Human Nutrition 2 PDF

Introduction to Human Nutrition  Macronutrients - Carbohydrates Carbohydrates play a major role in our life and make us healthy. Every cells of human body needs energy to do its work. People don't eat glucose directly, they eat carbohydrates. Then their bod...

Introduction to Human Nutrition  Macronutrients - Carbohydrates Carbohydrates play a major role in our life and make us healthy. Every cells of human body needs energy to do its work. People don't eat glucose directly, they eat carbohydrates. Then their bodies convert the carbohydrates into glucose for energy and to glycogen for reserve energy. Dietary carbohydrate provided the body's great source of fuel for energy.  Macronutrients - Carbohydrates The carbohydrates are compounds made of carbon (C), oxygen (O) and hydrogen (H). These atoms can form specified number of chemical bonds, carbon form four bonds, oxygen forms two and hydrogen forms one.  Macronutrients - Carbohydrates classification Carbohydrate Simple Complex Monosaccharide& disaccharide Polysaccharide Ex. Sugars Ex. Starch &fibers  Carbohydrate Monosaccharaide Disaccharide Polysaccharide Single sugars Double sugars Multiple sugars Sucrose lactose Starch Glucose Maltose Fructose Galactose  Monosaccharide ❑Most of the monosaccharides important in nutrition are hexoses. ❑Monosaccharides are the simplest form of carbohydrate that can not broke down to smaller units. ❑The three monosaccharides are important in nutrition, all have the same number and kinds of atoms(C6H12O6), but in different arrangement. ❑The three kinds of monosaccharaides have a different sweetness. →Glucose on the tongue gives a mildly sweet, →Galactose hardly tastes sweet at all, but → Fructose is intensely sweet.  Glucose ❖ The basic single sugar in body metabolism is glucose. ❖ Supply the primary fuel for cells. ❖ It is not usually found as such in the diet. ❖ The body supply comes mainly from the digestion of starch. ❖ It is also know as blood sugar or dextrose. ❖ Glucose is one of the two sugars in every disaccharide and the unit from which the polysaccharides are made almost exclusively.  Fructose ❖ Fructose is the sweetest of the sugars. ❖ Has the same chemical formula of glucose but with different structure. ❖ Fructose occurs naturally in fruits and honey. ❖ The amount of fructose in fruits depends on the degree of ripeness. ❖ As the fruit ripens, some of the stored starch turns to sugars. ❖ It is also called fruit sugar.  Galactose ❖ Galactose occurs naturally as a single sugar in only few foods. ❖ Galactose has the same number and kinds of atoms as glucose and fructose in yet another arrangement. ❖ Galactose also is not usually found as such in the diet. But rather as a part of disaccharide ”lactose=glucose+galactose” ❖ Milk is the primary food source of galactose. Comes mainly from digestion of milk sugars (lactose).  Disaccharides Disaccharides: pairs of monosaccharides linked together. Glucose occurs in all three, and the second member of the pair is either fructose, galactose, or another glucose. →are put together by a reaction called condensation(links two monosaccharaides together and gives out water). →and are taken apart by reaction called hydrolysis (is to break a disaccharide into two, and a molecule of water splits to provide the H & OH needed to complete the resulting monosaccharide). The hydrolysis often occurs during digestion.  Sucrose=glucose + fructose ❑ Occurs naturally in fruits ,vegetables and grains. ❑ To make a table sugar, sucrose is refined from the juices of sugarance ❑ and sugar beets, then granulated. Is common table sugar, and from sugar cane, sugar beets. ❑ Depending to the extent to which it is refined ,the product becomes ❑ the familiar brown, white, and powdered sugars available in the grocery stores. Sucrose is readily hydrolyzed by acids and by enzyme sucrase in the ❑ small intestine into glucose and fructose.  Sucrose ❑ Sucrose=glucose + fructose ❑ Occurs naturally in fruits ,vegetables and grains. ❑ To make a table sugar, sucrose is refined from the juices of sugarance and sugar beets, then granulated. ❑ Depending to the extent to which it is refined ,the product becomes the familiar brown, white, and powdered sugars available in the stores. ❑ Sucrose is readily hydrolyzed by acids and by enzyme sucrase in the small intestine into glucose and fructose.  Lactose= glucose+ galactose The principle CHO of milk. Known as milk sugar. The sugars derived primarily from plants, except for lactose and its components galactose, which come from milk and milk products. Lactose is the only common sugar not found in plants.  Lactose= glucose+ galactose The principle CHO of milk. Known as milk sugar. The sugars derived primarily from plants, except for lactose and its components galactose, which come from milk and milk products. Lactose is the only common sugar not found in plants. It is less soluble and less sweet than sucrose. Remains in the intestine longer than other sugar encourage the growth of certain useful bacteria. It is readily hydrolyses by enzyme lactase into glucose and galactose.  Lactose Lactose= glucose+ galactose The principle CHO of milk. Known as milk sugar. The sugars derived primarily from plants, except for lactose and its components galactose, which come from milk and milk products. Lactose is the only common sugar not found in plants. It is less soluble and less sweet than sucrose. Remains in the intestine longer than other sugar encourage the growth of certain useful bacteria. It is readily hydrolyses by enzyme lactase into glucose and galactose.  