A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | Y | W | X | Y | Z A Absorption: The process that follows digestion and results in nutrients being taken from the food into the cells of the intestine. Acid group: When referring to proteins, the acid part of the amino acid. Its chemical composition is NH2. Activity Movement. Activity is less strenuous than exercise. Adipose tissue Fat tissue. Predominant sites for women are hips and thighs; for men, the abdomen. Aerobic Energy process that requires oxygen. Alanine A nonessential amino acid that can be broken down to glucose under certain conditions. Aldosterone A hormone that influences the kidney to retain more sodium. As a result the body retains more water. Amino acid The basic unit of proteins. Amino group It is the part of the amino acid that contains nitrogen. Its chemical composition is O=C-OH. Ammonia NH3. Ammonia must be converted to urea and excreted from the body via the urine. Anaerobic Energy process that takes place in the absence of oxygen. Anemia Too few red blood cells or too little hemoglobin in red blood cells. There are several different kinds of anemia, although iron-deficiency anemia is the most common. Antibodies Proteins that are formed in response to the presence of a foreign substance. An important component of the immune system. Antidiuretic hormone A hormone that influences the kidney to retain more water by decreasing the amount of urine. Antioxidant A substance that protects other substances from the destructive effects of oxygen.   B Beta-carotene A vitamin A precursor found in plants and known to be a powerful antioxidant. Better fat burners Athletes who, through endurance training (i.e., exercising at high intensities), burn more fat than they would if they were untrained. Bile A fluid secreted into the intestine that helps in the breakdown of dietary fat. Branched-chain amino acid Three essential amino acids (leucine, isoleucine, and valine) whose structure is distinguished from other amino acids by the branched chain. They can be used for energy when muscle glycogen stores are low.   C Calcium A mineral necessary for proper contraction of muscle and a primary component of bone. Calorie A measure of energy. Abbreviated C. The term kilocalorie (abbreviated kcalorie) may be used interchangeably. These are the scientifically correct terms for the measurement of energy. calorie The amount of heat needed to raise one gram of water one degree Celsius. Abbreviated cal. Although not technically correct, it is also generally used to refer to the amount of energy contained in food or the amount of energy expended through exercise. Capillaries Very small blood vessels. Carbohydrates Compounds made up of carbon, hydrogen, and oxygen. Also known as sugars and starches. Cardiorespiratory fitness The ability of the heart and lungs to support prolonged exercise. Cardiovascular disease A general term for diseases of the heart and blood vessels. Cardiovascular system The heart and blood vessels. Carnitine A substance that facilitates the transfer of fatty acids into the mitochrondia. Chloride One of the electrolytes. Carries a negative charge (Cl-). Cholesterol A fat-like substance found in animal foods. It is also manufactured by the liver. Chronic disease Disease that develops over a long period of time. Examples include heart disease and osteoporosis. Chylomicron One of the lipoproteins that is necessary for the digestion and absorption of fat. Coenzyme A substance (often a vitamin) that activates an enzyme. Complementary proteins Two plant proteins that provide the equivalent amino acids found in animal protein. Complete protein A protein that contains all of the essential amino acids in the proper quantities and proportions to support growth. All animal proteins are complete proteins and many soy products also qualify. Complex carbohydrates Starches. Examples include whole-grain breads, cereals, and vegetables.   