The Basics of Human Nutrition

Transcription

1 The Basics of Human Nutrition Taken as a whole, all of the elements and materials that we eat or drink, and which our bodies require for good health, are referred to as our Nutritional Requirements. These requirements have only been studied and become fully known in this century: the Recommended Dietary Allowances and the United States Recommended Daily Allowances. The Recommended Dietary Allowances (RDA s) have been defined by the Food and Nutrition Board of the National Academy of Sciences. They are the recommended daily intake of every known nutritional requirement, broken down by age, weight, and sex. The Cambridge formulas meet 100% of the RDA s and the USRDA s. The United States Recommended Daily Allowances (USRDA s) have been specified by the Food and Drug Administration (FDA) to create standards for use in food labeling. USRDA s have been specified for protein, most vitamins, and selected minerals. In most instances, the USRDA s represent the highest RDA suggested for any age, weight, or sex group for each nutrient. The Major Nutritional Elements Nutritional elements can be broken down into major categories. They are Macronutrients, Micronutrients, Dietary Fiber, and Water. Let s take a closer look at each one of these categories. Macronutrients refer to the major nutrients, which are required by the body in large quantities: Protein, Carbohydrate, and Fat. Macronutrients are all calorie-containing nutrients, while vitamins and minerals (micronutrients) contain no calories. Protein is required to build and repair body tissue. Each gram of protein contains 4 calories. Protein is made up of amino acids. Of the 22 amino acids that comprise the various protein structures in the body, nine are classified as essential (must be supplied from foods); the remainders are non-essential (can be synthesized by the body). The Cambridge formulas contain all the essential amino acids. Carbohydrates are the principal dietary source of energy, being readily metabolized, and with very little being stored in the body. Each gram of carbohydrate contains 4 calories. Carbohydrates are classified in three basic groups: Essential Amino Acids Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Proline Serine Tyrosine Cystine Non-Essential Amino Acids Alanine Arginine Aspartic Acid Citrulline Glutamic Acid Glycine Hydroxyglutamic Acid Hydroxyproline Monosaccharide - Simple sugars (glucose, fructose, and galactose) that are quickly absorbed and used as fuel by the body. Disaccharide - More complex carbohydrates (sucrose, maltose, and lactose), which must be broken down before they can be used as, fuel by the body. Polysaccharide - Very complex carbohydrates (starch and cellulose) that require relatively long periods of time to be broken down before they can be used as fuel by the body.

2 Fats Fats are concentrated sources of energy, which are digested more slowly and stored, in the fat tissues of the body, our main energy reserve. Each gram of fat contains 9 calories. A small amount of fat is essential in the diet to provide transport for fat-soluble vitamins, structural support for tissue, and to maintain body temperature. Dietary fat also serves as a source of essential fatty acids. There are two kinds of fats: saturated fats and unsaturated fats. Saturated fats are solid at room temperature and are generally derived from animal and dairy sources, such as butter or the fat in meat. The exceptions are coconut and palm oils. Unsaturated fats, as a general rule, are liquid at room temperature, such as most vegetable oils. Diets high in saturated fat are often associated with elevated blood cholesterol levels and coronary heart disease. Their partial replacement by diets containing unsaturated fats is often recommended. Micronutrients Micronutrients are nutrients required by the body in smaller amounts and include vitamins, minerals, and electrolytes. Although the quantities required are small, the function of each is very important. Vitamins are organic substances derived from plants and animals and are needed daily in small amounts (milligrams or micrograms) to maintain health and/or promote growth. None provide energy; however, some facilitate the release of energy from protein, carbohydrates, and fats. All are essential nutrients, which must be provided by the diet. There are 13 recognized vitamins and they fall into two categories: fat soluble vitamins and water-soluble vitamins. Fat Soluble Vitamins (A, D, E and K) are absorbed through the intestinal membranes into the body proper with the aid of fats in the diet or bile produced by the liver. They