. Another review looked at 28 trials and found that all but 5 trials showed probiotic benefits in regards to respiratory tract infection outcomes.  

So what does all of this research mean? 

Based on the current preliminary research certain strains of probiotics may help reduce the risk of developing viruses and infections and may decrease the duration and severity of illnesses. The probiotics that seem to help in this way are:

• Lactoccus lactus 
• Lactobacillus rhamnosus (originally thought to be a subspecies of L. casei) 
• L. casei 
• Lactobacillus plantarum 

Some products that contain these specific immune supportive probiotics are: 

• DanActive 
• Yakult 
• Ultraflora Immune Booster 

Fiber

Fiber is important for our immune system as well, and prebiotic fiber has a positive effect on our gut health! Prebiotic fiber promotes a healthy gut by feeding the “good” bacteria in our gut (35, 36). In fact, research found that “good” bacteria plummeted in mice who were fed a low fiber diet.  In this study the intestinal mucosal layer in the gut thinned so much that the bacteria ended up close to the intestinal wall. This triggered an immune reaction in the mice.  

 Up and coming research also suggests that large amounts of soluble fiber can speed up the recovery from bacterial infections. Moreover, eating more fiber seems to lower mortality rates. (35) 

So what should I eat to get more Fiber? 

To get more gut healthy, immune supportive fiber in your diet eat foods like beans, nuts, fruit, whole grains, and vegetables. You can find a more detailed list of high fiber and immune supportive foods in The Nourishing Meal Builder.  

Herbs and Spices and the Immune System

Fresh spices like Thyme, Turmeric, Cinnamon, Ginger, Rosemary, Sage, Garlic, and Cilantro are full of antioxidants. According to research, Turmeric and garlic also have antibacterial, antifungal, and antiviral properties as well! Cinnamon, Ginger, and Cilantro have antibacterial properties, and Cilantro also has antifungal affects as well. Cinnamon has some fiber and iron too! Along with having antiviral properties, garlic is also a prebiotic and a good source of vitamin C and selenium.

Turmeric

Curcumin found in Turmeric have been shown to have antiviral affects (6, 7) 

Curcumin found in turmeric supports a healthy immune system and has anti-inflammatory properties. However, the amount of curcumin in turmeric is small. Also, to get the benefits of turmeric, turmeric needs to be eaten with black pepper. Still, turmeric can add lots of interesting flavors to your foods and may have several health benefits. So why not incorporate turmeric and black pepper into a healthy diet? (38)  

Garlic and the Immune System

Garlic contains a substance called alliin. When garlic is crushed or chewed, alliin becomes a compound called allicin. Allicin in garlic has been shown to slightly enhance the disease-fighting response of some white blood cells that encounter viruses, particularly viruses that cause the common cold and flu. More specifically, research shows that garlic may have antiviral, antibacterial, and anti-prozoal properties. Early research suggests that garlic may reduce the frequency of common cold viruses and reduce the duration and severity if you do get the common cold. (75, 76, 77, 85)  In vitro, garlic showed activity against Flu A and Flu B (86).

In a 2015 study, researchers found that garlic improved survival rates by inhibiting lung inflammation in polymicrobial sepsis patients (87).   

According to a systemic review of 146 participants, garlic lowered the risk of getting the common cold by 63% and for those who did get the cold, the duration was 70% shorter when compared to the placebo groups (88).  

Another study found that when people took 2.56 grams of garlic extract per day, the duration of the common cold was 61% shorter. 

Fresh uncooked garlic seems to have more benefits than powdered or cooked garlic, so if you cook your garlic, you will need to consume more for the same effect. Just 60 seconds in the microwave and 45 seconds in the oven deactivated alliinase (78).

Take Home Message on Garlic

Fresh garlic has many nutritional benefits and may even have antiviral, antibacterial, and anti-prozoal activities; therefore, fresh garlic can be a nutritious and beneficial addition to a healthy diet.  

Ginger 

 Although research is preliminary, studies suggest that fresh ginger may have anti-viral activity against RSV. (42). Research showed that ginger extract increased the number of days without ventilation support in people with acute respiratory distress syndrome and reduce the time spent in ICU (89).

