Nutrition test 1
Digestion in the small and large intestines
By the time food leaves the stomach, digestion of all three energy-yielding nutrients has begun, but the process gains momentum in the small intestine. There, the pancreas and the liver contribute additional digestive juices through the duct leading into the duodenum, and the small intestine add intestinal juice. These juices contain digestive enzymes, bicarbonate, and bile. Digestive Enzymes- pancreatic juice contributes enzymes that digest fats, proteins and carbohydrates. Glands in the intestinal wall also secrete digestive enzymes. Biocarbonat- the pancreatic juice also contains sodium bicarbonate, which neutralizes the acidic chyme as it enters the small intestine. From this point on, the contents of the digestive tract are neutral or slightly alkaline. The enzymes from both the intestine and the pancreas work best in this environment. Bile- Bile is secreted continuously by the liver and is concentrated and stored in the gallbladder. The gallbladder squirts bile into the duodenum whenever fat arrives there. Bile is not an enzyme but an emulsifier that brings fats into suspension in water. After the fats are emulsified, enzymes can work on them, and they can be absorbed. Thanks to all these secretions, all three energy-yielding are digested in the small intestine. Rate of digestion- the rate of digestion of the energy nutrients depends on the contents of the meal. If the meal is high in simple sugars, digestion proceeds fairly rapidly. On the other hand if the meal is rich in fat, digestion is slower. protective factors- The intestines contain bacteria that produce a variety of vitamins, including biotin and vitamin k (although bacteria alone cannot meet the need for these vitamins). The GI bacteria also protect people from infections. Provided that the normal intestinal flora are thriving, infectious bacteria have a hard time getting established and launching an attack on the system. In addition, the small intestine and the entire GI tract manufacture and maintain a strong arsenal of defenses against foreign invaders. Several different types of defending cells are present there and confer specific immunity against intestinal diseases. The final stage- the story of how food is broken down into nutrients that can be absorbed is now nearly complete. The three energy-yielding nutrients-carbohydrate, fat, and protein-are disassembled to basic building blocks before they are absorbed. Most of the other nutrients-vitamins, minerals, and water-are absorbed as they are. Undigested residues, such as some fibers, are not absorbed but continue through the digestive tract as a semisolid mass that stimulates the tracts muscles, helping them remain strong and able to perform peristalsis efficiently. Fiber also retains water, keeping plenty of water in conjunction with eating foods high in fiber supplies fluid for the fiber to take up. This is the basis for the recommendation to drink water and eat fiber-rich foods to relieve constipation. The process of absorbing the nutrients into the body is discussed in the next section. For the moment, let us assume that the digested nutrients simply disappear from the GI tract as they are ready. Virtually all nutrients are gone by the time the contents of the GI tract reach the end of the small intestine. Little remains but water, a few salts and body secretions, and undigested materials such as fiber. These enter the large intestine (colon). In the colon, intestinal bacteria degrade some of the fiber to simpler compounds. The colon itself retrieves from its contents the materials that the body is designed to recycle-water and dissolved salts. The waste that is finally excreted has little or nothing of value left in it. The body has extracted all that it can use from the food.
The chemists views of carohydrates 2
Disaccharides- in disaccharides, pairs of single sugars are linked together. Three disaccharides are important in nutrition: maltose, sucrose, and lactose. All three contain glucose as one of their single sugars. The other monosaccaride is either andother glucose (in maltose), fructose (in sucrose), or galactose (in lactose). Sucrose- sucrose is the most familiar of the three disaccharides and is what people mean when they speak of "sugar". This sugar is usually obtained by refining the juice from sugar beets or sugar cane to provide the brown, white, and powdered sugars available in the supermarket, but it occurs naturally in many fruits and vegetables. When a person eats a food containing sucrose, enzymes in the digestive tract split the sucrose into its glucose and fructose components. Lactose- lactose is the principal carbohydrate of milk. Most human infants are born with the digestive enzymes necessary to split lactose into its two monosaccharide parts, glucose and galactose, so as to absorb it. Breast milk thus provides a simple, easily digested carbohydrate that meets an infants energy needs; many formulas do, too, because they are made from milk. Maltose- The third disaccharide, maltose, is a plant sugar that consists of two glucose units. Maltose is produced whenever starch breaks down-as happens in plants when they break down their stored starch for energy and start to sprout and in human beings during carbohydrate digestion.
Using Nutrient Recommendations
EAR are most appropriately used to develop and evaluate nutrition programs for groups such as school children or military personnel. RDA or AI can be used to set goals for individuals. The UL help to keep nutrient intakes below the amounts that increase the risk of toxicity. -These values are recommendations for safe intakes, not minimum requirements, except for energy, they include alot lot of margin of safety. -the values reflect daily intakes to be achieved on average, over time. They assume that intakes will vary from day to day, and they are set high enough to ensure that body nutrient stores will meet nutrient needs during periods of inadequate intakes lasting a day or two for some nutrients and up to a month or two for others. -the values are chosen in reference to specific indicators of nutrient adequacy, such as blood nutrient concentrations, normal growth, and reduction of certain chronic diseases or other disorders when appropriate, rather than prevention of deficiency symptoms alone. -the recommendations are designed to meet the needs of most healthy people. medical problems alter nutrient needs. -the recommendations are specific for people of both genders as well as various ages and stages of life: infants, children, adolescents etc.
