Fructose malabsorption

Question 1

Fructose malabsorption signs/symptoms?

Answer 1

1. Gastrointestinal (Choi et al, 2003)
   * flatus; abdo discomfort; bloating; belching; altered bowel habit
   * nausea (can occur within minutes of intake)(Beyer et al, 2005)
2. Potential extra-intestinal (Wilder-Smith et al, 2010)(Ledochowski et al, 2000)
   * fatigue; headache; diminished concentration; myalgia; arthralgia;
   depression

Question 2

Fructose Malabsorption
* Aetiology?

Answer 2

• malabsorbers may have lower expression or activity of the
  GLUT5 transporter in the apical membrane of the small
  bowel epithelial cells (Barrett et al, 2009)
• unabsorbed fructose in the colon has an osmotic drawing
  effect that results in increased fluid in the colonic lumen (Skoog
  et al, 2004)
• may result in softer stools and increased stool frequency
• bacterial fermentation of fructose in the colon results in gas
  formation and the production of SCFAs
• may result in abdominal pain, bloating, distension, and nausea

Question 3

Fructose Malabsorption * Diagnosis?

Answer 3

• US Breath Testing recommendations: (Rezaie et al, 2017)
• 25g fructose in a 10% solution is recommended
• rise in hydrogen by 20 ppm above basal (baseline levels) after fructose
  ingestion is considered positive
• 10ppm methane at any time point considered positive for Intestinal
  Methanogen Overgrowth (IMO)
• Diagnosis?
• Blinded fructose tolerance test
• 25g of either fructose or glucose in 250ml (1 cup) water
• Taken on an empty stomach first thing in the morning
• Patients observe S&S after ingestion
• choose non-work day!
• Empirical trial of low-fructose diet (Skoog et al, 2004)(Latulippe and Skoog, 2011)
• assess improvements in S&S

Question 4

Fructose Malabsorption -
Consequences?

Answer 4

• decreased plasma tryptophan levels (Ledochowski et al, 2001)
• may play a role in the development of depressive symptoms via limitations
  in serotonin biosynthesis
• fructose may bind to tyrptophan in the gut forming a fructose-L-tryptophan
  complex with limited absorbability
• decreased plasma folate concentrations (Ledochowski et al, 1999)
• Plasma folate was significantly lower in fructose malabsorbers (7.14 mg/L)
  than in normal fructose absorbers (9.1 mg/L); P<0.01
• fructose malabsorption may reduce transit time in the upper gut and thus
  reduce the absorption of folate
• decreased serum zinc concentrations (Ledochowski et al, 2001b)
• increased incidence of zinc deficiency (9.8% vs 0% in controls)
• presence of fructose in lumen may decrease bioavailability of zinc
• no changes in serum albumin, iron, ferritin, or transferrin

Question 5

Fructose Malabsorption Myths –
Commonly Heard but Unsubstantiated?

Answer 5

• Fructose malabsorption/intolerance causes damage to
  intestinal cells
• no evidence
• physiologically unlikely
• Fructose malabsorption is a cause of SIBO
• no evidence
• SIBO is a frequent cause of FI though!
• Fructose malabsorption causes dysbiosis or overgrowth of
  pathogenic bacteria in the gut
• no evidence

Question 6

diet for fructose intolerance?

Answer 6

low fructose/low FODMAP

Question 7

What are the potential issues with low FODMAP diet

Answer 7

• Eliminate many healthy foods:
• e.g., legumes:
• rich sources of fibre
• rich in antioxidants (Amarowicz et al, 2008)
• rich in protein
• microbiota-nourishing (Miquel et al., 2014)
• improve glycaemic control (Sievenpiper et al, 2009)
• lower total and LDL cholesterol

Negative effects on the microbiota (Halmos et al, 2015)
* Low FODMAP diet associated with:
* higher faecal pH (7.4)
* reduced bacterial total abundance
* decreased abundance of Clostridium cluster XIVa, Clostridium cluster
IV, Akkermansia muciniphila, Faecalibacterium prausnitzii,
Ruminococcus spp., lactobacilli and bifidobacteria

Question 8

Fructose Malabsorption – Management
Overview

Answer 8

• Dietary Modifications:
• Start with trial of low fructose and sugar alcohol diet (see prev. slides)
• OR could start with trial of strict FODMAP diet
• But this option is harder compliance-wise, cuts out more healthy foods, and
  negatively alters the health of the colonic ecosystem (Vandeputte & Joosens, 2020)
• once asymptomatic, reintroduce of galactan and fructan-containing foods
• minimise elimination of health-promoting foods
• +/- concurrent supplementary glucose
• can be used to offset the impact of a food “treat” (e.g., mango)
• +/- concurrent supplementary amino acids
• can be used to offset the impact of a food “treat”
• alanine – most effective
• glutamine – primary food source for enterocytes
• +/- concurrent supplementary xylose isomerase
• can be used to offset the impact of a food “treat”