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Macronutrients.pptx

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This document summarizes the key components and properties of dietary fibre. It discusses the different types of soluble and insoluble fibre, their sources, and how they function in the gastrointestinal tract. Specifically, it describes how soluble fibres can increase viscosity and water holding capacity in the gut, slowing digestion and nutrient absorption. It also explains how fibres can bind to enzymes, lipids, and bile acids in the GI tract, reducing their absorption and increasing excretion.

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MACRONUTRIENTS
Macronutrients.pptx
Fibre Occurrence Chemical Nature Source Insoluble fibre Cell wall constituents Polysaccharide -glucose 1-4 linkage Amylase Whole wheat flour, Bran, Root, Vegetables, Legume, Peas, Outer covering of seeds, Apples Cellulose Hemicellulose Secretions, Cell wall material Polysaccharide Pentose, Hexoses, Uronic acid Hydrolysis: dilute acids, digestive juices Fermentability by intestinal micro flora is influenced by structure and type of sugar Bran Whole grains Lignin Woody parts of plants Part of plant cell wall and contributes to the structural rigidity of plants Function: Resistance of cell wall to microbial degradation Insoluble in water Not digested by colonic bacteria Mature root vegetables such as carrot, fruits with edible seeds, strawberries COMPONENTS OF DIETARY FIBRES
Fibre Occurrence Chemical Nature Source Soluble fibres Intracellular cementing material Galacturonic acids anhydro galacturonide residues Hydrolysis: Galacturonic acid + Galactose + Arabinose Water soluble Gel: In presence of sucrose and citric acid Completely metabolised by colonic bacteria Apple, Guavas, Citrus fruits, Carrots, Strawberries Pectins Gums Secreted at the cite of plant injury by specialised secretory cells and can be exuded from the plants Sugar and sugar derivatives Galactose, glucuronic acid and uronic acid Highly fermented by colonic bacteria Gum Arabic, Oatmeal, Barley, Legumes COMPONENTS OF DIETARY FIBRES
SOURCES OF DIETARY FIBRE Soluble dietary fibre: Green leafy vegetables (100g/day) and majority of fresh fruits (30%) Grain: Whole grains and bran Pericarp (Insoluble fibre) and aleurone layer (insoluble and soluble fibre) Low amount of dietary fibre: Refined and processed foods No dietary fibre: Sugar, Oil, Milk and Meat Soluble dietary fibre: Mango, orange, papaya, sweet lime (rich source) THERE IS NO EFFECT OF COOKING ON DIETARY FIBRE CONTENT
PROPERTIES OF DIETARY FIBRE 1. Water-holding capacity and viscosity: Depends on pH of GIT, solubility, size of the fibre particles and degree of processing foods Pectins, gums and hemicelluloses high water-holding capacity Delayed gastric emptying: Viscous gel or hydrate form Release of chyme from stomach is delayed Nutrients remain in the stomach longer Slows down digestion process Post prandial satiety Reduced mixing: Presence of viscous gels in the GIT can impair the ability of the nutrients in the food to interact with the digestive enzymes
PROPERTIES OF DIETARY FIBRE Reduced enzyme function: Viscous gel-forming fibers interfere with enzymatic hydrolysis Hydrocolloids may inhibit intestinal peptidases and pancreatic lipase. Fibre directly may decrease the activity of these enzymes or act by reducing the rate of enzyme penetration into the food. Decreased nutrient diffusion rate: Absorption of nutrients: Lumen of the small intestine through glycoprotein (mucin) rich water layer lying on top of the enterocytes The hydrated gel increases the thickness of the water layer and decreases the diffusion rate of nutrients; consequently, maximal absorption is reduced.
PROPERTIES OF DIETARY FIBRE Altered small intestine transit time: Soluble fibres with decreased diffusion rates, with increased transit time may result in decreased nutrient absorption. This is due to insufficient time for the nutrients to be in contact with enterocytes. Soluble fibres with the viscosity increasing property slow down passage and delay gastric emptying. A high intake of dietary fibre generally causes reduced transit time in the colon and faster bowel emptying. This is attributed to accelerated colonic mobility by increased intraluminal mass. Higher the faecal bulk, lower will be the transit time in the large intestine.
ADSORPTION OR BINDING CAPACITY Lignins, gums, pectins and hemicelluloses have the ability to bind substances such as enzymes and nutrients in the gastrointestinal tract. The ability of these fibres to adsorb substances depends in part on gastrointestinal pH, particle size, food processing and fermentability. Mucilaginous fibres such as guargum, pectin and psyllium delay glucose absorption, lower blood glucose concentration and affect hormonal response to the absorbed nutrient. Such effects reduce post prandial blood glucose concentration and insulin needs and beneficial for diabetic patients.
DIMINISHED ABSORPTION OF LIPIDS Soluble and insoluble fibres may affect lipid absorption by adsorbing fatty acids, cholesterol and/or bile acids within the digestive tract. Fatty acids and cholesterol that are bound to fibre cannot form micelles and cannot be absorbed in this bound form. Fibre bound lipids are typically not absorbed in the small intestine and pass into the large intestine, where they will be excreted in the faeces or degraded by intestinal bacteria.
INCREASED FAECAL BILE ACID EXCRETION Adsorption of bile acids to fibres prevents the use of bile acids for micelle formation. Like fibre bound fatty acids, bile acids bound to fibre cannot be reabsorbed and recirculated and excreted or undergo colonic microflora degradation.
LOWERED SERUM CHOLESTEROL CONCENTRATION Psyllium, guar gum, oat and pectin lower serum cholesterol. Oat bran and soyabean fibres have intermediate effects. Corn, wheat and rice bran appear to be ineffective. Fruits and vegetables decrease serum cholesterol concentration.
Macronutrients.pptx

