By Whitney Crouch, RDN & Kirti Salunkhe, MD
What is stress?
Stress can be defined as a constellation of events, starting with a stimulus or stressor that causes a reaction in the brain leading to the stress response commonly known as the “fight-or-flight” reaction that can affect many body systems.1 Unfortunately, stress is a fact of life that we all experience at some time or another. Stressors that are acute, or short-lived, are often physical or physiological. Psychological or emotional stress is usually chronic in nature.
The immune system and stress
The immune system is made up of cells, tissues, and organs working together as the body’s defense mechanism to protect us from illness. Scientists say short-term stress (lasting from minutes to a few hours) may be beneficial for our immune health, as it stimulates immune activity and prepares us for possible periods of longer stress—a “fire drill” of sorts. However, chronic stress is actually harmful.2
White blood cells (WBC) are critical for the body’s immune response to foreign invaders. These cells are produced, and stored, in many areas of the body including the spleen, bone marrow, and thymus (a small gland found behind the sternum and between the lungs).3 There are two types of WBCs associated with the immune system: Phagocytes, which actively attack foreign organisms, and lymphocytes, which remind the body to recognize previous invaders and help destroy them.4 The main phagocyte is the neutrophil. Neutrophils primarily fight bacteria and infections. The main lymphocytes are the B lymphocytes or B-cells and T lymphocytes or T-cells. B-cells start out and mature in the bone marrow. T-cells start out in the bone marrow but mature in the thymus. These two cell types are the “special ops” of the immune system and have specific functions. B-cells make antibodies to fight bacteria and viruses and T-cells directly attack invading organisms.4
Acute stress and the immune response
One of the most familiar reactions to acute stress is the “fight-or-flight” response. This physiological reaction usually occurs during an emergency or a fearful mental or physical situation.3 When a threat is perceived, there is a release of hormones to prepare you to either stay and deal with the threat or to run away to safety. It represents choices our ancient ancestors made when faced with dangerous situations. Nowadays, it’s more likely those dangerous situations are ones leading to a wound or infection, but our body reacts the same way.3 During periods of short-term stress, our sympathetic nervous system releases “stress hormones:” epinephrine (adrenaline) and norepinephrine (noradrenaline), as well as corticotropin-releasing hormone (CRH), adrenocorticotropin (ACTH), and cortisol from the adrenal glands.3 These work together to prepare the body for “fight-or-flight” by increasing alertness, focusing the mind, elevating heart and breathing rates, as well as increasing blood flow to skeletal muscles and brain.4
Interestingly, research has shown acute stress activates the immune system. Immune activation is critical to respond to immediate demands of a stressful situation that may lead to a wound or an infection. Acute stress triggers immune cells and stimulates production of proteins known as cytokines. The two major types of cytokines are: pro-inflammatory cytokines and anti-inflammatory cytokines. The pro-inflammatory cytokines process the pain often found with inflammation; the anti-inflammatory cytokines work by controlling, or limiting, the spread of inflammation. Both are necessary for normal healing.3
While acute, or short-term, stress acts as an “immune stimulator,” readying the body’s immune system for an adverse situation, situations involving long-term or chronic stress actually suppress and dysregulate the body’s immune responsiveness, leading to illness and poor outcomes.3
Chronic stress and the immune response
Just as we all have differing genetic and biochemical composition, we also have varying perceptions of stress and individual responses to how we process and cope with it.5
Occasionally, there can be a crossover between the mind and body, as in the “fight-or-flight” response. A mentally stressful situation may require a physical response or action, but what about those psychological or emotional stressors that may be difficult but don’t actually pose any pressing physical dangers? Stressors related to pressures of a work project requiring focused concentration over long days and nights, or the continual emotional drain from a difficult relationship or other similar circumstance?
Studies have shown prolonged mental stress can adversely affect regular lifestyle routines, including decisions we make about sleep, nutritional intake, and exercise and can even persuade us to use poor judgement regarding alcohol and drug intake.5,6 These studies have also shown the adverse effects (acute and chronic) that mental and emotional stress places on physical health and wellbeing and have been directly linked to suppression of the immune system.5 How acute mental stress affects physical health was seen in a recent study of college students during their final exams.7 To understand the link between mental stress and changes in blood biomarkers, researchers took blood samples and administered questionnaires about anxiety and depression to 24 college students during finals week. Baseline values had been established by prior blood draws and questionnaires completed midsemester. When compared to baseline levels, during finals week, there were elevations in pro-inflammatory cytokines along with increased reports of anxiety and stress.7 Other studies have noted increased stress can lead to prolonged wound healing time with reduced levels of anti-inflammatory cytokines and increases in pro-inflammatory cytokines.6
Multiple studies have evaluated the immune response in conditions of long-term and emotional stress. These conditions are similar to those found with caregiving of an ill or elderly relative, experienced after a difficult divorce and have even been reported as related to loneliness.7-9 Findings from these studies showed links between emotional stress and increased risk for viral illness, reemergence of latent viruses (Epstein-Barr, herpes simplex, and cytomegalovirus), and onset of autoimmune disease.5,10,11 Other studies have shown long-term psychological stress was linked to detrimental cardiovascular health12-14 as well as increased risk for immunologic conditions including inflammatory bowel disease, allergies, atopic dermatitis, and celiac disease.15-18
Even the most vulnerable members of the population, our children, can be affected by psychological stress that results in a reduced immune response. Investigators evaluated children who had a history of recurrent colds and flu and reported higher levels of psychological stress. The data demonstrated the children had reduced salivary immunoglobulin ratios (IgA/albumin). A reduction in this ratio supports a potential link between reduced immune function with a greater susceptibility to colds and flu.19
Lifestyle approaches to stress management
While the effects of stress can be useful on some occasions, adverse effects of stress can play a role in both acute and chronic illness. While there are a number of strategies that come into play with stress management, evidence supports the benefits of lifestyle modification and improved dietary or nutritional intake as a part of a comprehensive strategy.
Recommended lifestyle modifications:
This information is for educational purposes only. This content is not intended as a substitute for professional medical advice, diagnosis, or treatment. Individuals should always consult with their healthcare professional for advice on medical issues.
Whitney Crouch, RDN, CLT
Whitney Crouch is a Registered Dietitian who received her undergraduate degree in Clinical Nutrition from the University of California, Davis. She has over 10 years of experience across multiple areas of dietetics, specializing in integrative and functional nutrition and food sensitivities. When she’s not creating educational programs or writing about nutrition, she’s spending time with her husband and young son. She’s often found running around the bay near her home with the family’s dog or in the kitchen cooking up new ideas to help her picky eater expand his palate.
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