Human Nutrition Chapter 4

Chapter 4     monosaccharides:  glucose  galactose  fructose o disaccharides:  sucrose (glucose + fructose)  maltose (glucose + Glucose)  lactose (lactose + galactose) Complex or Polysaccharides: o chains of glucose linked together o plant forms: starch and fibre  human digestive enzymes can break the bonds between glucose units in starch but not in fibre (cellulose) o animal form: glycogen (more branched)  human digestive enzymes can break the bonds  found in liver and muscle (meat) - broke down at slaughtering Recommendations: o DRI: 45-65% of energy from carbohydrates, emphasis on complex and whole grain  <25% of energy from added sugars o Nutrition recommendation Canadians (2003)  55% energy from CHO o food sources: pasta, rice, cereals, breads, milk/milk products, fruits, starchy vegetables (potatoes, peas, corn, squash) Dietary fibre: o suggested intake:  WHO: >25g per day  DRI: <50 years: males 38g/day; females 25g/day  >50 years; males 30g/day females 21g/day o    carbohydrates: carbon, hydrogen, oxygen (CHO) energy cycles: o through photosynthesis, plants combine carbon dioxide, water and the sun’s energy to form glucose o when humans metabolize glucose, energy and carbon dioxide are release Types: o simple CHO (sugars) o complex CHO or polysaccharides (fibre and starch) Simple sugars: o Types of fibre:  water soluble fibre:  types: gums, mucilages, pectins, psyllium, some hemicellulose  sources: oats, oat bran, barley, rye, seeds, fruits, vegetables, legumes  benefits: lower blood cholesterol  slow glucose absorption  slow transit of food through upper digestive tract  hold moisture in stools, softening them  yield small, fat like molecules after fermentation that the colon can use for energy  lower risk of heart disease and diabetes  water insoluble fibre:  types: cellulose, lignin, and some hemicellulose  sources: brown rice, wheat bran, whole grains, seeds, fruits, vegetables, legumes  benefits: increased fecal weight      Consumer corner:  whole grain bread, enriched and unenriched bread How carbohydrates in food becomes glucose in the body o mouth: minor digestion by salivary amylase o small intestine: digestion by pancreatic amylase (starch —> disaccharides) and enzymes on intestinal wall  (Disaccharide —> monosaccharides) o Fibre travels unchanged to the colon o Absorption of glucose, fructose and galactose into bloodstream —> liver o Liver converts galactose and fructose to glucose o All digestible CHO becomes glucose in the body and is used for  Energy (directly or from glycogen stores)  Glycoproteins (CHO attached to proteins)  E.g. mucus, cell membranes Postprandial CHO metabolism o Blood glucose rises after eating CHO and amount of increase reflects:  Amount of CHO consumed  Rate of digestion and rate of glucose entry into bloodstream  Rate of glucose uptake by the cells o Blood glucose: under homeostasis: is tightly regulated  Normal fasting blood glucose level is 4 —6 mmol/L  Hypoglycaemia = low blood glucose  Hyperglycaemia = high blood glucose o   increase colonic transit alleviate constipation reduce risk or diverticular disease (intestinal wall bulges out due to weakening of muscle layers) hemorrhoids, and appendicitis provide bulk and feeling of fullness weight management When blood glucose is high (fed state), the pancreas releases insulin  2/3 glucose taken up by muscle and stored as glycogen  1/3 glucose taken up by liver and stored as glycogen or converted to fat o Glucose is transported into most cells via insulin (hormone) i.e. insulin “open the gate” to let glucose into the cells  Except brain, nerves, red blood cells, mammary glands o When blood glucose is low, the pancreas releases glucagon (hormone)  Breakdown of liver glycogen — glucose — blood — tissues for energy  Glucose is produced from protein (gluconeogenesis)  If this occurs on a longterm basis (e.g. disease states) then muscle wasting o Human Nutrition - 07.02.2020  Ketosis: Need minimum 130g CHO/day to prevent ketosis and to spare protein (muscle) Usually consume 200-400 CHO/d Liver glycogen lasts 4-6 hrs depending on CHO intake, exercise etc. If liver glycogen is depleted, then ketosis occurs In-class Quiz:  Glycemic index (GI) refers to a rise in the following after a meal  Goes into blood  All sugar is transformed into glucose in the body  The low GI of kidney beans is because it is high in amylose (not amylopectin)  Takes more time to digest- linear structure  In starches, the linear chain is amylose and enzymes have a hard time penetrating  Which of the following does not lower the GI of a food?  