D Deaminate Removal of the amino group (which contains nitrogen) from an amino acid. Dehydration Loss of body water. Diabetes Abnormal carbohydrate metabolism due to a lack of insulin or decreased insulin activity. Diarrhea Watery feces. Dietary fat Fat found in food. Generally refers to triglycerides. Dietary fiber Indigestible portion of carbohydrate food. Humans cannot digest fiber because they lack the necessary enzymes. Dietary Reference Intakes (DRI) A guideline for dietary intake that has been established for some but not all nutrients. Digestion The process of mechanically and chemically breaking down food into smaller components so absorption may take place. Dipeptide Two amino acids joined together. Disaccharide Two monosaccharides joined together. Dried peas and beans The dried seeds of various legumes such as kidney beans, pinto beans, or split peas. Duodenum The upper part of the small intestine. It is connected to the stomach. The duodenum is about 10 inches long. Duration (of exercise) Amount of time spent exercising.   E Electrolytes Electrically charged particles. Endurance-trained athlete An athlete who engages in exercise that strengthens the cardiorespiratory system and supports sustained, prolonged exercise. Also known as aerobic training. Energy The capacity to do work. Energy in food (measured in calories) is chemical energy. The body can convert the chemical energy in food to other kinds of energy, such as mechanical, electrical, or heat. Enzyme A substance that speeds up a chemical reaction but is not used up or changed in the reaction. Epinephrine A hormone that is released in response to the stress of exercise. It stimulates the breakdown of stored fat. Essential amino acid An amino acid that cannot be manufactured by the body and must be consumed in food. Essential fatty acid A fatty acid that cannot be manufactured by the body and must be consumed in food. Estrogen One of the female sex hormones. Estrogen is a powerful influence on bone calcium levels. Exercise Structured physical activity. More strenuous than activities of daily living. Extracellular fluid Fluid that is found outside of the cells. Some is found in the blood and some is found between cells.   F Fatigue Mental and/or physical tiredness. Fats Generally refers to triglycerides found in food. Fatty acid An acid made up of chains of carbons. Fiber See Dietary fiber. Folate One of the B vitamins necessary for proper cell development. Folic acid or folacin are interchangeable terms. Folic acid See Folate. Free radical An unstable chemical substance in which there is an unpaired electron. Free radicals damage cells unless they are counteracted by antioxidants. Fructose A monosaccharide (one sugar unit) found in fruit.   G Galactose A monosaccharide (one sugar unit). Galactose and glucose join to form lactose (milk sugar). Gall bladder A small sac attached to the liver that stores bile. Glucagon A hormone that helps regulate blood glucose levels. Glucagon is released in response to a low blood glucose level. It influences the breakdown of liver glycogen, causing glucose to be released from storage into the blood. Glucogenic Capable of being made into glucose. Some amino acids are glucogenic. Gluconeogenesis The formation of glucose from noncarbohydrate sources such as protein. Gluconeogenesis takes place in the liver under low-carbohydrate, starvation conditions. Glucose A monosaccharide (one sugar unit). It is a component of all disaccharides (two sugar units). Blood sugar and dextrose are interchangeable terms. Glucose polymers Short chains of glucose. Some sports drinks include glucose polymers as a carbohydrate source. Glycemic index How much and to what extent blood glucose rises when a food is consumed. The index is based on a scale of 100; pure glucose is given a score of 100. Glycerol A 3-carbon compound that is the backbone of all triglycerides. Fatty acids will be attached to the glycerol molecule. Glycogen The storage form of glucose in the body. Glycogen is found in the muscles and liver. Glycogen synthaseñAn enzyme responsible for the synthesis of glycogen. Gram A unit of weight. One ounce is equal to approximately 28 grams. Gram is the unit of measure for carbohydrates, proteins, and fats. Abbreviated g or gm.   H Hemoglobin The oxygen-carrying protein found in red blood cells. Hemo means blood; globin means protein. High-density lipoprotein (HDL) One of the lipoproteins involved in cholesterol transport. Referred to as "good" cholesterol because it favors the transport of cholesterol from the arteries to the liver, where the cholesterol can be broken down. High-density refers to the amount of protein in the lipoprotein. High-intensity exercise Exercise greater than 75% V\od\O2max. High-intensity activity is fueled primarily by carbohydrate. Hormone A regulator of body processes. For example, the hormone insulin helps regulate blood glucose levels. Hormone-sensitive lipase An enzyme that helps break down stored fat (triglycerides) into fatty acids, which are released and used as energy. This enzyme is stimulated by the hormone epinephrine. Hyperglycemia Elevated blood glucose levels. Hyperthermic Elevated body temperature. Hypoglycemia Low blood glucose levels. Hyponatremia Low blood sodium levels. Hypothalamus A part of the brain that regulates body temperature, thirst, hunger, and appetite. Hypothermic Low body temperature.   