Why Am I Suddenly Sensitive to FODMAPs? FODMAP Sensitivity Explains What’s Happening. It Doesn’t Explain Why
The low FODMAP diet can be a useful short-term tool for reducing symptoms in IBS such as bloating, abdominal discomfort and changes in bowel habits. However, it was never intended to be a permanent way of eating.
If you’ve developed FODMAP intolerance later in life, the more important question may not be which foods you’re reacting to, but why you’re reacting to them in the first place.
Understanding that “why” can often uncover changes in gut function, such as SIBO , hydrogen sulphide-producing bacteria, visceral hypersensitivity or changes within the gut microbiome itself.
What Are FODMAPs?
FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.
While the name sounds technical, these are simply naturally occurring carbohydrates found in many healthy foods including garlic, onion, apples, pears, legumes, dairy products and whole grains.
These carbohydrates are not completely absorbed in the small intestine. Instead, they continue further down the digestive tract where they are fermented by bacteria. That fermentation process produces gas and draws water into the bowel.
For some people, this can trigger symptoms such as bloating, abdominal pain, excessive gas or altered bowel habits.
The Low FODMAP Diet Was Never Meant to Be Forever
The low FODMAP diet was developed by researchers at Monash University as a way of helping people manage symptoms associated with IBS, or Irritable Bowel Syndrome.
What many people don’t realise is that it was designed as a temporary therapeutic intervention.
The original protocol involves a short restriction phase, followed by a systematic reintroduction process designed to identify which foods are genuinely problematic and which can safely return to the diet.
Monash themselves say: “The diet begins with a 2-6 week period of high restriction and then transitions to a more relaxed diet where certain foods are gradually re-introduced.”
Yet one of the most common stories I hear in clinic is, “I went low FODMAP years ago and never came off it.” The symptoms improved, so the diet stayed.
The Question I Always Ask
When someone tells me they can’t tolerate garlic, onion, legumes or certain fruits, one of the first questions I ask is:
“Were these foods always a problem?”
If the answer is yes, that’s one conversation.
But if the answer is no, it immediately changes the questions I ask you next.
People tell me they ate these foods for decades without any issue. Then somewhere along the way they developed bloating, digestive discomfort or food reactions and gradually started eliminating more and more foods.
This is where I think our conversation becomes much more interesting.
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“If the food wasn’t always a problem, then perhaps the food isn’t the real problem.”
Kate Troup, Naturopath
Something else has changed.
FODMAP Sensitivity Is the What, Not the Why
This is the distinction I think many people miss. FODMAP sensitivity explains what’s happening. It explains why symptoms occur after eating certain foods.
It does not explain why those foods suddenly became problematic.
In the same way that a headache tells you something is happening, but doesn’t necessarily tell you why, food intolerance is often a clue rather than a diagnosis.
The real question is what changed in your digestive system to make those foods difficult for you to tolerate?
Could It Be SIBO?
One of the most common explanations I see is Small Intestinal Bacterial Overgrowth, or SIBO.
Normally, most fermentation happens in the large intestine. With SIBO, excessive numbers of bacteria are present in the small intestine, so carbohydrates begin fermenting much earlier than they should.
When this happens, foods containing FODMAPs often trigger bloating, gas and discomfort very quickly after eating. The FODMAP food gets blamed, but the underlying issue may actually be the location and behaviour of the bacteria.
The food has simply exposed the problem.
Could It Be Hydrogen Sulphide Instead?
One clue I often see is that someone reacts strongly to garlic and onions, yet doesn’t respond to a typical low-FODMAP approach in the way we’d expect. Instead, we need to ask whether you’re really reacting to the fermentable carbohydrate in FODMAP foods, or whether sulphur metabolism and hydrogen sulphide-producing bacteria are playing the bigger role.
Garlic and onions are among the foods most commonly blamed by people following a low FODMAP diet. However, these foods are also rich sources of sulphur compounds.
You can end up spending years focusing on fermentable carbohydrates when the real issue lies elsewhere.
Again, the reaction explains what’s happening but it doesn’t necessarily explain why.
What If the Gut Has Become Overly Sensitive?
Sometimes neither the amount of fermentation nor the type of bacteria is the primary issue. Instead, the problem lies in how the nervous system perceives what is happening inside the digestive tract.
This is known as visceral hypersensitivity.
All of us produce gas during digestion. Fermentation is not only normal, it’s an important part of a healthy digestive system. Most people barely notice it.
However, when the nerves of the digestive tract become sensitised, even normal amounts of gas or movement can feel uncomfortable.
In these situations, the fermentation itself may not be abnormal at all: the gut’s perception of it is.
Visceral hypersensitivity is common in IBS and can contribute significantly to pain and discomfort, even when digestion itself is relatively normal.
People with IBS are often advised to follow a low FODMAP diet to help reduce symptoms because less fermentation means fewer sensations. However, that doesn’t necessarily address the underlying sensitivity driving the symptoms.
Could Changes in the Microbiome Be Contributing?
Your gut microbiome can influence how carbohydrates are fermented and how your digestive system responds to them. Some people have fewer bacteria that help break down these carbohydrates efficiently, while others have an overgrowth of microbes that produce excessive gas or inflammatory by-products during fermentation.
In these situations, the issue may not be the FODMAP food itself, but the gut environment it’s entering. This is one reason why two people can eat exactly the same food yet have very different digestive responses.
The Forgotten Benefit of FODMAP Foods
One of the reasons I’m cautious about long-term FODMAP restriction is that many high-FODMAP foods are also some of the most valuable foods for the gut microbiome.
Many of these carbohydrates act as prebiotics. They provide fuel for beneficial bacteria living in the large intestine.
As these microbes ferment prebiotic fibres found in FODMAPs, they produce compounds that support the gut lining, regulate inflammation and contribute to overall digestive health.
The irony is that many of the foods people fear most are also some of the foods that nourish the very microbial communities we are often trying to rebuild.
This doesn’t mean everyone should immediately start eating large amounts of foods that trigger symptoms.
It does mean that long-term avoidance without understanding the underlying cause can sometimes create new problems while trying to solve the original one.
Frequently Asked Questions
Can FODMAP sensitivity develop later in life?
Many people tolerate FODMAP foods for years before symptoms appear. This often suggests that something has changed in the digestive system, such as gut motility , the microbiome, visceral sensitivity, digestive function or the development of SIBO.
Can FODMAP sensitivity go away?
In many cases, yes. The goal of a low FODMAP diet is usually symptom control while investigating why those foods became problematic. Addressing underlying factors may improve tolerance over time.
What causes sudden FODMAP intolerance?
Common contributors include SIBO, changes in gut motility, infections, alterations in the microbiome, stress, visceral hypersensitivity, or other digestive dysfunction.
The Goal Isn’t More Restriction
The low FODMAP diet is one of the most useful tools we have for symptom management, but it should be viewed as a tool, not a destination.
If you’ve been following a low FODMAP diet for months or years, it may be worth asking a different question.
Not “Which foods can’t I eat?”
Instead ask: “Why did I lose the ability to tolerate these foods in the first place?”
Restriction can be a useful short-term strategy, but recovery is the ability to eat a wider range of foods with confidence.
If you’ve been low FODMAP for months or years, it may be time to stop asking which foods are causing symptoms and start asking why your body became sensitive to them in the first place.
