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Stressed Out: Health and Nutritional Implications of Modern Lifestyles Suggested CDR Learning Codes: 2060, 2070, 2090, 2100, 4040, 4050, 4090; Level 2 Everyone complains about stress, but most people do not understand what it is. Few can define the term, and fewer realize that stress is an “equal opportunity” event. Even rats placed in restraints and subjected to electric shock treatments or extreme temperatures, kept hungry or sleep deprived, or kept in crowded or isolated situations all show similar physical responses: enlarged adrenal glands, shrinkage of the thymus gland, and ulceration of the gastrointestinal (GI) tract. Humans aren’t any different. Our bodies respond in the same way to different stressors, although the intensity and duration of the response—“the rate of wear and tear”—may be determined in part by the intensity of the stressor. Every body eventually wears out, and stress accelerates the process. As dietitians, we see patients and clients whose dietary habits and nutritional status are affected by stress. This article will explain the physiological processes, health effects, and nutritional consequences of prolonged or severe wear and tear. Organs that are genetically more susceptible to stress than others will be the first to show signs of dysfunction. The organs most affected by stress control multiple functions of the body. The adrenal glands produce hormones that regulate many bodily functions; the thymus gland is the master gland of the immune system; ulcers of the GI tract change how foods are digested and absorbed and may alter immune function; and the heart pumps blood supplying oxygen and nutrients to all body tissues. All are subject to accelerated wear and tear by stressful stimuli. Types of Stress There are four categories of stress. The first is physical stress, which usually means physical damage to the body: lacerations, broken bones, surgery, infections, burns, and extreme pain and temperature. This type of stress usually places the greatest demand on the body and can literally cause organs and systems to shut down (eg, when someone goes into shock). The second category is environmental stress: air and noise pollution, crowding, occupational pressure, and traffic. The third category is psychological stress, also known as life event stress or emotional stress. Events of an extreme nature are well understood, and we have developed elaborate processes and rituals for coping with them. The death of a spouse, friend, or loved one, especially if sudden and unanticipated, is considered the most intense type of psychological stress. However, the “stressors of modern living” are also profound: financial gains and losses, employment disruption, relationship problems, legal troubles, and moving are examples of stressors for which we have no automatic mitigation ritual or process. These three categories of stress are considered negative; they cause the body to react physiologically with the involvement of the adrenal glands, thymus gland, GI tract, and immune cells. They have the potential to cause physical harm or disease—to accelerate the rate of wear and tear beyond the body’s ability to recover. But not all stress is negative. Eustress, a reaction to a positive event, can also alter the physiology and biochemistry of the body, though usually without causing harm. A good example is a romantic encounter: The body mobilizes for action but does not experience the same debilitating reactions as it would if it were threatened. Job promotion, athletic achievement, and marriage are stressful but not usually debilitating. Some events could be placed in both the psychological stress and eustress categories. A step up the career ladder, with the positive effects of a higher salary and status, can place a person in conflict with former peers who are now subordinates or subject him or her to unfamiliar pressures with deleterious effects. Obviously, the intensity of a reaction to a stressor varies from person to person. What we believe tends to determine our reactions to an event. If a person has been taught to view a situation as threatening or has experienced many traumatic events in life, he or she will respond physiologically much differently than someone who has not had those experiences. In a sense, “Stress is in the mind of the beholder.” We now recognize posttraumatic stress disorder as a real phenomenon and speak of stress-related disorders, accepting that every stressor has consequences beyond the relief of the immediate situation. Psychosomatic disease—psyche (mind) and soma (body)—is the interaction and interdependence of psychological and physical factors, and we might say that the leading causes of death (coronary heart disease and cancer) and the most common debilitating diseases (arthritis, diabetes, autoimmune diseases, and respiratory disease) have a psychosomatic component because stress is a factor in their development and/or the severity of symptoms. Subclinical conditions