Brock University Carbohydrates Lecture PDF

Faculty of Applied Health Sciences Department of Health Sciences Carbohydrates NOTE: If its important and needed to know for midterm’s then it is also VERY IMPORTANT for the final exam  Faculty of Applied Health Sciences Departme...

Faculty of Applied Health Sciences Department of Health Sciences Carbohydrates NOTE: If its important and needed to know for midterm’s then it is also VERY IMPORTANT for the final exam  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrates Learning goals 1. Identify the monosaccharides, disaccharides, and polysaccharides and list their major food sources. 2. Explain the process of carbohydrate digestion, absorption, transport, and storage. 3. Describe the glycemic index and explain how it may be used. 4. Explain how hormones control blood glucose concentrations. 5. Identify the health benefits of, and recommendations for, starches and fibers. 6. Define limits of added sugars and describe how alternative sweeteners may help to limit kcalories and sugar intake. 47 Faculty of Applied Health Sciences Department of Health Sciences Carbohydrates (CHO) 48  Faculty of Applied Health Sciences Department of Health Sciences Source Plants convert sunlight into carbohydrates through photosynthesis (process in which green plants use sunlight to make their own food) CHO (glucose) are formed from carbon dioxide and water during the process of photosynthesis (carbo=carbon, hydrate=water) Glucose and oxygen are the final products of photosynthesis 49  Faculty of Applied Health Sciences Department of Health Sciences Simple carbohydrates Monosaccharide (single sugar units, mono=one, saccharide=sugar) – glucose – fructose – galactose NEED TO KNOW WHICH ARE THE MONOSACCHARIDES 50  Faculty of Applied Health Sciences Department of Health Sciences Glucose (Monosaccharide) Most important carbohydrate – one of the two sugars in disaccharides (sucrose, lactose, maltose)glucose – unit from which polysaccharides are made of – focus of CHO metabolis Also called “Blood sugar” or “dextrose” Most cells rely on glucose for fuel Brain and nervous system rely on it almost exclusively Obtained from carbohydrates Body maintains glucose blood levels within limits that allow for cell nourishment (homeostatic regulation of this through insulin and grenilen system) 51  Faculty of Applied Health Sciences Department of Health Sciences Fructose Known as fruit sugar (fruct=fruit) – found naturally in fruits, vegetables, honey, and part of table sugar – sweetest of the monosaccharides – it is used as a sweetener – high fructose corn fructose syrup – along with glucose, the most common monosaccharides in nature g the second stage of photosynthesis, glucose is transformed into fructose and other sugar molecules 53  Faculty of Applied Health Sciences Department of Health Sciences Galactose Rarely occurs alone in foods (not found by itself) galactose Mostly occurs as part of lactose (milk sugar, disaccharide) Byproduct of digestion (freed from lactose during digestion) 54  Faculty of Applied Health Sciences Department of Health Sciences NEED TO KNOW THE TYPES Disaccharides Disaccharides (pairs of sugar units bonded together, di=two) – maltose In all of these at least one of the two sugars is – sucrose glucose – lactose Combination of pairs of monosaccharides All disaccharides have glucose as one of the single sugars, combined with a second Link two monosaccharides by condensation Break up into two mono-saccharides by hydrolysis 55  Faculty of Applied Health Sciences Department of Health Sciences Condensation Form a bond between two compounds Water is released Condensation Glucose Fructose Sucrose 57  NEED TO BE AWARE OF THE CHEMICAL REACTION ANF COMPARE B/W TH Faculty of Applied Health Sciences Department of Health Sciences Hydrolysis Bond is broken (“lysis”) Water is required for this Hydrolysis reaction (“hydro”) 58  Faculty of Applied Health Sciences Department of Health Sciences Maltose Maltose (glucose + glucose) Plant sugar Composed of two glucose units Known as “Malt sugar” Does not generally occur naturally in foods (but occurs in plants during break down of stored starch and