E 218 eating disorders A class of diseases based on obsessive behavior related to eating: ANOREXIA NER- VOSA, BULIMIA NERVOSA, and compulsive overeat- ing. Eating disorders affect people from all socioeconomic classes, and ages range from 3 to 90. Although both men and women can develop eat- ing disorders, predominantly women are affected. Though factors vary among individuals, the cycle of eating disorders seems to be initiated by psychological injury, including physical and psy- chological abuse among family members, reduced self-esteem, oppression, social isolation, and nutri- tional insults, including faulty diet, abuse of drugs, alcohol, and medications, and food intolerance. The resulting behavioral changes and altered eating can lead to a cycle of altered diet, altered APPETITE, and hunger mechanisms worsened by nutritional imbalances, leading to further eating changes and compulsive behavior. Anorexia nervosa, self-induced starvation out of an intense fear of becoming obese, was first described 100 years ago. It now occurs in an esti- mated 1 percent of American women. Although there is a genetic predisposition, social factors play key roles in determining the occurrence of anorexia nervosa. Symptoms include a markedly distorted body image and self-restricted dieting, leading to extreme weakness, muscle wasting, and loss of 25 percent of original body weight, and ces- sation of menstruation. Anorexia nervosa is poten- tially life-threatening. Bulimia nervosa is characterized by recurring episodes of binge eating (rapid, excessive eating), followed by purging. Most bulimics are women. Bulimia was first described in the United States in 1980 and the incidence in America is increasing. It is characterized by frequent attempts to lose weight by severely restricted diets, followed by episodes of bingeing, followed by deliberate vomiting or abuse of diuretics or laxatives, to lose weight. Bulimics generally possess low self-esteem and fear an inability to stop eating. Frequent fluctuations in body weight are common. The third category is compulsive overeating, which refers to episodes of excessive overeating or bingeing in secret. Compulsive overeating is ac- companied by repeated attempts to lose weight and diet. The increased occurrence of compulsive over- eating among American teenagers parallels their increased prevalence of OBESITY. Compulsive over- eating can substitute for confronting life issues and dealing with emotions and their sources. Hazards associated with eating disorders other than obesity include starvation, electrolyte and fluid imbalances, liver damage, kidney damage, stroke, cessation of menstruation, diabetes, inter- nal bleeding, and ultimately death. Eating disorders are complex conditions that profoundly affect health, and therapy entails mul- tiple approaches including psychological counsel- ing, support groups, nutrition counseling, and, in extreme cases, medical intervention. Strategies that focus on weight reduction or diet modification alone are of limited effectiveness in treating eating disorders because they fail to resolve underlying psychological issues. The most comprehensive treatment programs address emotional, social, physical, and spiritual components. Extended aftercare services as well as active participation in self-help groups support recovery. Claude-Pierre, Peggy. The Secret Language of Eating Disor- ders: The Revolutionary Approach to Understanding and Curing Anorexia and Bulimia. New York: Random House, 1998. eating patterns 219 eating patterns Trends in food consumption in the United States; patterns of eating behavior, reflecting food choices based on personal habits, taboos, customs, and family traditions. Food costs and food availability profoundly influence day-to- day food choices. Many personal values affect food choices: political conviction, such as conviction about the environment, or religious preferences (for example Catholic, Muslim, or Jewish); percep- tions of social status; conditioning through adver- tising. Food purchases are often made according to health concerns, thus recent trends in eating fewer EGGS, less whole MILK, and less red MEAT are based in part upon consumers’ concerns about CHOLES- TEROL and clogged arteries. The typical American diet, indeed the common pattern in industrialized nations, is low in fresh FRUIT and VEGETABLES and high in meat and processed food that is high in FAT , sodium, and sugar. Such a diet does not supply adequate FIBER, TRACE MINER- ALS, VITAMINS, and substances in plant foods whose antiaging and anticancer properties are still being discovered. Sweets and alcohol displace nutrient- rich foods, and lifestyle choices such as cigarette smoking and lack of EXERCISE alter nutrient needs. Meal time has changed from eating at home with family to eating quick meals away from home. For many Americans, half of every dollar spent on food goes to outside meals. Generally, the odds of eating a less nutritious meal increase the more meals are eaten away from home. Often the choices rely on convenience foods and snack foods that contain high levels of fat, sugar, and sodium. Teenagers often obtain 20 percent of their food from such snacks, which has a long-term impact on their health. The typical U.S. diet is imbalanced due to nutri- ent inadequacy and nutrient excess. The typical diet supplies too many CALORIES and too much FAT. Sweeteners in SOFT DRINKS, snacks, candy, ice cream, and pastry supply 25 percent of the calories. Each succeeding generation of Americans appears to get fatter. The typical diet supplies more fat than recommended to lower the risk of cancer and of heart disease. Paradoxically, women often have a problem in finding diets that will provide all the vitamins and minerals they need, while lowering their fat and calorie intake. Results of Surveys Surveys provide insight about what Americans are eating and how they make food