In the wake of the COVID-19 pandemic, it is likely a better time than ever to discuss the topic of the immune system.
The immune system helps us combat infectious diseases. It consists of innate immunity, which is a general inflammatory response against potentially harmful pathogens. As well as acquired immunity, using antibodies to recognize previously encountered pathogens, which is the basis behind vaccinations (1,2).
Like many other systems in the body, the immune system seems to have bidirectional relationships between many modifiable lifestyle factors such as sleep, stress, nutrition, exercise, and social connection (1-10). Similar to everything else in our bodies, our immune system also ages, known as immunological aging. Factors such as exercise, sleep, and other lifestyle interventions have been suggested to delay this aging process (1). So let’s look at each of these modifiable lifestyle factors, how they relate to immunity, and what we can do to improve our natural defenses against infectious pathogens such as influenza and COVID-19
SLEEP
The interactions between sleep and the immune system are well known. When we are sick, we generally feel more tired and we increase our sleep. And it is generally accepted that if we don’t sleep enough, our immune system is weakened (3).
This is indeed the case, as detailed by Ibarra-Coronado et al., stating, “Many studies have demonstrated that total sleep deprivation and rapid eye movement (REM) sleep deprivation modify various components of the immune system… conversely, sleep patterns are altered during the immune response, suggesting that sleep and the immune response are linked through bidirectional communication” (2).
It has also been found that receiving adequate sleep stimulates an “optimal vaccination response” (3).
For these reasons, it is recommended that adults get 8 hours of sleep per night (4).
Keeping normal sleep/wake routines can potentially also have an impact on immunity. As with many body processes, such as sleep and digestion, immune functions are controlled by our natural 24 hour circadian rhythms, or our body’s natural clock. Different varieties of immune cells have been found to be circadian regulated, giving us a more efficient immune response when it most needed (5).
STRESS
Stress is the body’s response to any physical, emotional, or mental demand (5). This process prepares an individual for intense activity, which is why it is known as the fight-or-flight response (6). While short-term stress can be beneficial and result in positive adaptations, prolonged or chronic stress can have a negative effect on the immune system (1,6,7). Stress has been found to be a major factor in immunological aging, and chronic stress potentially having “the most detrimental immune health effects” (1).
This chronic stress can come in many forms in our daily lives, such as environmental and socioeconomic stressors, caring for aging relatives, work deadlines, family arguments, caring for children, car problems, and the list goes on (1).
Being able to minimize the physiologic response of these stressors can therefore play a role in the efficiency of our immune system and ability to fight off disease.
NUTRITION
“You are what you eat.” Our bodies use the nutrients, vitamins, and minerals from the foods we eat to make new cells, repair damaged cells, and replace old cells. It uses what we eat to replenish energy stores, make hormones and enzymes, and affects every system and process in our bodies, including the immune system.
Due to this, it is important that we maintain a diet that provides us with enough energy, enough nutrients to recover and repair, and to “maintain the body’s natural defenses against disease-causing viruses and bacteria” (8). A number of factors related to diet and nutrition-status can affect our ability to maintain an optimal immunity.
For example, obesity is associated with increased susceptibility to infections such as influenza, as well as a decreased response to influenza vaccinations. On the opposite end of the spectrum, malnutrition can also lead to declines in numbers of disease fighting immune cells (9). It has been found that intentional weight loss by placing the body in energy deficit with the combination of hard exercise can negatively affect the immune system (8).
In order to maintain a healthy immune system, it is recommended to maintain a varied diet that meets energy needs based on activity levels, and includes adequate nutrients (carbohydrates, protein, and fats), vitamins, and minerals (8,9).
EXERCISE
Everyone is aware that exercise is good for our health, yet 80% of American adults and youth do not meet the minimum recommended Physical Activity Guidelines put out by the American Medical Association (10).
While many of the associations between exercise and immune function are unknown, there is emerging research pointing to a relationship between exercise and the natural bacteria in our gut. As stated by Cook, et al., “Participation in regular physical activity and moderate exercise improves overall immune function” which is “thought to involve the anti-inflammatory effects of exercise in the gut.” They go on to describe how “exercise training initiates significant changes in the gut microbiome” and “a normal gut microbiome has an integral role in the development of healthy… cellular immunity” (11).
HEALTHY LIVING
So, in order to decrease the chances of having a depressed immune system, be vigilant in controlling the modifiable lifestyle factors in your daily life. If you’re going to worry, spend that energy on these things which you can actually change. Get adequate sleep quantity and quality. Keep life stresses to a minimum, while practicing stress-relieving techniques. Maintain a healthy varied diet of whole, less-processed foods which provides adequate nutrients. Engage in deliberate and purposeful exercise, but avoid over-training and chronic fatigue. Have meaningful relationships with those around you.
… And please remember to wash your hands on a regular basis even during times outside of global pandemic.
REFERENCES
(1)Reed RG. Stress and Immunological Aging. Curr Opin Behav Sci. 2019;28:38–43. doi:10.1016/j.cobeha.2019.01.012
(2)Ibarra-Coronado EG, Pantaleón-Martínez AM, Velazquéz-Moctezuma J, et al. The Bidirectional Relationship between Sleep and Immunity against Infections. J Immunol Res. 2015;2015:678164. doi:10.1155/2015/678164
(3)Besedovsky L, Lange T, Haack M. The Sleep-Immune Crosstalk in Health and Disease. Physiol Rev. 2019;99(3):1325–1380. doi:10.1152/physrev.00010.2018
(4)Halson SL. Sleep in elite athletes and nutritional interventions to enhance sleep. Sports Med. 2014;44 Suppl 1(Suppl 1):S13–S23. doi:10.1007/s40279-014-0147-0
(5)Labrecque N, Cermakian N. Circadian Clocks in the Immune System. J Biol Rhythms. 2015;30(4):277–290. doi:10.1177/0748730415577723
(6)Bottaccioli AG, Bottaccioli F, Minelli A. Stress and the psyche-brain-immune network in psychiatric diseases based on psychoneuroendocrineimmunology: a concise review. Ann N Y Acad Sci. 2019;1437(1):31–42. doi:10.1111/nyas.13728
(7)Adamo SA. The effects of stress hormones on immune function may be vital for the adaptive reconfiguration of the immune system during fight-or-flight behavior. Integr Comp Biol. 2014;54(3):419–426. doi:10.1093/icb/icu005
(8)Gleeson M. Immunological aspects of sport nutrition. Immunol Cell Biol. 2016;94(2):117–123. doi:10.1038/icb.2015.109
(9)Alwarawrah Y, Kiernan K, MacIver NJ. Changes in Nutritional Status Impact Immune Cell Metabolism and Function. Front Immunol. 2018;9:1055. Published 2018 May 16. doi:10.3389/fimmu.2018.01055
(10)Piercy KL, Trolano RP, Ballard RM, et al. The Physical Activity Guidelines for Americans. JAMA. 2018; doi:10.1001/jama.2018.14854
(11)Cook MD, Allen JM, Pence BD, et al. Exercise and gut immune function: evidence of alterations in colon immune cell homeostasis and microbiome characteristics with exercise training. Immunol Cell Biol. 2016;94(2):158–163. doi:10.1038/icb.2015.108