The Immune System – A Primer

Immune Health

Our immune health is a multivariable and complicated process which intertwines with our other body functions. And, our own specific genetics add another layer of complexity.

Therefore, absolutely proving (i.e. conducting valid studies) the cause and effect of any particular diet or exercise on a benefit is very difficult. 

So, you should be very leery if you hear or see someone touting some magic “elixir” or behavior that directly correlates to some stated benefit.   

My general learning from all my readings and video viewings is that there is no shortcut to improving your health.

You know what you have to do (see my articles : Diet and Fitness Plan and Nutritional Guidelines with Supplement Comments)

1. Get regular checkups so you can stay ahead of any issues. 
2. Try to maintain a reasonable body weight (defined by BMI for example).
3. Exercise regularly and mix in both aerobic and strength training routines.
4. And maybe try a few other things to chill you out (stretch, meditate, take short or long walks , etc.).
5. Follow the Dietary Guidelines for Americans.
6. Supplement nutrients that you otherwise are not getting from your normal diet. 
7. Don’t smoke and try to not drink too much alcohol.

In the following sections, I list nutrients and best practices that most people agree will have a positive impact on your immune health. Not surprisingly these things will contribute to an improved overall health as well. Links to the References (e.g. Ref 1) are listed at the end of this section on Immune Health. 

You’re Getting Older 

As you age, you will be more susceptible to disease and infection.

• Are you making sure you are adequately monitoring your body? 
• Are you up to date on your vaccines?
• Are you getting regular medical checkups?
• Are your lifestyle habits (exercise, what you eat and drink and how much you sleep) consistent with your desire for a long and pain free life?  

(Ref 7) “As we age, our internal organs may become less efficient; immune-related organs like the thymus or bone marrow produce less immune cells needed to fight off infections. Aging is sometimes associated with micronutrient deficiencies, which may worsen a declining immune function.”

Avoid Getting Infected

Ref 3; Ref 5;Ref 7, Ref 9

• (Ref 3) “Wash your hands for 20 seconds, don’t touch your face and take social distancing seriously when around anyone who seems sick”
• Wash Hands (Ref 7; “when coming in from outdoors, before and after preparing and eating food, after using the toilet, after coughing or blowing your nose”).
• Cook food sufficiently

Get Regular Medical Screenings

Ref 6; Ref 9;

• (Ref 9) “Get regular medical screening tests for people in your age group and risk category.”
• For guys (prostate check, colonoscopies) and for women (breast checks, colonoscopies) 

Don’t Smoke

Ref 1; Ref 4; Ref 5;Ref 6; Ref 7; Ref 9

• (Ref 1) “Smoking can make the body less successful at fighting disease. Smoking increases the risk for Immune System problems, including rheumatoid arthritis.“
• (Ref 4) “Smoking exacerbates pathogenic immune responses and/or reduces immune defenses.” 

Exercise (Including Meditation and Stretching)

Ref 1; Ref 3; Ref 4; Ref 5;Ref 6; Ref 7; Ref 8; Ref 9; Ref 11; Ref 12; Ref 14

Exercise_(References 1 – 11)

• (Ref 1) “Emerging research also suggests that physical activity may potentially benefit immunity.”
• (Ref 1) “..being physically active may help lower your chances of dying from the flu or pneumonia.”
• (Ref 4) “Exercise changes immune regulation by affecting cells and has anti-inflammatory effects.” 
• (Ref 8) Reduces Inflammation 
• (Ref 9, Ref 11); Weekly Target:  2 strength training sessions and 150 minutes of moderate cardiovascular activity 
• (Ref 11); “Moderate cardiovascular exercise can increase the activity of virus-killing cells. This includes White Blood Cells and antibodies.
• (Ref 11);  “Muscle tissue preserved from strength training secretes anti-inflammatory substances called myokines.”

Exercise_(Reference 14)

• (Ref 14) Exercise helps decrease your chances of developing heart disease and keeps your bones healthy and strong,
• (Ref 14) Flushes bacteria out of the lungs, reducing chance of getting a cold, flu, or other illness.
• (Ref 14) White Blood Cell antibodies circulate more rapidly, thus detecting illnesses earlier than normal.
• (Ref 14) Body temperature rise might fight infections better (similar to when you have a fever)
• (Ref 14) Slows down the release of stress hormones, some of which increase the chance of illness. 

