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

What is FODMAP?

FODMAPs are Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols - short-chain carbohydrates that are poorly absorbed in the small intestine and rapidly fermented by gut bacteria, causing gastrointestinal symptoms in susceptible individuals. 1, 2

Components of FODMAPs

• Fermentable - These carbohydrates are rapidly broken down (fermented) by gut bacteria 2
• Oligosaccharides - Including fructans (found in wheat, rye, onions, garlic) and galacto-oligosaccharides (in legumes) 1, 3
• Disaccharides - Primarily lactose, found in dairy products 3
• Monosaccharides - Mainly fructose, when present in excess of glucose (in honey, apples, high-fructose corn syrup) 2
• Polyols - Sugar alcohols such as sorbitol and mannitol (in some fruits and artificial sweeteners) 2

Mechanism of Action

• FODMAPs are poorly absorbed in the small intestine, drawing water into the intestinal lumen through osmotic effects 1
• They are rapidly fermented by gut bacteria in the large intestine, producing gas 1
• The combination of increased water and gas production leads to intestinal distension 3
• In susceptible individuals, this distension triggers symptoms such as bloating, abdominal pain, flatulence, and altered bowel habits 3, 2

Clinical Applications

• The low FODMAP diet is primarily used for managing symptoms in irritable bowel syndrome (IBS), with evidence showing effectiveness in 50-60% of patients 3, 4
• It may also be beneficial for patients with inflammatory bowel disease (IBD) who have concomitant IBS-like symptoms 1
• Athletes with exercise-associated gastrointestinal symptoms often implement a low FODMAP diet pre-exercise to reduce symptoms 1
• The diet is implemented in three distinct phases 3, 5:
  1. Restriction phase (4-6 weeks): Complete elimination of high-FODMAP foods
  2. Reintroduction phase: Systematic challenge with foods containing single FODMAPs
  3. Personalization phase: Development of an individualized long-term diet based on tolerance

Implementation Considerations

• The low FODMAP diet should be implemented under the guidance of a trained dietitian 3, 2
• The restriction phase should not exceed 4-6 weeks to avoid negative impacts on gut microbiome 3
• Long-term strict restriction is not recommended as it may reduce beneficial gut bacteria and lead to nutritional inadequacies 3, 2
• A multivitamin supplement may be needed during the restriction phase 2
• Patients with moderate to severe anxiety or depression may be poor candidates for the full restriction approach 3

Effectiveness and Evidence

• Multiple randomized controlled trials show the low FODMAP diet is effective for managing IBS symptoms 6, 7
• The diet is particularly effective for reducing abdominal bloating, pain, and improving stool consistency 3, 6
• In one US trial, 52% of IBS-D patients on a low FODMAP diet reported adequate symptom relief 6
• The British Society of Gastroenterology suggests that a low FODMAP diet may be used to treat functional bowel symptoms in IBD patients 1

Limitations and Considerations

• The diet is complex and potentially restrictive, requiring significant patient education and commitment 3
• It may alter the gut microbiome, particularly reducing beneficial bifidobacteria 3, 4
• If no symptom improvement occurs within 4-6 weeks, the diet should be discontinued 2
• Screening for eating disorders before implementing restrictive diets is recommended 3, 2