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Macronutrients.pptx

  • 3. Fibre Occurrence Chemical Nature Source Insoluble fibre Cell wall constituents Polysaccharide -glucose 1-4 linkage Amylase Whole wheat flour, Bran, Root, Vegetables, Legume, Peas, Outer covering of seeds, Apples Cellulose Hemicellulose Secretions, Cell wall material Polysaccharide Pentose, Hexoses, Uronic acid Hydrolysis: dilute acids, digestive juices Fermentability by intestinal micro flora is influenced by structure and type of sugar Bran Whole grains Lignin Woody parts of plants Part of plant cell wall and contributes to the structural rigidity of plants Function: Resistance of cell wall to microbial degradation Insoluble in water Not digested by colonic bacteria Mature root vegetables such as carrot, fruits with edible seeds, strawberries COMPONENTS OF DIETARY FIBRES
  • 4. Fibre Occurrence Chemical Nature Source Soluble fibres Intracellular cementing material Galacturonic acids anhydro galacturonide residues Hydrolysis: Galacturonic acid + Galactose + Arabinose Water soluble Gel: In presence of sucrose and citric acid Completely metabolised by colonic bacteria Apple, Guavas, Citrus fruits, Carrots, Strawberries Pectins Gums Secreted at the cite of plant injury by specialised secretory cells and can be exuded from the plants Sugar and sugar derivatives Galactose, glucuronic acid and uronic acid Highly fermented by colonic bacteria Gum Arabic, Oatmeal, Barley, Legumes COMPONENTS OF DIETARY FIBRES
  • 5. SOURCES OF DIETARY FIBRE Soluble dietary fibre: Green leafy vegetables (100g/day) and majority of fresh fruits (30%) Grain: Whole grains and bran Pericarp (Insoluble fibre) and aleurone layer (insoluble and soluble fibre) Low amount of dietary fibre: Refined and processed foods No dietary fibre: Sugar, Oil, Milk and Meat Soluble dietary fibre: Mango, orange, papaya, sweet lime (rich source) THERE IS NO EFFECT OF COOKING ON DIETARY FIBRE CONTENT
  • 6. PROPERTIES OF DIETARY FIBRE 1. Water-holding capacity and viscosity: Depends on pH of GIT, solubility, size of the fibre particles and degree of processing foods Pectins, gums and hemicelluloses high water-holding capacity Delayed gastric emptying: Viscous gel or hydrate form Release of chyme from stomach is delayed Nutrients remain in the stomach longer Slows down digestion process Post prandial satiety Reduced mixing: Presence of viscous gels in the GIT can impair the ability of the nutrients in the food to interact with the digestive enzymes
  • 7. PROPERTIES OF DIETARY FIBRE Reduced enzyme function: Viscous gel-forming fibers interfere with enzymatic hydrolysis Hydrocolloids may inhibit intestinal peptidases and pancreatic lipase. Fibre directly may decrease the activity of these enzymes or act by reducing the rate of enzyme penetration into the food. Decreased nutrient diffusion rate: Absorption of nutrients: Lumen of the small intestine through glycoprotein (mucin) rich water layer lying on top of the enterocytes The hydrated gel increases the thickness of the water layer and decreases the diffusion rate of nutrients; consequently, maximal absorption is reduced.
  • 8. PROPERTIES OF DIETARY FIBRE Altered small intestine transit time: Soluble fibres with decreased diffusion rates, with increased transit time may result in decreased nutrient absorption. This is due to insufficient time for the nutrients to be in contact with enterocytes. Soluble fibres with the viscosity increasing property slow down passage and delay gastric emptying. A high intake of dietary fibre generally causes reduced transit time in the colon and faster bowel emptying. This is attributed to accelerated colonic mobility by increased intraluminal mass. Higher the faecal bulk, lower will be the transit time in the large intestine.
  • 9. ADSORPTION OR BINDING CAPACITY Lignins, gums, pectins and hemicelluloses have the ability to bind substances such as enzymes and nutrients in the gastrointestinal tract. The ability of these fibres to adsorb substances depends in part on gastrointestinal pH, particle size, food processing and fermentability. Mucilaginous fibres such as guargum, pectin and psyllium delay glucose absorption, lower blood glucose concentration and affect hormonal response to the absorbed nutrient. Such effects reduce post prandial blood glucose concentration and insulin needs and beneficial for diabetic patients.
  • 10. DIMINISHED ABSORPTION OF LIPIDS Soluble and insoluble fibres may affect lipid absorption by adsorbing fatty acids, cholesterol and/or bile acids within the digestive tract. Fatty acids and cholesterol that are bound to fibre cannot form micelles and cannot be absorbed in this bound form. Fibre bound lipids are typically not absorbed in the small intestine and pass into the large intestine, where they will be excreted in the faeces or degraded by intestinal bacteria.
  • 11. INCREASED FAECAL BILE ACID EXCRETION Adsorption of bile acids to fibres prevents the use of bile acids for micelle formation. Like fibre bound fatty acids, bile acids bound to fibre cannot be reabsorbed and recirculated and excreted or undergo colonic microflora degradation.
  • 12. LOWERED SERUM CHOLESTEROL CONCENTRATION Psyllium, guar gum, oat and pectin lower serum cholesterol. Oat bran and soyabean fibres have intermediate effects. Corn, wheat and rice bran appear to be ineffective. Fruits and vegetables decrease serum cholesterol concentration.