such as backaches, headaches, chest pains, and fatigue that do not require medical treatment are often stress related. During stress, the body is in an excited state, ready for action. Muscles contract and prepare to exert. When the person begins to relax, exhaustion from being in a “ready” state for a prolonged period manifests. Sometimes, people under daily stress from situations that cannot be solved simply or immediately manifest sadness and lethargy and feel powerless to the point of becoming clinically depressed. The best remedy is to release the stress through activities such as exercise, biofeedback, hypnosis, and yoga, but since those require positive action, people may feel unable or unmotivated. That goes for counseling, support groups, exercise classes, and positive social events, which could make these symptoms disappear on their own. But many people don’t exercise or interact with other people to relieve stress. Rather, they interact with their refrigerator, sometimes indulging in “comfort foods” with little nutritional value. Eating empty calories while the body is mobilized for action and demands optimal nutrition is a recipe for problems. The Stress Response But real physical threats are rare. Most threats are from environmental and psychological stressors, but the body responds the same way. The energy that has been mobilized is internalized, and the rate of wear and tear increases. The response to a threat involves all body systems. The adrenal glands flood the body with epinephrine (adrenaline), the heart rate accelerates, blood pressure increases, muscles tense, hands become cold and sweaty, pupils dilate, the face becomes pale, the body begins to sweat and tremble, and blood rushes from the periphery of the body to the internal organs. The stress response works like this: The brain perceives a threat. The message is sent via the reticular activating system, a column of nerves, to the hypothalamus at the base of the brain. The hypothalamus is connected to the pituitary gland and a portion of the brain responsible for various aspects of emotions and behavior. The hypothalamus controls eating, sleeping, body temperature, the autonomic nervous system (ANS), and the endocrine system via the pituitary gland. It can respond to emotional and psychological stimuli from the limbic system or intellectually perceived stress stimuli from the cortex of the brain. Once the stress stimuli are sent, the hypothalamus responds by activating the ANS via nerve impulses and the pituitary gland via corticotropin-releasing factor (CRF). The ANS, comprised of the sympathetic and parasympathetic nervous systems, controls organs and body functions. When stimulated during stress, it tenses and constricts involuntary muscles; shunts blood from the periphery and nonvital functions to the muscles, heart, and liver; increases heart rate; tenses skeletal muscles; dilates the pupils; “locks” the diaphragm; and causes the pelvis to be rigid and the genitals to be numb. The production of catecholamines—epinephrine and norepinephrine—is stimulated by the ANS and involved in the fight-or-flight reaction. The production of epinephrine increases to as much as 10 times the normal level. These catecholamines have a life of seconds to minutes, so they are continually produced during a stress response and impact immune function. A greater amount of epinephrine is produced than norepinephrine. The pituitary gland is activated by the hypothalamus via CRF. The posterior pituitary secretes vasopressin, which contracts artery walls and raises blood pressure. The anterior pituitary secretes adrenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH), which stimulate the cortex of the adrenal gland and the thyroid gland, respectively, to produce specific hormones. Growth hormone and prolactin are produced directly from the anterior pituitary gland. The glucocorticoids—cortisol, cortisone, and deoxycorticosterone—mobilize fuels, particularly glucose, raising blood sugar. Constant production of cortisol lowers the immune response and inflammation. These are the hormones responsible for the long-term negative effects of stress. Aldosterone, the major mineralocorticoid, maintains electrolyte balance. The life of the steroid hormones is hours to days. Thyroxine, produced by the thyroid gland, increases the rate of energy use by cells, increases the amount of protein the cells manufacture, and governs physical growth. During stress, thyroxine intensely stimulates the tissues of the body, causing sweating, shakiness, nervousness, increased heart rate, rapid breathing, and increased basal metabolic rate, causing a person to be easily fatigued. Thyroxine production occurs early in the stress response and then normalizes quickly. Growth hormone production, increasing under stress, promotes growth of tissue and cellular repair. The hormonal changes of the stress response alter the body’s metabolism. If the stress is of a short duration and in a well-nourished individual, the likelihood of harm