choices. Recent polls to discover whether Americans are becoming more concerned about nutrition offer conflicting results. On the one hand, many Americans realize that diet is a factor in health risks. On the other hand, some results suggest that Americans have become less concerned about limiting high choles- terol food and obtaining adequate nutrients like vitamins. While heads of households have become more interested in many foods high in fiber and lower in fat and CHOLESTEROL, many also say that their health habits have not significantly changed. Sixty percent of American adults do not get enough physical activity and more than 25 percent are not active at all in their leisure time. Only about one- fourth of adults eat the recommended five or more servings of fruits and vegetables each day. Recent data indicate that Americans are getting fatter; obesity has reached epidemic proportions. A 2000 survey by the U.S. Centers for Disease Con- trol and Prevention (CDC) found that more than 45 million adults (about 60 percent of the adult population) are obese. The number of young peo- ple (age 6 to 17) who are considered overweight has more than doubled in the last two decades. That the average American now weighs more than 20 years ago is perhaps related to the fact that food consumption has increased 20 pounds per person. The DIETARY GUIDELINES FOR AMERICANS rec- ommend a diet that is low in saturated fat and cho- lesterol, yet more than half the adult population fails to meet the recommendations for saturated fat intake. The guidelines recommend no more than 30 percent of daily calories come from fat; the aver- age adult gets 33 percent. Adults also consume too many foods high in sugar. Americans consume on average 20 teaspoons of sugar daily. Sodium con- sumption, too, exceeds recommended levels. The guidelines suggest limiting intake to no more than 2,400 mg a day. On average, men consume 4,000 mg and women consume 3,000 mg. Eating healthier means changing one’s lifestyle. A number of experts recommend gradual change and moderation, with ample information to enable people to make and support wise choices. A variety of food substitutions can be implemented in a step- wise fashion to achieve a gradual change to health- ier alternatives. The following illustrates initial substitutions: Food Healthy Alternative Healthier Alternative whole milk low-fat milk nonfat milk cottage cheese low-fat cottage nonfat cottage cheese cheese sugar cereal nonsugar cereal whole-grain cereal, non-processed fruit drink orange juice whole orange soft drink with diet soft drink sparkling water or sugar, caffeine fruit juice white bread brown bread 100 percent whole- wheat bread bologna ham turkey (See also FAT, HIDDEN.) Liebman, Bonnie. “The Changing American Diet,” Nutri- tion Action Healthletter, 22:5 (1995): 9–10. Physical Activity and Good Nutrition: Essential Elements to Pre- vent Chronic Diseases and Obesity. Atlanta, Ga.: Centers for Disease Control and Prevention, 2000. Woteki, Catherine. “Consumption, Intake Patterns and Exposure,” Critical Reviews in Food Science and Nutrition, 35:1,2 (1995): 143–147. echinacea (Echinacea angustifolia; E. purpurea) A perennial herb that stimulates the body’s immune system. Echinacea is native to North America, from Texas to the prairies of Canada. Native American tribes have long used this herb as an antiseptic and as an analgesic (pain reliever). The dried root is used most often. It contains echinacin, a polysac- charide (complex carbohydrate) that speeds wound healing and helps maintain connective tissue. Echi- nacea contains inulin, a polysaccharide composed of fructose that activates the “alternative” comple- ments pathway, a system that increases defenses against viruses and bacteria, and speeds the migra- tion of defensive white cells (such as neutrophils, monocytes, and lymphocytes) to injured or infected regions. Echinacea stimulates T-lymphocytes, which help direct immune defenses. It also stimu- lates the production of interferon (antiviral defense) and of lymphokines, chemicals of the immune system that stimulate natural killer cells and scavenger cells (macrophages). Echinacea is regarded as a safe herb. eclampsia (toxemia of pregnancy) A serious medical condition that can accompany pregnancy. “Preeclampsia” is the early stage characterized by high blood pressure, headache, protein in urine, and swelling ( EDEMA) of legs and feet. If untreated, the patient may develop true eclampsia. Eclampsia develops in 0.5 percent of patients with preeclampsia. Convulsive seizures can occur between the 20th week of pregnancy and the first week after birth; eclampsia is usually fatal if untreated. In addition to the symptoms of preeclampsia, symptoms of eclampsia include severe headaches, dizziness, abnormal pain, nau- sea, convulsions, and possibly coma. The kidney, liver, brain, and placenta are affected. The causes of eclampsia are unknown. HYPERTENSION and kidney disease contribute to the problem. Treatment of eclampsia is medical. Salt restriction is not part of the treatment, and the use of DIURETICS may simply mask signs and symptoms. Poor nourishment may predispose a woman to preeclampsia. Some studies indicate that poorly nourished women develop preeclampsia more often, but studies of calcium supplementation for preventing preeclampsia have had mixed results. A recent study showed that supplemental vitamin C and vitamin E may reduce preeclampsia in high- risk women, but the authors caution that it is too soon to recommend supplementation. Pregnant women should make sure their diet is adequate in food sources of these vitamins and take only the supplements prescribed by their prenatal care provider. Anyaegbungm, A., and C. Edwards. “Hypertension in Pregnancy,” Journal of the National Medical Association 86 (April 1994): 289–293. Walsh, Scott W. “The Role of Fatty Acid Peroxidation and Antioxidant Status in