Module 4 Carbohydrates PDF

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Module 4 Carbohydrates...

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Module 4: Carbohydrates 4.1: Carbohydrates-Our Most Important Energy Source - Carbs are a main fuel source for some cells - Provide about 4 kcal per gram - Form of both glucose and glycogen - Glycogen stored in the liver can be used to maintain blood glucose concentrations when you have not eaten for several hours or the food you eat does not supply enough carbs - Regular intake of carbs are important bc liver glycogen stores can be depleted in about 18 hours if no carbs are consumed - After this point, body is forced to produce carbs, from breakdown of protein or fat stores - Can lead to health problems, including the loss of muscle tissue - To obtain adequate energy, recommends that 45% to 65% of the calories we consume each day come from carbs - Choosing whole grain carbs sources and limiting the intake of refined carb sources contributes to a healthier dietary pattern

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Translated into simple terms - 6 molecules of CO2 combined with 6 molecules of H20 using energy from sun to form 1 molecule of Glucose and release 6 molecules of oxygen into the air Converts solar energy into chemical bonds in the sugar is a key part of the process of PHOTOSYNTHESIS

4.2: Forms of Carbohydrate - Most carbs are composed of C, H and O atoms - Simple forms of carbs are called sugars - Larger, more complex forms are primarily called either starches or fibers, depending on their digestibility

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Starches are digestible Fibers are not digestible

- Simple carbs contain only one or two sugar units called MONOsaccharides and DIsaccharides Monosaccharides; Glucose, Fructose and Galactose - Monosaccharides are the simple sugar units - Server the basic unit of all carb structures - Most common monosaccharides in foods are glucose, fructose, and galactose - Chemical composition remains the same in each

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- C6H1206 Glucose - Major monosaccharide found in the body

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Also known as dextrose and in the bloodstream it is called blood sugar Important energy source for human cells Most glucose comes from the digestion of starches and sucrose - Sucrose is made up of the monosaccharides glucose and fructose - Fructose - Also mono - Found naturally in fruits and forms half of each sucrose molecule - Much is converted to glucose, but excess fructose may form other compounds such as fat - Most of the free fructose in the food we eat comes from the use of high fructose corn syrup (HFCS) in highly processed foods like candy and canned foods - Galactose - Nearly the same structure as glucose - Large quantities of pure galactose does not exist in nature - Usually found bonded to glucose in lactose - During digestion - Lactose is broken down to galactose and glucose and then absorbed - When arrives in liver it is either transformed into glucose or further metabolized into glycogen, depending on the body’s energy needs at the time Disaccharides: Sucrose, Lactose and Maltose - Disaccharides are formed when two mono are combined - Sucrose, lactose and maltose - All of which contain glucose - Sucrose - Forms when two sugars, glucose and fructose, bond together - Found naturally in sugarcane, sugar beets, honey and maple sugar - Lactose - Forms when glucose bonds with galactose during the synthesis of milk - Maltose - Results when starch is broken down to just two glucose molecules bonded together - Important role in the beer and liquor industry - Starches are converted to simpler carbs by enzymes present in the grains - Breakdown products are then mixed with yeast cells in the absence of oxygen - Yeast cells convert most of the sugars to alcohol and CO2 through a process called fermentation Polysaccharides: Starch, Glycogen and Fiber - Starch - Numerous single-sugar units bonded together form a chain known as polysaccharide - Plants store carbs in two forms of scratch digestible by humans - Amylose - A long, straight chain of glucose units, comprise about 20% of the digestible starch found in vegetables, beans, bread, pasta and rice - Amylopectin - Highly branched chain structure and makes up the remaining 80% of digestible starches in the food we eat

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The enzymes that break down starches to glucose and other related sugars act only at the end of a glucose chain - Amylopectin, because it is branched, provides many more sites for action - Therefore, digested more rapidly and raises blood glucose much more readily than amylose