can reach toxic levels if consumed in excessive quantities because they are stored in the fat tissues of the body. The main roles of these vitamins are as follows: Vitamin A assists in the formation and maintenance of healthy skin, hair, and mucous membranes; aids in the ability to see in dim light (night vision); and is needed for proper bone growth, tooth development, and reproduction. The U.S.RDA for Vitamin A is 5000 IU. Vitamin D aids in the formation and maintenance of bones and teeth and assists in the absorption and use of calcium and phosphorus. The U.S.RDA for Vitamin D is 400 IU. Vitamin E aids in the formation of red blood cells, muscles, and other tissues and protects Vitamin A and essential fatty acids from oxidations. The U.S.RDA for Vitamin E is 30 IU. Vitamin K aids in the synthesis of substances needed for the blood to clot and helps maintain normal bone metabolism. Vitamin K is naturally synthesized in the human body from other nutrients. There is no U.S.RDA for Vitamin K. Water Soluble Vitamins (B-complex and C) These vitamins do not require fat or bile to be absorbed and, for the most part, are not stored in the body. Water-soluble vitamins must be replenished frequently since they are used by the body or excreted. Because they are soluble in water, these vitamins are more easily lost in food storage, processing, or preparation (such as prolonged washing or cooking). Thiamine (B1) helps release energy from carbohydrates and aids in the synthesis of an important nervous system chemical. The U.S.RDA for Thiamine is 1.5 mg. Riboflavin (B2) helps release energy from carbohydrates, proteins, and fats and aids in facilitating energy production in cells. The U.S.RDA for Riboflavin is 1.7 mg.vitamin B6 aids in the absorption and metabolism of proteins, helps the body use fats, and assists in the formation of red blood cells. The U.S.RDA for Vitamin B6 is 2 mg. Folic Acid acts with vitamin B12 in synthesizing genetic material and aids in the formation of hemoglobin in red blood cells. The U.S.RDA for Folic Acid is 400 mcg. Pantothenic Acid helps in the metabolism of carbohydrates, proteins, and fats and aids in the formation of hormones and nerve regulating substances. The U.S.RDA for Pantothenic Acid is 10 mg.

3 Biotin aids in the formation of fatty acids and helps release energy from carbohydrates. The U.S.RDA for Biotin is 300 mcg. Vitamin C aids in the formation of collagen; helps maintain capillaries, bones, and teeth; helps protect other vitamins from oxidation; and, may block formation of cancer causing nitrosamine. The U.S.RDA for Vitamin C is 60 mg. Because vitamins are chemical compounds, sophisticated chemical and biological techniques allows technology to isolate them and synthesize most of them; the body recognizes the chemical structure and does not differentiate between natural and synthetic sources in assimilation and metabolism. Anti-Oxidant Vitamins such as Vitamin C, Vitamin E, and Beta Carotene (the chemical parent of Vitamin A) are vitamins having anti-oxidant properties. Anti-oxidant vitamins taken in amounts higher than the Recommended Daily allowances have been shown to diminish the negative effect of free radicals. Free radicals are molecules with an unpaired electron that roam through the body stealing electrons from other healthy molecules. They are naturally present in the body but their numbers are dramatically increased by stress or trauma of almost any kind (including dieting). Free radicals wreak havoc by damaging DNA, altering biochemical compounds, corroding cell membranes and by killing cells out-right. Many researchers are convinced that the cumulative effect of free radicals underlies the gradual deterioration that is the hallmark of aging. Anti-oxidant nutrients are made up of molecules with an extra electron. When they encounter free radicals in the body, the free radical takes the extra electron and is neutralized. Once a free radical has paired its electron, it can do no damage to healthy cells thus reducing the health risk, and, some think, retard the aging process. Opinions differ as to the required amounts of anti-oxidants necessary to have a significant effect. However, it seems clear that effective and safe levels fall into the following ranges: Vitamin C 200 mg to 2, 000 mg Vitamin E 100 IU to 500 IU Beta Carotene 10,000 IU to 25,000 IU Minerals are inorganic elements, which have a variety of essential functions in body compounds and reactions, such as nerve and muscle function, bone and tooth formation. There are three general classes of minerals; Macro Minerals, Trace Minerals and Electrolytes. Macro Minerals are