in humans during carbohydrate digestion) 59  Faculty of Applied Health Sciences Department of Health Sciences Sucrose Sucrose (glucose + fructose) Composed of glucose and fructose “Table sugar” from sugar beets or sugar cane (sucro=sugar) 60  Faculty of Applied Health Sciences Department of Health Sciences Lactose Glucose and galactose Lactose (glucose + galactose) Known as “Milk sugar” (lact=milk) NEED TO KNOW THIS! Lactose intolerance (inability to digest lactose due to the loss or reduction of the intestinal enzyme, lactase) – develops in premature babies but improves over time – develops as we age – injury to small intestines (e.g. infection, celiac disease, Inflammatory Bowel Disease IBD) – genetic disorder 61  Faculty of Applied Health Sciences Department of Health Sciences Summary – Simple carbohydrates TABLE 3-1 The Major Sugars Monosaccharides Disaccharides Glucose Sucrose (glucose + fructose) Fructose Lactose (glucose + galactose) Galactose (found primarily as part of Maltose (glucose + lactose glucose) 62  Faculty of Applied Health Sciences KNOW THE MAJOR OF EACH THESE TYPES Department of Health Sciences Complex carbohydrates Oligosaccharides & polysaccharides More than two monosaccharides (e.g. glucose) – starch – glycogen – fibre Starch, glycogen and fibers are major polysaccharides 63  Faculty of Applied Health Sciences Department of Health Sciences Starch Multiple glucose units (occasionally branched or unbranched) Storage form in plants (grains ex. rice, legumes ex. beans, tubers ex. potatoes) Major source of digestible CHO in the diet (some starches are not digestible – resistant starch e.g. unripe bananas) Resistant starches are carbohydrates that do not break down into sugar and are not absorbed by the small intestine. Similar to insoluble fibre, they pass through most of the digestive system unchanged, usually fermenting in the colon. 64 Faculty of Applied Health Sciences Department of Health Sciences Starch (cont’) resistant starch short chain fatty - acids (butyrate) via bacterial fermentation 65  Faculty of Applied Health Sciences Department of Health Sciences Glycogen This is how we storage CHO within the body!!!! Multiple glucose units Not a significant food source of carbohydrate (you do not really need this in your diet/ not a large aspect of your deit) Important role in carbohydrate storage in the body – muscle – liver 66  Faculty of Applied Health Sciences Department of Health Sciences Fibres Non-starch polysaccharides Structural part of plants (found in all plant-derived foods ex. vegetables, fruits, whole grains, legumes) Similar to starches but indigestible (digestive enzymes cannot break bonds, some fibres can be digested only by bacteria) 67  Faculty of Applied Health Sciences Department of Health Sciences NEED TO KNOW THE DIFFERENCE Fibres (cont’) Dietary fibre (soluble and insoluble) is the non-digestible part of plants (e.g. grains, rice, seeds, legumes, fruits), and it is found naturally in foods, has health benefits Functional fibre is non-digestible carbohydrate extracted from plants and added to foods and supplements (e.g. cellulose, guar gum, pectin, psyllium), has health benefits Total fibre = dietary fibre + functional fibre Different types of fibre have different properties Traditionally classified as soluble fibre and insoluble fibre 68  Faculty of Applied Health Sciences Department of Health Sciences Soluble fibres Absorb water to form a gel Fermented and broken down by bacteria in colon producing gasses and short chain fatty acids Examples: pectins, gums, and mucilages (found in fruits, oats, barley, legumes like beans and peas, vegetables) Just need to know what they do Slow GI motility briefly and know the examples – delay gastric emptying + highlighted area – lower blood cholesterol (talk more about this in upcoming lecture) – delay glucose absorption – enhance satiety (feeling full for longer) 70  Faculty of Applied Health Sciences Department of Health Sciences Know the examples and at least the highlighted part Non-soluble fibres Do not dissolve in water and do not form a gel Non-fermentable – provide bulk and feeling of fullness; enhance satiety – may help with weight management – help with constipation: enhance stool formation (add bulk to the stool), speed fecal passage through colon e.g. lignin, cellulose, and hemicellulose (found in wheat, vegetables, whole grain cereals like bran flakes, and breads) Insoluble fibre does not dissolve in water. Insoluble fibre can add bulk to the stool. Sources include wheat bran, whole grain cereals and breads, and many vegetables. 