I Ileum The lower part of the small intestine. It connects to the colon. The ileum is approximately 15-30 feet long. Incomplete protein A plant protein that is missing one or more of the essential amino acids in the proper quantities or proportions. Insulin A hormone that regulates blood glucose levels. Insulin is released in response to elevated blood glucose levels and makes possible the uptake of glucose from the blood to the cells. Intensity (of exercise)The degree or extent of exercise. Intensity of an activity is often measured by taking a heart rate or by determining V\od\O2max. Intracellular fluid Fluid that is found within the cells. Intrinsic factor A compound necessary for the absorption of vitamin B12. Iron A mineral that is part of several compounds in the body including hemoglobin and myoglobin. Iron-deficiency anemia A disease that results from the inadequate intake or absorption of the mineral iron. Iron-deficiency anemia results in decreased hemoglobin in red blood cells, which leads to fatigue.   J Jejunum Middle part of the small intestine. The duodenum precedes it and the ileum follows it. The jejunum is about 8 feet long. K Ketogenic Capable of being made into fat. Some amino acids are ketogenic. Ketone bodies The end products of fat metabolism. Ketosis The accumulation of excess ketone bodies. Ketosis is a result of the incomplete metabolism of fatty acids when carbohydrate is not available.   L Lactase An enzyme needed to split the disaccharide lactose into glucose and galactose. Lactic acid A result of the incomplete breakdown of glucose under anaerobic conditions. Lactose A disaccharide (two sugars joined together) made up of glucose and galactose. The enzyme lactase is necessary to split the disaccharide into the two monosaccharides. Also known as milk sugar. Lentils The small, flat seeds of one type of legume. Leucine One of the essential amino acids. It is one of three branched-chain amino acids. Linoleic acid An essential polyunsaturated fatty acid. Lipid A general term for fats and oils. Lipoprotein A general term for a fat and protein complex that transports fats in the blood. Lipoprotein lipase An enzyme that helps break down lipoproteins and release glycerol and fatty acids. Liver A major organ involved in the metabolism of nutrients. Liver glycogen A storage form of glucose in the body. Under the influence of the hormone glucagon, liver glycogen is broken down and glucose is released from storage into the blood, where it helps raise blood glucose levels. Long-chained fatty acid A fatty acid whose chain contains 12 or more carbons. Low-density lipoprotein (LDL) One of the lipoproteins involved in cholesterol transport. Referred to as "bad" cholesterol because it favors the deposition of cholesterol in the arteries. Low-density refers to the amount of protein in the lipoprotein. Low-intensity activity Exercise less than 50% V\od\O2max. Low-intensity activity is fueled primarily by fat.   M Maltase An enzyme needed to split the disaccharide maltose into two glucose molecules. Maltose A disaccharide (two sugars joined together) made up of two glucose molecules. The enzyme maltase is necessary to split the maltose. Medium-chained fatty acid A fatty acid whose chain contains 6ñ12 carbons. Medium-chained fatty acids are absorbed and transported directly to the liver via the portal vein. Menopause Permanent cessation of menstrual activity. Fifty percent of women have experienced menopause by the age of fifty. Metabolism All the physical and chemical changes that take place in the cells of the body. Often used to refer to the breakdown of substances that produce energy for the cells. Microgram A unit of weight. One millionth of a gram. Microgram is the unit of measure for folate, vitamin B12, vitamin A, and vitamin D. Abbreviated mcg. Milligram A unit of