Module 4

• KIN275 Introduction to Nutrition Module 4 Carbohydrates
• Julia Totosy de Zepetnek, PhD
• Carbohydrates


  Are they fattening?
• Misconceptions about Carbohydrates


  • They will make you fat
  • They are "bad" for you
  • They will give you diabetes
• You need carbohydrates as part of a healthy, balanced diet
• Body mass is best controlled by diets high in complex CHO & fiber, and low in dietary fat
• Any macronutrient consumed in excess of the body's needs will increase body fat
• Dietary Carbohydrates


  • Module 4 Learning Objectives
  • 1. Discuss carbohydrates and the refining process
  • 2. Compare and contrast the types of dietary carbohydrates
  • 3. Discuss blood-glucose regulation

  
• Types of dietary carbohydrates

  • Simple: Monosaccharides & disaccharides
  • Complex: Oligosaccharides & polysaccharides

  
• Carbohydrates


  Chemical compound consisting of carbon, oxygen, hydrogen, arranged as monosaccharides

  
• Types of Carbohydrates


  • Simple carbohydrates or "sugars": Monosaccharides, Disaccharides
  • Complex carbohydrates (starches, dietary fibre): Oligosaccharides, Polysaccharides

  
• Unrefined carbohydrates


  • Fruits
  • Vegetables
  • Milk
• Refined carbohydrates


  • Table sugar
  • Brown sugar
  • Molasses
• Monosaccharides: Hexoses


  6 carbon sugars: Glucose, Fructose, Galactose

  
• Monosaccharides: Hexoses


  • Structural differences account for differences in sweetness: Fructose > glucose > galactose
  • Found in fruits, vegetables, milk
  • Approximately 10% of the carbohydrate that we consume
  • Highest proportion of glucose, then fructose, then galactose

  
• Monosaccharide: Glucose


  • Other names: "blood sugar", "dextrose"
  • Present in all disaccharides
  • Primary component of polysaccharides
  • Primary form of CHO in body cells and blood
  • Common food sources: Fruit, vegetables, honey, sugar, candy, juice

  
• Monosaccharide: Fructose


  • Other names: "levulose", "fruit sugar"
  • Found commonly in fruits, honey
  • Does not cause as great a rise in blood glucose as other sugars
  • Does not require insulin to enter body cells
  • Less cariogenic than glucose
  • Sweetest of all simple sugars

  
• Monosaccharide: Galactose


  • Seldom found free in nature
  • Usually bound with glucose in lactose (milk sugar)
  • Important molecule in nervous tissue

  
• Carbohydrates absorbed in form of monosaccharide (e.g. glucose) through specific carriers

  
• • Active transport of monosaccharides
  • Absorbed by intestinal microvilli into the capillaries where they travel via the portal vein to the liver
  • In the liver, galactose and fructose are converted to glucose
  • Glucose is transported via blood to all body cells

  
• Monosaccharides


  • Glucose, fructose, galactose

  
• Disaccharides


  Pairs of monosaccharides joined through condensation reactions
• Disaccharides: Condensation


  2 reactants combine to form a larger product
• Disaccharides: Hydrolysis


  Broken down by addition of H2O, hydrogen (H) added to one reactant, hydroxyl (OH) group added to the other
• Disaccharides


  • Lactose, maltose, sucrose

  
• Disaccharide: Lactose


  • 1 glucose + 1 galactose
  • "milk sugar"
  • Enhances intestinal calcium absorption

  
• Lactose Intolerance


  • Not enough of the enzyme lactase in the small intestine to digest milk sugar lactose
  • Undigested lactose passes into large intestine; draws in water, metabolized by bacteria producing acids and gas
  • Symptoms: abdominal distension, flatulence, cramping, diarrhea

  
• Infants usually have enough lactase for their all milk diet; enzyme activity may begin to decrease at ~2y; may not be evident until adulthood
• Disaccharide: Maltose


  • 2 glucose molecules
  • Formed when starch breaks down
  • Slightly sweet taste if bread is kept in mouth for a few min (salivary amylase begins digesting starch)
  • Fermentation process produces alcohol

  
• Disaccharide: Sucrose


  • 1 glucose + 1 fructose
  • "table sugar"
  • Produced from the refinement of sugar cane and sugar beets

  
• Sugary Terms


  • Free sugars
  • Added sugars
  • Naturally-occurring sugar
  • Total sugar
• Free/Added sugars are widely incorporated into foods during processing or preparation
• When a person eats a food that contains simple sugars in honey and table sugar, the body does not distinguish whether the end products of digestion (glucose and fructose) came from table sugar or honey
• 1 tsp table sugar

  4 grams of sugar
• 62% of sugars in the Canadian food supply come from free and added sugars
• 10/17 food categories have >50% of sugars from free sugars
• Sugars & Dental Caries

  • Occur when bacteria that live in the mouth form colonies on teeth (plaque)
  • If plaque is not brushed or flossed away, bacteria metabolize CHO in the mouth and create acid --> dissolves tooth enamel and underlying structures of teeth and gums
  • Chance of dental caries increases the longer the sugar is in the mouth
• Major dietary guidelines recommend <5-10% energy from free/added sugars
• Dietary Carbohydrates - Sugars


  Sugars (e.g. glucose, sucrose, fructose) that come from table sugar or honey

  
• 1 tsp table sugar = 4 grams of sugar