How to Optimize Your Immune System

By Hidaya Aliouche, B.Sc.Reviewed by Emily Henderson, B.Sc.

The immune system is a central difference in the protection against pathogenic organisms. Several factors influence the strength of the immune system; some of these factors are not capable of being modified, such as genetics and stage of life, but several modifiable factors can influence the immune system. By optimizing each of these modifiable factors, the immune system can be optimized for function.

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What are the modifiable factors affecting the immune system?

Several risk factors are capable of being modified by individuals to ensure that their immune system is optimized for function. The following represent the most salient factors that can be modified:

• Alcohol consumption: alcohol can suppress a wide range of immune responses, including disrupting communication between the gut microbiome and the intestinal immune system. Alcohol also damages the epithelial cell barrier, compromises T cell and neutrophil function, therefore disrupting the gut barrier function. These effects are also seen in acute binge drinking. Therefore, moderate alcohol consumption can optimize immune response
• Smoking status: cigarettes contain several compounds which act as pro-inflammatory and immunosuppressive agents; these include nicotine, formaldehyde, carbon monoxide, tar, benzopyrene, acetone, cadmium, nitrogen oxides, ammonia, and hydroxyquinone. Nicotine in particular results in a decreased phagocytotic activity of neutrophils, in addition to inhibiting homing, and the release of reactive oxygen species, therefore compromising neutrophil activity. Overall, the inflammatory agents compound tissue destruction on further release of inflammatory agents that can lead to chronic inflammatory syndrome. Therefore, smoking cessation is the best way to optimize immunity.
• Stress
• Diet: this includes total nutrient intake (macro and micronutrient)
• Level of exercise, physical fitness, and body fat percentage

The factors that cannot be modified include age, illness, infection and infection history, genetics, vaccination status, got to microbiota profile, frailty, time of day, and stage of the life course (i.e., pregnancy status, menopause, etc.)

The effect of obesity on immunity

The competence of the immune system can be diminished as a consequence of being overweight or obese. This effect occurs because of the reduced activity of helper T cells, cytotoxic T cells, B cells, and natural killer cells.

Moreover, there is reduced antibody and interferon-gamma production. Consequently, those with obesity are increasingly susceptible to a range of pathogenic infections relative to healthy-weight individuals and demonstrate poor responses to vaccination.

An example of this effect was seen during the 2009 H1N1 influenza A pandemic; obese individuals demonstrated weakened and delayed antiviral responses to the infection. Obese individuals also recovered poorly relative to healthy weight counterparts. Studies in both animals and humans have demonstrated an increased period of viral shedding, indicating impaired viral control and targeting.

Studies have demonstrated the number of activated, interferon-gamma producing, and granzyme expressing cytotoxic T cells are reduced in obese individuals relative to healthy individuals. Moreover, obesity is correlated with increased inflammatory mediators, indicating an underlying state of chronic low-grade inflammation. Subsequently, those with obesity are predisposed to contracting chronic conditions.

Ensuring that body fat percentage is kept within a healthy range through the maintenance of a healthy weight. This can be aided in part by maintaining a healthy diet, exercising regularly, and getting adequate sleep.

The importance of diet on the immune system

Nutrition plays a central role in optimizing immune system function. A balanced diet provides:

• Energy for the cells in the immune system to function
• Material for the production of RNA, DNA, and protein production (receptive, acute phase proteins, antibodies, cytokines, etc.) and new immune cells
• Factors capable of regulating the immune cell metabolism (i.e., Vitamin A and zinc)
• Nutrients with antibacterial or antiviral capabilities (i.e., vitamin D and zinc)
• Oxidative and inflammatory stress regulators (e.g., vitamin C, vitamin E, selenium, zinc, omega 3 fatty acids, selenium, and plant polyphenols)
• Fuel for the intestinal microbiota which can modulate the immune system

In the absence of a nutritionally balanced diet, the immune system is not provided with adequate quantities of nutrients to function optimally. Subsequently, individuals with poor diets are at increased susceptibility to infection and demonstrate a poor ability to control infection. The following table outlines the effects of micronutrients on different aspects of immunity:

Adapted from Calder PC, et al.

The optimization of the immune system can be achieved through the modification of several lifestyle factors. Of these nutrition and exercise are key. Immunity is markedly compromised in elderly people, particularly those who are frail, those with obesity, those who are insufficiently nourished, and then those with an inadequate intake of micronutrients.

Nutritional inadequacy has been shown to increase susceptibility to illness and allow dysregulation of inflammation and oxidative stress, which results in a poor outcome of infection.

References:

• Childs CE, Calder PC, Miles EA. (2019) Diet, and Immune Function. Nutrients. doi:10.3390/nu11081933.
• Calder PC. (2021) Nutrition and immunity: lessons for COVID-19. Nutr Diabetes. doi:10.1038/s41387-021-00165-0.
• Bae YS, Shin EC, Bae YS, et al. (2019) Editorial: Stress and Immunity. Front Immunol.;10:245. doi:10.3389/fimmu.2019.00245.
• Alagawany M, Attia YA, Farag MR, et al. (2021) The Strategy of Boosting the Immune System Under the COVID-19 Pandemic. Front Vet Sci. doi:10.3389/fvets.2020.570748.

Further Reading

• All Immune System Content
• What is the difference Between a Phagocyte, Macrophage, Neutrophil and Eosinophil?
• Does the Immune System Differ between Men and Women?
• What is Immune Fitness?
• Effects of Tobacco on the Immune System