The Carbohydrates Sugars Starches and Fibers Lancelot Mc

The Carbohydrates: Sugars, Starches, and Fibers Lancelot Mc. Lean, Ph. D lmclean@llu. edu Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Introduction § Brain use: § Glucose § Muscles use: § Glucose § Glycogen § Fat § Sources of carbohydrates § All plant foods: whole grains, vegetables, legumes and fruits § Milk also contains carbohydrates Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrates § Carbohydrate family § Monosaccharides § Glucose, fructose, galactose § Disaccharides § Maltose = glucose + glucose § Sucrose = glucose + fructose § Lactose = glucose + galactose § Polysaccharides § Glycogen = glucose units § Starches (amylose and amylopectin) = glucose units § Fibers (soluble and insoluble) Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrates Monosaccharides • Glucose and fructose – principal monosaccharides found in food • Glucose – abundant in fruits, sweet corn, corn syrup and honey • Free fructose – found together with free glucose and sucrose in honey and fruits Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrates Monosaccharides Ø High fructose corn syrup (HFCS) – Corn syrups that have undergone enzymatic processing to convert their glucose into fructose and have been mixed with pure corn syrup (100% glucose) to produce a desired sweetness – In the US HFCS 55 (55% fructose and 42% glucose) is commonly used as a substitute for sucrose in beverages, including soft drinks – HFCS 42 (42% fructose and 53% glucose) used in processed foods Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrates Disaccharides • Sucrose – Table sugar • Lactose – Principal sugar in milk • Maltose – Found in significant quantities in beer and malt liquors Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrates Polysaccharides • Complex carbohydrates – do not have a sweet taste • Examples: – Starch found in plants – Glycogen in animals • Common sources of starch: – – wheat and other grains potatoes dried peas and beans vegetables Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrates Fiber • Nondigestible carbohydrates and lignin (complex polymer of phenylpropanoid subunits) present intact in plants • Provides little energy but has several beneficial effects – Adds bulk to the diet – Can absorb 10 -15 times its own weight in water drawing fluid into the lumen of the intestine and increasing bowel motility – Delays gastric emptying – Lower LDL cholesterol by increasing fecal bile acid excretion and interfering with bile acid absorption – Decrease risk of constipation, hemorrhoids and diverticulitis Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrate Digestion § Ultimate goal § Glucose for absorption and use § Hydrolysis via enzymes § Mouth § Amylase hydrolyze starch to shorter polysaccharides and to maltose § Stomach acid & protein-digesting enzymes § Fiber delay gastric emptying; provides a feeling of fullness Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrate Digestion § Small intestine § Most carbohydrate digestion § Pancreatic amylase § Continues breakdown of polysaccharides to shorter glucose chains and maltose § Specific disaccharide enzymes § Maltase breaks down maltose § Sucrase breaks down sucrose § Lactase breaks down lactose § Large intestine § Fibers attract water which soften stools for passage without straining Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Carbohydrate Absorption Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Breaking Down Nutrients for Energy Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Lactose Intolerance § Lactase activity § Highest immediately after birth § Declines with age § Symptoms of intolerance § Bloating, abdominal discomfort, and diarrhea § Prevalence § Genetically determined Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Blood Glucose Homeostasis Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Blood Glucose Homeostasis § Diabetes § Blood glucose rises after a meal and remains above normal levels § Insulin is either inadequate or ineffective § Type 1 diabetes: § Pancreas fails to produce insulin § Type 2 diabetes § Cells fail to respond to insulin Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Blood Glucose Homeostasis § Hypoglycemia § Blood glucose below normal level § Poorly managed diabetes is most common cause § Too much insulin § Strenuous physical activity § Inadequate food intake § Illness that causes blood glucose levels to plummet § Rare in healthy people Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Glycemic Index § Glycemic response § How quickly glucose is absorbed after a person eats, how high blood glucose rises, and how quickly it returns to normal § Low glycemic response § Desired Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Glycemic Index • Some carbohydrate-containing foods produce a rapid rise followed by a steep fall in blood glucose concentration, whereas others result in a gradual rise followed by a slow decline (differ in glycemic index) Glycemic index (GI) is a method of classifying foods according to their potential to raise blood glucose. Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Glycemic Index • Low glycemic index foods tend to create a sense of satiety over a longer period of time • How much a typical serving size of a food raises blood glucose is termed glycemic load (GL) Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Glycemic Index of Selected Foods Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Effects of Sugars on the tooth § Dental caries § Bacteria ferment sugars producing acid § Food factors associated with tooth decay § Time of food in mouth § Sticky foods stay on teeth longer § Sugar in juice consumed quickly is less likely to cause caries than sugar in pastries § Frequency of sugar consumption § Bacteria produce acid for 20 -30 minutes after each exposure § It’s better to eat 3 pieces of candy at once than at 3 separate times Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Effects of Sugars on the tooth § Dental caries § Nonsugary foods can help remove sugar from tooth surfaces § Better to eat sugar with meals than between meals § Foods such as milk and cheese are helpful against caries § § Neutralize acids Stimulates salivary flow Inhibit bacterial activity Promote remineralization of damaged enamel Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Effects of Sugars on the tooth § Drinks that contribute to caries § Soft drinks § Orange Juice § Sports Drinks § Contain sugar as well as have a low p. H § Acidic drinks can erode tooth enamel and may explain why the prevalence of dental erosion is steadily growing Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Oral microbi 0 ta and sugars • The oral microbiota is predominantly saccharolytic and the major fermentation end product is lactic acid • Bacteria metabolizing aerobically exude CO 2 and H 20. • Bacteria metabolizing anaerobically exude Lactic acid • The deeper the plaque, the more anaerobic, the more acid and the lower the p. H • At p. H 5. 5 the enamel begins to dissolve- Demineralization!!!!!!! Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Oral microbi 0 ta and sugars • These lactic acid forming bacteria have a think outer cell wall (gram +ve) which allows them to tolerate the low p. H caused by the lactic acid they are producing § Primary causative agents § Streptococcus mutans § Lactobacillus spp § Lactobaillus casei can survive p. H 1 for a few hours Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Sucrose It is evident that European populations suffered little from caries before the late 18 th century The rise of caries coincided with increased sucrose consumption The most compelling evidence for sucrose causing caries was obtained by comparing the sucrose intake in 12 -year old children from 47 countries (obtained from the WHO’s Global Oral Epidemiology Bank during the 1970 s) with the DMFT (decayed, missing, and filled teeth) during this period The number of affected teeth increased by about 1 DMFT for every 25 g of sugar consumed daily Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Sucrose and Dental Caries Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Effects of Sugars on the tooth • Sucrose is required for growth of Streptococcus mutans, the causative agent for dental caries. • Frequent sucrose consumption causes a 100 fold increase in S. mutans which are the cause of caries • In populations which have inadequate fluoride, the frequent consumption of sucrose guarantees endemic universal caries Whitney & Rolfes – Understanding Nutrition, 12 th Edition