required in amounts of 100 mgs or more per day. They are Calcium, Phosphorus, and Magnesium. Calcium is necessary for the formation of the body s skeletal system in early life. Calcium is also required for efficient blood clotting and the proper function of nerve and muscles. Calcium in the adult body is found in the skeleton in combination with Phosphorus as the main structural material. However, the small amount of Calcium that is found in the soft tissues and in body fluids, such as blood, is of critical importance. The U.S.RDA for Calcium is 1000 mg. Phosphorus is of vital importance in energy metabolism. For the most part, Phosphorus is found in bones in combination with Calcium. The calcium Phosphate present in bones and teeth is an important structural material. About 10% of the Phosphorus is found in the nervous system and in other soft tissues. The U.S.RDA for Phosphorus is 1000 mg. Magnesium interacts with over 200 enzymes in the body and is essential to all biosynthetic processes and transmission of genetic codes. It is primarily found in the soft tissue and skeletal structures. The U.S.RDA for magnesium is 400 mg. Trace Minerals are Iron, Copper, Zinc, Iodine, Fluoride, Chromium, Selenium, Manganese, and Molybdenum. They are required in smaller quantities and each has a specific function in the body. Iron is an essential component of hemoglobin, which transports oxygen in the blood from the lungs to cells where oxygen is needed for energy metabolism. Iron also forms part of myoglobin, a pigment which transports oxygen within muscle cells, and the cytochrome system, which is involved in energy release processes within all cells. The U.S.RDA for Iron is 18 mg. Copper forms part of many enzyme systems. Its metabolism in the body is closely related to that of iron. The U.S.RDA for Copper is 2 mg. Zinc plays a vital role in metabolism as well as cell growth and repair. It is also important in maintaining the function of the immune system. Bioavailability in natural food sources varies widely. Seafood (especially oysters), eggs, and red meats are the best natural sources of Zinc. Because the body does not store Zinc for future use, it is important to insure that a regular supply is provided in the diet. The U.S.RDA for Zinc is 15 mg. Iodine is required for the synthesis of thyroid hormones, which regulate many body functions. The U.S.RDA for Iodine is 150 mcg.

4 Fluoride is important for bone strength and provides resistance of tooth enamel. It is usually provided through drinking water or tooth care products. There is No U.S.RDA for Fluoride. The RDA is 50 mcg to 150 mcg. Chromium is required for maintaining normal glucose metabolism and acts as a cofactor for insulin. Chromium is important for maintaining lean body tissue, can increase the metabolism of fat and is thought to have an appetite suppressing effect. There is no U.S.RDA for Chromium. The RDA for Chromium is 50 mcg to 200 mcg. Selenium forms part of an essential system that guards against damage to cell membranes and interacts with Vitamin E. There is no U.S.RDA for Selenium. The RDS for Selenium is 50 mcg to 75 mcg. Manganese functions in several enzyme systems involved in protein and energy metabolism, the central nervous system, and in normal bone structure. There is no U.S.RDA for Manganese. The RDA for Manganese is 2 mg to 5 mg. Molybdenum forms a vital part of several enzyme systems within the cells of the body. The effect of inadequate intakes of this trace element has not been described or demonstrated because it is difficult to produce a diet with low enough content of Molybdenum. Molybdenum may help prevent dental cavities. There is no U.S.RDA for Molybdenum. The RDA for Molybdenum is 75 mcg to 250 mcg. Note: As with some vitamins, certain minerals may be toxic if taken in excessive amounts. Electrolytes are Sodium, Potassium, and Chloride. They are required in a balanced relationship to maintain the acid base content of the body. Sodium is important in maintaining the correct distribution of water between the inside of the cells and the fluids surrounding them. Sodium deficiency is usually associated with dehydration due to excessive sweating in hot environments, heavy exercise, or fever. In such circumstances, the volume of fluids outside the cells is reduced and the blood volume is low. Sodium is widely distributed in the body in fluids outside cells. The U.S.RDA for Sodium has not been established. Potassium is essential for the proper functioning of the nervous system and the maintenance of acid base balance in body fluids. It is found inside the muscle cells where it is essential for their correct