Anatomy of the Digestive tract
GI tract is a flexible muscular tube extending from the mouth to the anus.
The involuntary Muscles and the Glands
Gastrointestinal Motility- once you have swallowed, materials are moved through the rest of the GI tract by involuntary muscular contractions. This motion, known as gastrointestinal motility, consists of two types of movement, peristalsis and segmentation. Peristalsis propels, or pushes; segmentation mixes, with more gradual pushing. Peristalsis- peristalsis begins when the bolus enters the esophagus. The entire GI tract is ringed with circular muscles, which are surrounded by longitudinal muscles. When the rings tighten and the longs muscles relax, the tube is constricted. When the rings relax and the long muscles tighten, the tube bulges.These actions alternate continually and push the intestinal contents along. If you have ever watched a bolus of food pass along the body of a snake, you have a good picture of how these muscles work. The waves of contraction ripple through the GI tract at varying rates and intensities depending on the part of the GI tract and on whether food is present. Peristalsis, aided by the sphincter muscles located at key places, keep things moving along. However, factors such as stress, medicines, and medical conditions may interfere with normal GI tract contractions. Segmentation-the intestines not only push but also periodically squeeze their contents as if a string tied around the intestines were being pulled tight. This motion, called segmentation, forces the contents back a few inches, mixing them and promoting close contact with the digestive juices and the absorbing cells of the intestinal walls before letting the contents slowly move along again. Liquefying Process- besides forcing the intestinal contents along, the muscles of the GI tract help to liquefy them to chyme so that the digestive juices will have access to all their nutrients. The mouth initiates this liquefying process by chewing, adding saliva, and stirring with the tongue to reduce the food to a course mash suitable for swallowing. The stomach then further mixes and kneads the food. Stomach Action-The stomach has the thickest walls and strongest muscles of all the GI tract organs. In addition to circular and longitudinal muscles, the stomach has a third layer of diagonal muscles that also alternately contract and relax. These three sets of muscles work to force the chyme downward, but the pyloric sphincter usually remains tightly closed so that the stomach's contents are thoroughly mixed and squeezed before being released. Meanwhile, the gastric glands are adding juices. When the the chyme is thoroughly liquefied, the pyloric sphincter opens briefly, about three times a minute, to allow small portions through. At this point, the intestinal contents no longer resemble food in the least.
regulation of blood glucose
If blood glucose falls below normal, a person may become dizzy and weak; if it rises substantially above normal, the person may become fatiqued. Left untreated, fluctuations to the extremes-either high or low-can be fatal. Blood glucose homeostasis is regualted primarily by two hormones: insulin, which moves glucose from the blood into the cells , and glucagon, which brings glucose out of storage when blood glucose falls (as occurs between meals.) Insulin- after a meal, as blood glucose rises, the pancreas is the first organ o respond. It releases the homone insulin, which signals body tissues to take up surplus glucose. Muscle tissue responds
DRI
Nutrition experts have produces a set of standards that define the amounts of energy, nutrients, and other dietary components, and physical activity that best support health.
Absorption of Nutrients
Once a molecule has entered a cell in a villus, the next step is to transmit it to a destination elsewhere in the body by way of the body's two transport systems-the blood- stream and the lymphatic system. Both systems supply vessels to each villus. Through these vessels, the nutrients leave the cell and either enter either the lymph or the blood. In either case, the nutrients end up in the blood, at least for a while.The water-soluble nutrients (and the smaller products of fat digestion) are released directly into the bloodstream by way of the capillaries, but the larger fats and the fat-soluble vitamins find direct access into the capillaries impossible because these nutrients are insoluble in water (and blood is mostly water). They require some packaging before they are released. The intestinal cells assemble the products of fat digestion into larger molecules called triglycerides. These triglycerides, fat-soluble vitamins (when present), and other large lipids (cholesterol and the phospholipids) are then packaged for transport They cluster together with special proteins to form chylomicrons, one kind of lipoproteins. Finally, the cells release they chylomicrons into they lymphatic system. They can then glide through the lymph spaces until they arrive at a point of entry into the bloodstream near the heart. Thus, some materials from the GI tract initially enter the lymphatic system but soon reach the bloodstream.
