As 2022 begins, there is still an evident focus on enhancing immune function by health-minded individuals seeking an edge in fighting viral illness. Viruses can be deadly, but the ability of any virus to infect to the point of wreaking havoc or causing death is dependent on a person's immune function. And that is something that everyone can work towards improving.

We are exposed to microorganisms that can cause infection every day, yet we can fight off these invaders because of our immune system. Whether one of us will get sick or not comes down to the "infection equation." For example, if a virus is strong and our immune system is weak, a more serious infection will occur. On the flip side, if our immune system is strong, it can effectively fight off the infection to reduce its severity.

  • A weak immune system + strong virus = Severe infection
  • A strong immune system + strong virus = Less severe to no infection

Factors such as age, nutritional status, lifestyle, and the presence of pre-existing health conditions referred to as "comorbidities" are associated with impaired immune function, more severe viral infection, and higher mortality rates due to a viral illness. 

In 2021, people became familiar with the term "variant," which describes how a virus can adapt to become more lethal, infective, or escape our immune system. The silver lining is that viruses generally want to mutate to a less deadly form. After all, if the virus kills the host, its chance of long-term survival drops precipitously. However, if a person's immune system is not functioning correctly, even a less powerful variant can still produce significant illness and even death.

One reason why there is no vaccine for the common cold attests to how viruses adapt to evade the immune system. When we are exposed to a new virus or a variant that is much different than a virus that caused a previous infection, we do not have antibodies against that virus or variant. So, even if we have had a prior infection to an earlier version of the virus, the variant has changed enough to make it essentially a new virus as far as our immune system is concerned.

Once exposed to a new virus or variant, it takes between 10 to 20 days to produce an antibody response. Antibodies bind to proteins on invading organisms to neutralize and destroy them, but that process takes time. And in most cases, by the time an antibody response happens in an infection caused by a new virus or variant, the infection has pretty much been dealt with 100% by other ways in which our immune system fights viral infections. 

Antibodies provide a head start for the immune system when exposed to a virus that caused a previous infection. In an acute infection due to a new virus or variant other components of the immune system must be functioning correctly, particularly non-specific and cell-mediated immunity, since there is not yet an antibody response.

When it comes to fighting an infection to a new virus or variant, the functioning of non-specific and cell-mediated immunity is critical. Antibodies bind to organisms that are "extracellular," meaning they are not inside human cells. Once inside a cell, an organism is somewhat shielded from antibody attack by our cell membranes. Most viruses are "intracellular "pathogens. Meaning they wreak the most havoc because they reside inside our cells. Cell-mediated is much better at recognizing and destroying intracellular pathogens than antibody-based or humoral immunity. 

The thymus gland is the master control of cell-mediated immunity. Inside the thymus, immature white blood cells formed in the bone marrow transform into T lymphocytes (the T stands for "thymus-dependent"). There are several types of T lymphocytes or T cells. Particularly deadly to viruses are cytotoxic T cells. These killer T cells directly kill virus-infected cells.

A Quick Guide to the Immune System

The entire human body is a highly complex living system, and, in many ways, the immune system is perhaps its most complex subsystem as it is also composed of numerous interrelated subsystems.

  • Barrier function: The first lines of defense are the physical barriers that viruses, bacteria must cross, i.e., the skin and the mucous membranes that line digestive, respiratory, and reproductive tracts. Poor barrier function increases the risk of infection.
  • Non-specific immunity: This system is composed of specialized immune cells and chemical factors that are non-specific in their function in fighting against viruses and other invaders. The non-specific immune system not only protects but is also a sensor and message relay system to activate specific immune processes involved in adaptive immunity. The ability of non-specific immunity to respond quickly is one of the safeguards against severe viral infection.
  • Adaptive immunity: A potent part of our immune responses in which specialized cells and antibodies that attack specific viruses and other organisms adapt to respond to a particular organism. It has two branches: 
    • Cell-mediated immune responses enlist special immune cells to attack viruses and/or infected cells directly.
    • Humoral immune responses utilize particular antibody proteins produced by a white blood cell known as a B cell. Antibodies bind to compounds on the virus or other organism that ultimately trigger the destruction of the invader.
  • Other Components of the Immune System
    • The thymus gland: This vital tissue serves as the master control of many aspects of the immune system, especially regarding protecting against and fighting viral infections.
    • The spleen and lymphatic systemThe spleen and lymphatic system are the heart and vessels of the immune system.
    • The gut and immune function: Since 70% of the immune system resides in the gastrointestinal tract, an– discussion of immunity must devote significant attention to what gut factors enhance or disrupt immune function, including gut barrier integrity and the intestinal microbiome.