weight. One thousandth of a gram. Milligram is the unit of measure for thiamin, niacin, riboflavin, vitamin B6, pantothenic acid, vitamin C, vitamin E, iron, calcium, and cholesterol. Abbreviated mg. Mineral An inorganic (does not contain carbon) element. Examples include iron, calcium, sodium, and chloride. Mitochondria The structure within the cell responsible for the aerobic production of energy. Known as the "powerhouse" of the cell. Moderate-intensity activity Exercise at 50-75% V\od\O2max. Monosaccharide A one-sugar unit. Glucose, fructose, and galactose are monosaccharides. Monounsaturated fatty acid A fatty acid that contains a single double bond (this bond is not saturated with hydrogen). Mono means one. Muscle glycogen A storage form of glucose in the body. An important fuel source for athletes. Muscle mass The amount of muscle fibers. Musculoskeletal system The muscles and bones of the body. Myoglobin An iron-containing protein found in muscle cells. Myoglobin transports oxygen from the cell membrane to the mitochondria.   N Neural-tube defect A defect in the development of the neural tube that forms the brain and the spinal cord. Can be a result of inadequate folate in the very early days and weeks of pregnancy. Niacin One of the B vitamins necessary for energy metabolism. Nonessential amino acid An amino acid that can be manufactured by the body. Nutrition Facts The panel on a food label that lists information about the ingredients and nutrients found in packaged foods.   O Obesity Excess body fat. Omega-3 fatty acid A polyunsaturated fat that has a double bond between the third and fourth carbon (the omega carbon). Abundant in fish oils and thought to be heart healthy. An example is linolenic acid. Omega-6 fatty acid A polyunsaturated fat that has its last double bond six carbons from the end of the chain. An example is linoleic acid. Osteoporosis Decreased bone mass. Osteo means bone; poros means porous. Oxidative damage Damage to cells that is caused by oxygen. Oxidative enzyme An enzyme that is needed to produce energy under aerobic conditions. Oxidation is any reaction that involves oxygen. Oxygen The most important and abundant element.   P Pancreas A gland that secretes important hormones and enzymes such as insulin, glucagon, and pancreatic amylase. Pancreatic amylase An enzyme that helps break down starch. Pancreatic lipase An enzyme that helps break down fat. Pantothenic acid One of the B vitamins necessary for energy metabolism. Phospholipid A fat that is similar to a triglyceride except that one of the fatty acids contains a phosphorus. Phospholipids help move fats across cell membranes. Phosphorus An essential mineral concentrated in bone crystal but widely distributed in the body. Polypeptide More than ten amino acids joined together. Poly means many. Polysaccharide Long strands of glucose joined together. Poly means many; saccharide means sugar. Complex carbohydrate is an interchangeable term. Polyunsaturated fatty acid A fatty acid that contains two or more double bonds (carbon-to-carbon bonds that are not saturated with hydrogen). Portal vein Large blood vessel that carries blood to the liver. Potassium The principal positive ion in intracellular fluid. Precursor One that precedes, or comes before. A compound may give rise to another compound; for example, beta-carotene is a precursor to vitamin A. Proteins Compounds made up of carbon, hydrogen, oxygen, and nitrogen. The basic structural unit of proteins is an amino acid Pyridoxine A B vitamin necessary for protein metabolism. Also known as vitamin B6.   R Recommended Dietary Allowances (RDA) A guideline for nutrient intake. The average amount needed per day to meet the nutrient needs of healthy people. Red blood cell A cell responsible for carrying oxygen and carbon dioxide to and from tissues. There are approximately 35 trillion red blood cells in the body. Rehydration The process of taking in fluid to reverse dehydration. Resistance-trained athlete An athlete who engages in exercise that increases muscle strength and power. Resorb To remove by absorption. Calcium is removed from bone when bone-resorbing cells (osteoclasts) absorb the calcium that has been previously deposited. Respiratory system The intake of oxygen from the air and the transport and exchange of oxygen and carbon dioxide between the lungs, the blood, and the cells. Riboflavin One of the B vitamins necessary for energy metabolism. Also known as vitamin B2.   