Sleep (7-9 hours/day)

Ref 1; Ref 4; Ref 5;Ref 6; Ref 7; Ref 9; Ref 11; Ref 12

• (Ref 4) “Sleep loss
  • reduces natural killer cell activity, which increases the risk for cancer and viral infections;
  • generates production of inflammatory Cytokines, which increases the risk for cardiovascular and metabolic disorders;
  • and reduces production of antibodies, which increases the risk for infections. 
• (Ref 11, Ref 13) Sleep deprivation might reduce the release of  Cytokines which help fight off infection.

Maintain a Healthy Weight

Ref 1; Ref 5;Ref 6; Ref 7; Ref 9 

Are you in a healthy weight range? You can use information in my Diet and Fitness Plan to estimate your Body Mass Index or BMI. 

• (Ref 1) “Obesity, defined as a body mass index (BMI) of 30 or more in adults, is linked to impaired immune functions.”
• (Ref 1) “Obesity may also lower vaccine effectiveness for diseases like influenza, hepatitis B, and tetanus.”
• (Ref 7)  “Obesity is associated with low-grade chronic inflammation.
  • Fat tissue produces Adipocytokines that can promote inflammatory processes.
  • Research is early, but obesity has also been identified as an independent risk factor for the influenza virus, possibly due to the impaired function of T-cells, a type of White Blood Cell. “

Stay Hydrated

• (Ref 2) “Water helps your body produce lymph, which carries White Blood Cells and other Immune System cells,”.
• (Ref 2) “…try eating more hydrating foods, such as cucumbers, celery and watermelon.”

Control your Blood Pressure

Ref 9

• Your regular yearly (at least) medical checkups should include a blood pressure check.
• If it’s too high (discuss with your doctor), you guys need to come up with a plan to manage it. Avoid being a victim of this “silent killer”. 

According to the World Heart Federation (accessed 8/18/2024):

• “Hypertension is the number one risk factor for death globally, affecting more than 1 billion people.
•  It accounts for about half of all heart disease and stroke-related deaths worldwide.
• Hypertension does not cause any symptoms on its own, which is why it’s often referred to as “the silent killer”.

A high blood pressure patient probably has some or all of the following:  inflammation, endothelial dysfunction, oxidative stress, and altered immune cell function.

But are these symptoms or causes?

Recent studies have suggested that inflammation caused by the Immune System ultimately results in chronic hypertension. This is an ongoing research area. 

Drink Alcohol in Moderation

Ref 1; Ref 4; Ref 5;Ref 6; Ref 7; Ref 9;

(Ref 4) Alcohol disrupts immune pathways, contributes to organ damage, and impedes recovery from tissue injury.  

Diet (Follow the American Dietary Guidelines)

Ref 1; Ref 3; Ref 4; Ref 5;Ref 6; Ref 7; Ref 11; Ref 12; Ref 15

Follow the American Dietary Guidelines. Supplement to fill the gaps but try to get as much as possible through food. 

You can use the guidelines as a baseline from which to begin. You can tweak according to your own experimentation and feedback from your body.

Diet_(Refences 1 – 4)

• (Ref 1) “Eating well means emphasizing plenty of fruits and vegetables, lean protein, whole grains, and fat–free or low–fat milk and milk products.”
• (Ref 1) “Eating well also means limiting saturated fats, salt, and added sugars.”
• (Ref 3) “Choosing whole, unprocessed foods does wonders for overall health.”
• (Ref 3) Garlic (Allicin) can  boost the Immune System.
• (Ref 3) Prebiotics: Robust gut bacteria protect us against infection. Keep those bacteria healthy with prebiotics that contain fiber, specifically inulin fiber.”
• (Ref 3) Vitamin C-rich foods: Vitamin C is known to boost immunity. 
• (Ref 3) Antioxidants: “Colorful fruits and vegetables including berries, carrots and spinach have antioxidants that protect you against oxidative stress, which translates to a stronger Immune System.”
• (Ref 4) “Eat as many fresh fruits and vegetables as you can, every day.” – For Zinc and Vitamin A for example.
• (Ref 4) ” The fiber from fruit and vegetables can help your gut’s microbiome produce important compounds for a healthy Immune System.”