Glycogen - Consists of a chain of glucose units with many branches, providing even more sites for enzyme action than amylopectin - Because of its highly branched structure that can be broken down quickly, glycogen is an ideal storage form of carbs in the body - Liver and muscles are major storage sites for glycogen - Amount of glucose is immediately available in bodily fluids can provide only about 80 to 120 kcal, the carb energy stored as glycogen is extremely important - Although animals store glycogen in their muscles, animal products such as meats, fish and poultry are not good sources of carbs because glycogen stores quickly degrade after the animal dies Fiber - Mainly made up of poly - Differ from scratches as the chemical bonds that join the individual sugar units cannot be digested by human enzymes in the GI tract - This prevents the small intestine from absorbing the sugars bc they can’t be released from the various fibers - Fiber is not a single substance but is a group of substances of similar characteristics - Carb cellulose, hemicelluloses, pectins, gums and mucilages, and noncarb lignin - Nutrition facts label the individual forms of fiber together under the term dietary fiber - This type of fiber is commonly referred to as roughage - Cellulose, hemicelluloses and ligning form the structural part of plants - Bran layers form the outer covering of all grains and are rich in hemicelluloses and lignin - Whole grains are good sources of bran fiber - Bc majority of these fibers are not readily dissolved by water and not easily metabolized by intestinal bacteria, they are called insoluble or non fermentable fibers - Found in wheat bran, buts, fruit skins and some other veggies - Acts as a natural laxative bc it speeds up the transit time food through the GI Tract - Pectins, gums and mucilages are contained around and inside plant cells

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- Either dissolve or absorb water and are therefore called soluble or viscous fibers Readily fermented by bacteria in large intestine Found in beans, oats, oat bran, some fruits and veggies Soluble fibers slow the rate of absorption by attracting water into the GI tract, reduces blood cholesterol and controls blood glucose

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Definition of fiber has recently been expanded to include - Dietary fiber - Describes the nondigestible carbs and lignin that are naturally occurring and intact in plants - Functional fiber - Consists of the isolated nondigestible carbs that are added to food because they have beneficial physiological effects in human beings Dietary fiber is an important substrate for the gut microbiota, so the dietary fiber alterations have an immediate and direct impact on gut microbes Gut microbiota is also intimately linked to immune fxn Probiotics are live organisms that colonize the GI tract and confer health benefits on the host Postbiotics refers to products or metabolic by products that are secreted by live bacteria -

4.3: Carbs in Foods - Most dietary carbs comes from starches - Because plants store glucose in the form of starches, plant based foods are the best sources of starch - Sugar sweetened beverages (SSBs) are liquids that are sweetened with added sugars - The food sources that yield the highest percentage of calories from carbs are table sugar, honey, jam, jelly, fruit and plain baked potatoes Whole Grains - Dietary Guidelines recommend that we consume at least half of all grains as whole grains - We can increase whole grain intake by replacing refined grain with whole grains and limiting the consumption of foods that contain refined grains - Guidelines define whole as the entire grain seed or kernel made of three components, bran, germ and endosperm -

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Although fiber is one of the primary advantages of whole grains, many benefits of whole grains are thought to be due to the combined effects of several compounds - Fiber, minerals, trace minerals, vitamins, carotenoids and other phytochemicals Guideline recommend consuming two to four services of whole grains per day - Risks of cardiovascular disease, DBT, metabolic syndrome, some cancers and obesity Estimated that about 95% of people don’t meet the whole grain recommendation that at least half of all grains consumed by whole grains Reasons - Taste, texture, cost, availability of whole grains compared to products made with refined flour To confirm that products contain 100% of whole grain, look for whole as the first on the ingredient list

