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Building Natural Immunity During Flu Season

Medically reviewed by 
Building Natural Immunity During Flu Season

The cold is here, which means the flu is too. During these winter months, the flu affects about 3% to 11% of the United States population. With the pandemic restrictions withdrawn, we have seen the emergence of the flu much earlier than in previous years.

Getting ahead of the game by implementing preventative measures and lifestyle changes can help decrease your odds of contracting the flu. Optimizing your immune system can change the trajectory of contracting viral infections, shorten the duration of symptoms if infected, and promote overall vitality. Understanding the flu and all your options will help you make the best decision to support yourself and your family.


When is Flu Season?

Data shows that influenza peaks between December and February, although it can be detected year-round. Predictions for flu season are made based on numbers from the southern hemisphere, primarily Australia, since they are about a season ahead of us. The CDC collaborates with many organizations to predict future flu impacts using a forecasting system. Since influenza is an airborne contagion, it is easily spread.  

What is the Flu?

The flu, short for influenza, is a viral pathogen that affects the respiratory system. Influenza inhabits and causes symptoms in the nose, throat, and lungs. It's spread through respiratory droplets from person to person, thus making it a highly contagious virus. The flu virus can be detected through a nasal swab test about a day before symptoms start. On average, those with the virus are contagious in the first three to four days of their symptoms. There are three types of flu viruses- A, B, and C, with Influenza A being the primary strain leading to respiratory flu illness.

Flu Signs & Symptoms

The flu is often mistaken for a common cold. The overlapping symptoms of sneezing, runny nose, and sore throat may be what initially throws you for a loop. The distinguishing feature is that flu symptoms come on rapidly, are often more severe, and are persistent. You can experience any (or all) of these symptoms, typically lasting 4 to 7 days.

  • Fever
  • Muscle or body aches
  • Chills and sweating
  • Headaches
  • Dry, persistent cough
  • Shortness of breath
  • Tiredness
  • Weakness
  • Runny or stuffy nose
  • Sore throat
  • Eye pain
  • Vomiting and diarrhea (more common in children)

How to Build Immunity During Flu Season?

You can do many things to support your immune system before and during flu season. When deciding what is best for your overall health and well-being, it is best to make an educated decision. Knowing your risk, benefits, and alternatives is vital when optimizing your body's ability to ward off any pathogen.

From a lifestyle perspective- eating well, exercising, getting adequate sleep, managing stress, and taking supplements can help build a robust immune system.

Functional Medicine Testing for Immunity During Flu Season

Optimizing health is a critical factor in strengthening your immunity for flu season. One avenue we all could benefit from is optimizing our gut health. Science has shown that our gut microbiome significantly influences our immune system. When our microbiome is out of balance, this could lead to decreased immune function. Here is one test that could assess gut health.

The GI Effects® Comprehensive Profile by Genova Diagnostics analyzes microorganisms to determine your microbiome's overall health status. This test is used to determine if dysbiosis is present, whether overgrowth of opportunistic bacteria is present, or if there is a lack of beneficial microbial diversity. Information from this test can help support immunity by supporting microbiome health.

Micronutrient testing by SpectraCell Laboratories tests 31 levels of vitamins, minerals, antioxidants, fatty acids, and amino acids. Much like gut health, having optimal micronutrients is essential to immune function. One review on the topic looked at how micronutrient status can impact immune function and rates of infection. Immunocompetence can be heavily influenced by various micronutrients not limited to, but especially vitamins A, C, E, D, and B12 and the minerals Selenium and Zinc.  

IgA testing may be warranted if you are someone who frequently gets sick or you have a chronic illness. Immunoglobulin A (IgA) is the primary antibody that lines the mucosal membrane of your GI tract and respiratory tract. Its role is to help fight off infections. Deficiency in IgA is one of the most common primary immunodeficiency syndromes and can sometimes go undetected unless tested. If you have a family history of Selective IgA Deficiency or are prone to infection, this test would be helpful for precaution and treatment purposes.

Building Immunity During Flu Season

Low Inflammatory-High Phytonutrients Diet

A well-balanced low inflammatory, high in phytonutrients diet can help your body obtain valuable nutrients that support immune function. For flu prevention, it's recommended by the American Dietetic Association to consume foods that are nutrient-dense, such as vegetables, fruits, whole grains, lean protein, healthy fats, and high in antioxidants. Consuming whole foods can also help reduce inflammation in the body, which can, in turn, bolster immunity. An excellent guideline for eating this way is by following the Mediterranean diet.

Avoiding Sugar

Amongst the medical and scientific community, sugar is known to impact immune capacity. Although not many studies show exactly how it alters immune function, we know that added sugar triggers an inflammatory response which can then negatively influence immunity.

One study looked at young men who consumed low-to-moderate sugar-sweetened beverages. The results revealed that regardless of the intervention group (high or low added fructose or glucose) they were in, all participants had elevated fasting glucose and Hs-CRP. High-sensitivity C-Reactive Protein (Hs-CRP) is a key marker of inflammation and, when present, can indicate acute or chronic inflammation.