Normal Pregnancy and in Preg- nancy Complicated by Preeclampsia,” World Review of Nutrition and Diet 76 (1994): 114–118. eczema (atopic dermatitis) Persistent itchy and inflamed skin, often with scales, crusts, scabs, or small blisters. Eczema may be dry or there may be 220 echinacea a discharge; the condition is not infectious. Aller- gies may be involved; many eczema patients test positive for allergies and they may exhibit hay fever symptoms. Emotional upset and stress can aggravate itching. Contact with chemical irritants can trigger eczema. Inheritance is a risk factor for eczema, and dietary factors are involved. The Role of Diet Often, eczema symptoms improve with an ELIMINA- TION DIET in which suspected allergy-producing foods are avoided, suggesting a linkage to food allergy in some cases. In infants, cow’s MILK is the most common food allergy associated with eczema. ESSENTIAL FATTY ACIDS can help limit the inflamma- tory process. Omega-3 fatty acids are the essential fatty acids found in flaxseed oil and fish oils, while omega-6 fatty acids are found in EVENING PRIMROSE OIL and BORAGE oil. Vitamin C and FLAVONOIDS, plant substances that serve as ANTIOXIDANTS, appear to help control or limit inflammatory processes also. Vitamin A plays a key role in skin develop- ment and maintenance, and deficiencies should be corrected. Many eczema patients are ZINC deficient, and zinc supplementation may be helpful. This may be linked to the fact that low stomach acid is very common in patients with eczema, and low stomach acid contributes to mineral malabsorption, ultimately leading to eczema. Zinc is necessary to convert essential fatty acids to PROSTAGLANDINS, hormone-like substances that regulate inflamma- tion, among other processes. The diet of eczema sufferers should minimize convenience foods that supply high levels of fat, sugar, and other additives, while emphasizing whole foods, particularly fresh fruit and vegetables. Increasing consumption of polyunsaturated FAT (like SAFFLOWER oil) and FISH OIL may help decrease inflammation and boost the immune system. (See also ACNE; ALLERGY, FOOD; BREAST-FEEDING; LEUKOTRIENES.) edema The swelling of any part of the body due to fluid accumulation. Allergies can cause edema when the allergic response releases HISTAMINE and other inflammatory agents that make capillaries porous so that fluid from BLOOD can then leak into surrounding tissue, causing puffy eyes and a swollen face, for example. Edema is also one of the symptoms of preeclampsia in pregnancy. General- ized edema can result from serious medical condi- tions such as HYPOTHYROIDISM, kidney failure, liver disease, and congestive heart failure. Nutritionally-related causes of edema include excessive SODIUM, certain nutrient deficiencies, and food allergies. Excessive sodium can cause edema in about 20 percent of the American population who are sensitive to high salt intake. Edema is also associated with severe nutritional deficiency dis- eases such as BERIBERI (due to a deficiency of THI- AMIN) and with protein MALNUTRITION. Edema is often treated with DIURETICS (water pills), which increase urine production to remove water and salt from the body. The use of diuretics is considered potentially dangerous during preg- nancy. Reduced salt intake can be helpful and low- sodium diets may be prescribed. (See also ALDOSTERONE; ECLAMPSIA; HYPERTENSION; KWASH- IORKOR; SODIUM.) edible portion The portion of food usually con- sumed. For example, husks, hulls, rinds, peels, seed, bones and gristle are usually excluded from weight measurements and nutrient compositions. EDTA (ethylenediaminetetraacetic acid; disodium EDTA) A FOOD ADDITIVE used as an ANTIOXIDANT and a preservative to trap unwanted metal ion con- taminants. As an antioxidant, EDTA blocks the for- mation of highly reactive forms of oxygen that attack fats and oils. Attack of food molecules by oxygen requires metal ions as catalysts. When metal ion contaminants are trapped by EDTA, they do not form free radicals. EDTA is often combined with butylated hydroxytoluene ( BHT) and PROPYL GALLATE , which work together as antioxidants in processed foods. EDTA is added to salad dressings, MARGARINE, MAYONNAISE, potatoes, peas, and vegetables. EDTA traps metal ions in canned SHELLFISH that would promote off-color and altered taste. In BEER it pre- vents excessive foaming and turbidity. SOFT DRINK producers use EDTA to stabilize ARTIFICIAL FOOD COLORS . Excessive EDTA would trap essential nutri- ents in the body, such as trace mineral nutrients and CALCIUM, and therefore typical usage is 0.01 EDTA 221 percent in foods and beverages. The body absorbs only about 5 percent of an oral dose, and absorbed EDTA is excreted in the urine. EDTA is considered a safe additive. In medicine, EDTA is used to treat metal ( LEAD) poisoning and as an alternative treat- ment in cardiovascular disease. (See also CHELATE.) EFA See ESSENTIAL FATTY ACIDS . egg As food, typically, the ovum of domestic fowl. Eggs are an inexpensive, nutrient-rich food that provides high-quality PROTEIN with all essential amino acids. Egg protein is often used as a refer- ence protein in nutritional studies because it is readily digested and supplies a well balanced mix- ture of amino acids that are readily absorbed. A popular food, nonfertile chicken eggs are mass- produced, inexpensive, readily available, and easily prepared. Hens’ eggs contain an inner fluid (the egg white) which contains half of the protein but no cholesterol; proteins protect the yolk from bac- teria, such as AVIDIN, which tenaciously binds the B vitamin BIOTIN. Bacteria requiring this vitamin can- not grow in the egg white. The yolk provides many nutrients such as min- erals, vitamins, all of the CHOLESTEROL (213 mg), and 5 g of fat. The yellow color is due to the plant pigment xanthophyll (lutein). The egg yolk is also rich in LECITHIN, a phospholipid used to emulsify