Diet_(Refence 7)

• (Ref 7) “Eat a balanced diet with whole fruits, vegetables, lean proteins, whole grains, and plenty of water. A Mediterranean Diet is one option that includes these types of foods”
• (Ref 7) “… a Western diet high in refined sugar and red meat and low in fruits and vegetables can promote disturbances in healthy intestinal microorganisms, resulting in chronic inflammation of the gut, and associated suppressed immunity.”
• (Ref 7) “If a balanced diet is not readily accessible, taking a multivitamin containing the RDA for several nutrients may be used.”
• (Ref 7) “Certain dietary patterns may better prepare the body for microbial attacks and excess inflammation, but it is unlikely that individual foods offer special protection.”
• (Ref 7) Vitamin C, vitamin D, zinc, selenium, Iron, and Protein (e.g. glutamine) are identified as critical for the growth and function of immune cells
• (Ref 7) “The gut is a major site of immune activity and the production of antimicrobial proteins.  The diet plays a large role in determining what kinds of microbes live in our intestines.”
• (Ref 7) “A high-fiber plant-rich diet with plenty of fruits, vegetables, whole grains, and legumes appear to support the growth and maintenance of beneficial microbes.”
• (Ref 7) Prebiotics break down fibers into short chain fatty acids, which have been shown to stimulate immune cell activity. 
• (Ref 7) A diet containing probiotic (gut helpful bacteria) and prebiotic foods (feed and maintain these bacteria) may be beneficial.

Diet_(Refences 11 -15 )

• (Ref 11) “Minimally processed whole foods — especially whole plant foods — may reduce inflammation by improving gut health.”
• (Ref 15) “Consuming adequate amounts of several vitamins and minerals—including vitamin A, vitamin C, vitamin D, vitamin E, selenium, and zinc—is important for proper immune function,…”
• (Ref 15) “and clinical deficiencies of these nutrients weaken immunity and can increase susceptibility to infections”

Vitamins and Minerals

Vitamin_A

• (Ref 15) “Vitamin A plays a critical role in vision and growth. It is also required for the formation and maintenance of epithelial tissue and the differentiation, maturation, and function of Macrophages and other cells of the innate Immune System” 
• (Ref 15) “Vitamin A’s impact on adaptive immunity is less clear, but it is involved in the maturation of CD4+ T-Cells, the function of B-cells, and the regulation of inflammatory Cytokines”
• (Ref 15) “Vitamin A deficiency is associated with increased susceptibility to infections, altered immune responses, and impairment in the ability of epithelial tissue to act as a barrier to pathogens”

Vitamin_B6

• (Ref 2) “B6 is vital to supporting biochemical reactions in your Immune System. One of its major roles is in producing White Blood Cells and T-cells.” 

Vitamin_C

Ref 2; Ref 7; Ref 11; Ref 15

• (Ref 2) “Vitamin C acts as an antioxidant, meaning it can protect your body from toxins that cause inflammation in your body.”
• (Ref 11) Maybe help with cold recovery.
• (Ref 15) “Vitamin C plays an important role in both innate and adaptive immunity, probably because of its antioxidant effects, antimicrobial and antiviral actions, and effects on Immune System modulators.”
• (Ref 15) “Vitamin C helps maintain epithelial integrity, enhance the differentiation and proliferation of B- Cells and T-Cells, enhance Phagocytosis, normalize Cytokine production, and decrease Histamine levels”
• (Ref 15) “It might also inhibit viral replication””
• (Ref 15) “Vitamin C deficiency impairs immune function and increases susceptibility to infections”

Vitamin_D

Ref 3, Ref 7; Ref 11; Ref 15 

• (Ref 3) “…a deficiency may increase your susceptibility to infection,.. Get outside for fresh air and sunshine, but also consider taking a daily supplement of 1,000 to 2,000 IUs of vitamin D.”
• (Ref 11) Make sure you are getting the RDA for Vitamin D. Helps safeguard adaptive immune cells that decline with age. RDA (600 IU <70 yrs age and 800 IU for >70 yrs age.)
• (Ref 15) “Vitamin D appears to lower viral replication rates, suppress inflammation, and increase levels of T-regulatory cells and their activity.”
• (Ref 15) “In addition, almost all immune cells (e.g., B Lymphocytes and T Lymphocytes) express the vitamin D receptor, and some immune cells (e.g., Macrophages and Dendritic Cells) can convert 25(OH)D to the active 1,25(OH)2D form. These capabilities suggest that vitamin D can modulate both innate and adaptive immune responses” 

Vitamin_E

Ref 2;Ref 15

• (Ref 2) “Vitamin E is a powerful antioxidant that helps your body fight off infection… it helps keep your T-cells working at peak performance.”
• (Ref 15) “… plays an important role in immune function by helping maintain cell membrane integrity and epithelial barriers and by enhancing Antibody production, Lymphocyte proliferation, and natural killer cell activity.”
• (Ref 15) “Vitamin E also limits inflammation by inhibiting the production of proinflammatory Cytokines”.
• (Ref 15) “Human and animal studies suggest that vitamin E deficiency impairs humoral and cell-mediated immunity, is associated with reduced natural killer cell activity, and increases susceptibility to infections.”