functioning. The U.S.RDA for Potassium hasn t been established. Chloride is important for maintenance of fluid and electrolyte balance; many chemical reactions within the body are dependent on the correct acid base balance. The U.S.RDA for Chloride has not been established. Dietary Fiber All fiber comes from the cell walls of plants, which give plants their firm structure, and from non-structured substances that are mixed with plain starches. There are many different kinds of fiber and each has different properties.dietary fiber is generally defined as the sum of carbohydrates and carbohydrate-like components of foods, such as cellulose, lignin, hemicellulose, pentosan, gums, and pectin. These non-digestible substances provide bulk in our diet and aid elimination.the most common sources of dietary fiber are obtained from whole grains, fruits, and vegetables. Fiber is not considered an essential nutrient, but can be especially beneficial in weight loss. The more fiber your diet contains, the few calories you re likely to consume, because fiber takes more time to chew, which slows the eating process and allows time for the brain to receive the signal of being full.each of the Original Cambridge Diet and the Cambridge Diet Food For Life formulas contain dietary fiber, which is important to the body s digestion and elimination process. Specific fiber content varies within the different products. Water While water is not a nutrient in the strictest sense, it is very important and is often overlooked in discussions of nutrition. While we can survive many days without food, we cannot exist for more than a few days without water. Water makes up about 60% of our body weight; provides the main transport systems (blood, lymph and digestion) for carrying nutrients and oxygen to cells; carries electrolytes to regulate acid base balance; regulates body temperature; is essential to digestion and absorption of food; and aids in removing waste products. While water requirements vary with levels of activity, as a general rule eight or more eight-ounce glasses per day are recommended. Common Nutritional Terms You May Encounter Cholesterol - is a component of fat, which is derived from animal fats and is also synthesized in the body. An excess of cholesterol accumulated in the blood can be deposited on the walls of the arteries, often causing clogging.energy Balance - Energy balance refers to the point at which the number of calories consumed on a daily basis is equal to the number of calories burned as fuel by the body on a daily basis. The point at which energy balance is reached (measured in calories) varies with metabolic rates, people require differing quantities of food to perform the same functions. While each individual will have a different energy balance point,

5 for most people the balance point will be between 1,500 and 3,000 calories per day.ketosis - Ketosis occurs when carbohydrates are not readily available as an energy source and the body is breaking down fat to meet its energy needs. When in ketosis, ketone bodies are produced in the blood. When the body is not able to excrete the ketone bodies through the urine rapidly enough, they concentrate in the blood, producing ketosis. Mild ketosis such as that produced while on a very-low-calorie diet produces a chemical state in the body that reduces hunger levels, making it easier to stay on the diet. Lactose Intolerance - Some people have difficulty digesting the carbohydrate in milk (lactose). Before lactose can be absorbed through the intestinal tract, it must first be broken down into its component sugars (glucose and galactose) by an intestinal enzyme called lactase. In almost all humans, lactase levels are high at birth and for the first two years. After that, lactase levels begin to drop with age, and in some people, nearly disappear.lactose intolerance results when people are unable to digest most or all of the lactose. It can cause a variety of digestive problems including excessive intestinal gas and diarrhea, when milk products are consumed. Lactose is present in The Original Cambridge Diet formula; however, all Cambridge Food For Life products have been specially produced with low lactose content. Protein Efficiency Rating - The Protein Efficiency Rating or PER, is a method for determining protein quality and amino acid content. The FDA standard for protein quality is a PER of 2.5 for food labeling purposes. All Cambridge shakes, soups, cereals, and bar contain protein with a PER of 2.5 or higher. Very Low Calorie Diet - Very low calorie diet or VLCD is a term used to describe any diet providing fewer than 800 calories per day