other lipids. As food, eggs have limitations: Their CALCIUM content is low and they lack VITAMIN C. In recipes, egg yolks can often be substituted by using double the amount of egg white. Most commercial EGG SUBSTITUTES use egg whites only. Eating more than a few eggs a week can raise blood cholesterol in sensitive people. On the other hand, moderate consumption seems safe for most healthy people. Perhaps as many as one-third of Americans are extremely sensitive to dietary cho- lesterol; their blood levels rise significantly when they eat cholesterol-rich foods. These individuals should limit their dietary cholesterol to no more than 300 mg per day. Particularly those with a fam- ily history of early heart disease or high cholesterol levels need to be watchful. More important than monitoring cholesterol in the diet is limiting fat consumption, especially consumption of SATURATED FAT . With a low-fat diet, egg cholesterol seems to have little impact on blood cholesterol levels. Organic chicken eggs, farm fresh eggs, and mass-produced eggs contain the same amount of cholesterol, although mineral and vitamin content can vary according to the chicken feed. Efforts are being made to increase the content of ESSENTIAL FATTY ACIDS of eggs by varying the hens’ diets. Eggs can be contaminated by trace amounts of PESTICIDES from feed, so purchasing organic eggs might be desirable. Because raw or undercooked eggs can transmit food poisoning ( SALMONELLA), raw cracked eggs should be discarded, and eggs should be cooked thoroughly. Eggs should be refrigerated to prevent bacterial contamination and age-related changes. One chicken egg (58 g) con- tains 79 calories; protein, 6.1 g; fat 5.6 g; choles- terol, 213 mg; calcium, 28 mg; iron, 1.04 mg; zinc, 0.61 mg; vitamin A, 78 retinol equivalents; thi- amin, 0.04 mg; riboflavin, 0.15 mg; niacin, 0.03 mg. (See also BIOLOGICAL VALUE; ORGANIC FOODS.) egg allergies A very common type of food allergy, usually due to a sensitivity to egg whites. Egg allergies may trigger symptoms quickly, includ- ing hives, asthma, watery eyes, swelling, and nau- sea shortly after the egg is consumed. Alternatively, a delayed sensitivity with symptoms such as headaches, DIARRHEA, or CONSTIPATION, can develop hours after the food is consumed. Because eggs are so common in processed foods, food labels of baked goods should be read carefully. (See also ALLERGY, FOOD ; BIOLOGICAL VALUE; FOOD SENSITIVITY.) eggplant (Solanum melongena; aubergine) A large, pear-shaped member of the NIGHTSHADE FAM- ILY that includes potatoes, tomatoes, and peppers. This vegetable probably originated in India and has been cultivated since antiquity. Eggplant is often dark purple with a glossy skin, but white, yellow, and striped varieties are also cultivated. It is a good source of FIBER and is an ingredient in many Mid- dle Eastern dishes. Ratatouille, a dish based on egg- plant, is part of southern French cuisine. Unripened eggplant may contain the toxic alka- loid SOLANINE, which also occurs in green potatoes. Solanine can cause neurological symptoms and damage red blood cells. 222 EFA One cup of cooked eggplant (160 g) contains 45 calories; protein, 1.3 g; carbohydrate, 10.6 g; fiber, 6 g; calcium, 10 mg; iron, 0.56 mg; potassium, 397 mg; vitamin A, 10 retinol equivalents; thiamin, 0.12 mg; riboflavin, 0.03 mg; niacin, 0.96 mg; vita- min C, 2 mg. egg substitutes Cholesterol-free alternatives to eggs. By eliminating the yolk, food manufacturers have developed several cholesterol-free products. Egg substitutes usually contain egg white (egg albumin); a partially HYDROGENATED VEGETABLE OIL like CORN OIL; together with ARTIFICIAL FOOD COL - ORS, GUMS, EMULSIFIERS, and several VITAMINS and MINERALS found in a typical egg. Soy protein–based egg substitutes are also marketed. eicosapentaenoic acid (EPA) A large, complex POLYUNSATURATED FATTY ACID found in FISH and fish oils. EPA belongs to the omega-3 family of polyun- saturates, derived from the ESSENTIAL FATTY ACID, ALPHA LINOLENIC ACID. EPA, with 20 carbons and five double bonds, is the parent compound for PROSTAGLANDINS (PGE 3 series) and thrombaxane A 3 , hormone-like substances that help counterbal- ance inflammatory processes triggered by other prostaglandins (PGE 2 series) and other thrombox- ane A 2 . The latter come from ARACHIDONIC ACID,an omega-6 polyunsaturate prevalent in meat. There- fore EPA and fish oil tend to balance some of the effects of a meat-heavy diet. Recent research has focused on the relationship between EPA and heart disease. Population studies indicate that death due to heart disease is lower among those who consume an average of 30 g of fish daily, as compared with those who eat meat daily. Other studies have yielded mixed results. While the results are sugges- tive, it is not yet clear which of the constituents of fish oils are more important. EPA could reduce the risk of coronary heart disease by several mecha- nisms: EPA can inhibit clot formation indirectly. It blocks the formation of thromboxane A 2 , a potent factor that causes platelets to clump. Clumping of these cellular fragments in the blood helps form blood clots within vessels. EPA is also converted to PGI 3 , a prostaglandin that directly blocks platelet aggregation. EPA and related lipids seem to lower blood fat levels. They may lower serum cholesterol, if initial levels are elevated and diets are high in saturated fat, by depressing the formation of LOW- DENSITY LIPOPROTEIN (LDL), the undesirable form of cholesterol. EPA and its relatives may also block the early stages of atherosclerosis. The improvement of glucose utilization in diabetics who use fish oil sup- plement remains controversial. Using fish oil as a supplemental source of EPA carries potential hazards. Depending on the source, it may contain industrial pollutants. Fish liver oil may contain high levels of VITAMIN A and vitamin D, which can be