S Salivary amylase An enzyme that helps break down starch. Saturated fatty acid A fatty acid that contains no double bonds between carbons (all carbon-carbon bonds are saturated with hydrogen). Saturated fatty acids are thought to raise blood cholesterol levels. Saturated To fill or load to capacity. A saturated fat has carbon-carbon bonds that are filled to capacity with hydrogen. Sedentary Inactive. Short-chained fatty acid A fatty acid whose chain contains six or less carbons. Simple carbohydrates Refers to sugars rather than starches. Is often used to refer to white (table) sugar. Skeletal muscles Muscles that attach to and move the skeleton (bones). Skeletal muscle is one classification of muscle; smooth and cardiac muscles are the other classifications. Small intestine The organ that connects the stomach to the colon and is responsible for digestion of food and most of the absorption of nutrients. The small intestine is made up of the duodenum, the jejunum, and the ileum. Sodium The principal positive ion in extracellular fluid. Starches Plant polysaccharides (many glucose units). Also known as complex carbohydrates. Steroid hormone A sex hormone. Examples include estrogen and testosterone. Strict vegetarian A person who consumes no animal products. Also known as a vegan. Sucrase An enzyme needed to split the disaccharide sucrose into glucose and fructose. Sucrose A disaccharide (two sugars joined together) made up of glucose and fructose. The enzyme sucrase is necessary to split the disaccharide into the two monosaccharides. Also known as white (or table) sugar. Sugar Any of the monosaccharides or disaccharides. The term sugar is often used to refer to sucrose, or white sugar.   T Testosterone A male sex hormone. It has a tissue-building influence. Thermoregulatory system The process, controlled by the hypothalamus, that helps regulate body temperature. Thiamin One of the B vitamins necessary for energy metabolism. Also known as vitamin B1. Training Regular exercise that leads to adaptations by the body such as increased muscular strength (resistance training) or increased aerobic capacity (endurance training). Triglyceride The major class of fat in food and in the body. Triglycerides consist of three fatty acids attached to a glycerol molecule. Tripeptide Three amino acids joined together.   U Ultraendurance athlete An athlete who engages in a sport that lasts for hours and days and covers great distances. The Tour de France bicycle race, which covers 2,500 miles in 22 days, is an example. Ultraviolet light Beyond the visible light at the violet end of the spectrum. Sunlight produces ultraviolet rays, which the body can convert into vitamin D. Unsaturated fatty acid A fatty acid that contains one or more double bonds between carbons (carbon-carbon bonds that are not saturated with hydrogen). Urea The end product of amino acid breakdown. Urea is excreted from the body via the urine.   V Very low-density lipoprotein (VLDL) One of the lipoproteins involved in triglyceride, cholesterol, and phospholipid transport. Vitamin A A fat-soluble vitamin necessary for the proper growth of tissues and bones. Too much vitamin A in the form of retinol can be toxic. Vitamin B12 One of the B vitamins necessary for proper cell development. Works with folate to ensure proper red blood cell development. Also known as cyanocobalamin. Vitamin B6 One of the B vitamins necessary for protein metabolism. Also known as pyridoxine. Vitamin C A water-soluble vitamin that is necessary for proper iron absorption. In conjunction with vitamin E, it is a powerful antioxidant. Also known as ascorbic acid. Vitamin D A fat-soluble vitamin that acts as a hormone and helps regulate calcium metabolism. The body can convert ultraviolet light to vitamin D. Also known as cholecalciferol. Vitamin E A fat-soluble vitamin that may decrease exercise-induced oxygen damage to the muscles and may prevent cardiovascular disease. It is a powerful antioxidant. Also known as tocopherol. Vitamin K A fat-soluble vitamin necessary for proper blood clotting. Vitamins Substances that perform specific functions in the body. V\od\O2max Maximum oxygen uptake. W Water H2O. An essential fluid. Whole grains Grains that have not been refined. Whole grains have much more fiber than grains that have been refined (processed).