the chemists view of carbohydrates 3
Polysaccarides- unlike the sugars, which contain the three monosaccharides-glucose, fructose, and galactose-in different combinations, the polysaccharides are composed almost entirely of glucose (and, in some cases, other monosaccharides). Three types of polysaccharides are important in nutrition: glycogen, starch, and fibers. Glycogen is a storage form of energy for human begins and andimals; starch plays that role in plants. Both glycogen and starch are built entirely of glucose units; fibers are composted of a variety of monosaccharides and other carbohydrate derivatives. Glycogen- molecules, which are aslo mad of chains of glucose, or more highly branched than starch molecules. Glycogen is found in meats only to a limited extent and not at all in plants. For this reason, glycogen is not a significant food source of carbohydrate, but it does play an important role in the body. The human body stores much of its glucose as glycogen in the liver and muscles. Starch- a long straight or branched chain of hundreds or thousands of glucose units linked together. These giant molecules are packed side by side in grains such as rice or wheat, in root crops and tubers such as yams and potatoes, and in legumes such as peas and beans. When a person eats the plant, the body splits the starch into glucose units and uses the glucose for energy. All starchy foods come from plants. Grains are the riches food source of starch. Second important is beans (legume), Third important is Root Vegetebles (tubers) like potatoes. Fibers- dietary fibers are the structural parts of plants and thus are found in all plant derived foods-vegetables, fruits, whole grains, and legumes. Most dietary fibers are polysaccharides-chains of sugars-just as starch is, but in fibers the sugar units are held together by bonds that human digestive enzymes cannot break. Consequently, most dietary fibers pass through the body, providing little or no energy for its use. In addition to cellulose, fibers include the polysaccharides hemicellulose, pectins, gums, and mucilages, as well as the nonpolysaccharide lignins. Cellulose is the main constiuent of plant cell walls, so it is foun in all vegetables, fruits and legumes. Hemicellulose is the main constituent of cereal fibers. Pectins are abundant in vegetables and fruits, especially citrus fruits and apples. The food industry uses pectins to thicken jelly and keep salad dressing from separating. Fibers are divdes into two general groups by their chemical and physical properties. In the first group are fibers that dissolve in water (soluble fibers). These form gels (are viscous) and are more readily gidested by bacteria in the human large intestine (are easily fermented). Commonly found in barley, legumes, fruits, otas, and vegetables, these fibers are often associated with lower risks of chronic disaeses. Soluble fibers add consistency like jelly and salad dressing to thicken. Other fibers do not dissolve in water (insoluble fibers) do not form gels (are no viscous), and are less readily fermented. Insoluble fibers, such as cellulose and many demicelluloses, are found in the outer layers of whole grains, the strings of celery, the hulls of seeds, and the skins of corn kernels. These fibers retain their structure and rough texture even after hours of cooking. In the body they aid the digestive system by easing elimination.
AMDR
The DRI committee considers prevention of chronic disease as well as nutrient adequacy when establishing recommendations. To that end, the committee established healthy ranges of intakes for the energy-yielding nurtients-carbohydrate, fat, and protein-known as Acceptable Macronutrient Distribution Ranges (AMDR). Each of these three energy-yielding nutrients contributes to a persons total energy(kcalorie) intake, and those contributions vary in relation to each other. The DRI committee has determined that a diet that provides the energy-yielding nutrients in the following proportions provides adequate energy and nutrients and reduces the risk of chronic disease. 40 to 65 percent of kcalories from carbohydrate 20 to 35 percent of kcalories from fat 10 to 35 percent of kcalories from protein
The system at its best
The GI tract is the first organ in the body to deal with the nutrients that will ultinately maintain the health and nutrition staus of the whole body. The intricate architecture of the GI tract makes it sensitive and responsive to environmental conditions.
transport of nutrients 2
The Lymphatic System- the lymphatic system is one-way route for fluids to travel from tissue spaces into the blood. The lymphatic system has no pump; instead, lymph is squeezed from one portion of the body to another like water in a sponge, as muscles contract and create pressure here and there. Ultimately, the lymp collects in a large duct behind the heart. This duct terminates in a vein that conducts the lymph into the heart. Transport of Lipids: Lipoproteins- within the circulatory system, lipids always travel from place to place bundled with protein, that is, as lipoproteins. When physicians measure a persons blood lipid profile, they are interested in both the types of fat present (such as triglycerieds and cholesterol) and the types of lipoproteins that carry them. VLDL, LDL, and HDL-As mentioned earlier, chylomicrons transport newly absorbed(diet-derived) lipids from the intestinal cells to the rest of the body. As chylomicrons circulate through the body, cells remove their lipid contents, so the chylimocrons get smaller and smaller. The liver picks up these chylomicron remnants. When necessary, the liver can assemble different lipoproteins, which are known as very-low-density lipoproteins (VLDL). Cholesterol returning to the liver for metabolism or excretion from other parts of the body is packaged in lipoproteins known as high-density lipoproteins (HDL). HDL are synthesized primarily in the liver. The density of lipoproteins varies according to the proporiton of lipids and proteins they contain. The more lipids in the lipoproein molecule, the lower the density; the more protein, the hight the density. Both LDL and HDL carry lipids around in the blood, but LDL are larger, lighter, and filled with more lipid; HDL are smaller, denser, and packaged with more protein. LDL deliver cholesterol and triglycerides from the liver to the tissues; HDL scavenge excess cholesterol from the tissues and return it to the liver for metabolism or disposal.
kcalorie
The amount of energy that carbohydrates, fats, and proteins release can be measured in calories- tiny units of energy so small that a single apple provides tens of thousands of them. To ease calculations, energy is expressed in 1000-calorie metric units known as kilocalories (shortened to kcalories, but commonly called "calories", understand that it means 100 kcalories. If a person takes in more energy then he or she expands the result is increase in energy stores and weight gain.