Maintaining adequate hydration helps your mucosal tissue maintain its integrity and promotes cellular function. We are made up of approximately 60% water, with each cell in our body containing water. Water aids in regulating body temperature, lubricates the membranes of your eyes, nose, and mouth, carries nutrients and oxygen amongst cells, and lubricates joints. Without adequate water, our body has a difficult time maintaining homeostasis. Keeping all systems balanced through hydration is a simple way to support wellness and prevent illness.

To stay hydrated, it is suggested that a person drink about half an ounce to an ounce of water for each pound they weigh daily. Adding electrolytes can help increase fluid retention in the body.

For example, if you weigh 150 pounds, you should consume approximately 75 to 150 ounces of water daily. If you're living in a hot climate or exercise daily, consuming an ounce of water per pound is recommended.


There are many benefits to exercising, including immune system support. Scientists recently explained that exercise could help our immune system find and kill infected cells. Regular exercise can also slow down how your immune system changes with aging, thus making you less susceptible to infections. A general consensus on a healthy exercise routine for adults is 150 minutes of moderate aerobic activity a week plus two days of strength training.


Getting adequate and restorative sleep aids the body's ability to fight infections. Sleep deprivation has been said to suppress your immune system, which makes you more susceptible to things such as the flu. Incorporating a sleep hygiene routine can help ensure you get enough sleep to support your immune function.

Immunity Building Supplements

Science-backed immunity-building supplements are a great way to give your immune system a boost. These supplements provide essential vitamins, minerals, and nutrients that can help your body fight off infections, viruses, and diseases. Many of these supplements contain natural ingredients, such as herbs, probiotics, and antioxidants, that have been scientifically proven to help strengthen the immune system. When taken regularly in the correct dosage, these supplements can be an effective way to reduce the risk of colds, flu, and other illnesses. They can also help to reduce fatigue and improve overall health. Talk to your doctor about the best supplements for your specific needs.

Vitamin C

This vitamin is a potent antioxidant that can help scavenge and protect barriers in the epithelial layer of our skin. It supports both the innate and adaptive immune systems, which can aid in protecting against pathogens. The best way to get vitamin C is through the foods you eat. Foods high in vitamin C include citrus fruits such as oranges and lemons, bell peppers, broccoli, kiwi, Brussels sprouts, strawberries, cantaloupe, papaya, and pineapple. You can also get some vitamin C by taking a multivitamin or supplement.

Vitamin D

A deficiency in vitamin D has been linked to an increased susceptibility to infection. Vitamin D is a fat-soluble vitamin primarily produced from sun exposure. When it becomes active Vitamin D, it binds to the VDR (vitamin D receptor). This receptor is expressed on the surface of many cells in our body, including immune cells. It then aids in communicating with other immune cells when invading pathogens are present so that the proper fighter cells can be released. Vitamin D can be obtained through a combination of food sources, sunlight exposure, and supplementation.

Food sources high in vitamin D include fatty fish such as salmon, mackerel, and tuna, dairy products such as milk, yogurt, and cheese, egg yolks, and fortified foods such as orange juice, cereal, and oatmeal. Sunlight exposure is the most natural and effective source of vitamin D. Spending 10-15 minutes in the sun each day is a great way to get your daily dose of vitamin D. Finally, vitamin D supplements are also an option. Speak to your doctor before taking any supplements as they can interact with other medications and cause side effects.


If you are low in the mineral Zinc, optimizing this micronutrient could help ward off colds and viral infections. Completing a micronutrient panel would tell you if Zinc is a beneficial supplement to add to your wellness routine. A balanced diet that includes foods rich in zinc, such as oysters red meat, poultry, seafood, beans, nuts, whole grains, and fortified cereals, will help you get adequate quantities of this mineral. You can also take a zinc supplement to ensure you're getting enough zinc.


The primary function of probiotics is to provide the gut with beneficial microbes. In doing so, the immune system, 80% of which resides in the gut, will be enhanced. A review of 12 randomized controlled trials looked at the benefits of probiotics and the prevention of acute upper respiratory tract infections. The results revealed that probiotics are more beneficial than placebo in preventing acute URTIs. Foods that are naturally rich in probiotics include yogurt, kefir, sauerkraut, kimchi, miso, tempeh, and some types of pickles. You can also take probiotic supplements. It's important to speak to your doctor before taking any supplements to make sure they're safe for you.


Adaptogenic botanicals support your body's response to stress by influencing multiple organ systems such as the adrenal glands, thyroid, and immune system. Some adaptogens have more immune-supportive properties than others. If you're looking to use botanicals to support immune function, Asian Gingseng, Astragalus, Eleuthero, Reishi, Cordyceps, and Maca all have distinct ways to help modulate the immune system.


Sambucus Nigra, commonly knowns as Elderberry, is one of the most versatile botanicals. It's a natural remedy used for centuries to treat flu symptoms and stress. A unique benefit of this healing plant is that it can support your immune system in preventing illness but also be used throughout respiratory infections to reduce the severity. People commonly take elderberry as a supplement in the form of liquid extract, capsules, tablets, or dried berries. Elderberry can also be taken as a syrup, tea, jam, or added to smoothies.