Vegetables - Valuable source of carbs in the form of starch and fiber - Naturally low in fat, calories and come packed with many other nutrients vital for health including potassium, folate, vitamin A and C - Amount of vegetables depends on age, sex and level of physical activity Fruits - Provide carbs primarily in the form of natural sugar and fiber - Eating fruits provides health benefits similar to those discussed for vegetables - Dietary fibers from fruits help reduce blood cholesterol levels, lower risk of disease and important for proper BM and fxn Dairy - Provide carbs in the form of lactose - Also provide other key nutrients, like Ca, K, Vitamin D and protein Nutritive Sweeteners - Nutritive Sweeteners - Provide calories for the body - Alternatives sweetness, provide no calories - Much sweeter on a per gram basis than nutritive sweeteners - Sugars - All mono and disaccharides are nutritive sweeteners bc they provide calories - Dietary guidelines recommend that we reduce the intake of calories from added sugars - NHANES indicate that 13% of our total energy intake is from added sugars and that 39% of the added sugars comes from SSB - Guidelines recommend a dietary pattern has less than 10% of calories from added sears - HFCS is a sweetener - Average american consumes about 24 lb of HCFCS each year - Sugar Alcohols - Are carbs with a chemical structure that partially resembles both sugar and alcohol, but doesn’t contain alcohol - Incompletely absorbed and metabolized by the body and consequently contribute fewer calories than most sugars - Used as nutritive sweeteners but contribute fewer calories than sugars - Absorbed and metabolized to glucose more slowly than are simple sugars - Must be listed on labels Alternative Sweeteners - Yield few or no calories when consumed in amounts typically used in food products - Not metabolized by bacteria in the mouth so they do not promote dental caries - Current evidence suggests that alternative sweeteners can be used safely by adults and children and they are considered safe during pregnancy

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Acesulfame K - Approved for use as a general purpose Sweetener Advantame - Safe for cooking Allulose - Safe for cooking Aspartame Saccharin Stevia LuoHan Guo Sucralose

4.5: Making Carbohydrates Available for Body Use Starch and Sugar Digestion - When starches are heated, the starch granules well as they soak up water, making them easier to digest - The enzymatic digestion of scratch begins in the mouth, when the saliva, which contain an enzyme called salivary amylase, mixes with carbohydrate containing food products during the chewing of food - Breakdown scratch into smaller units - Usually food is in the mouth for such a short amount of time that this phase of digestion is negligible - Once the food moves down the esophagus and reaches the stomach, the acidic environment inactivates salivary amylase

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When the carbs reach the small intestine, the more alkaline environment of the intestine is better suited for further carb digestion - Pancreas releases enzymes to aid the last stage of starch digestion - The disaccharides are digested to their single monosaccharide units once they reach the wall of the small intestine, where the specialized enzymes on the absorptive cells digest each disaccharide into monosaccharides Lactose Maldigestion and Lactose Intolerance - The most common form of this condition s primary lactose maldigestion, a normal pattern of physiology that often begins around ages 3-5 years old - Estimated to present in about 75% of the world’s population - Secondary lactose maldigestion, temporary condition, lactase production is decreased to another condition, such as intestinal diarrhea - Rarely, lactase production is absent from birth, a condition known as congenital lactase

deficiency - Sx: gas, abd bloating, cramps, diarrhea when lactose is consumed - Diarrhea is caused by undigested lactose in the large intestine as it draws water from the circulatory system into the large intestine - When significant sx develop after lactose intake, it is then called lactose intolerance - Important to note that lactose maldigestion and resultant lactose intolerance are not equivalent to a milk allergy - In North America, only about 25% of adults show signs of decreased lactose digestion in the small intestine - Asian, African and Mexican american are the most likely to suffer from lactose maldigestion Carbohydrate Absorption - Mono found naturally in food and those formed as by products of starch and disaccharide digestion in the mouth and small intestine generally follow an active absorption process - Pumped into the absorptive cells along with Na - Fructose is taken up by the absorptive cells via facilitated diffusion - Carrier is used, but no energy input is needed - Large doses of fructose are not readily absorbed and can contribute to diarrhea as the monosaccharide remains in the small intestine and attracts water - Once glucose, galactose, and fructose enter the absorptive cells, some fructose is metabolized into glucose - Single sugars in the absorptive cells are then transferred to the portal vein that goes directly to the liver - Liver then metabolizes those sugars by transforming the monosaccharides galactose and fructose into glucose - Releases it directly into the bloodstream for transport to organs such as the brain and kidneys and to muscles and adipose tissues - Produces glycogen for storage of carbs - Produces fat when carbs are consumed in high amounts and overall calorie needs are exceeded Fiber and Intestinal Health - Bacteria in the large intestine ferment soluble fibers in such products such as acids and gases - Acids once absorbed provide calories for the body - Many gas forming foods are good sources of soluble fiber - Bc insoluble fiber is an indigestible carb, it remains in the intestinal tract and supplies bulk to the feces, making elimination much easier - When enough fiber is consumed, the stool is large and soft bc many types of plant fibers attract water - The larger size stimulates the intestinal muscles to contract, which aids elimination - Less pressed is necessary to expel the stool - When too little fiber is eaten, the opposite can occur - Very little water is presented in the feces, making it small and hard - Forces individual to have high pressure when defecating - High pressure can cause surrounding bands of muscle to form many small pouches called diverticula

