The Best Immune Supplements

These days everyone claims to have the best immune system supplement. In this post, we review some of the science behind why you should look to these ingredients for immune support: Vitamin A, C, E, Selenium, Zinc, and Garlic.

Beta-carotene (Vitamin A)

Beta-carotene is considered an antioxidant and is a major component of the body’s natural defense against free radicals, as well as a source of vitamin A. This compound helps maintain healthy skin and also plays a vital role in eye health.

Vitamin A is important for maintaining mucosal integrity, which is the first line of immune defense. Vitamin A also stimulates the production and activity of white blood cells and regulates cell growth and division.

Research has demonstrated that vitamin A deficiency decreases the body’s resistance to foreign pathogens, reducing innate immune function. “VitA has both promoting and regulatory roles in both the innate immune system and adaptive immunity; therefore, it can enhance the organism’s immune function and provide an enhanced defense against multiple infectious diseases” (Huang et al, 2018).

Vitamin C

Vitamin C is a potent antioxidant with increasingly diverse uses in health promotion and disease prevention. While often taken for granted, vitamin C is becoming increasingly important for improving immune function, cardiovascular health, and avoiding degenerative diseases.

Vitamin C is essential because the human body cannot synthesize it. Vitamin C is water soluble and needs to be constantly replenished. During stressful events, such as dieting and exercise, plasma vitamin C levels decrease.

Vitamin C is the fuel that drive the activity of immune cells. This is why it is especially important to increase vitamin C intake during illness. Vitamin C deficiency has been associated with an increased frequency and duration of colds. A deficiency of vitamin C broadly affects the various key aspects of immune function, including the production of antibodies that fight known infections. As a result of vitamin C’s wide-ranging impact on the immune system, a deficiency could leave us vulnerable to infections. A weakened immune system caused by low vitamin C levels can make any infection more serious.

The benefits of Vitamin C are not limited to the immune system. Adults with higher vitamin C levels exhibit lower weight, BMI, and waist circumference, and better measures of metabolic health, including lower HbA1c, insulin, and triglycerides, all risk factors for type 2 diabetes. A 2015 study involving obese patients with high blood pressure and/or diabetes showed that daily doses of vitamin C resulted in reductions of inflammation, serum glucose levels, and triglyceride levels.

As an antioxidant, vitamin C can protect against damage done by oxidative stress. Regular exercise is an important part of a healthy lifestyle. However, the increased delivery of oxygen-rich blood during exercise is a source of destructive free radicals which are associated with muscle soreness and post-exercise recovery.

In a mouse model of vitamin C deficiency and premature aging, a higher dose of supplemental vitamin C (equivalent to about 1300 mg per day in a 175 lb person) was compared with a lower dose (equivalent to about 130 mg per day in a 175 lb person). After one year, mice receiving the higher dose of vitamin C exhibited greater immune cell counts than mice receiving the lower dose (Uchio 2015).

Results from a large analysis of placebo-controlled trials indicate vitamin C supplementation reduces the duration of colds, with an 8% reduction in adults and a 14% reduction in children. In addition, the analysis found vitamin C supplements reduced the incidence of colds by half in people undergoing extreme physical exertion, such as marathon runners (Hemila 2013).

Vitamin C plays an important role in the creation of white blood cells, enabling your immune system to function optimally, and improves immune response by increasing levels of interferons – warning signals that trigger immune mechanisms. Studies have found that vitamin C can reduce the duration of colds while a lack of vitamin C can make you more prone to getting sick.

Vitamin E

Vitamin E is a fat-soluble antioxidant that stops the production of free radicals formed by fat oxidation. Numerous studies have demonstrated the benefits of vitamin E for cardiovascular, immune function, DNA repair, and protection against free radicals. Scientists are investigating whether vitamin E might help prevent or delay the chronic diseases associated with free radicals by limiting free-radical production and possibly through other mechanisms.

A variety of animal studies have shown vitamin E deficiency can trigger immune suppression. Meanwhile, clinical evidence has shown vitamin E supplementation can increase resistance to infection, especially in older individuals (Wu 2014; Wu 2008; Han 2006).

In a study in elderly men and women, supplementation with 200 mg per day vitamin E significantly enhanced immune parameters including neutrophil, T-cell, B-cell, and NK-cell function, bringing their values close to those of younger healthy adults (De la Fuente 2008).

Increased vitamin E intake has been shown to restore the decline in T-cell function associated with aging. This improvement in T-cell function results from vitamin E’s direct impact on T cells as well as inhibition of prostaglandin E2, a mediator of inflammation and a T-cell suppressor (Wu 2014; Wu 2008; Han 2006). In a mouse model, vitamin E supplementation reversed the age-associated decline in naïve T-cell function (Adolfsson 2001).

