Lecture 4- 3 October 2013 Fibre metabolism and regulation

1. The new normal-Globe and Mail- 30 September 2012- parents do not recognise when they and/or others including kid(s) is/are overweight or obese Fat is the new normal

2. Lecture 4- 3 October 2013 Fibre metabolism and regulation Most of this lecture derived from Chapter 4 of Gropper

3. Outline of lecture 4 Definition of Dietary Fibre Plants and Fibre Dietary Fibre

4. Outline of lecture 4 Some Properties-dictate physiological and metabolic effects of fibre             a) Water Solubility             b) Water Holding/Hydration Capacity as well as viscosity                      Slowed Gastric emptying Reduced mixing of gastrointestinal contents with digestive enzymes                      Reduced enzyme function                      Decreased nutrient diffusion rate                      Altered small intestine transit time

5. Outline of lecture 4 Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                     Diminished absorption of lipids                     Increased faecal bile excretion                     Lowered serum cholesterol                     Altered mineral balance

6. Outline of lecture 4 Some Properties-dictate physiological and metabolic effects of fibre d) Degradability or fermentability              Fermentable fibres                    Increased water and sodium absorption in colon                    Mucosal cell proliferation                    Provision of energy                    Acidification of luminal environment Non-fermentable fibres                    Detoxification                    Increased faecal bulk

7. Outline of lecture 4 Recommended Intake of Fibre             Implications in Disease Prevention and Management Fibre-Based Herbal Medicines

8. Outline of lecture 4 Summary

9. More detailed information Definition of Dietary Fibre         -not a single entity and therefore no universal definition         -one attempt at definition- "plant polysaccharides and lignin which are resistant to hydrolysis by the digestive enzymes of man"- Trowell et al quoted in Chapter 5, Gropper 3rd edition         -however, there are problems with this definition

10. Problems with definition-direct quote from Gropper, Chapter 5 “fails to include all the digestible residue from food that may reach the colon. It uses the ability to be digested as the basis for the definition when undigested food reaching the colon does not necessarily lack the ability to be digested nor is it necessarily unavailable to the body”

11. Plants and Fibre        -fibre is derived from plant cells        -plant cell wall contributes more than 95 percent of dietary fibre         -figure 5.1 –Gropper         -figure 5.3-Gropper

12. Plants and Fibre

13. Plants and Fibre

14. Fibre- water insoluble and water soluble

15. Fibre- water insoluble -cellulose-bran, legumes, peas, root vegetables, cabbage family veggies, apples, outer covering of seeds          -poorly fermented generally

16. Fibre- water insoluble -hemicellulose-not water soluble if do NOT have acid side chains -bran and whole grains(not clear if water or water insoluble or both) -fermentability depends on sugar and acid composition-eg hexose and uronic acid are more accessible to bacterial enzymes

17. Fibre- water insoluble lignin-a non-carbohydrate component of fibre- wheat, fruits with edible seeds (eg strawberries) , mature root veggies (eg carrots)            -poorly fermented

18. Fibre- water soluble -water soluble-refers to hot water

19. Fibre- water soluble -water soluble-refers to hot water                  -hemicellulose-water soluble if have acid side chains

20. Fibre- water soluble -pectin-gel forming -apples, strawberries and citrus fruits                       -easily fermented

21. Fibre- water soluble        -gums                        -oatmeal, barley and legumes                        -eg: gum arabic                        -easily fermented

22. Fibre- water soluble -mucilages           -similar in structure to gums           -synthesised by plant secretory cells           -carrageenan and agar-dervived from seaweed and algae                 -used as stabilisers in ice cream for example -degraded by colonic bacteria

23. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre             a) Water Solubility                      -generally water soluble -delay gastric emptying                                     -increase transit time                                     -decrease nutrient (glucose absorption)

24. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre             a) Water Solubility                      generally water insoluble                                     -decrease transit time -increase faecal bulk

25. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity              -ability of fibre in food to bind water-ie sponge effect              -water soluble fibres have greater hydration capacity than?

26. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding (whc)/Hydration Capacity as well as viscosity              -water holding capacity dependent on water solubility, pH of gastrointestinal tract, size of fibre particles and degree of food processing -increased pH increases whc              -coarsely ground bran has higher hydration capacity

27. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in:                       Slowed gastric emptying-satiety                       Reduced mixing of gastrointestinal contents with digestive enzymes- physical barrier

28. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in:                     Reduced enzyme function -eg inhibit -intestinal peptidases                                              -pancreatic lipase                                              -mechanism is unclear

29. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in:               Decreased nutrient diffusion rate and hence nutrient absorption                        -passage through mucin layer is reduced

30. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in:               Decreased nutrient diffusion rate and hence nutrient absorption                        -reduced convective currents

31. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in:         Decreased nutrient diffusion rate and hence nutrient absorption                  -results in decreased absorption of amino acids and fatty acids due to viscous fibre

32. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in: Decreased nutrient diffusion rate and hence nutrient absorption                          -pectin, psyllium and viscous mucilaginous gums (eg guar gum) lower blood glucose and hence hormonal response to glucose

33. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre b) Water Holding/Hydration Capacity as well as viscosity -water holding by fibre creates viscous solutions resulting in:             Altered small intestine transit time                 -soluble -increase transit time- good- why?                 -insoluble-decrease transit time- bad-why?                                         -net effect?

34. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre      c) Absorption or Binding Ability                 -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract -dependent on gi pH, particle size, food processing and fermentability

35. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract -results in-diminished lipid absorption                                      -lowered blood cholesterol                                      -increased faecal bile excretion -changed mineral balance

36. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract Diminished Absorption of Lipids                               -pectin, guar gum, oatbran, lignin- adsorb fatty acids, cholesterol, bile acids                                -consequence of such adsorption

37. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                 -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract Diminished Absorption of Lipids Increased faecal bile excretion                       -similar mechanistic consequence seen under diminished absorption of lipid

38. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                 -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract Lowered serum cholesterol                                 consequently more plasma cholesterol is used to synthesise bile                               

39. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                 -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract Altered mineral balance                                 -fibre containing uronic acid can form cationic bridges with minerals

40. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                 -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract Altered mineral balance                                 -lignins also thought to play a role                                 -slower the fermentation the higher the ability to bind minerals by bacteria

41. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre c) Absorption or Binding Ability                 -lignins, gums, pectins and some hemicelluloses have ability to bind(adsorb) enzymes, nutrients in gi tract Altered mineral balance                                 -more rapidly fermentable fibres eg pectin may have positive effect on mineral balance

42. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre d) Degradability or fermentability                    -principal metabolites of fibre and undigested starch fermentation are lactate and short chain fatty acids (SCFAs)                   -also get some hydrogen, CO2 and methane gases                   -pectin, gums, oat and wheat bran and psyllium produce SCFAs

43. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre d) Degradability or fermentability Fermentable fibres                      Increased water and sodium absorption in colon               -SCFA rapid absorption stimulates water and sodium absorption

44. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre d) Degradability or fermentability Fermentable fibres                      Mucosal cell proliferation                                -substrates from degradation of dietary fibre                      Provision of energy                                -SCFAs                      Acidification of luminal environment                            -SCFAs-calcium more available to bile and fatty acids- may be protective against colon cancer

45. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre d) Degradability or fermentability Non-Fermentable fibres                       -principally cellulose and lignins-promote proliferation of colonic microbes                        Detoxification                                 via proliferation of colonic microbes

46. Dietary Fibre Some Properties-dictate physiological and metabolic effects of fibre d) Degradability or fermentability Non-Fermentable fibres                    Increased faecal bulk-good laxative effect                          bulk consists of undigested fibre, salts and water                        -wheat bran and especially rice bran particularly good at this

47. Dietary Fibre Recommended Intake of Fibre/Implications in Disease Prevention and Management                         25- 35 grams per day-DRI-40 tops, 50 obstruction soluble fibre- hypocholesterolemic -hypoglycemic insoluble fibre- laxative

48. Dietary Fibre How is fibre metabolism regulated in humans? A few examples -intake(form and quantity) -food preparation -regulation of bacterial enzymes and pathways since we cannot use our own enzymes to digest.

49. Fibre-Based Herbal Medicines  Echinacea -few controlled studies      -immune response boost-prevention or treatment of cold, flu or other infections active agents -hmw polysaccharides among others -side effects-allergic reactions may occur -use in systemic or immune system dysfunction is contraindicated

50. Fibre-Based Herbal Medicines Ginseng -cancer prevention -fatigue reduction -few controlled studies -active agents-saponin glycosides and ginsenosides- modulate hormones and central nervous system function -side effects-negative interactions with warfarin