How to Support Immune Function

It is essential to understand that immune function reflects our overall health. The healthier we are, the stronger our immune system is in fighting off infections. Following a healthy lifestyle, eating for health, managing stress effectively, getting enough sleep, exercising regularly, avoiding harmful habits, and other general measures are critical in optimal immune function.

In situations of poor immune functions, there may be ways to help boost immunity. For example, the older we get, the more difficult it is for our immune system to protect us from infection. However, research suggests that in many older people, the suppression of immune function may be related to nutrient insufficiencies such as low levels of vitamin D3B vitaminszincselenium, and others rather than just age.  Studies have shown that many elderly Americans are deficient in at least one nutrient, and most are lacking in many. Likewise, numerous studies show that taking a multivitamin supplement or a key nutrient for immune function can support immunity in these elderly subjects.1-3

Another significant factor linked to poor immune function is excess body fat. When a person is overweight or obese, they are at a much higher risk of developing more serious viral infections. They are also at a higher risk of dying from a viral infection. The good news is that losing weight will reduce those risks.

Poor blood sugar control is another factor that significantly reduces immune function. For example, while poorly controlled blood sugar levels in patients with diabetes were associated with an increased risk of dying from an acute viral illness, people with diabetes with well-controlled blood sugar fared much better.4 Again, immune function correlates with a person's general health status.

Nutrient Deficiency and Low Immune Function

It is challenging for a person to get everything their body needs through diet alone. Comprehensive studies have revealed overt nutrient deficiencies in a substantial portion of the US population (approximately 50%) and that for some selected nutrients in certain age groups, more than 80% of the group consumed less than the recommended dietary intake level.5 

Low immune function may be improved by the proper use of dietary supplements. Starting with a high potency multiple vitamin and mineral formula may help.

8 Recommended Dietary Supplements for Supporting Immunity


A robust multiple vitamin and mineral formula providing at least 100% RDA can help fill nutritional gaps.

Vitamin A

Vitamin A is necessary for maintaining the cells of the skin and the mucous membranes that act as the first lines of defense against infection. In addition, vitamin A is essential for proper white blood cell function and support many of your immune system's activities. 

Researchers recently conducted a double-blind study of high-dosage vitamin A supplementation versus a placebo in 100 patients with mild-to-moderate acute viral infection as well as 100 of their contacts.6 Patients were given vitamin A (200,000 IU) or a placebo for two days. In the patients with a viral infection, vitamin A produced significant improvement in symptoms and a shorter duration of illness. 

Warning: Dosages of vitamin A greater than 5,000 IU are not recommended for women at risk of pregnancy. Higher dosages of vitamin A (but not beta-carotene) can produce congenital disabilities and should be avoided in any woman who might be pregnant.

Vitamin A (retinol) – 3,000 mcg (10,000 IU) per day for men and 1,500 mcg (5,000 IU) per day for women. 

Vitamin D

Vitamin D3 has been studied for producing a wide range of immune-enhancing effects, including an ability to:

  • Up-regulate anti-microbial peptides to support clearance of virus and bacteria from mucous membranes and immune cells. 
  • Have direct effects on T cell activation. 
  • Help reduce the frequency of viral upper respiratory infections.

For children under the age of 5 years old, I recommend roughly 50 IU per pound per day. For children 5 to 9 years old, I recommend 2,000 IU per day. For children 9 to 12 years old, I recommend 2,500 IU per day. For children over 12 years old, I recommend the adult dosage of 2,000 to 5,000 IU per day. However, these are only guidelines. Adults may require a daily dosage of 2,000 to 5,000 IU of vitamin D3. But the only way to know what that dosage is exactly is through testing.

Vitamin C

When you have an infection or are under stress, your need for vitamin C increases. 