toxic in high doses, as well as pes- ticides and other contaminants. Guidelines regard- ing the optimal intake of EPA or of fish oil have not yet been established. (See also ESKIMO DIET; OMEGA- 3 FATTY ACIDS .) elastin A fibrous PROTEIN found in the lung, in large blood vessels and in the other elastic connec- tive tissue such as ligaments. Elastin differs from other fibrous proteins like COLLAGEN in that it is capable of undergoing a two-way stretch, like a trampoline net. Synthesis of elastin requires cop- per, and an inherited inability to absorb copper (Menke’s syndrome) causes defective arteries. electrolyte replacement See SPORT DRINKS . electrolytes Electrically charged atoms or mole- cules occurring in the blood and other body fluids and in solutions in general. Electrolytes control the distribution of water among the blood, cells, and tis- sues, and the spaces between them; thus, electro- lytes help regulate blood volume and composition. The electrical charge of electrolytes enables them to function in the transmission of nerve impulses and in muscle contraction, including heart muscle. Elec- trolytes also help regulate ACID-base balance to maintain the pH of body fluids close to neutrality. Electrolytes consist of positively charged ions (cations) and negatively charged ions (anions). The predominant cations are POTASSIUM, SODIUM, and MAGNESIUM, while the major anion is CHLORIDE. These electrolytes are not evenly distributed: Sodium and chloride are concentrated outside cells, while potassium and magnesium are concen- trated in the cytoplasm (within cells). electrolytes 223 Sodium, potassium, and chloride are nutrients. Low levels are excreted daily, and they must be regularly replaced through foods and beverages. The kidneys reabsorb these electrolytes and play an important role in regulating electrolyte balance. Electrolytes are secreted by the GASTROINTESTINAL TRACT in digestive juices and bile. For example, chloride is secreted by stomach glands as hydrochloric acid and pancreatic secretion, and the small intestine releases sodium and bicarbonate. However, much of sodium and chloride is reab- sorbed and recycled. The body malfunctions when electrolytes are lost—through vomiting, diarrhea, excessive urina- tion caused by certain medications (diuretics) or uncontrolled diabetes, or through excessive perspi- ration. Too little sodium causes fatigue, muscle weakness, or even convulsions. Potent diuretics most frequently cause potassium losses because they rid the body of excess water. Diabetes, severe burns, and dietary deficiencies can also cause low potassium. Symptoms of potassium loss include a weak pulse, general weakness, and low blood pres- sure. Magnesium deficiency can be the result of diarrhea, chronic alcoholism, inflamed pancreas (pancreatitis), kidney disease, and inadequate diet. Chloride loss can occur with diarrhea and intestinal disease. Because chloride helps prevent excessive bicarbonate, which is alkaline, low chloride can cause the body to become excessively alkaline. Mild losses of sodium and chloride are easily replaced by common beverages and processed foods. Potassium and magnesium are obtained from whole grains, green leafy vegetables, and fruits and juices. The loss of electrolytes and water can lead to life-threatening situations more rapidly than for losses of any other nutrient. With pro- longed electrolyte imbalance, the brain, heart, and lungs do not function normally, and medical atten- tion is required to replace fluids and electrolytes intravenously. (See also BULIMIA NERVOSA; DEHY- DRATION; KETONE BODIES.) electron transport chain A collection of ENZYMES responsible for the final stages of oxidation of FATTY ACIDS , CARBOHYDRATES, AMINO ACIDS, and other fuels in the presence of oxygen. The electron transport chain is part of the machinery of the MITOCHOND- RIA, the cell’s powerhouses. The oxidation-reduc- tion enzymes are called CYTOCHROMES. Electrons pass sequentially from one cytochrome to the next like a bucket brigade. Nutrients like IRON and COEN- ZYME Q are required for this process. In the last step, the enzyme cytochrome oxidase transfers electrons to molecular oxygen to yield water. Cyanide poi- sons cytochrome oxidase, accounting for the toxic- ity of this substance. An essential feature of electron transfer between cytochromes is the simultaneous synthesis of ATP, which is the cell’s energy currency. Chemical energy trapped in ATP meets almost all energy requirements of cells. (See also KREB’S CYCLE ; OXIDATIVE PHOSPHORYLATION.) elemental diet A DIET in which nutrients are pre- sent in their simplest, least combined forms. Free AMINO ACIDS and the simple sugar GLUCOSE are typ- ical ingredients. Generally they contain no FIBER and very little FAT. Elemental diets require minimal digestive action in order to be absorbed and utilized by the body. Elemental diets are prescribed for INFLAMMATORY BOWEL DISEASE and other conditions in which the digestive and absorptive functions of the gastrointestinal tract are severely compro- mised: preparation for gastrointestinal surgery, treatment of burn victims, pancreatitis, and severe diarrhea. (See also DIGESTION; GASTROINTESTINAL DISORDERS .) elimination diet/challenge test A simple way of detecting food allergies. During the initial phase of an elimination diet, all foods suspected of causing allergies are avoided for five to 14 days, to provide time for the IMMUNE SYSTEM to recover from the irritant. During the recovery phase, the diet is lim- ited to “safe” foods and might include foods gener- ally considered to be nonallergenic, such as lamb, rice, pears, and pure spring water or a chemically defined meal replacement that incorporates hydrolyzed protein such as rice protein. When symptoms have diminished or disap- peared, individual foods are added back to the diet, one at a time, for example, every two days. During this challenge period, the