Vitamin E is a powerful antioxidant that helps the body fight off infection and is important for maintaining T-cell membrane integrity


The therapeutic use of garlic dates back over 5000 years. Garlic has strong antiviral effects and can support healthy immune function. Studies have shown that garlic reduces the risk of becoming sick in the first place, as well as how long you stay sick. Garlic contains a compound called allicin, which is quickly converted into compounds which have been shown to boost the response of white blood cells in the body when they encounter viruses, such as the viruses that cause the common cold or flu.

Studies have demonstrated garlic’s effectiveness in reducing oxidative stress in animals with high blood lipid levels. Supplementation with garlic significantly countered the lipid-related depletion of intracellular antioxidants in the liver and blood. A separate 6-month human study found that garlic notably lowered levels of the oxidative marker malondialdehyde in plasma and red blood cells.

A detailed review of data from published clinical trials found garlic supplements significantly reduce the number, duration, and severity of upper respiratory tract infections. This review also found garlic supplements stimulate immune function by increasing macrophage activity, numbers of NK cells, and production of T and B cells (Ried 2016). In a clinical trial, 120 healthy participants, 21–50 years old, were assigned to use 2.56 g aged garlic extract or placebo daily for 90 days during cold and flu season. Garlic supplementation was associated with reduced cold and flu severity, as well as increased cytotoxic T-cell and NK-cell proliferation and activity (Percival 2016). In animal research, garlic has been shown to increase antibody production and enhance the cell-killing activity of macrophages, cytotoxic T cells, and NK cells (Ghazanfari 2000). Other animal research suggests aged garlic extract may prevent immune suppression associated with psychological stress (Kyo 1999).

One study gave 146 healthy volunteers either garlic supplements or a placebo for three months. The garlic group had a 63% lower risk of getting a cold, and their colds were also 70% shorter. Another study found that colds were on average 61% shorter for subjects who ate 2.56 grams of aged garlic extract per day, compared to a placebo group. Their colds were also less severe

Garlic has also been demonstrated to suppress the overactive immune response associated with allergic reactions. Data from experimental studies indicate aged garlic extract may reduce histamine release and modify the function of immune cells involved in allergic reactions (Kyo 2001).


Zinc is an essential trace mineral that is critical to healthy immune function. Zinc can be effective in warding off the common cold because it binds to the same cell receptor sites, preventing viruses from binding to them. In other words, zinc can prevent viruses from entering the cell, which helps stop viruses from replicating.

Zinc deficiency is common in older individuals, and may lead to negative changes in immune function including diminished thymus function, decreased antibody response to vaccines, and impaired function of phagocytic and NK cells (Haase 2009; Cabrera 2015). In a study in healthy older volunteers, daily intake of 45 mg zinc for one year resulted in a 67% reduction versus placebo in incidence of infections (Prasad 2007). In a study of individuals in nursing homes, residents with normal zinc levels had a significantly lower incidence of pneumonia compared with zinc-deficient individuals. Zinc-replete individuals also had shorter pneumonia duration and 50% lower usage of antibiotics, as well as lower all-cause mortality (Meydani 2007).


Selenium is essential for many operations of a healthy immune system. “Selenium influences both the innate, “nonadaptive” and the acquired, “adaptive” immune systems” (Arthur et al, 2003). Thus, selenium deficiency impairs several components of the immune system response. A study which treated selenium-deficient mice with varying doses of selenium found a dose-dependent increase in the activity of neutrophils, a type of white blood cell which forms an essential part of the innate immune system (Arthur et al, 2003). “Overall, there is considerable evidence strengthening the notion that Se affects different types of immune responses in different ways” (Hoffmann, 2008).


Anderson, T. W., Beaton, G. H., Corey, P., & Spero, L. (1975). Winter illness and vitamin C: the effect of relatively low doses. Canadian Medical Association journal, 112(7), 823–826.

Kiecolt-Glaser, J. K., Glaser, R. (1993). Mind and immunity. Mind/Body Medicine (pp. 39-59). New York: Consumer Reports.

Hagan, P. (2010). Dieting really CAN harm your health. Daily Mail UK. Retrieved from:

Ellulu, M., Rahmat, A., Patimah, I., Khaza’ai, H., & Abed, Y. (2015). Effect of vitamin C on inflammation and metabolic markers in hypertensive and/or diabetic obese adults. Drug Design. Retrieved from:

Goepp, J. (2008). Newly Discovered Health Benefits of Vitamin C. Life Extension. Retrieved from:

Laifer, S. (2005). Garlic: Medical Science Discovers New Uses for an Ancient Herb. Life Extension.

