What we’ll cover:

• What FODMAPs are and their impact on digestion
• Why some people experience discomfort from FODMAPs
• The science behind FODMAP sensitivity

For some people, certain carbohydrates, known as FODMAPs, can cause bloating, gas, and irregular digestion. These naturally occurring compounds can be tricky for the body to absorb, leading to discomfort for those with gut sensitivities or conditions like IBS. But why do some people react while others don’t?

What Are FODMAPs?

FODMAPs are a group of carbohydrates and sugar alcohols that the human gut struggles to absorb. The name stands for:

• Fermentable
  FODMAPs reach the large intestine undigested, where gut bacteria ferment them, producing gas that can lead to bloating and discomfort.
• Oligosaccharides (found in wheat, onions, and garlic)
  These carbohydrates are poorly digested due to a lack of necessary enzymes, meaning they pass into the colon, where fermentation can cause bloating and gas.
• Disaccharides (e.g. lactose in dairy)
  Lactose requires the enzyme lactase to be broken down, and without enough of it, dairy consumption can lead to bloating, stomach pain, and diarrhoea.
• Monosaccharides (e.g. fructose in apples and honey)
  Some people struggle to absorb excess fructose, which can pull water into the gut and cause bloating and loose stools.
• Polyols (e.g. sugar alcohols found in fruits & sweeteners)
  Polyols are only partially absorbed in the gut, and when consumed in large amounts, they can trigger bloating and diarrhoea.

How FODMAPs Affect Digestion

Once eaten, FODMAPs move through the small intestine without being fully absorbed. They pull extra water with them as they travel through the digestive system, which can contribute to bloating and discomfort.

When FODMAPs reach the large intestine, gut bacteria ferment them, producing gas as a byproduct. This is a normal part of digestion and is, in parts, beneficial to the gut bacteria. However, for people who are sensitive to FODMAPs, the excess gas can cause the following symptoms:

• Bloating and stomach swelling
• Excessive gas
• Diarrhoea or constipation (this can vary as FODMAPs also affect how quickly food moves through our digestive system)
• Cramps and abdominal pain
• Feeling full after small meals

Why Some People Are More Sensitive

Not everyone has issues with FODMAPs. Some people can eat them freely, while others experience discomfort from even small amounts. That said, there are factors which vary in each person that can impact how much FODMAP we can tolerate:

• Gut sensitivity: Some digestive systems react strongly to gas and water shifts, which is common in IBS.
• Absorption issues: Some people lack the enzymes to properly break down certain FODMAPs, like lactose or fructose.
• Gut bacteria balance: Some microbiomes ferment FODMAPs more aggressively, leading to increased gas and discomfort.

The diagram below illustrates how our FODMAP threshold affects symptoms. If we consume more FODMAPs than our body can tolerate, symptoms are likely to occur. This can happen in two ways:

• Eating a single food or meal high in FODMAPs can rapidly push us over the threshold, as shown in the second spike.
• Consuming multiple FODMAP-containing foods, where smaller amounts accumulate (e.g. multiple meals or snacks eaten close together), gradually exceeding the threshold (see the series of spikes on the right side of the chart).

The Science Behind FODMAPs

Scientific research has confirmed the link between FODMAPs and digestive discomfort, especially in IBS and gut disorders.

• IBS & FODMAPs: Studies, including research from Monash University, show that reducing high-FODMAP foods can significantly reduce bloating, pain, and gut symptoms in IBS patients.
• Gut microbiome effects: While some fermentation is healthy, excess FODMAP intake may disrupt gut bacteria balance, leading to symptoms.
• Lactose intolerance: Many people struggle with lactose digestion, and studies confirm that removing lactose can ease symptoms in those affected.

Summary

FODMAPs are a normal part of many foods, but for those with sensitive digestion, they can lead to unwanted symptoms and discomfort. If you regularly experience bloating, gas, or irregular bowel movements, FODMAPs could be playing a role.

If you suspect FODMAPs are affecting your digestion, speak to a healthcare professional before making big dietary changes. In our next article, we’ll explore how a low-FODMAP diet, under a specialised dietitian's guidance, can help identify your triggers and manage symptoms.