This botanical has been widely used clinically to help modulate the immune system. A study of 755 healthy subjects showed that Echinacea reduced the total number of colds and prevented the contraction of viral infections when used therapeutically. Common ways to take echinacea is in pill or capsule form, although it can also be taken as a liquid extract, tincture, or in a tea.

Other Strategies


Immersing yourself in nature is a free and effective way to enhance immunity. Earthing, also known as Grounding, is the act of walking barefoot, letting your feet connect with our natural elements- sand, soil, rock, or water. Evidence suggests that Earthing can decrease inflammation, shift us into a relaxed (parasympathetic) state, and activate immune cell responses.

Stress Management

Chronic stress can weaken your immune system and raise inflammation in the body. Both of which can leave you more susceptible to infection of any kind. Implementing stress management techniques can help relieve the build-up of chronic stress while giving you tools to ease your mind. Here are three effective stress reduction techniques.

  • Vagus Nerve Stimulation: Cranial nerve number 10, also known as the Vagus nerve, primarily controls our parasympathetic nervous system. The parasympathetic branch of the autonomic nervous system can help your body adapt to stressful situations by communicating between different organ systems in the body. There are multiple ways to activate this nerve, which can ultimately lead to more states of relaxation. Three popular ways to stimulate the Vagus nerve are meditation, breathwork, and cold exposure.
  • Meditation: Incorporating meditation into your life is a helpful tool that you can access from anywhere to address moments of stress. While short spurts of meditation can help acute stress, the long-term beneficial effects of meditation come from making it a consistent part of your lifestyle.
  • Breathwork: Retraining your breathing patterns from short and shallow to slow, mindful, and deep breathing patterns can reduce feelings of anxiety and stress.
  • Yoga: is a mind and body practice that can help you manage stress. One study looked at stress reduction outcomes of 52 women who incorporated 12 sessions of yoga practice into their life. The results showed that the mean stress scores before and after this intervention had decreased by a statistically significant amount.

Hand Washing

Hand washing with soap and water for a minimum of 20 seconds is the most effective way to eliminate germs like bacteria and viruses. When we wash our hands, the soap and water form pockets called micelles that trap and remove germs, harmful chemicals, and dirt from our hands.

Avoiding Smoking and Alcohol

Smoking and alcohol can significantly decrease the body's ability to fight off infections and chronic diseases, making it more difficult for the body to stay healthy.

Smoking alters the immunological response in the body, which is responsible for fighting off infections. Studies have also shown that smoking can increase the risk of developing various infections, including pneumonia and tuberculosis.

Alcohol has a similar effect on the body's immune system, affecting its ability to fight off bacteria and viruses. Alcohol can also interfere with the body's ability to absorb essential vitamins and minerals, weakening the immune system. In addition, alcohol can increase inflammation in the body, leading to a greater risk of developing chronic diseases.

What If I'm Interested in The Flu Vaccine?

The CDC's primary recommendation to create antibodies against the flu is yearly vaccination for those six months and older. The flu shot for the 2022-2023 season is expected to protect against the four main influenza virus strains predicted to be most common this season.

How Do Flu Vaccines Work?

The concept behind vaccination is that it will work on the adaptive immune system to, in theory, create antibodies that will mount an immune response when exposed to the live virus. The flu vaccine is most commonly administered as an inactivated (dead) pathogen injection but can also be given as a live nasal mist. Regardless of the form of administration, the goal is for the antigen (inactivated or live attenuated) to create antibodies, which your body will then release in the form of memory B cells when you come in contact with the virus in the community. The flu vaccine aims to create an immune response, generating memory cells that should activate when that same strain invader is present.

How Effective Is The Flu Vaccine

Flu vaccine effectiveness varies year-to-years. You can see statistics from previous years' influenza shots by exploring the CDC's tracking system. According to the tracking system, since reporting began in 2004, the lowest vaccine effectiveness was 10% (2004-2005 season), and the highest has been 60% (2010-2011 season).

Two factors impact vaccination protection- the characteristics of the person vaccinated (age and health) and how well the strain predictions match up with the viruses that appear in communities.

Institutes such as the Mayo Clinic state that while the vaccine does not entirely prevent the flu, it may lower illness severity and hospitalizations. They also suggest you take additional measures such as frequent hand washing, avoiding crowds during the peak, cleaning and disinfecting your home regularly, and practicing good health habits such as exercise, adequate sleep, and a healthy diet.


While the flu may significantly affect a small percentage of our population, it is still worthwhile to focus on your health throughout the year to increase immunity and lower your risk of severe complications during flu season.

Considering all your options, including lifestyle changes, nutrient support, botanical supplementation, and stress management techniques, is the best way to build immunity for flu season.

Utilizing labs such as micronutrient testing, gut microbiome evaluations, and IgA antibody levels can also help you optimize your immune system. While most of the interventions can be implemented on your own, working with a skilled practitioner can help guide you in making healthy choices that best fit your needs.

If you are interested in the vaccine for flu prevention, it is still best to focus on building immunity through lifestyle factors to help lower the risk of severe complications during flu season.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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