is minimal. If the stress is chronic and in a poorly nourished individual, the health consequences can be severe. Metabolic Alterations Cytokines also alter metabolism during stress, particularly interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-alpha. These cytokines increase the counter-regulatory hormones (hormones that oppose insulin): cortisol, catecholamines, and glucagon. IL-1 works on the hypothalamus to release ACTH and CRF. The ACTH increases the release of cortisol, while CRF signals the sympathetic nervous system (SNS) to release catecholamines.1 By increasing the production of counter-regulatory hormones, cytokines alter metabolism. The metabolic alterations during stress have a common goal: to increase the glucose supply. To that end, the catecholamines increase the blood supply to the liver so that glycogen, protein, and fat can be converted into glucose. Glucocorticoids stimulate glucose synthesis. Protein in peripheral tissues is broken down so the glucogenic amino acids can be utilized for energy. Triglycerides, released from fat cells, are broken down for glycerol, which can be converted to glucose. Aldosterone protects the body from electrolyte imbalances that can occur when cells are destroyed and potassium is released into the surrounding fluid. Catecholamines, glucocorticoids, and growth hormone all cause insulin resistance and hyperglycemia during stress. While there is hyperglycemia, the glucose supply to some of the cells is low, stimulating the liver to produce more glucose and the adipose tissue to release free fatty acids that can be burned for energy. Increased fasting blood sugar levels are an early metabolic response to stress. Glycosuria, elevated glucose levels in the urine, may result. Persons with diabetes may need more insulin during stress. If they aren’t taking insulin, people with type 2 diabetes may have a more difficult time controlling blood sugars when they are stressed. If the cells are resistant to insulin due to the hormonal changes, both diet and medication and/or insulin needs should be reevaluated. When working with an individual with diabetes who has erratic swings in blood sugar, evaluate his or her stress level to determine whether it is influencing blood sugar levels. Individuals prone to diabetes may have the disease manifest itself when they are undergoing a stressful period in their lives. Fat metabolism is altered during stress, with an increase in the rate of fat used for energy. Free fatty acid production in response to the increases in catecholamines and cortisol can be so rapid that the liver becomes overloaded, with too many free fatty acids to metabolize at once. When this happens, the liver will reesterify the fatty acids to triglycerides. These will remain in the liver if the fat cells, due to altered metabolism, are not able to store them. Another problem with the rise in circulating fats during stress is the buildup of arterial plaque. A person with a history of atherosclerosis who has elevated cholesterol levels or other risk factors for heart disease will be at an increased risk for premature coronary heart disease. During stress, the metabolism of protein is altered. Protein is mobilized for energy, even if adequate fat is available. As protein synthesis decreases, there is decreased amino acid incorporation into protein by the spleen, lymphocytes, reticulocytes, bone cells, and thymus—organs and cells of the immune system. During chronic stress, the decrease in protein synthesis by the immune system can compromise immune function. Steroid hormones are produced from cholesterol. The body will increase cholesterol levels during stress to ensure an adequate supply of cholesterol. The metabolic changes described above cause the body to change from an anabolic to a catabolic state. No longer building tissue, the body dips into its nutrient stores to supply energy. Protein and fat break down and are not replaced. Instead of building tissue, the body destroys tissue. In addition, stress causes a shift to a “pro-oxidant” state due to the increase in cortisol, which shifts the immune response to nonspecific immunity, and continued stimulation, which increases free radical production.2 The increase in free radicals necessitates an increase in antioxidants to prevent oxidative stress and the corresponding diseases. When an individual is healthy, nonstressed, and well nourished, his or her nutrient gas tank is “full”; during stress, the body begins to use more energy and nutrients, with an increased rate of nutrient turnover. The increased metabolic rate places higher demands on the readily available nutrient stores, causing them to be depleted, and the gauge moves toward “empty.” Starvation is the extreme catabolic state, when almost no food enters the body and it must destroy itself to survive (although the metabolic rate falls to preserve tissues). Even with adequate calories, protein, and fat available, the body will be in a catabolic state due to the effect of the stress hormones. The