Fructose - monosaccharide  Would raise the GI of food  Cirrhosis of the liver comes form excess fat synthesis  Alcohol stimulates fat synthesis in the liver both acutely and chronically  Liver deterioration: fatty liver — fibrosis - cirrhosis o o o o    Diabetes: o Type 1: early or mid-life, (<10% of cases)  Hyperglycaemia due to little or no insulin produced by the pancreas  Auto-immune response  Untreated: glucose wasting (urine) and weight loss  Treatment: insulin is injected to match food intake and physical activity o Type 2: (usually adult, now children/teens; >90% cases)  Hyperglycaemia due to insulin resistance (associated with overweight and obesity)  Pancreas produces lots of insulin but cells response poorly  Chronic hyperglycaemia increases risk of cardiovascular disease, kidney disease, cataracts / blindness, amputations Risk factors:  Family history  Sedentary lifestyle  Overweight/obses  Moderate weight gain in adulthood  History of gestational diabetes  Genes: Aboriginal, African American, hispanic, Asian, Pacific Island descent o Warning signs of diabetes  Excessive urination and thirst  Glycosuria (glucose in urine)  Weight loss, nausea, weakness, irritability  Cravings for food, especially sweets  drowsiness  Vision disturbances  Frequent infections (e.g. skin and itching)  Slow healing of cuts and bruises  Pain in legs, feet or fingers  Abnormally high glucose tolerance test results o Management  Of type 2 diabetes  Diet and physical activity NB  10% weight loss is beneficial  Oral agents  Sometimes insulin injections Glycemic index of food o Extent to which foods elevate blood glucose compared to a glucose solution or white break o Low number is best: legumes and peas o High number: white bread, juice o Factors:  Type of food  Apple < apple juice  Cooking method  Baked potato < mashed  Eaten alone or part of a mixed meal CHO Counting o Simple, flexible meal planning tool o Want consistent CHO intake at meals o Grains, fruits, milk, sweets all CHO choices  1 grain & starch of choice = 15g CHO  1 fruits choice = 15g CHO  1 milk & alternatives choice = 15g CHO o Meat and alternatives, and fat choices do not contain CHO Lactose intolerance o Insufficient lactase enzyme activity to digest lactose — glucose + galactose  Develops in adults of non-Northern European background o    Signs: nausea, pain diarrhea and gas  More osmotic particles draws water  Bacterial fermentation in intestine o Management  Consume milk in small amounts (1/2 - 1 cup) with meals  Yogurt, aged cheeses  Products treated with lactase  Lactic milk etc.  Add enzyme drops to milk-based foods  Lactic pills Milk allergy o Immune response to protein in milk o  Need non-dairy sources of calcium  Calcium fortified soy milk and orange juice  Canned sardines or salmon with bones  Vegetables (broccoli, boh choy)  Consider a calcium supplement Controversy 4: Sugars in health o Obesity? Aggravating diabetes? Increased risk for heart disease? Behavioural problems? Dental problems? o Use sugar in moderation <10% calories from added sugars (DRI: <25%)  200 calories = 13 teaspoons Sweeteners o Sugar alcohols  Members of chemical alcohol family (structure0  Sorbitol, mannitol, xylitol, isomalt, Maltitol, lactitol  Not readily used by mouth bacteria  All have 3-5 calories/g but poorly absorbed o Articifical sweeteners  Aspartame (200x sweeter than sucrose)  Acesulfame-K (600x sweeter than Sucralose)  Cyclamate and saccharin have restricted uses in Canada  Calorie free since so little is used  Safety:  Acceptable daily intake (ADI) is the estimated amount of sweetener that can be consumed daily over a person’s lifetime without adverse effects  40mg/kg of body weight for aspartame in Canada  150lb (68kg) person: ~72 packets of Equal or ~13 soft drinks o  