Selenium

Ref 2; Ref 7; Ref 15

• Selenium, Selenoproteins and Viral Infection; 
• (Ref 2) “Dietary selenium is a one-two punch for keeping you healthy. Researchers say it not only activates your Immune System when there’s a threat, but it also tells your Immune System when to pump the brakes.
• (Ref 2) “…it can keep your Immune System from going overboard, protecting you from chronic inflammation and autoimmune diseases, like rheumatoid arthritis, Crohn’s disease and psoriasis.
• (Ref 15) “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.”
• (Ref 15) “It may also reduce the risk of infections.”
• (Ref 15) “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”
• (Ref 15) “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” 

Zinc

Ref 2, Ref 4; Ref 7; Ref 11; Ref 15

• Zinc as a Gatekeeper of Immune Function

Zinc_(References 2 – 11)

• (Ref 2) “Zinc is an anti-inflammatory and antioxidant. Researchers call it the “gatekeeper” of your Immune System because it’s responsible for making all your immune cells function properly.”
• (Ref 4) “Taking Zinc supplements at the beginning of a respiratory infection can reduce the severity and duration of symptoms. Ask your doctor to recommend brands and appropriate dose for you.”
• (Ref 11) May help with cold recovery.

Zinc_(Reference 15)

• (Ref 15) “Zinc is involved in numerous aspects of cellular metabolism. It is necessary for the catalytic activity of approximately 100 enzymes and it plays a role in many body processes, including both the innate and adaptive Immune Systems” 
• (Ref 15) “Zinc also has antiviral and anti-inflammatory properties, and it helps maintain the integrity of tissue barriers, such as the respiratory epithelia.”
• (Ref 15) “Zinc deficiency adversely affects immune function by impairing the formation, activation, and maturation of Lymphocytes.”
• (Ref 15) “Zinc deficiency decreases ratios of helper to suppressor T-Cells, production of interleukin-2, and activity of natural killer cells and cytotoxic T-Cells” 
• (Ref 15) “Zinc deficiency is associated with elevated levels of proinflammatory mediators. These effects on immune response probably increase susceptibility to infections [163] and inflammatory diseases, especially those affecting the lungs.”

Extra Dosages of Vitamins

• (Ref 9) “So far, there is no evidence that taking extra amounts of any vitamin will improve your Immune System or protect you if you don’t have micronutrient deficiencies.
• (Ref 9) “However, older people, who are more likely to have such deficiencies, should discuss this question with a physician who is well versed in geriatric nutrition.”

Botanicals

Andrographis

• (Ref 15) “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”

Echinacea

• (Ref 15) “Echinacea might have antibacterial activities, stimulate monocytes and natural killer cells, and inhibit virus binding to host cells. It might also reduce inflammation by inhibiting inflammatory Cytokines.”

Elderberry (European Elder)

• (Ref 15) “Elderberry contains many compounds—including anthocyanins, flavonols, and phenolic acids—that might have anti-inflammatory, antiviral, antimicrobial, and immune-stimulating effects”

Garlic

• (Ref 15) “Researchers have studied garlic mainly to determine whether it lowers blood pressure and cholesterol levels, but it might also have antiviral properties”

Ginseng

• (Ref 15) “Animal and laboratory studies suggest that ginseng stimulates B-Lymphocyte proliferation and increases production of some interleukins and interferon-gamma [251]; these Cytokines affect immune activation and modulation.
• (Ref 15) “Ginseng might also inhibit virus replication and have anti-inflammatory activity.”

Tea and tea catechins

• (Ref 15) “Tea is one of the richest sources of catechins, which are polyphenolic flavonoids, especially epigallocatechin gallate (EGCG)”
• (Ref 15) “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.”
• (Ref 15) “Laboratory studies suggest that catechins might also have antiviral effects against the influenza A and B viruses”

Other Nutrients

Glutamine

• (Ref 15) “In the Immune System, glutamine is involved in Lymphocyte proliferation and Cytokine production as well as Macrophage and Neutrophil function [286]. Low glutamine levels are associated with poor immunologic function and an increased risk of mortality in patients in the ICU” 

N-acetylcysteine and Glutathione

• (Ref 15) “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.”
• (Ref15) “NAC might improve Immune System function and suppress viral replication”
• (Ref 15) “NAC also appears to decrease levels of interleukin-6 and have other anti-inflammatory effects”
• (Ref 15) “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”.
• (Ref 15) “Glutathione may also have anti-inflammatory effects via altered Cytokine expression.”
• (Ref 15) “Adequate glutathione levels are needed for optimal innate and adaptive Immune System function, including proper T-cell activation and differentiation” 

Omega 3 Fatty Acids

• (Ref 15) “Higher intakes and higher blood levels of EPA and DHA are associated with lower levels of inflammatory Cytokines, such as Interleukin-1 and Interleukin-6”.
• (Ref 15) “Immune system cells can easily incorporate EPA and DHA, which might also affect immune function by upregulating the activity of Macrophages, Neutrophils, T-Cells, B-Cells, natural killer cells, and other immune cells. “
• (Ref 15) “In addition, omega-3s may have antimicrobial and antiviral effects.”