Cinnamon 

Cinnamon may have antiviral, ant-fungal, and antibacterial properties (38, 43 ) This yummy herb appears to inhibit bacteria by damaging the cell membrane and altering the lipid profile of the bacteria (39) In a 2007 study, mice infected with acute respiratory infections, were put into either the control group or the “cinnamon-taking” group. The survival rate in the mice in the cinnamon group increased to 70—100%. The survival rate of mice in the control group was only 20%. (41) 

Supplementing with too much cinnamon can be toxic especially for the liver; therefore, I would only use cinnamon as a flavor enhancer in certain dishes.

Rosemary and the Immune System

Rosemary not only has antimicrobial and antibacterial properties, but also has antioxidant and anti-inflammatory properties as well, according to some research (46). One study showed antiviral activity against human RSV (115). This is yet another delicious herb that can add a nice flavor to a recipe.

Thyme 

 Some research shows that taking thyme in combination with other herbs like ivy, improves symptoms of bronchitis, upper respiratory tract infections, and the common cold such as cough, fever, and decreases production of sputum. Along with having antibacterial properties, Thyme may also have antifungals properties (55). Flavonoids are an antioxidant found in Thyme that can relax the throat muscles and lessen inflammation (55).

Horseradish

If you have ever eaten horseradish dip, you know it can give you a sensation of “clearing your sinuses,” but can horseradish do more than give you that burning/clearing sensation in your nose? Preliminary research says maybe. One large cohort study found that horseradish was as effective as antibiotics at treating acute sinusitis and bronchitis (111) . Bronchitis is defined as inflammation of bronchi in the lungs that can cause coughing, wheezing, shortness of breath, and fever. Acute bronchitis usually lasts around three weeks, while chronic bronchitis is defined as a wet cough that lasts for 3 months per year for at least 2 years. Ninety percent of acute bronchitis is caused by viral infections. A small number is caused by bacterial infections. Horseradish appears to have both antiviral and antibacterial properties. Similar to bronchitis, Sinusitis is defined as inflammation; however, sinusitis is the inflammation of nasal cavities. Sinusitis can be triggered by colds or allergies.

A Note about Supplementation 

Just a reminder that while I take an optimistic approach with food and their benefits, I am more cautious with supplements for two reasons. One, they can be expensive, and two, we can take too much and become toxic. In the case of food, however, even if the research is preliminary and conflicting as far as a particular benefit; if the food is generally healthy, why not incorporate it in our diets? 

Supplements and the Immune System 

Echinacea 

Echinacea is an herb most often taken in supplement form. This herb is high in the antioxidants: flavonoids, cichoric acid, and rosmarinic acid, as well as aklomides, which enhances antioxidant activity. Several studies have found that Echinacea may help the immune system fight infections and viruses and help you recover faster from illness (47).

Not only does Echinacea appear to help combat a cold once you get it, some evidence suggests this herb may also reduce the risk of getting the cold in the first place. A review of 14 studies found that taking echinacea may lower the risk of colds by more than 50% and shorten the duration by 1.5 days (13). However, research is a little bit mixed. Some research shows that taking echinacea can reduce the risk of catching the cold by anywhere between 10-58%. Other research shows echinacea does not prevent the common cold when you have been exposed to a virus (47).

Echinacea and the Flu

A few studies have looked at whether echinacea could prevent or treat the flu. One study found that taking a combination of echinacea and elderberry 5 times a day for 3 days, then 3 times a day for 7 days improved flu symptoms similar to Tamiflu (47).  

So What is the Take Home Message for Echinacea

There is no magic supplement that is going to stop you from getting the cold and flu; however, Echinacea is one supplement that has promising results. Hygiene is going to be the most powerful defense you have against colds, flus, and other viruses. If you have implemented hygiene habits and eating an overall balanced immune supportive diet, and you still want to add something else, then echinacea supplements may be an option. Please talk with your doctor before taking supplements and check for any drug/supplement interactions.  

Black Elderberry 

Black elderberry is a fruit with strong antioxidant affects. The antioxidants found in elderberry include phenol acids, anthocyanins, and flavonoids. According to research, Elderberry may shorten the duration of the flu by 56% when taken within 48 hours of the first symptoms. Elderberry may shortens the duration and severity by blocking a viruses ability to spread. (14) 

Relief occurs within 2-4 days of treatment. Although elderberry seems to shorten the duration and severity, it does not seem to prevent the common cold and other viruses.  