patient is in- structed to record the recurrence of allergy symp- 224 electron transport chain toms when a questionable food is added back to the diet. This is a practical way to identify the offending food. However, patients should not stay on an elimi- nation diet for a long time because it is too restric- tive, and patients on such a diet risk inadequate intake of vitamins and minerals. This method is also cumbersome when there are multiple food allergies and requires patience and persistence. For severe food allergy symptoms, medical supervision should be obtained before suspected foods are eaten. (See also ALLERGY, FOOD.) ELISA (Enzyme-linked immuno-absorbent assays) These are sensitive analytical methods used in clin- ical diagnostic testing. These highly sensitive lab tests use manufactured ANTIBODIES (monoclonal antibodies), which bind with great specificity to a particular class of molecules, such as steroid HOR- MONES, tumor markers, viral antigens, parasitic antigens, and even other types of antibody mole- cules. The antibody used in the test is tagged with marker enzymes to permit measuring the degree of its binding. ELISA assays provide a previously unattainable window for assessing nutrient condi- tions and fundamental physiologic mechanisms, like circadian rhythm of hormone secretion, food allergies, and disease processes such as HIV-related (human immunodeficiency virus) conditions. (See also ALLERGY, FOOD.) Emden–Meyerhoff pathway See GLYCOLYSIS. emesis Vomiting of stomach contents, and possi- bly of intestinal contents in severe situations. Potential causes of emesis include food poisoning; chemical poisoning; viral infections; drug side effects; nervous conditions like brain injury, migraines, meningitis, seasickness; stimulation of the brain’s vomiting center; gastric conditions such as cancer and peptic ulcers; and intestinal disorders like intestinal obstruction. Aggravating factors include excessive pain, sensitivity to certain foods, and toxic chemicals. Odors, shock, nervousness, anxiety, hysteria, morning sickness, coughing, and irritation of the pharynx can cause reflexive vom- iting. Chronic vomiting can lead to ELECTROLYTE loss and tooth erosion due to gastric acid, DEHYDRATION and MALNUTRITION. (See also BULIMIA NERVOSA; EAT- ING DISORDERS.) emetic Any agent causing vomiting. Chemicals such as ipecac syrup, mustard, and zinc sulfate in- duce vomiting by local stimulation. Chemical emet- ics may be dangerous in pregnancy, GASTRIC ULCERS, CARDIOVASCULAR DISEASE , or hernia. Drinking large amounts of warm water can also induce vomiting. (See also BULIMIA NERVOSA; STOMACH ACID.) empty calories Calories derived from burning food that provide excessive FAT, sugar, and/or white flour but contain far fewer key nutrients than those found in minimally processed foods. In particular, trace MINERALS, VITAMINS, PROTEIN, and FIBER are likely to be deficient. Foods supplying empty calo- ries are said to have low NUTRIENT DENSITY.Alco- holic beverages, SOFT DRINKS, natural sweeteners like syrup and sugar, many manufactured foods, pastry, DESSERTS, CHIPS, and similar high-fat snacks lack the balance of nutrients found in whole foods and tend to crowd out more nutritious foods. Most healthy people can tolerate an occasional splurge on junk food. However, problems arise when eating empty calorie foods becomes a habit. The more junk food a person eats, the more impor- tant it is for the remainder of the diet to supply important nutrients to make up for the deficiency. All too often, nutrient deficiencies such as folic acid, iron, calcium, even fiber occur. High-fat foods provide excessive calories, which favors weight gain. OBESITY is a growing problem for both Amer- ican adults and children. Excessive fat and inade- quate ANTIOXIDANT nutrients like VITAMIN C, VITAMIN E , and BETA-CAROTENE are linked to CARDIOVASCU- LAR DISEASE, AGING, and CANCER. (See also CONVE- NIENCE FOOD; DEGENERATIVE DISEASES; EATING PATTERNS ; FAST FOOD; REFINED CARBOHYDRATES.) emulsified vitamins Fat-soluble VITAMINS like vit- amins A, D, and E that are processed as water- soluble emulsions. While not true solutions, emul- sions consist of microscopic particles uniformly dis- persed and stabilized so that oil and water do not separate. Like FAT, these vitamins are normally emulsified vitamins 225 insoluble in water. Emulsified fat-soluble vitamins are absorbed directly by intestinal cells. Emulsifica- tion facilitates their uptake, an important consider- ation for individuals with MALABSORPTION. (See also VITAMIN A; VITAMIN D; VITAMIN E; VITAMIN K.) emulsifiers (stabilizers, surfactants) A class of FOOD ADDITIVES widely used in manufactured foods to suspend oily materials in water. These chemicals, related to detergents, can suspend oils and lipids (water-insoluble materials) such as dyes in water as tiny droplets that do not coalesce or separate upon standing. The most common commercial emulsifiers are DIGLYCERIDES, MONOGLYCERIDES, LECITHIN, POLYSOR- BATES , and sorbitan mono-stearate. Emulsifiers are used to keep bread from becoming stale; to stabilize fat in NONDAIRY CREAMERS for COFFEE; to keep cakes fluffy; to suspend flavors and food coloring in processed foods; and to stabilize ice cream. Egg lecithin is used to emulsify vegetable oils and vine- gar to create MAYONNAISE. (See also CONVENIENCE FOOD .) endive (Cichorium endivia) This bitter biennial or annual herb is a member of the aster family. It was used by ancient Egyptians and Romans and may have originated in India. Endive was adapted as food in France in the 14th century and is culti- vated as a salad plant. Closely related to CHICORY, which it resembles, endive is a slightly bitter salad green. The leaves are finely divided and curly and are clustered in a loose head. To decrease their bit- terness, the leaves are covered several weeks before harvest. It is an excellent source of