71  Faculty of Applied Health Sciences Department of Health Sciences Digestion – Digestible CHO Mouth and salivary glands – salivary amylase – breaks down starch into small polysaccharides (a lot of glucose connected) and maltose Stomach – acid inactivates salivary amylase, halting starch digestion For ex. if you eat carbohydrate foods like bread, pasta, crackers etc their digestion will start in the mouth. 72  Faculty of Applied Health Sciences Department of Health Sciences Digestion – Digestible CHO & Absorption Pancreas – pancreas secretes pancreatic amylase into small intestine to digest starch into small polysaccharides and maltose Small intestine – Enzymes (maltase, sucrase, lactase) hydrolyze disaccharides (maltose, sucrose, lactose) into monosaccharides (glucose, fructose and galactose) (break down via hydrolysis) – Monosaccharides are absorbed across the microvillus membrane of the small intestine into Portal Vein the portal vein (blood system) for transport to the liver. 73  Faculty of Applied Health Sciences Department of Health Sciences Glucose Absorption Glycemic response 73 – glucose absorption after a meal 38 Glycemic index – potential to raise blood glucose – measures how quickly carbohydrate in food is absorbed – compared to pure glucose (GI=100) 78 74  Faculty of Applied Health Sciences Department of Health Sciences Glycemic index DO NOT NEED TO KNOW NUMBERS BUT NEED TO KNOW WHAT IT IS? & WHAT IT MEASURES? 75  Faculty of Applied Health Sciences Department of Health Sciences Glycemic index Factors that influence glycemic index (GI): starch structure, fiber content, presence of fat and protein, food processing, mixture of foods in a meal, individual glucose tolerance Some research indicates low-GI diet may decrease risk for some chronic diseases (e.g. type 2 diabetes & heart disease) More research needed to confirm 76  Faculty of Applied Health Sciences Department of Health Sciences Storage - CHO Excess carbohydrate stored as glycogen – main storage form of glucose – excess carbohydrates can also be stored as fat – Stored 1/3 within the liver and 2/3 within the muscles - Galactose is quickly and almost completely metabolized to glucose in the liver. 2/3 - Fructose is digested in the liver to produce mainly glucose. - Glucose travels through the bloodstream to all organs and muscles, where it is 1/3 transformed into energy. 77  Faculty of Applied Health Sciences Department of Health Sciences Glucose homeostasis Glucose is an important fuel – preferred fuel source for neural tissue (including brain) and developing erythrocytes (red blood cells) 78  Faculty of Applied Health Sciences NEED TO KNOW Department of Health Sciences Glucose homeostasis Insulin – produced by beta cells of the pancreas – helps cells take-in glucose from the blood – facilitates glucose uptake by muscles and adipose tissue – stimulates the liver and muscle to take up glucose and convert it to glycogen – overall effect of lowering blood glucose - Insulin is the key that unlocks the glucose channels to allow glucose uptake from the blood stream into a cell - Glucose channel is a type of glucose transporter (GLUT). GLUTs are proteins that form channels in cell membranes to allow glucose to pass through. 79  Faculty of Applied Health Sciences Department of Health Sciences Glucose homeostasis Glucagon produced by alpha cells of the pancreas stimulates the breakdown of glycogen to glucose (glucose is exported from liver but not muscle) more glucose is available to cells of the body stimulates gluconeogenesis – the production of glucose from amino acids in the liver overall effect: increases the concentration of glucose within the blood (increases blood glucose) 80  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrate Recommendations RDA (Recommended dietary amount, Health Canada) of 130 g of digestible carbohydrates /day for adults o Adequate for normal brain function ONLY (PUT IN HELP SHEET) o DOES NOT account for daily activities 130 g per day for adequate supply to the brain NOT daily activities! 