Dietary Guidelines
The dietary guidelines for Americans 2010 provie evidence-based advice to help people attain and maintain a healthy weight, reduce the risk of chronic diseases, and promote overall health through diet and physical activity. The first area focuses on balancing kcalories to manage a healthy body weight by improving eating habits and engaging in regular physical activity. The second area advises people to reduce their intakes of such foods and food components as sodium, solid fats (and the saturated fats, trans fats, and cholesterol they contain), added sugars, refined grain products and alcoholic beverages (for those who partake). The third area encourages consumers to select a variety of fruits and vegetables, whole grains, low-fat milk products, and protein foods (including seafood). The fourth are helps consumers build healthy eating patterns that meet energy and nutrient needs while reducing the risk of food-borne illnesses. Together, the dietary guidelines for Americans 2010 point the way toward longer, healthier, and more active lives.
digestion and absorption of carbohydrates
The ultimate goal of digestion and absorption of sugars and starches is to break them into small molecules-chiefly glucose-that the body can absorb and use. The large starch molecules require extensive breakdown; the disaccharides need only be broken once and the monosaccharides not at all. Most fiber passes intact through the small intestine to the large intestine. There, bacteria digest many soluble fibers to produce short-chain fatty acids, which are rapidly absorbed by the large intestine.
UL
Tolerable upper intake levels are indispensable to consumers who take supplements. Consumers need to know how much of a nutrient is too much. The UL are also of value to public health officials who set allowances for nutrients that are added to foods and water.
food label health claims
Until recently, the FDA held manufacturers to the highers standard of scientific evidence before allowing them to place health claims on food labels. When a label stated, "diets low in sodium may reduce the risk of high blood pressure", for example, consumers could be sure that the FDA had examined much scientific evidence and found substantial support for the claim. Such reliable health claims still appear on food labels, and they have a high degree of scientific validity. Today, however, the FDA also allows other claims backed by weaker evidence to appear on labels. These are qualified claims, in the sense that labels bearing them must also state the strength of the scientific evidence backing them up. Unfortunately, most people are not knowledgeable enough to distinguish between scientifically reliable claims those that are best ignored.
Dietary Ideals
a nutritious diet at six characteristics: adequacy- an edquate diet has enough energy and enough of every nutrient to meet the needs of healthy people. Balance- the food choices do not over emphasize one nutrient or food type at the expense of another i,e meat is rich in iron but bad in calcium. kcalorie(energy) control- the foods provide the amount of energy needed to maintain a healthy body weight not more not less. The key to kcalorie control is to select foods that deliver the most nutrients for the least food energy. Nutrient Density-a measure of the nutrients a food provides relative to the energy it provides. the more nutrients and the fewer kcalories, the higher the nutrient density i,e a can of soda and a handful of grapes may both provide about the same number of kcalories but grapes deliver many more nutrients. A person who makes nutrient-dense choices, can meet daily nutrient needs on a lower energy budget. Moderation-the provision of enough, but not too much, of a substance.a person who practices moderation eats such foods only on occasion and regularly selects foods low in solid fats and added sugars. Variety- the foods chosen differ from one day to the next. consumption of a wide selection of foods within and among the major food groups
Food Labels
all packaged foods must list all ingredients on the label in descending order of predominance by weight. Knowing that the first ingredient predoinates by weight, consumers can glean much information. Serving Size- because labels present nutrient information per serving, they must identify the size of a serving. The FDA has established specific serving sizes for various foods and requires that all labels for a given product use the same serving size. For example, the serving size for all ice creams is 1/2 cup and for all beverages, 8 fluid ounces. Daily Values- it sets adequacy standards for nutrients that are desirable in the diet such as protein, vitamins, minerals, and fiber, and they also set moderation standards for other nutrients that must be limited, such as fat, saturated fat, cholesterol, and sodium. "the % daily value" provides a ballpark estimate of how individual foods contribute to the total diet. It compares key nutrients in a serving of food with the daily goals of a person consuming 2000 kcalories. Most labels list, at the bottom, Daily Values for both a 2000-kcalorie and a 2500 kcalories. most lables list, at the bottom, Daily Values for both a 2000-kcalorie and a 2500-kcalorie diet, but the "% Daily value" column on all labels applies only to a 2000-kcalorie diet. Nutrient Quantities- in addition to the serving size and the servings per container, the FDA requires that the "Nutrition Facts" panel on a label present nutrient information in two ways- in quantities (such as grams) and as percentages of the Daily Values. The Nutrition facts panel must provide the nutrient amount, percent Daily Value, or both for the following: Total food energy(kcalories), Food energy from fat(kcalories), Total Fat (grams and percent Daily Value), Trans fat (grams), Cholesterol (milligrams and percent Daily Value), 'Total carbohydrate, including starch, sugar, and fiber (grams and percent Daily Value)', Dietary fiber (grams and percent Daily Value), 'sugars (grams), including both those naturally present in and those added to the food, protein(grams). the labels must also present nutrient content sinformation as a percentage of the Daily Values for the following mitamins and minerals: Vitamin A, Vitamin C, Iron, Calcium. The FDA developed the Daily Values for use on food labels because comparing nutrient amounts against a standard helps make them meaningful to consumers. A person might wonder, for example, whether 1 miligram of iron or calcium is a little or a lot. The daily value for iron is 18 milligrams, so 1 milligram of iron is enough to take notice of: it is more than 5 percent. But the Daily lVaue for calcium on food labels is 1000 milligram, so 1 milligram of calcium is a negligible amount.