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Hemorrhoids may also result from excessive straining during defecation In about 80% of people affected with diverticular, no sx are present The asymptomatic form of this disease is called diverticulosis - Feces become trapped within diverticula, the diverticula may become inflamed or infected, a painful condition known as diverticulitis

Very high intake of fiber, about 60 grams a day, can also provide health risks and should only be done under the care of a PCP Increased fluid intake is extremely important with a high fiber dietary pattern Many population studies shown a link between increased fiber intake an a decrease in colon cancer development Overall the health benefits to the colon that stem from a high fiber dietary pattern are partially due to the nutrients that are most commonly present in most high fiber foods, such as vitamins, minerals, phytochemicals and in some cases fatty acids

4.5: Putting Carbohydrates to Work in the Body Providing Energy - Main fxn of glucose is to supply calories for use by the body - Certain issues in the body can only use glucose and other simple carbs for fuel - In that case, the brain can use partial breakdown products of fat, called ketone bodies, for energy needs - Other body cells, including muscle cells, can use simple carbohydrates as fuel, but many of these cells can also use fat or protein for energy needs - Dietary pattern that supplies enough digestible carbs to prevent breakdown of proteins for energy needs is considered protein sparing - Under nl circumstances, digestible carbs end up as blood glucose and protein is reserved for fxn such as building and maintain muscles and vital organs - If you don’t eat enough carbs, body is forced to make glucose from body proteins, draining the

pool of amino acids available in cells for other critical functions During long term starvation, the continuous withdrawal of proteins from the muscles, heart and liver and kidneys can result in weakness, poor function and even failure of body systems - Wasting of protein can be life threatening - In addition to loss of protein, the metabolism of fats is inefficient - Fast are not broken down completely in metabolism and instead form ketone bodies - Ketosis Regulating Blood Glucose - The liver works together with the pancreas to regulate blood glucose - When the concentration of glucose in the blood is high, the pancreas releases the hormone insulin to the blood stream - Insulin delivers two different messages to various body cells to cause the level of glucose in the blood to fall - First, insulin directs muscle, adipose and other cells to remove glucose from the bloodstream by taking it into those cells - Second, insulin directs the liver to store glucose as glycogen - By doing so, insulin keeps the concentration of glucose from rising too high in the blood -

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On the other hand, when a person has not eaten for a few hours and blood glucose begins to fall, the pancreas releases the hormone glucagon Glucagon has the opposite effect of insulin - Prompts the breakdown of liver glycogen into glucose and the generation of glucose from non carbohydrate substances, which is then released into the bloodstream to keep blood glucose from falling too low A different mechanism increases glucose during times of stress - Epinephrine (adrenaline) is the hormone responsible for the fight or flight response

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These hormones can cause glycogen in the liver to be quickly broken down into glucose - The resulting rapid flood of glucose from the liver into the bloodstream helps fuel quick mental and physical reactions - Hyperglycemia (high blood glucose) - Hypoglycemia (low blood glucose) - Type 1 Diabetes is an example of underproduction of insulin - Lifestyle Management and Blood Glucose Control - Individuals are encouraged to consume a primarily plant based dietary pattern rich in carbs, from vegetables whole grains and fruits to dairy products - Less sugar intake - Glycemic Response and Blood Glucose - The effects of various food on blood glucose are important to know because foods that result in higher blood glucose level cause a larger release of insulin from the pancreas - When this higher insulin output occurs frequently, it leads to delirious effects on the body - As insulin rapidly pulls glucose from the blood and into cells, hunger regulating hormones are released, thus promoting increased carb intake - Overtime, this increase in insulin output may also cause the muscles to become resistant to the action of insulin and eventually lead to type 2 diabetes in some people - The GI (Glycemic Index) is a measuremen...