What is a Low FODMAP (Fermentable Oligo-, Di-, Mono-saccharides, and Polyols) diet?

What is a Low FODMAP Diet?

A low FODMAP diet is a structured dietary approach that restricts fermentable carbohydrates (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) to reduce gastrointestinal symptoms, particularly in patients with irritable bowel syndrome (IBS). 1, 2

Definition and Components

• FODMAPs are short-chain fermentable carbohydrates that have low digestibility in the upper gastrointestinal tract and undergo rapid bacterial fermentation in the proximal colon 1
• The acronym FODMAP stands for:
  • Fermentable - these carbohydrates are broken down by bacteria in the large intestine
  • Oligosaccharides - fructans and galacto-oligosaccharides (GOS)
  • Disaccharides - primarily lactose
  • Monosaccharides - primarily fructose
  • And
  • Polyols - sugar alcohols like sorbitol and mannitol 2, 3

How FODMAPs Affect the Body

• FODMAPs can trigger gastrointestinal symptoms through several mechanisms:
  • Their small size and high osmotic activity draw water into the intestine
  • They cause abdominal distention and increased gas production through fermentation
  • They foster water mobilization in the intestine 1
• These effects can lead to symptoms such as gas, diarrhea, and abdominal bloating, particularly in individuals with visceral hypersensitivity 1, 4

Implementation of the Low FODMAP Diet

The low FODMAP diet is implemented in three distinct phases:

1. Restriction Phase (4-6 weeks):

   • Substantially reduce intake of all FODMAPs
   • Monitor symptom response (typically improvement occurs within 2-6 weeks)
   • Consider daily multivitamin supplementation 2, 5

2. Reintroduction Phase (6-10 weeks):

   • Systematically challenge with foods containing single FODMAPs
   • Introduce foods in increasing quantities over 3 days
   • Monitor symptom responses to identify specific triggers 2, 6

3. Personalization Phase:

   • Develop a long-term sustainable diet based on individual tolerance
   • Reintroduce well-tolerated FODMAPs to improve dietary variety 2, 5

Efficacy and Evidence

• The low FODMAP diet has been shown to be effective in approximately 70% of IBS patients 2
• It is particularly effective for reducing bloating and abdominal pain 1, 7
• Long-term studies show sustained symptom relief with an adapted FODMAP approach in 50-60% of patients 1, 7

Important Considerations and Limitations

• The diet should be implemented under the guidance of a registered dietitian with gastrointestinal expertise 2, 7
• Strict long-term restriction may negatively impact the intestinal microbiome, particularly reducing beneficial bifidobacteria 2, 5
• The diet imposes significant dietary restrictions and may lead to nutritional deficiencies if not properly managed 8
• Screening for eating disorders is recommended before starting this restrictive diet 1, 2
• Poor candidates include those with few trigger foods, risk of malnutrition, food insecurity, eating disorders, or moderate to severe anxiety/depression 2, 7

Alternative Approaches

• For patients with comorbid mental health conditions, a gentler "bottom-up" approach focusing on selected high-FODMAP foods rather than complete restriction may be more appropriate 1
• The Mediterranean diet shows some benefit for IBS symptoms and may be appropriate for those with mild gastrointestinal symptoms 1
• Soluble fiber supplementation can be beneficial, particularly for constipation-predominant IBS 1, 7