recommended daily food amounts
all vegetables provide an array of vitamins, fiber, and the mineral potasium, but some vegetables are especially good sources of certain nutrients and beneficial phytochemicals. For this reason, the vegetable group is sorted into five subgroups. The dark green vegetables deliver the B vitamin folate; the red and orange vegetables provide vitamin A; legumes supply iron and protein; the starchy vegetables contribute carbohydrate energy; and the other vegetables fill in the gaps and add more of these same nutrients. One way to help ensure selections for all of the subgroups is to eat vegetables of various colors- for example, green broccoli, orange sweet potatoes, black beans, yellow corn, and white cauliflower. Intakes of vegetables are appropriately averaged over a week's time- it isn't necessary to include every subgroup every day.
carbohydrates, fats, and proteins, vitamins
contain carbon which is found in all living things. They are organic(alive). During metabolism three of these four provide energy the body can use. These energy yielding nutrients continually replenish the energy you spend daily. Carbohydrates and fats meet most of the body's energy needs; proteins make a significant contribution only when other fuels are unavailable. carbohydrates yeilds 4 kcalories of energy from each gram, and so does protien. Fat yields 9 kcalories per gram, thus fat has a greater energy density than either carbohydrate or protein. If you know how many grams of each nutrient a food contains, you can derive the number of kcalories potentially available from the food. simply multiply carbohydrate grams times 4, the protein grams times by 4, and the fat grams times 9, and add the results together (the accompanying "how to" describes how to calculate the energy a food provides.)
notable nutrients
eat more vegetables, fruits, whole grains, seafood, and fat-free or low-fat milk and milk products. eat less sodium, saturated fat, trans fat, and cholesterol, and fewer refined grains and foods and beverages with solid fats and added sugars.
Fitness Guidelines
emphasize the benefits of increasing physical activity and reducing sedentary activities to achieve or maintain a healthy body weight and reduce the risk of chronic disease. What does a person have to do to reap the health rewards of physical activity? The guidelines recommend longer or shorter times for activity depending on whether the activity clarity and effectiveness, a minimum length of 10 minutes for short bouts of aerobic physical activity is recommended. Rest and sleep- occur naturally after periods of physical activity, nutritional health- physical activity expends energy and thus allows people to eat more food. Optimal body composition- a balanced program of physical activity limits body fat and increases or maintains lean tissue. optimal bone density-builds bone strength. low risks of some types of cancers, strong circulation and lung function, low risk of cardiovascular disease, low risk of type 2 diabetes, reduce risk of gallbladder disease, low incidence and severity of anxiety and depression, strong self image, long life and high quality of life in the later years.
Food Choices
healthy food choices do not ensure health and long life, people often choose foods based on factors other than health, changing eating habits is difficult, healthcare professionals must understand the dynamics of food choices in order to help elicit change, cultural competence is an important aspect of honoring individual preferences.
EAR
in addition to the RDA and AI, the DRI committee has established another set of values. Estimated Average Requirements (EAR). Theses values establish average requirements for given life stage and gender groups that researchers and nutrition policymakers use in their work.
Setting energy recommendations
in contrast to the vitamin and mineral recommendations, the recommendation for energy EER Estimated Energy Requirement is not generous because excess energy cannot be excreted and is eventually stored as body fat. Rather, the key to the energy recommendation is balance. For a person who has a body weight, body composition, and physical activity level consistent with good health, energy intake from food should match energy expenditure so the person achieves energy balance. Enough energy is needed to sustain a healthy, active life, but too much energy leads to obesity.
Energy nutrients in foods
most foods contain mixtures of all three energy-yielding nutrients, although foods are sometimes classified by their predominant nutrient. To speak of meat as "a protein" or of bread as "a carbohydrate", however, is inaccurate. Each is rich in a particular nutrient, but a protein rich food such as beef contains a lot of fat along with the protein, and carbohydrate-rich food such as beef contains a lot of fat along with the protein, and a carbohydrate-rich food such as cornbread also contains fat (corn oil) and protein. Only a few foods are exceptions to this rule, the common ones being sugar (which is pure carbohydrate) an oil (which is pure fat).
how to calculate the energy available from foods
multiply the number of grams of carbohydrate, protein, and fat by 4, 4, and 9, respectively. Then add the results together. For example, one slice of bread wit 1 tablespoon of peanut butter on it contains 16 grams of carbohydrate, 7 grams of protein, and 9 grams of fat: 16 g carbohydrate x 4 kcal/g= 64 kcal 7 g protein x 4 kcal/g= 28 kcal 9 g fat x 9 kcal/g= 81 kcal total= 173 kcal from this information, you can calculate the percentage of kcalories each of the energy nutrients contributes to the total. To determine the percentage of kcalories fromfat, for example, divide the 81 fat kcalories by the total 173 kcalories: 81 fat kcal / 173 total kcal=.468 (rounded to .47) then multiply by 100 to get the percentage: .47 x 100=47% dietary recommendations that urge people to limit fat intake to 20 to 35 percent of kcalores refer to the day's total energy intake, not individual foods. Still, if the proportion of fat in each food choice throughout a day exceeds 35 percent of kcalories, then the day's total surely will, too. knowing that this snack provides 47 percent of its kcalories from fat alerts a person to the need to make lower-fat selections at other times that day.