Take home message 

Taking Black Elderberry may be helpful during cold and flu season or at the first sign of symptoms.  Speak with your doctor about drug nutrient interactions before taking this supplement. I like the Airborne Elderberry gummies because they not only contain elderberry, but also other immune supportive nutrients like Vitamin D, zinc, and Vitamin C.

Ginseng 

There is very little and conflicting research on Ginseng and cold and flu prevention and treatment. One study looked at a specific supplement containing Ginseng called Cold-fX. This research showed that taking Cold-fX for several months during flu season decreased the risk of cold and flu. According to preliminary research Cold-fX may also reduce the duration and severity of colds or the flu. (91) Cold-fx may also reduce the severity and symptoms of respiratory tract infections (92). According to a 2020 review, ginseng may be helpful in relieving the symptoms and reducing the risk and duration of colds and flu (93).

Andrographis  

According to a 2014 review, andrographis may exhibit antimicrobial, antiinflammatory, anti-protazoan, antioxidant, and anti-infectous activity. (48)

Early evidence indicates that Andrographis may decrease the risk and the duration of illnesses caused by viruses like the cold and flu. (14) Moreover, Andrographis may even improve a cough and sore throat for people suffering from the common cold, and some research suggests that taking Andrographis for 2 months, may even prevent the cold.  

In a 2017 review, researchers looked at 33 studies and found that andrographis appeared to relieve acute upper respiratory tract infections when compared to a placebo, herbs, or general standards of care. This review also found that andrographis shortened the duration of a cough, sore throat, and even number of sick days (50, 51).

Some combinations of Siberian ginseng and andrographis appeared to improve the common cold within 72 hours of feeling sick, with the symptoms taking around 4-5 days to completely go away.  

One particular study divided 158 people with the common cold into two groups. The first group received andrographis and the second group received a placebo for 5 days. By day 4, the andrographis group all reported less severe symptoms. The improved symptoms included headaches, tiredness, sore throat, nasal secretions, phlegm, and cough (52). 

In another study, researchers looked at 223 patients with upper respiratory tract infection. The patients who took daily andrographis had a significant decrease in symptoms compared to the the placebo group (54).  

In a study that looked at 152 patients, researchers found that those who took a daily dose of andrographis had less fever and sore throat by the third day. The symptoms of those that were given 3 grams improved; however, those who were given 6 grams saw the greatest improvements (53).

Star Anise 

 There have been minimal studies on Star Anise, and many of the studies have been in vitro or on mice. However, based on very limited research, Star anise may have antimicrobial, antifungal, and antiviral properties. In fact, Star Anise contains shikimic acid, which is the active ingredient in Tamiflu. Star anise may not only be antiviral, but also have antibacterial effects as well. Some research suggest star anise may inhibit bacterial growth and may be as effective as antibiotics against drug-resistant bacteria. (97, 98).

N-acetyle cysteine

N-acetyl cysteine is an antioxidant and the supplement form of the amino acid, cysteine. NAC is another beneficial nutrient for times when we are ill. N-acetyl cysteine may help with complications that can occur from upper respiratory tract infections. N-acetyl cysteine helps treat collapsed lungs caused by mucus blockage. A meta-analysis of 13 studies suggest it can significantly reduce symptoms like coughing and shortness of breath in people with chronic bronchitis (113). Chronic bronchitis is defined as prolonged inflammation of the lungs caused by mucus build-up. NAC also seems to reduce flu symptoms as well. Cysteine is found in chicken, eggs, turkey, yogurt, and legumes.

Some very preliminary research suggests the following herbs and supplements may have immune supportive, antiviral, and antibacterial properties as well: 

Moringa: May have antimicrobial properties (100)  

Oregano: Some test tube studies show that Oregano has antiviral and antibacterial properties (56, 101)  

Ivy Leaf : Very few studies (and some are poorly done and lack a placebo), suggests Ivy Leaf may be helpful for upper respiratory tract infections. After 7 to 10 days, symptoms like a cough significantly improved (102).

So What Immune Supportive Foods Should I be Eating?

Remember antioxidants are a biggie, so eat lots of fruits, vegetables, nuts, legumes, and whole grains to get plenty of antioxidants, vitamin C, and fiber. Many of these foods are prebiotics as well so they may help improve gut health too!