The mineral in teeth is a highly substituted hydroxyapatite Acid makes hydroxyapatite more soluble Flourine makes it more insoluble The unit cell has the formula Ca 10 (PO 4)6(OH)2 Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Dental Caries Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Effects of Sugars on the tooth § Good oral hygiene § Regular brushing and flossing § At least twice a day with a fluoride toothpaste § Restricting sugary food and drink intake Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Recommended intakes for carbohydrate • The absence of dietary carbohydrate leads to ketone body production, and degradation of body protein whose constituent amino acids provide carbon skeletons for gluconeogenesis • Adults should consume 45 -65% of their calories from carbohydrates • Recommended that added sugar represent no more than 25% of total energy because of concerns that sugar may displace nutrient-rich foods from the diet Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Alternative sweeteners § Artificial sweeteners (non-nutritive sweeteners) § Provide virtually no energy § Acesulfame potassium, aspartame, cyclamate, neotame, saccharin, sucralose, tagalose § Herbal products § Stevia § Sugar alcohols (polyols) § Provide kcalories, but fewer than their carbohydrate cousins, the sugars § Also referred to as nutritive sweeteners because they yield energy § Erythriol, isomalt, lactitol, maltitol, mannitol, sorbitol, xylitol Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Health Effects of Starch and Fibers § Heart disease § Whole grains and soluble fiber § Diabetes § High-fiber foods § Cancer § Dietary fiber and colon cancer § GI health § High-fiber foods § Ample fluids § Weight management § High-fiber foods and whole grains § Feeling of fullness Whitney & Rolfes – Understanding Nutrition, 12 th Edition

Health Effects of Starch and Fibers § Excessive fiber § Insufficient energy or nutrient needs § Abdominal discomfort, gas, diarrhea § GI obstruction § Limit nutrient absorption Whitney & Rolfes – Understanding Nutrition, 12 th Edition