Transport of Nutrients 1
once a nutrient has entered the bloodstream or the lymphatic system, it may be transported to any part of the body, from the tips of the toes to the roots of the hair, where it becomes available to any of the cells. The circulatory systems are arranged to deliver nutrients wherever they are needed. The vascular system- The vascular or blood circulatory system is a closed system of vessels through which blood flows continuously in a figure eight, with the heart serving as a pump at the crossover point. On each loop of the figure eight, blood travels a simple route: heart to arteries to capillaries to veins to heart. The routing of the blood through the digestive system is different, however. The blood is carried to the digestive system (as it is to all organs) by way of an artery, which (as in all organs) branches into capillaries to reach every cell. Blood leaving the digestive system, however, goes by way of a vein. The hepatic portal vein directs blood not back to the heart but to another organ-the liver. This vein again branches into a network of small blood vessels so that every cell of the liver has access to the newly absorbed nutrients that the blood is carrying. Blood leaving the liver again collects into a vein, called the hepatic vein, which returns the blood to the heart. The route is thus heart to arteries to capillaries (in intestines) to hepatic portal vein to sinusoids (in liver) to hepatic vein to heart. The liver is located in the circulation system at the point where it will have the fist chance at most of the materials absorbed from the GI tract. In fact the liver is the body's major metabolic organ and must prepare the absorbed nutrients for use by the rest of the body. Furthermore, the liver stands as a gatekeeper to waylay intruders that might otherwise harm the heart or brain.
RDA and AI
one advantage of the DRI is that they apply to the diets of individuals. The DRI committee offers two sets of values to be used as nutrient intake goals by individuals: a set called the Recommended Dietary Allowances (RDA) and a set called Adequate Intakes (AI). RDA is based of the DRI. The AI values are based on less extensive scientific findings and rely more heavily on scientific judgment. The committee establishes an AI value whenever scientific evidence is insufficient to generate an RDA. An advantage of DRI is that, where appropriate, they take into account disease prevention as well as an adequate nutrient intake. For example, the RDA for calcium is based on intakes thought to reduce the likelihood of osteoporosis-related fractures later in life. To ensure that the vitamin and mineral recommendations meet the need of as many people as possible, the recommendations are set near the top end of the range of populations estimated average requirements. Small amounts above the daily requirement do no harm, whereas amounts below the requirement deficient, their nutrient stores decline, and over time this decline leads to deficiency symptoms and poor health.
Personal factors to food choices
preference- for certain tastes, some people inherit sensitivity to bitter taste. Habit- do it because you always do. Associations- foods eaten when sick, foods eaten on holidays. Ethnic Heritage and Regional Cuisines- every country and region has its own typical foods and ways of combining them into meals. Values- environmental. By choosing to eat some foods or to avoid others, people make statements that reflect their values. ex. no eating out of plastic containers Social interaction- celebrate a holiday or special event, renew old friendship, make new friends. Ex. business exec invites a prospective new client out to dinner in hopes of edging out the competition Emotional State- eat in response to a variety of emotional stimuli. Availability, convenience, and economy- you cannot eat foods if they are not available, or time to cook them, or get to grocery store. Age- children depend on adults to provide food, teens choose foods that are provided but want sweet foods.Adults want foods that depends on their weight. Health and Nutrition- make food choices they believe will improve their health. Foods that provide health benefits beyond their nutrient contributions are called functional foods.
serving equivalents
recommended daily amounts for fruits, vegetables, and milk are measured in cups and those fro grains and protein foods, in ounces. Portion size: the quantity of food served or eaten at one meal or snack; not a standard amount. 1/4 c dried fruit or nuts= a golf ball 1 c fruit or vegetables= a baseball 3 oz meat= a deck of cards 1/2 c ice cream= a racquetball 2 tbs peanut butter= ping pong ball
Alcohol is not a nutrient
the body derives energy from alcohol at the rate of 7 kcalories per gram. It is not a nutrient because it cannot support the body's growth, maintenance, or repair. There is no storage pool for alcohol.Alcohol suppresses the breakdown of fat for energy, leading to fat accumulation in the liver and the increased release of triglyceride-carrying lipoproteins. Most of alcohol is metabolized in the stomach, most of the alcohol consumed is quickly absorbed in the stomach or small intestine and passes readily into the body's cell.
energy storage in the body
the body first uses the energy-yielding nutrients to build new compounds and fuel metabolic and physical activities. Excesses are then rearranged into storage compounds, primarily body fat, and put away for later use. Thus, if you take in more energy than you expend, whether from carbohydrate, fat, or protein, the result is an increase in energy stores and weight gain. Similarly, if you take in less energy than you expend, the result is a decrease in energy stores and weight loss.