Probiotics

• (Ref 15) “Probiotics are live microorganisms that confer a health benefit on the host when administered in adequate amounts.”
• (Ref 15) Probiotics act mainly in the gastrointestinal tract [7]. They might improve immune function in several ways, including by enhancing gut barrier function, increasing immunoglobulin production, inhibiting viral replication, and enhancing the Phagocytic activity of White Blood Cells.”
• (Ref 15) Some studies suggest that probiotics increase levels of Natural Killer Cells, Lymphocytes, and monocytes and that they decrease levels of proinflammatory Cytokines, but other studies do not.”

Manage/Reduce Stress

Ref 3; Ref 4; Ref 5;Ref 6; Ref 7 ; Ref 12

• Mayclinic.org – Chronic stress puts your health at risk
• (Ref 3) Sleep, Meditate, Exercise (ideally 30 minutes a day; strength building plus cardio)
• (Ref 4) Psychological and physical stress weakens parts of your Immune System.  Example: Shingles flares up when people are experiencing chronic stress. 
• (Ref 4) “Stress can also cause “patrols” in your Immune System—certain cells that tell the Immune System to wind down an attack—to fail. When this happens, too much inflammation can occur. Hives are one example of a stress-induced breakdown in the Immune System’s patrols.” 
• (Ref 7) Exercise; Meditate; Have a hobby; Talk to a trusted friend; Practice regular and conscious breathing throughout the day and when feelings of stress arise. 
• (Ref3, Ref 7) “Stress releases hormones like cortisol that suppresses inflammation (inflammation is initially needed to activate immune cells) and the action of White Blood Cells.”

Keep Your Vaccinations Up To Date 

Ref 4; Ref 5; Ref 6; Ref 10; Ref 11

• (Ref 4) “Vaccines, also called immunizations, teach the Immune System to make antibodies that fight off infections before they make you sick.”
• (Ref 11) Keep your vaccinations up to date. “Vaccines introduce your Immune System to viruses in a very controlled manner”. This becomes more critical as you age and your Immune System weakens. 

It’s Difficult to “Prove” Many of the Suggested Benefits 

Ref 3; Reg 5; Ref 12; Ref 14)

Due to the complicated and interconnected nature of our body systems, it’s very difficult to scientifically prove many of the stated Immune System benefits.

• (Ref 3) “…there’s no magic “healthy pill””
• (Ref 5) “For now, there are no scientifically proven direct links between lifestyle and enhanced immune function.”
• (Ref 12) “I think a misconception is that there are supplements or products out there that can really boost the Immune System. Unfortunately, they haven’t really had robust evidence that they’re highly effective,..” 
• (Ref 14) “There is no strong evidence to prove that taking immune supplements along with exercising lowers the chance of illness or infections.”

That doesn’t mean you can’t find a reasonable approach to improving your overall health and assuming that your immune health will benefit also. 

References for Immune System Improvement Advice

1. CDC – Healthy Habits: Enhancing Immunity
2. Clevelendclinic.com – 5 Vitamins That Are Best for Boosting Your Immunity
3. Clevelandclinic.com – Strengthen Your Immune System With 4 Simple Strategies
4. Columbia.edu – what-you-really-need-do-boost-your-immunity
5. Harvard.edu – How to boost your Immune System
6. Harvard.edu – Immune boosts or busts? From IV drips and detoxes to superfoods
7. Harvard.edu – Nutrition and Immunity
8. Harvard.edu – Some Benefits of Exercise Stem from the Immune System
9. Harvard.edu – What can you do to improve your Immune System?
10. HHS.gov – Vaccines Protect You
11. Mayoclinic.org – Aging and the Immune System
12. Mayoclinic.org- How to maintain a healthy Immune System
13. Mayoclinic.org – Lack of sleep: Can it make you sick?
14. Medlineplus.gov – Exercise and Immunity
15. NIH.gov – Dietary Supplements for Immune Function and Infectious Diseases

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