Maltose= glucose + glucose The two single sugar units that composed maltose are both glucose. It is not usually found as such in the diet. Maltose is →produce whenever starch is break down-it is derived in the body from the intermediate digestive breakdown of starch. →occurs during the fermentation process that yields alcohol. → only a minor constituent of few food, most notably barely.  Maltose Maltose= glucose + glucose The two single sugar units that composed maltose are both glucose. It is not usually found as such in the diet. Maltose is →produce whenever starch is break down-it is derived in the body from the intermediate digestive breakdown of starch. →occurs during the fermentation process that yields alcohol. → only a minor constituent of few food, most notably barely.  polysaccharides Composed of many single sugar units linked together. The important polysaccharides in nutrition include starch, glycogen and dietary fiber.  Starch ❑ Starch: is long branches and unbranched chains of hundred or thousands of glucose molecules linked together. ❑ Is insoluble polysaccharide. ❑ Is the most dietary carbohydrates worldwide found in grains(rice and wheat), legumes(peas and beans) and tubers (potatoes and yams). ❑ When the plant is eaten, the body hydrolyzes the starch to glucose. ❑ Moist and heat causes grains to swell, cell may disrupt and the starch becomes soluble. Cooking renders the starch to become soluble and more accessible to digestive enzymes. ❑ Starch grains contains two polysaccharide derived from glucose(amylose and amylopectin).  Starch ❑ Because starch are more complex than simple sugars, they breakdown more slowly and supply energy over longer period of time. ❑ Dextrin's are degradation product of starch in which glucose chains have been broken down to smaller units by partial hydrolysis. ❑ The human body stores glucose as glycogen But plant cells store glucose as starch.  Glycogen ❖ Is found only to a limited extent in meats and not at all in plants. ❖ The human body stores much of its glucose as glycogen and it is found in the liver and muscles. ❖ In storage many glucose molecules linked together in highly branched chains. This arrangement permits rapid hydrolysis. ❖ When the hormonal message arrives at the storage sites, enzymes respond by attacking glycogen simultaneously, making a surge of glucose available. ❖ These small stores of glycogen help sustain normal blood sugar during fasting and provide immediate energy for muscle action. structure of glycogen and starch  Dietary fiber Dietary fibers are the structural parts of plants and thus are found in all plants derived foods-vegetables, fruits, whole grains ,and legumes. Most dietary fibers are polysaccharides. Fibers differ from starches in that the bonds between their monosaccharaides cannot be broken down by human digestive enzymes. (Non starch polysaccharide). Fibers pass through the body and they contribute no monosaccharide, and therefore little or no energy. The bacteria of the gastrointestinal tract can break some fibers down, this is important to digestion and health.  Dietary fibers into two groups →Soluble fiber: Indigestible food components that dissolve in water to form a gel(viscous). Are easily digested by bacteria in the colon(fermentable). Commonly found in oats, barely, legumes, and citrus fruit. They are mostly associated with protecting against heart disease and diabetes by lowering blood cholesterol and glucose level,repectively. An example is pectin from fruit, which is used to thicken jellies.  Dietary fibers into two groups → Insoluble fiber: Indigestible food components that do not dissolve in water. Don't form gels (nonviscous),and are less readily fermented. Found mainly in whole grains(bran),vegetables. It promotes bowel movements and alleviate constipation.  Types of fibers: 1- Cellulose: cellulose is the primary constituent of plant cell wall. Occurs in all vegetables, fruits and legumes. 2- Non-cellulose polysaccharides: such as pectin, gums and mucilage. 3- Lignin: woody parts of vegetables such as carrots and the small seeds of fruits (strawberries).  Clinical importance of fibers: 1-Constipation 2-Colon cancer 3-Obesity 4-Hypoglycemia 5-Hyperglycemia  Carbohydrate sources Table (1): Carbohydrate sources Chemical class name Class members Sources Polysaccharides Starch Grains and grains (Multiple sugar or complex products carbohydrates) Cereal, bread, pasta, rice, corn, legumes, potatoes and other vegetables. Glycogen Animal tissues, liver and muscle meats. Dietary fiber Whole grains, fruits, Vegetables, seeds, nuts. Chemical class name Class members Sources Disaccharides ( Double sugars, Sucrose Table sugar, sugar cane, simple carbohydrates) sugar beets, molasses. Lactose Milk. maltose Barley Monosaccharide (single Glucose Sweetener in food products sugars, simple carbohydrate) Starch digestion, final Corn syrup. Fructose Fruits, honey. Galctose Lactose (milk). Recommended intakes of carbohydrates Dietary recommendations suggest that, CHO provide more than half (55 to 60 %) of energy requirement. 5-9 servings daily of combinations of fruits and vegetables. 6-11 servings daily of combination of breads, cereals and legumes. The FDA (The Food and Drug Administration) set a daily value on food for fibers at 25 gram fiber daily. The American Dietetic Association suggests that 20 - 25 grams of dietary fibers daily. A high fiber diet is more than 40 gm/day.