The chemists view of carbohydrates
the dietary carbohydrates include the sugars, starch, and fiber. Chemists describe the sugars as: monosaccarides (single sugars), and disaccharides (double sugars). Starch and fiber are: polysaccharies-compounds composed of chains of monosaccharied units. All of these carbohydrates are composed of the single sugar glucose and other compounds that are much like glucose in composition and structure. Monosaccarides- three monosaccharieds are important in nutrition: glucose, fructose, and galactose. All three monosaccharids have the same number and kinds of atoms but in different arrangements. Glucose- most cells depend on glucose for their fuel to some extent, and the cells of the brain and the rest of the nervous system depend almost exclusively on glucose for their energy. The body can obtain this glucose from carbohydrates. To function optimally, the body must maintain blood glucoase within limits that allow the cells to nourish themselves. A section describes blood glucose regulation. Fructose- fructose is the sweetest of the sugars. Fructose occurs naturally in fruits, in honey, and as a part of table sugar. However, most fructose is consues in seet beverages such as soft drinks, in ready-to-eat cereals, and in other products sweetened with high-fructose corn syrup or other added sugars. Glucose and fructose are the most common monosaccharides in nature. Galactose-The third single sugar, galactose, occurs mostly as part of lactose, a disacharide also known as milk sugar. During digestion, galactose is freed as a single sugar
discretionary kcalories
the difference between the kcalories needed to supply nutrients and those needed to maintain weight might be considered discretionary kcalories. Discretionary kcalories allow a person to choose whether to: eat additional nutrient-dense foods, such as an extra serving of skinless chicken or a second ear of corn. Select a few foods with fats or added sugars such as reduced fat mild or sweetened cereal. add a little fat or sugar to foods, such as butter or jelly on toast. consume alcohol. Not use discretionary kcalories.
Health implications of LDL and HDL
the distinction between LDL and HDL has implications for the health of the heart and blood vessels. Elevated LDL concentratons in the blood are associated with a high risk of heart disease, and elevated HDL concentrations are associated with a low risk. These associations explain why some people refer to LDL as "bad" cholesterol and HDL as "good" cholesterol. Keep in mind, though, that there is only one kind of cholesterol molecule; the differences between LDL and HDL reflect proportions of lipids and proteins within them- not the type of cholesterol. Factors that improve the LDL-to-HDL ratio include weigh management, polyunsaturated or monounsaturated, instead of saturated, fatty acids in the diet, soluble fibers, physical activity.
The digestive organs
the process of digestion begins in the mouth. As you chew, your teeth crush and soften the food, while saliva mixes with the food mass and moistens it for comfortable swallowing. Saliva also helps dissolve the food so that you can taste it; only particles in solution can react with taste buds. The tongue allows you not only to taste food but also to move food around the mouth, facilitating chewing and swallowing. When you swallow a mouthful of food, it passes through the pharynx, a short tube that is shared by both the digestive system and the respiratory system. Mouth to the Esophagus: once a mouthful of food has been chewed and swallowed, it is called a bolus. Each bolus first slides across your epiglottis, bypassing the entrance to your lungs. During each swallow, the epiglottis closes off your trachea, the air passageway to the lungs, so that you do not choke. Esophagus to the stomach: the esophagus has a sphincter muscle at each end. During a swallow, the upper esophageal sphincter opens. The bolus then slides down the esophagus, which conducts it through the diaphragm to the stomach. The lower esophageal sphincter closes behind the bolus so that it cannot slip back. The stomach retains the bolus for a while, adds juices to it and transforms it into a semiliquid mass called chyme. Then, bit by bit, the stomach releases the chyme through another sphincter, the pyloric sphincter, which opens into the small intestine and then closes after the chyme passes through. The Small Intestine: At the beginning of the small intestine, the chyme passes by an opening from the common bile duct, which secretes digestive fluids into the small intestine from two organs outside the GI tract-the gallbladder and the pancreas. The chyme travels on down the small intestine through its three segments-the douodenum the jejunum, and the ileum. Together, the segments amount to a total of about 10 ft of tubing coiled within the abdomen. Digestion is completed within the small intestine. The Large Intestine(colon): Having traveled the length of the small intestine, what remains of the intestinal contents passes through another sphincter, the ileocecal valve, into the beginning of the large intestine (colon) in the lower right-hand side of the abdomen. Upon entering the colon, the contents pass another opening: the one leading to the appendix, a blind sac about the size of your little finger. Normally, the contents bypass this opening, however, and travel up the right-hand side of the abdomen, across the front to the left-hand side, down to the lower left-hand side, and finally below the other folds of the intestines to the back side of the body above the rectum. The Rectum: As the intestinal contents pass to the rectum, the colon withdraws water, leaving semisolid waste. The strong muscles of the rectum hold back this waste until it is time to defecate. Then the rectal muscles relax, and the last sphincter in the system, the anus, opens to allow the wastes to pass. Thus, food follows the path shown in the margin.
