HLTH 2001

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HLTH 2001 Human Nutrition Lecture 17 Dietary
Fibre II
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Soluble fibre- answer

• One adult dose of Metamucil Powder has 2.4 grams
  of this soluble fibre

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The Colon(large bowel) (large intestine)
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
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Physiological action of Dietary Fibre

• slows gastric emptying rate
• good for Diabetes Mx
• not good for athletes
• aids passage of faeces through colon

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Physiological action of Dietary Fibre

• increases faecal bulk
• keeps the insides fit

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Examples of faecal output

• Population Faecal Weight (g/day)
• Western 80 - 160
• Vegetarian 225
• Ugandan 470

Rural Africans eliminate waste in 1/3 time it
takes people from urban westernized cultures
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Health Benefits

• Colonic microflora partially or completely
  ferment CHO that resists digestion and absorption
  in the SI (soluble fibre)
• Fermentation products include short chain fatty
  acids
• Results in an increase in stool mass through
  bacterial proliferation
• Prevents/treats constipation
• Insoluble fibre is not fermented
• softens stool consistency
• Increases stool weight
• Frequency of defaecation

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Fermentation

• Fermentability of various fiber sources
• Titgemeyer, E.C. et al. (1991) Am.J.Clin.Nutr.
  , 53, 1418-1424
• hyperlink to journal article
• products of fermentation
• volatile fatty acids (VFA)
• short chain fatty acids (SCFA)
• butyric, propionic, acetic acids
• CO2, H2 methane

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Dietary Fibre-related diseases
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Physiological Benefits of Dietary Fibre

• Lowering of blood cholesterol
• Lower post-prandial blood glucose and insulin

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High Fibre- lower cholesterol

• Some types of dietary fibre (oatbran and pectin
  which are both soluble fibre) can decrease level
  of cholesterol in circulation
• Increase in excretion of bile acids
• Inhibit cholesterol synthesis in the liver
• Note wheat bran and wholemeal wheat have no
  effect on cholesterol (insoluble fibre)
• Possible not just fibre that has the effect-
  could be other components of the diet having the
  benefit See Flight and Clifton 2006 review

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Blood glucose benefits

• Soluble dietary fibre (oat gum or rolled oats)
  can
• Slow digestion of starch and subsequent
  absorption of glucose
• Note wheat bran and wholemeal wheat have no
  effect on blood glucose (insoluble fibre)

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Dietary fibre-related diseases

• LOW dietary fibre intake
• 1. Irritable bowel syndrome (IBS)
• symptoms
• lower abdominal cramps
• bloating
• diarrhoea
• constipation

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Irritable bowel syndrome (IBS)

• Causes
• Unknown
• associated with stress anxiety
• long-term low fibre intake?
• trigger foods?
• coffee, wheat bread, dairy foods?

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Irritable bowel syndrome (IBS)

• Treatment
• ?total fibre intake to 30-50g/day
• ? insoluble fibre intake while symptoms acute
• drugs eg. Cholefac

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Dietary fibre-related diseases

• 2. Diverticular disease
• Diverticula
• pouches in colon wall
• seen in 30 of people gt 60 years
• chronic low (lt10g/day) fibre intake?

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Picture of diverticula
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(No Transcript)
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Diverticular disease

• only 5-10 develop symptoms
• uncommon in 3rd world countries
• high fibre intake?

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Diverticular disease

• Symptoms
• spasms of colon painful
• inflammation of pouches pain
• (Diverticulitis)
• Click here for images of pouches and extended
  reading about complications

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Diverticular disease

• Treatment
• high fibre diet when symptom free
• low fibre diet when symptoms
• Medication Cholefac

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Dietary fibre-related diseases

• 3. Colon Cancer
• low incidence (0-5/100,000) in Africa
• high fibre diet?
• high incidence (15-35/100,000) in Western world
• low fibre diet?

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Colon Cancer

• theory
• high fibre diet reduces transit time
• decreased exposure time for carcinogens
• treatment
• bowel resection
• colostomy bag

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Colon Cancer

• Colorectal Cancer - Symptoms and Diagnosis
• (images of colon cancer)

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Colon Cancer

• prevention
• maintain high fibre intake throughout life
• People who ate most dietary fibre (35g/day)
  reduced their risk of colon cancer by 40
  compared with those wo ate the least fibre
  (15)
• Bingham et al (2003) Lancet
• dietary fibre supplements lack nutrients and
  phytochemicals which are found in whole sources
  of fibre
• thought to play a key role in cancer prevention

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• The Colonoscopy
• Sigmoid colon
• Descending colon
• Transverse colon
• Ascending colon
• Total distance ? 6ft

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Colonoscopy biopsy

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Recommended Reading

• Whitney, E Rolfes, S 2005
• Understanding Nutrition (10th Ed.)
• Chapter 4 The Carbohydrates
• pp. 108-110 Fibers
• pp. 126-129 Recommended intakes of starch and
  fibers
• Wahlqvist (2002)
• Food Nutrition (2nd Ed.)
• Chapter 12 Carbohydrates
• pp 189-198 Dietary Fibre