severity of the catabolic state depends on the intensity and duration of the stress and the individual’s nutritional status. Critically ill hospitalized patients feel the most severe stress, with the highest requirements. Even psychological stress can increase the utilization of nutrients and alter metabolism to some degree. A summary of the metabolic changes is found in Diagram 1. Health Consequences It appears that one link between stress and disease is an altered immune response that causes inflammation, as evidenced by an increase in the acute phase response, C-reactive protein, and proinflammatory cytokines IL-1, IL-6, IL-8, and TNF-alpha.3,4 Inflammation is an underlying cause of many chronic diseases: heart disease, diabetes, visceral-type obesity, autoimmunity, metabolic syndrome, and major depression.5 Heart Disease and Stress Now we have more information about exactly how these factors are implicated in the development of heart disease. The landmark Interheart Study investigated the risk factors for heart disease in 52 countries, with 262 participating centers and 24,676 participants. Among the nine risk factors for heart disease were psychosocial factors such as stress at home and at work, financial stress, and stress surrounding major life events. The study found that stress increased heart attack risk by 2.5 times—equal to the risk from hypertension and higher than the risk from abdominal obesity, which increased risk 2.2 times.6 A heart attack from coronary heart disease can be caused by plaque buildup in coronary arteries, a coronary artery spasm, or a blood clot. All cause a blockage of the coronary arteries, preventing blood from reaching the heart. Without blood, the heart is deprived of oxygen and energy and dies. Arterial injuries appear to be responsible for the series of events that leads to atherosclerosis.7,8 • Stress alone can cause the coronary arteries to spasm. If the spasm is severe enough, it can injure or totally block the artery. This causes a heart attack, even if no arterial plaque is found in the artery. • Inflammation. Many factors cause inflammation (emotional stress, diet, obesity, and immune response). Whatever the cause, the inflammation takes place in the endothelial cells of vessels. Once injured, the vascular epithelial cells secrete substances attracting immune cells to the site so they can begin the repair process. The result is plaque buildup in the arteries, a narrowing of the arteries, and reduced blood flow. • Immunity. Immune cells produce superoxide anions (free radicals) that increase vascular constriction and damage protein and DNA in the cell, leading to endothelial cell injury. Antioxidants have the ability to prevent the damage associated with superoxide anion injury.8 Platelets, also attracted to the injury site, produce platelet-derived growth factor (PDGF) and thromboxaneA2 (TXA2). The PDGF causes smooth muscle cells to reproduce, while the TXA2 increases the production of platelets, leading to more clots. • Diet. Diets high in omega-6 polyunsaturated fatty acids (PUFAs) increase production of the proinflammatory cytokines IL-1, IL-6, and TNF-alpha, which increase arterial plaque buildup and lead to blood clots. Omega-3 fatty acids decrease IL-1, IL-6, and TNF-alpha.9 Decreasing inflammatory mediators has the benefit of decreasing arterial plaque and preventing unstable plaque from breaking off the artery and blocking the blood vessel, either partially or totally. In addition, omega-3 fatty acids, especially fish oils, decrease production of TXA2, thereby decreasing the production of platelets and the ability of the blood to readily clot. Antioxidants are able to prevent epithelial cell injury from superoxide anions and free radicals, so there is no need for the localized immune response that leads to inflammation and plaque buildup. Nutrients that contribute to arterial plaque are total fat, cholesterol, omega-6 PUFAs, and lack of antioxidants, while omega-3 PUFAs, vitamin E, other antioxidants, and phytochemicals protect against it. The foods that protect against inflammation are often in short supply when someone is under stress, as those are the times individuals are less likely to eat well. It is precisely those times when eating well is most important so that the body can handle stress without getting sick. Many people know this and seek to compensate by taking so-called stress formula supplements. Vitamins and Minerals With the exception of physical stressors (eg, surgery, trauma, burns), little research exists on the changes in nutrient needs under stress, especially environmental and psychological stress. However, one study did show that for people working in hot, cold, or high-altitude environments, there is an increased need for energy, B vitamins, iron, and antioxidants.10 Many studies have cited an increased need for nutrients when under physical stress.10 For those under psychological, environmental, or emotional stress, calories, protein, zinc, vitamin C, calcium, phosphorus, vitamin