BETA- CAROTENE . Nutrient content of 1 cup (50 g) is 28 calories; protein, 0.6 g; carbohydrate, 1.7 g; fiber, 0.46 g; calcium, 30 mg; 1.026 retinol equivalents; vitamin C, 3.2 mg; niacin, 0.49 mg; and small amounts of other nutrients. endocrine system The collection of ductless glands that secrete HORMONES, chemical regulators of the body that travel to their target tissues via the bloodstream. As members of the body’s system of checks and balances, ENDOCRINE glands respond to signals from the brain and to changes in chemicals in the blood, including BLOOD SUGAR, CALCIUM, and hormones. The endocrine system consists of the ADRENAL GLANDS , PITUITARY (hypophysis), endocrine PAN- CREAS, THYROID, PARATHYROID, testes and ovaries, the pineal gland, and the thymus. The placenta also secretes hormones. Each endocrine gland produces a characteristic hormone, or set of hormones. Endocrine malfunctions create serious imbalances. Hyposecretion, in which inadequate levels of hor- mones are secreted, and hypersecretion, in which excessive amounts of hormones are secreted, cause many pathological conditions ranging from dia- betes to excessive FATIGUE and CATABOLIC STATE. The hypothalamus is the nerve tissue that links the brain with the pituitary gland. The hypothala- mus indirectly controls many functions. It inte- grates and controls the autonomic nervous system, the grouping of nerves that regulates involuntary processes such as smooth muscle contractions (for example, the movement of food through the GAS- TROINTESTINAL TRACT and glandular secretions). In response to signals from the brain, and its own sensing mechanisms, the hypothalamus releases hormones that regulate the release of six hormones from the pituitary. The hypothalamus also forms two hormones, oxytocin and ANTIDIURETIC HOR- MONE (ADH), which travel to the posterior pitu- itary where they are released. The functions of individual endocrine glands can be summarized as follows: Pituitary Although it is only the size of a pea, the pituitary is considered the “master” endocrine gland because it regulates the activity of so many dif- ferent glands throughout the body. ADH regulates SODIUM and WATER balance while oxytocin stimu- lates uterine contraction and the ejection of milk from mammary glands. The anterior pituitary makes “trophic hormones,” hormones that activate other glands of the endocrine system. Trophic hormones include melanocyte-stimulating hormone (MSH) to regulate pigmented cells (melanocytes); PROLACTIN for milk secretion in women and for TESTOSTERONE production in males; interstitial cell stimulating hor- mone (ICSH), for testosterone production (men); luteinizing hormone (LH), for ovulation and proges- terone production (women); follicle stimulating hormone (FSH), for development of ova and estro- 226 emulsifiers gen production (women) and sperm production in testes (men); thyroid stimulating hormone (TSH) for release of hormones from the thyroid gland; GROWTH HORMONE for tissue repair and maintenance; and ADRENOCORTICOTROPIC HORMONE (ACTH) for cortisol release from the adrenal cortex. The hypothalamus regulates the release of growth hormone, thyroid stimulating hormone, ACTH, FSH, and LH, and pro- lactin from the pituitary. Adrenal Glands In response to ACTH, the adrenal glands produce the stress hormones EPI- NEPHRINE and NOREPINEPHRINE from the inner region of the adrenals to increase blood sugar, raise blood pressure, increase pulse rate, and similar effects that adapt the body to stress. The outer region of the adrenals produce steroids, like GLUCO- CORTICOIDS , which raise blood sugar, increase the rate of breakdown of protein and fuels, and MINER- ALOCORTICOIDS, which conserve sodium and water. Thyroid Gland Thyroid hormones regulate the rate of energy production of cells, the rates of tissue growth and development, and activity of the ner- vous system. Calcitonin lowers blood calcium levels. Parathyroid Glands Parathyroid hormone raises calcium and phosphate ions and activates bone degradation. Thymus Thymic hormones, thymosins, acti- vate the immune system by promoting the prolif- eration of T cells, a major type of white blood cell. Islets of Langerhans Clusters of endocrine cells scattered throughout the pancreas. The islets contain the alpha cells that produce GLUCAGON to increase blood glucose; and the beta cells that pro- duce INSULIN to lower blood glucose. Ovaries ESTROGENS (from the follicles) are female sex hormones that control the growth and development of female reproductive organs and secondary female characteristics and protein syn- thesis. They also produce PROGESTERONE (from the corpus luteum), which helps prepare the endo- metrium for implantation of a fertilized egg, and promotes milk production. Gonads Produce testosterone in men. This hormone controls growth of male sex organs, body growth, secondary male characteristics, and sperm development. Pineal Gland Produces melatonin, which has an inhibitory effect on ovaries. The pineal gland helps regulate circadian rhythms and may inhibit reproductive activities. Placenta Serves as a temporary endocrine gland until birth. During pregnancy the placenta secretes chorionic gonadotropin, a hormone capa- ble of stimulating the growth and function of the gonads, as well as estrogen and progesterone. (See also HOMEOSTASIS.) endogenous carbohydrate Glucose that is syn- thesized in the body from noncarbohydrate com- pounds, excluding FATTY ACIDS, rather than obtained from the diet. The process, called GLUCO- NEOGENESIS , converts most AMINO ACIDS to glucose; thus, approximately 50 percent of dietary PROTEIN may be metabolized to glucose under normal (non- fasting) conditions. GLYCEROL from FAT breakdown yields glucose as does LACTIC ACID, PYRUVIC ACID, and such carboxylic acids of the KREB’S CYCLE as CITRIC ACID, SUCCINIC ACID, and OXALOACETIC ACID. (See also CARBOHYDRATE METABOLISM ; FASTING.) endoplasmic