Mushrooms 

Mushrooms that have been exposed to UV light are a fantastic source of immune supportive vitamin D as well as selenium, Iron, AND have anti-inflammatory properties. They also contain beta-glucans which help the natural killer cells in our bodies.

Whole Grains 

Whole grains like buckwheat, brown rice, wild rice, and whole wheat are a great source of fiber. 

Oats and quinoa are considered a prebiotic and a good source of fiber, zinc, and selenium (antioxidant). 

Legumes 

Legumes are a prebiotic full of immune supportive nutrients like zinc, iron, fiber and antioxidants.  

Water and Fluids 

“Drink lots of fluids” is one of the first things you will hear your doctor say when you are diagnosed with a cold or flu. Staying hydrated helps your body and your immune system function at its best. Also, drinking lots of fluids throughout the day thins mucus and soothes an irritated throat.  Hot fluids seem to be more effective than cold fluids in regards to thinning mucus.   

Chicken Noodle Soup 

We have all heard that chicken noodle soup helps a cold, but did you know that some research backs it up!?!? 

Studies have shown that chicken soup helps clear nasal congestion and ease cold symptoms, and here are some possible reasons why: 

-Hydration:

Hydration is one of the first and most crucial steps you can take when you come down with the common cold. Soup is a liquid so you will be hydrating your body as you eat the soup.  

-Steam:

Steam from the salt water (soup is usually pretty salty), makes it easier to breath and has a mild anti-inflammatory effect. Most symptoms related to a cold are a result of an inflammatory response.

-Warm Liquid:

Warm liquids can sooth a sore throat. Drinking warm liquids also helps thin mucus. 

-Vegetables:

Many chicken soups are loaded with vegetables. We talked about the importance of antioxidant with regards to the immune system earlier. A 2000 study found that one particular chicken soup recipe contained anti-inflammatory nutrients and appeared to reduce the symptoms of upper respiratory tract infections (57).

-Inhibit Neutrophil Migration:

Studies showed that chicken soup inhibited neutriphil migration. Neutrophil are circulatory white blood cells, and they are essential for the bacterial removal process. Neutrophils are also stimulators of mucus release; therefore, neutrophil migration may be one mechanism in which colds lead to coughs and phlegm. Cough and phlegm may be reduced by inhibiting the neutrophil migration.  

One small study in CHEST, showed that chicken soup cleared sinuses and improved symptoms of infection. In this study, tiny particles meant to mimic a bacteria or virus were inserted into the noses of 15 healthy volunteers. The activity of the particles were measured before and after the participants drank either cold water, hot water, or chicken soup. The hot chicken soup was the most effective in stimulating the mucocillary transport system, which helps the upper respiratory tract get rid of infection (105).

Immune Supportive Meats

Tuna and salmon are super sources of Omega-3, specifically DHA and EPA omega-3. Fish like tuna and Salmon are also a good source of immune supportive vitamin D and zinc.  

Chicken and turkey have zinc and selenium, which are both important for the immune system.  

Cage-free Omega-3 eggs have omega-3 and vitamin D.  

Healthy Fats: Olive Oil, Nuts, and Seeds 

Olive oil, nuts, and seeds are good sources of healthy fats and antioxidants. Walnuts is a good source of immune supportive Omega-3 as well.  Nuts are a fantastic source of fiber, iron, and Vitamin E as well. 

Chia seeds, flaxseeds, and hempseeds are good sources omega-3s, zinc, fiber and antioxidants; and sunflower seeds are a good source of the antioxidants vitamin E, selenium as well as Zinc, and fiber.

Dark Chocolate and Tea

Dark chocolate and black and green tea are good sources of immune supportive polyphenol antioxidants. Black, green, and Matcha green tea may help decrease stress hormones, and remember stress can negatively impact the immune system!

Nutritional Yeast

Nutritional Yeast is a complete protein and a good source of vitamin B12; therefore, this it is particularly beneficial to vegetarians. Along with these other healthy nutrients, Nutritional Yeast contains the immune supportive antioxidants, glutathione and selenomethionine. It also has another nutrient that may slightly help prevent and treat upper respiratory tract infections, and that nutrient is Beta-glucan (107). In a small human study, researchers found that Beta glucan may protect against upper respiratory tract infections and reduce the duration in older adults. The study only had 49 participants so larger studies are needed in the future (108).