A, thiamine, riboflavin, and niacin should be of concern.11-13 Increased antioxidants are needed to prevent oxidative stress. Urinary losses of zinc, calcium, magnesium, potassium, and protein increase. If an acute phase response is present, serum levels of vitamin A, iron, and zinc decrease, but the need for these nutrients may increase. Making recommendations concerning the necessary levels of vitamins and minerals during stress is difficult, as there is little hard data on altered needs. However, there is an increased need due to increased utilization and increased losses from urine. In a well-nourished person, short-lived stress may not increase the need for nutrients. But chronic, prolonged stress, with sustained metabolic changes, can definitely impact the nutritional needs of the body and is when intake becomes problematic. Vitamin C is found in highest concentration in the adrenal glands, where epinephrine is made. During stress, the concentration of vitamin C drops rapidly as epinephrine is produced. Whether extra vitamin C is required to maintain an adequate supply to meet the increased need is under debate. It appears there is a slightly higher need during stress, but the exact quantity is unknown. Antioxidant levels fall during physical stress to counteract the increased production of free radicals. Increased amounts of these nutrients will neutralize the free radicals and protect against oxidative stress. The key nutrients involved in maintaining the metabolic functions of the body during stress are the energy-producing B vitamins—thiamine, riboflavin, niacin, pantothenic acid, and biotin—along with vitamins A, B6, and C and the minerals iron, magnesium, zinc, copper, and chromium. The goal then is to maximize nutrient intake, including antioxidants, and avoid any inadequacies that can lead to marginal or overt deficiencies, which may require supplementing with low doses of vitamins and minerals in a broad-spectrum multivitamin and mineral tablet. — Dale Ames Kline, MS, RD, CNSC, is president of Nutrition Dimension, Inc. A former hospital chief clinical dietitian and nutrition educator in the Women, Infants, and Children Program, she has written and edited continuing education home study courses since 1984.
References 2. Chamlers AH, Blake-Mortimer JS, Winefield AH. The prooxidant state and psychologic stress. Environ Health Perspect. 2003;111(1):A16. 3. Black PH. The inflammatory response is an integral part of the stress response: Implications for atherosclerosis, insulin resistance, type II diabetes and metabolic syndrome X. Brain Behav Immun. 2003;17(5):350-364. 4. Steptoe A, Hamer M, Chida Y. The effects of acute psychological stress on circulating inflammatory factors in humans: A review and meta-analysis. Brain Behav Immun. 2007;21(7):901-912. 5. Eleknov IJ, Iezzoni DG, Daly A, Harris AG, Chrousos GP. Cytokine dysregulation, inflammation and well-being. Neuroimmunomod. 2005;12(5):255-269. 6. Yusuf S, Hawken S, Ounpuu S, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): Case-control study. Lancet. 2004;364:937-952. 7. Meydani M. Nutrition, immune cells, and atherosclerosis. Nutr Rev. 1998;56(1):S177-S182. 8. Tomaino RM, Decker EA. High-fat meals and endothelial function. Nutr Rev. 1998;56(6):182-185. 9. Connor SL, Connor WE. Are fish oils beneficial in the prevention and treatment of coronary artery disease? Am J Clin Nutr. 1997;66:1020S-1031S. 10. Askew EW. Environmental and physical stress and nutrient requirements. Am J Clin Nutr. 1995;61(Suppl):631S-637S. 11. Padayatty SJ, Doppman JL, Chang R, et al. Human adrenal glands secrete vitamin C in response to adrenocorticotrophic hormone. Am J Clin Nutr. 2007;86:145-149. 12. Okamoto H, Ishikawa A, Yoshitake Y, et al. Diurnal variations in human urinary excretion of nicotinamide catabolites: Effects of stress on the metabolism of nicotinamide. Am J Clin Nutr. 2003;77:406-410. 13. D’Amato G. Air pollution, reactive oxygen species and allergic bronchial asthma. In: Diet and Human Immune Function, Totowa, NJ: Humana Press; 2004.
Table 1 Glucocorticoids Aldosterone Growth Hormone Catecholamines Insulin Glucagon
Learning Objectives
Examination 2. The physiological response to stress is the same whether the stress is physical or psychological. 3. Which of the following best describes the purpose of the stress response? 4. During the stress response, the autonomic nervous system is responsible for which of the following physiologic responses to stress? 5. Why do people with diabetes have more difficulty controlling blood sugar when they are under stress? 6. How does the increase in cytokine production alter metabolism? 7. Which of the following metabolic changes occur under stress? 8. Which of the following recommendations would you make to someone under chronic stress? 9. Why do people get sick when under stress? 10. How does stress increase the risk of heart disease? |
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September
2008 Issue |
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