reticulum A membrane system found within the cytoplasm of many cell types. The endoplasmic reticulum functions in the synthesis, transport, and storage of a wide variety of exported products, such as DIGESTIVE ENZYMES. The endoplas- mic reticulum of the LIVER also houses enzymes for cholesterol synthesis, for completion of long-chain FATTY ACIDS , and for powerful oxidizing enzymes (detoxifying enzymes) needed to modify toxic mol- ecules and products of normal metabolism such as steroid hormones, to convert them to water- soluble materials that are more readily excreted. Long-term adaptation to repeated drug exposure produces a growth of “smooth” endoplasmic retic- ulum with increased levels of detoxifying enzymes in the liver. The portion of the endoplasmic reticu- lum devoted to protein synthesis machinery is called the “rough” endoplasmic reticulum. The cytoplasm of cells that manufacture huge amounts of protein, such as the PANCREAS and liver, is packed with rough endoplasmic reticulum to support their export of proteins. (See also CHOLESTEROL; CYTO- CHROME P450; DETOXIFICATION.) endorphins Brain chemicals involved in a wide variety of body processes, including pain control endorphins 227 [...]... Energy Balance Energy balance refers to the difference between calories consumed in food and the energy used for work and lost to the environment as heat and an increased state of disorder or randomness The body requires a steady input of chemical energy to maintain all energy-requiring processes of the cell At “energy equilibrium,” energy released from food consumed equals the work performed There... Therefore, the body requires fuel to produce energy to drive all of the processes of growth, maintenance, and repair of the body The major fuels are FATS, CARBOHYDRATE, and, to a lesser extent, PROTEIN Their oxidation yields a large amount of energy released as heat or trapped energy 229 as chemical energy in the form of ATP, the energy currency of the cell The end products of the complete oxidation of. .. for the observed differences in REE between men and women, and between younger and older adults In practice, the REE is easier to measure than the BASAL METABOLIC RATE (BMR), which is measured 12 hours after a meal, and soon after awakening in the morning REE differs from BMR by only 10 percent, and for convenience REE is often used A second category of energy expenditure is a heat factor called the thermic... considerations of the body, where energy storage equals the difference between food consumed and energy output Energy is released when organic compounds are oxidized or broken down On the other hand, the formation of bonds when biomolecules are assembled requires energy Reactions involved in building processes (biosynthesis) require the input of energy supplied by the breakdown and oxidation of foods Therefore,... and they stimulate regeneration of epithelial tissue of the uterus Estrogen levels increase in the postmenstrual phase of the menstrual cycle Together with progesterone, 240 ethanol estrogen prepares the endometrium for ovulation Women’s overall eating patterns are affected by the menstrual cycle, thus a decline in food consumption corresponds to a rise in estrogen levels at the time of ovulation Estrogen... Each person has somewhat different enzyme levels in body tissues These slight but important differences in the enzyme makeup are the result of differences in heredity, age, sex, exercise pattern, diet history, state of health, lifestyle, exposure to environmental pollutants, medications, and drugs The level of enzymes may increase as the body adapts to change Thus drug-destroying enzymes of the liver... connective tissue (See also INFLAMMATORY BOWEL DISEASE.) enterohepatic circulation The absorption of nutrients and other materials by the INTESTINE, their transport to the LIVER and reutilization A variety of substances released into the intestine can be reabsorbed by the intestine Thus BILE salts released from the GALLBLADDER are absorbed by the small intestine, where they pass into the capillaries and. .. Exercise Water Adequate water is essential for the body to use food and for the kidneys to dispose of waste Perspiration controls body temperature Drinking one to three cups of water or noncaffeinated beverage before exercise is recommended Dehydration and overheating can be problems with prolonged exercise, especially during warm weather Replacement of water losses may be needed before thirst is sensed,... intake is less than energy needs The difference is made up by burn- ing fat deposited in ADIPOSE TISSUE; muscle protein may also be broken down when calories are restricted With gradual weight loss, the pounds lost represent the consumption of body fat The total number of calories in food consumed represents the energy intake Energy expenditure consists of three categories The resting energy expenditure... tissues like the LIVER and PANCREAS, the urinary tract, the reproductive system, the respiratory tract and the blood vessels There are several fundamental types of epithelium Simple squamous epithelium forms a single layer of flat cells, like a tiled floor, and lines the lungs, kidneys, heart, blood vessels, lymph vessels, and CAPILLARIES Epithelial cells of the digestive tract (stomach, intestines, pancreas, . 60 percent of the energy output and reflects lean body mass. This accounts for the observed differences in REE between men and women, and between younger and older adults. In practice, the REE is easier. Individuals Each person has somewhat different enzyme levels in body tissues. These slight but important differ- ences in the enzyme makeup are the result of dif- ferences in heredity, age, sex, exercise. expenditure consists of three categories. The resting energy expenditure (REE) is defined as the energy required to breathe, to pump blood, to keep the neurons of the brain active; in general, to maintain all