The Process of Digestion
to digest food, five different body organs secrete digestive juices: the salivary glands, the stomach, the small intestine, the liver (via the gallbladder), and the pancreas. These secretions enter the GI tract at various points along the way, bringing an abundance of water and a variety of enzymes. Each of the juices has a turn to mix with the food and promote its breakdown to small units that can be absorbed into the body. The accompanying glossary defines some of the digestive glands and their juices. Digestion in the mouth- digestion of carbohydrate begins in the mouth, where the salivary glands secrete saliva, which contains water, salts, and enzymes (including salivary amylase) that break the bonds in the chains of starch. Saliva also protects the tooth surfaces and linings of the mouth, esophagus, and stomach from attack by molecules that might harm them. The enzymes in the mouth do not, for the most part, effect the fats, proteins, vitamins, minerals, and fiber that are present in the foods people eat. Digestion in the stomach- Gastric juice, secreted by the gastric glands, is composed of water, enzymes and hydrochloric acid. The acid is so strong that it burns the throat if it happens to reflex into the upper esophagus and mouth. The strong acidity of the stomach prevents bacterial growth and kills most bacteria that enter the body with food. You might expect that the stomach's acid would attack the stomach itself, but the cells of the stomach wall secrete mucus, a thick, slimy, white polysaccharide that coasts and protects the stomachs lining. The major digestive event in the stomach is the initial breakdown of proteins. Other than being crushed and mixed saliva in the mouth, nothing happens to protein until it comes in contact with the gastric juices in the stomach. There, the acid helps to uncoil (denature) the protein's tangled strands so that the stomach enzymes can attack the bonds. Both the enzyme pepsin and the stomach acid itself act as catalysts in the process. Minor events are the digestion of some fat by a gastric lipase, the digestion of sucrose (to a very small extent) by the stomach acid, and the attachment of a protein carrier to Vitamin B12. The stomach enzymes work most efficiently in the stomach's strong acid, but salivary amylase, which is swallowed with food, does not work in acid this strong. Consequently, the digestion of starch gradually ceases as the acid penetrates the bolus. In fact, salivary amylase becomes just another protein to be digested.
USDA food Patterns
usda provides a food group plan: the usda Food Patterns-that builds a diet from categories of foods that are similar in vitamin and mineral content. selecting foods from each of the groups eases the task of creating an adequate and balanced diet. 5 food groups: fruits, vegetables, grains, protein foods, milk and milk products.
vitamins, minerals, and water
vitamins are organic but do not provide energy to the body. They facilitate the release of energy from the three energy yielding nutrients. In contrast, minerals and water are inorganic nutrients. Minerals yield no energy in the human body,but, like vitamins, they help to regulate the release of energy among their many other roles. As for water, it is the medium in which all of they body's processes take place.
Six essential nutrients
water, carbohydrates, fats, proteins, vitamins, and minerals are the six classes of nutrients commonly found in spinach and others. definition- the nutrients that foods must supply
the absorptive system
within three or four hours after you have eaten a meal, you body must find a way to absorb million of molecules one by one. The absorptive system is ingeniously designed to accomplish this task. The small intestine- most absorption takes place in the small intestine. The small intestine is a tube about 10ft long and about an inch across, yet it provides a surface comparable in area to a tennis court. When nutrient molecules make contact with this surface, they are absorbed and carried off to the liver and other parts of the body. Villi and microvilli- how does the intestine manage to provide such a large absorptive surface area? its inner surface looks smooth, but viewed through a microscope, it turns out to be wrinkled into hundreds of folds. Each fold is covered with thousands of finger like projections called villi. The villi are as numerous as the hairs on velvet fabric. A single villus, magnified still more, turns out to be composed of several hundred cells, each covered with microscopic hairs called microvilli. The villi are in constant motion. A thin sheet of muscle lines each villus so that it can wave, squirm, and wiggle like the tentacles of a sea anemone. Any nutrient molecule small enough to be absorbed is trapped among the microvilli and drawn into a cell beneath them. Some partially digested nutrients are caught in the microvilli, digested further by enzymes there, and then absorbed into the cells. Specialization in the Intestinal Tract- as you can see, the intestinal tract is beautifully designed to perform its function. A further refinement of the system is that the cells of successive portions of the tract are specialized to absorb different nutrients. The nutrients that are ready for absorption early are absorbed near the top of the tract; those that take longer to be digested are absorbed farther down. The rate at which the nutrients travel through the GI tract is finely adjusted to maximize their availability to the appropriate absorptive absorptive segment of the tract when they are ready. They lowly "gut" turns out to be one of the most elegantly designed organ systems in the body. They myth of "food combining"- some popular fad diets advocate the idea that people should not eat certain food combinations (for example fruit, meat) at the same meal because the digestive system cannot handle more than one task at a time. This is a myth. The art of "food combining" (which actually emphasizes "food separating") is based on this idea, and it represents faulty logic and a gross underestimation of the body's capabilities. In fact, the opposite is often true: foods eaten together can enhance each others use by the body. For example, vitamin c in a pineapple or citrus fruit can enhance the absorption of iron from a meal of chicken and rice or other iron-containing foods. Many other instances of mutually beneficial interactions are presented in later chapters.