Beta Glucan

Also based on the results of a 2017 review, Beta glucan significantly decreased the incidence of upper respiratory tract infections in people susceptible to upper respiratory tract infections; however, there was no difference in incidence in healthy people (109). Although the evidence is insufficient, some evidence suggests that consuming beta glucan for 4 weeks after a marathon may prevent upper respiratory tract infections in runners (110).

The Take Home Message About Nutritional Yeast

Is Nutritional Yeast going to have this massive impact on our ability to fight off an upper respiratory tract infection? Probably not…but Nutritional Yeast IS a complete protein and a great source of nutrients like vitamin B12 and antioxidants. So incorporating Nutritional Yeast into your diet is a good idea and according to some research may even help protect against and treat upper respiratory infections for some people.

Foods that Could have a Negative Impact on the Immune System 

Sugar, refined carbohydrate, fried foods, trans fat, alcohol, ultra processed foods, and vegetable oils promote poor gut health, increase inflammation, and increase the risk of developing other chronic diseases. All of these scenarios can negatively impact the immune system. So to help your immune system be at it’s best, limit your intake of these foods.

Based on all the above research, what are the key points?

• Practice good hygiene, first and foremost. This is going to have the greatest impact on reducing your risk of getting sick.
• Get adequate sleep
• Find ways to cope with stress
• Incorporate the immune supportive foods listed below into your diet

Nutrition and the Immune System: Eating to Support the Immune System

• Eat a diet rich in antioxidants. Antioxidant-rich foods include fruits, vegetables, nuts, whole grains, green tea, dark chocolate, nutritional yeast, and olive oil.
• Eat foods high in Vitamin D like tuna, salmon, Cage-free Omega-3 eggs, and mushrooms exposed to UV light.
• Eat foods that contain zinc like tuna, salmon, chicken and turkey; and vegetarian options like whole grains, nuts, beans, flaxseed, chia seed, pumpkin seeds, and hemp seed.
• Eat foods containing Vitamin C like kale, Brussel Sprouts, broccoli, chili peppers, papayas, strawberries, and oranges. Supplements may even be beneficial for extreme athletes. Check with your doctor.
• Eat foods rich in protein to get adequate amounts of immune supportive amino acids.
• Drink Antioxidant-rich and stress reducing green tea. Ginger green tea and peppermint tea may help soothe a cough and sore throat that often comes with getting sick.
• Keep a variety of fresh herbs and spices on hand and add them to your recipes and dishes. These herbs include garlic, turmeric (with black pepper), ginger, cinnamon, Rosemary, and Thyme.
• Eat foods that contain probiotics, prebiotics, and fiber to support gut health. Probiotic-rich foods include yogurt, kefir, kombucha, fermented sauerkraut, fermented pickles, miso, tempeh, and kimchi. Probiotics that seem particularly helpful to the immune system are Lactoccus lactus, Lactobacillus rhamnosus (originally thought to be a subspecies of L. casei), L. casei, and Lactobacillus plantarum. Prebiotics include foods like bananas, garlic, asparagus, and oats. High fiber foods include fruits, vegetables, whole grains, beans, and nuts.
• According to preliminary research, these supplements may either reduce the risk and/or reduce the duration and severity of colds, flus, virus and/or bacterial infections: Elderberry, Echinacea, garlic and Androghraphis. Do not take supplements without talking to your doctor. *More research is needed
• Limit refined carbohydrates, fried foods, trans fat, sugar, alcohol, ultra processed food, and vegetable oils.

* You can find a more complete list of foods, nutrients, and their benefits in the ebook, The Nourishing Meal Builder. Once you purchase the ebook, you automatically get the updated versions when they come out.

About Lacy Ngo, MS, RDN

Lacy Ngo, MS, RDN is a registered dietitian and owner of Mindfulness in Faith and Food, LLC. Mindfulness in Faith and Food, LLC focuses on how to live your healthiest, happiest, most meaningful life through faith-based mindfulness and evidence-based nutrition.
Ngo is nationally known as one of the top experts in faith-based mindfulness and nutrition and also the author of several books including, 18 Weeks to a Healthier, Happier, More Purposeful Life, Mindfulness in Faith and Freezer Meals, and The Nourishing Meal Builder. You can also find evidence-based nutrition articles, recipes, convenient healthy snack lists, and faith-based mindfulness techniques on her blog, Mindfulness in Faith and Food.

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