Uchio R, Hirose Y, Murosaki S, Yamamoto Y, Ishigami A. High dietary intake of vitamin C suppresses age-related thymic atrophy and contributes to the maintenance of immune cells in vitamin C-deficient senescence marker protein-30 knockout mice. The British journal of nutrition. Feb 28 2015;113(4):603-609.

Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. The Cochrane database of systematic reviews. 2013;1:Cd000980.

Bucher, A., & White, N. (2016). Vitamin C in the Prevention and Treatment of the Common Cold. American journal of lifestyle medicine, 10(3), 181–183.

Wu D, Meydani SN. Age-associated changes in immune and inflammatory responses: impact of vitamin E intervention. J Leukoc Biol. Oct 2008;84(4):900-914.

Wu D, Meydani SN. Age-associated changes in immune function: impact of vitamin E intervention and the underlying mechanisms. Endocrine, metabolic & immune disorders drug targets. 2014;14(4):283-289.

Han SN, Meydani SN. Impact of vitamin E on immune function and its clinical implications. Expert review of clinical immunology. Jul 2006;2(4):561-567.

De la Fuente M, Hernanz A, Guayerbas N, Victor VM, Arnalich F. Vitamin E ingestion improves several immune functions in elderly men and women. Free radical research. Mar 2008;42(3):272-280.

Adolfsson O, Huber BT, Meydani SN. Vitamin E-enhanced IL-2 production in old mice: naive but not memory T cells show increased cell division cycling and IL-2-producing capacity. Journal of immunology (Baltimore, Md.: 1950). Oct 1 2001;167(7):3809-3817.

Cabrera AJ. Zinc, aging, and immunosenescence: an overview. Pathobiol Aging Age Relat Dis. 2015;5:25592.

Haase H, Rink L. The immune system and the impact of zinc during aging. Immunity & ageing: I & A. 2009;6:9.

Kyo E, Uda N, Kasuga S, Itakura Y. Immunomodulatory effects of aged garlic extract. The Journal of nutrition. Mar 2001;131(3s):1075s-1079s.

Kyo E, Uda N, Ushijima M, Kasuga S, Itakura Y. Prevention of psychological stress-induced immune suppression by aged garlic extract. Phytomedicine: international journal of phytotherapy and phytopharmacology. Nov 1999;6(5):325-330.

Ghazanfari T, Hassan ZM, Ebtekar M, Ahmadiani A, Naderi G, Azar A. Garlic induces a shift in cytokine pattern in Leishmania major-infected BALB/c mice. Scandinavian journal of immunology. Nov 2000;52(5):491-495.

Meydani SN, Barnett JB, Dallal GE, Fine BC, Jacques PF, Leka LS, Hamer DH. Serum zinc and pneumonia in nursing home elderly. The American journal of clinical nutrition. Oct 2007;86(4):1167-1173.

Percival SS. Aged Garlic Extract Modifies Human Immunity. The Journal of nutrition. Feb 2016;146(2):433s-436s.

Prasad AS, Beck FW, Bao B, Fitzgerald JT, Snell DC, Steinberg JD, Cardozo LJ. Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress. The American journal of clinical nutrition. Mar 2007;85(3):837-844.

Ried K. Garlic Lowers Blood Pressure in Hypertensive Individuals, Regulates Serum Cholesterol, and Stimulates Immunity: An Updated Meta-analysis and Review. The Journal of nutrition. Feb 2016;146(2):389s-396s.

Meydani SN, Barnett JB, Dallal GE, Fine BC, Jacques PF, Leka LS, Hamer DH. Serum zinc and pneumonia in nursing home elderly. The American journal of clinical nutrition. Oct 2007;86(4):1167-1173.

McElhaney JE, Zhou X, Talbot HK, et al. The unmet need in the elderly: how immunosenescence, CMV infection, co-morbidities and frailty are a challenge for the development of more effective influenza vaccines. Vaccine. 2012;30(12):2060–2067. doi:10.1016/j.vaccine.2012.01.015

Arthur, J. R., McKenzie, R. C., & Beckett, G. J. (2003). Selenium in the immune system. The Journal of nutrition, 133(5 Suppl 1), 1457S–9S.

Hoffmann, P. R., & Berry, M. J. (2008). The influence of selenium on immune responses. Molecular nutrition & food research, 52(11), 1273–1280.