81  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrate Recommendations NEED TO KNOW- PUT INTO HELPING SHEET Total carbohydrates: 45-65% caloric input (Health Canada’s recommendation) – 200-330 g/day men – 180-230 g/day women Erythrocytes (red blood cells) use only glucose Brain and nervous tissue primarily rely on glucose Major source of energy 82  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrate Recommendations Does 290 g of CHO satisfy Health Canada’s recommendations assuming a 2000 kcal/day diet? MAY ASK US: this on exam Need to convert g to kcal – 290 g X 4 kcal/g = 1160 kcal Compare kcal of CHO to total kcal – 1160 kcal CHO/ 2000 kcal total = 58% Reference against Health Canada’s recommendation of 45-65% 2300 kcal total 150g x 4kcal/g= 600kcal Eats 150g of CHO 600kcal CHO/ 2300 kcal X 100 =26% Therefore, this is not within the Health Canada recommendations 83  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrate Recommendations Carbohydrates spare proteins by preventing their breakdown as an energy source When carbohydrate intake is low, proteins are used for gluconeogenesis (break down of protein to glucose) Relying on body or dietary protein as a source of energy (glucose) may lead to problems (i.e. development, repair, maintenance) 84  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrate Recommendations Total fibre About 14 g of dietary + functional fibre/1000 kcal/day NEED TO REMEMBER THIS Grains Fruit e.g. if someone has energy intake of 2000kcal/day, the recommended intake of fibre per day is about 28 g Ex. 2500 kcal/day, you need 35g of fibre per day Vegetables Legumes & nuts 85  Faculty of Applied Health Sciences Department of Health Sciences Carbohydrate Recommendations Added sugars Simple CHO in our diets – fruit, vegetables, and milk (healthy) – “added sugars”, defined as sugars and syrups added to foods during processing or preparation According to WHO: NEED TO KNOW THIS limit added sugars to 10% or less of total daily energy (for a 2000 kcal /day diet, that is equivalent to ~12.5 tsp of sugar!) (10% is equal to 200kacl/4kcal= 50g) greater benefits expected from an intake of less than 5% of day’s total kcalories 86  Faculty of Applied Health Sciences Department of Health Sciences Sugar alternatives Control kcals and limit added sugar intake Two types – nutritive sweeteners (sugar alcohols) – non-nutritive or artificial sweeteners 87  Faculty of Applied Health Sciences Do not need to know the numbers Department of Health Sciences Nutritive Sweeteners Sugar alcohols Relative Energy sugarlike compounds which Sugar alcohol sweetness compared (calories) Food found in per gram occur naturally in fruits and to sucrose vegetables or manufactured Candies, Isomalt 0.5 2.0 from CHO chewing gum “sugar-free” but not “calorie- Candies, Lactitol 0.4 2.0 free” chewing gum most sugar alcohols less sweet Candy Maltitol 0.9 2.1 than sucrose coating metabolized different than Bulking sucrose (sugar), lower Mannitol 0.7 1.6 agent, chewing gum glycemic response side effects: gas, abdominal Sorbitol 0.5 2.6 Candies, discomfort, and diarrhea chewing gum Nutritive sweeteners: sweeteners that yield energy, including both the sugars and the sugar alcohols 88  Faculty of Applied Health Sciences DO NOT NEED TO KNOW NUMBERS Department of Health Sciences Non-nutritive sweeteners Provide little or KNOW THESE FOUR ARE NON-NUTRITIVE SWEATENERS no energy Sweetener Relative sweetnes Energy (calories) ADI (mg/kg Products Examples Examples more sweet than s per gram body wt/day) sucrose Aspartame 200 4* 50 Equal, (e.g. 600 times) Nutrasweet “Safe” with Saccharin 300 0 5 Sweet n’ Low (US) established Sucralose 600 0 5 Splenda acceptable daily Stevia 200-300 0 4 Truvia, intakes (ADI) PurVia Non-nutritive sweeteners: synthetic or natural food additives that offer sweet flavor but with negligible or no kcalories per serving 89