An interesting study of vitamin C is an analysis from the 2003-2006 National Health and Nutrition Examination Surveys (NHANES) conducted in the United States general, non-institutionalized adult population.7 The researchers used blood plasma levels of vitamin C to create five categories: deficiency (<11 μmol/L), hypovitaminosis (11-23 μmol/L), inadequate (23-49 μmol/L), adequate (50-69 μmol/L), and saturating (≥70 μmol/L). Results indicated 42% of the US adult population have insufficient levels (deficiency, hypovitaminosis, and inadequate) of this critical nutrient. Those at greatest risk are males between 20 and 59 years old, black and Mexican Americans, smokers, are overweight or obese, and poor. These results are shocking but can be corrected by eating more vitamin C-rich foods and supplementation. During these times of increased stress and immune system demand, taking at least 250 mg of vitamin C per day is recommended. 


Zinc is the "Gate Keeper" of immunity as it is directly involved with so many aspects of immune function on so many levels. When zinc levels are low, immunity drops considerably due to plummeting levels of specific virus-fighting white blood cells, as well as declines in key immune system activators and hormones from the thymus gland. Zinc is also critical to a healthy respiratory and gastrointestinal tract lining and the proper absorption of nutrients by the intestinal tract. If zinc is not there insufficient levels, the entire immune system is compromised.


Selenium is involved in critical antioxidant mechanisms that protect the thymus gland – the master gland of the immune system. People who are low in selenium have reduced immune function. Selenium works, in part, by enhancing the ability of white blood cells to produce interleukin-2, a chemical that stimulates white blood cells to proliferate and attack viruses and other foreign cells. SelenoExcell is a unique form of selenium that originates from a particular strain of non-GMO baker's yeast (Saccharomyces cerevisiae) that incorporate selenium into proteins that enhance the absorption and utilization of selenium. SelenoExcell has shown more significant biological effects compared to other forms of selenium. 

The recommended dosage of selenium is 100 to 200 mcg per day.


Quercetin is a flavonoid, a group of plant pigments with beneficial health effects. Quercetin, in particular, has a remarkable impact on immune system health and promotes enhanced immunity. There has been a lot of attention on quercetin recently for its effects on immune function and its ability to increase the intracellular level of ionic zinc—the form of zinc that inhibits an enzyme known as replicase that viruses use to replicate within human cells. Quercetin facilitates the transfer of ionic zinc into cells through channels known as ionophores. 


N-acetylcysteine (NAC) is a stable form of the sulfur-containing amino acid cysteine. It is used to form glutathione, the major antioxidant and detoxifying compound in the human body. It is essential in protecting the mitochondria, the energy-producing compartments of cells. NAC protects the brain, respiratory tract, lungs, and body tissues.

In addition to its use as a dietary supplement, NAC has been used as a mucus modifying agent to support the respiratory tract.12 The dosage is generally 500 to 1,000 mg daily to protect and boost glutathione levels. NAC is very safe and has been used by many people on an ongoing basis for many years. 


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  2. High KP. Micronutrient supplementation and immune function in the elderly. Clin Infect Dis 1999;28:717-22.
  3. Villamor E, Fawzi WW. Effects of vitamin a supplementation on immune responses and correlation with clinical outcomes. Clin Microbiol Rev. 2005;18(3):446-464. 
  5. Reider CA, Chung RY, Devarshi PP, et al. Inadequacy of Immune Health Nutrients: Intakes in US Adults, the 2005-2016 NHANES. Nutrients. 2020;12(6):1735.
  6. Al-Sumiadai M, Ghazzay H, Al-Ani R. Therapeutic effect of vitamin A on COVID-19 patients and its prophylactic effect on contacts. Systematic Reviews Pharmacy 2021;12:207-210.
  7. Crook J, Horgas A, Yoon SJ, Grundmann O, Johnson-Mallard V. Insufficient Vitamin C Levels among Adults in the United States: Results from the NHANES Surveys, 2003-2006. Nutrients. 2021;13(11):3910.
  8. Martineau Adrian R, Jolliffe David A, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ 2017;356:i6583. See
  12.  Schwalfenberg GK. N-Acetylcysteine: A Review of Clinical Usefulness (an Old Drug with New Tricks). J Nutr Metab. 2021;2021:9949453.