A low FODMAP diet is a common approach to managing irritable bowel syndrome. FODMAPs are rapidly Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyls.
The problem with FODMAPs is that they ferment rapidly and are poorly absorbed. So they stick around and feed bacteria that cause gas and bloating.
Most people have no issue with FODMAPs, though they can certainly overdo it. But people with IBS are sensitive to FODMAPs for one reason or another. So when they eat them, they get major gastrointestinal discomfort.
A diet low in FODMAPs works very well in people with IBS to manage their symptoms. It’s also useful as an approach to personalize their diet in an effort to center it around foods they tolerate.
But how does it improve their symptoms? Furthermore, does it lead to changes in their gut that may allow them to consume more FODMAPs from time to time?
The microbiome-gut-brain axis
People with IBS have a few things going on that may promote their condition. Overall, many believe IBS to be a dysfunction of the microbiome-gut-brain axis.
The microbiome-gut-brain axis is a bi-directional communication super-highway between the gut and brain. The gut has its own enteric nervous system that regulates things like enzyme secretion and motility. However, the brain also plays a role in regulating these processes.
Furthermore, the microbiome regulates both the enteric and central nervous systems. When microbes in our gut ferment components in our food, they create metabolites. These metabolites can interact with nerves in the gut or enter the blood to exert their effects elsewhere, including the brain.
A healthy microbiome-gut-brain axis is dependent on many things. You need:
- Healthy microbes
- Proper digestion
- Good wiring(healthy nerves)
- Enteroendocrine cells(Hormone secreting cells in the gut)
- Receptors to receive signals
If any of these components go screwy, dysfunction ensues in the microbiome-gut-brain axis.
Individuals often think of the microbiome-gut-brain axis as a much more simpler network than it is. They think the microbiome talks to the gut, while the gut and brain communicate bi-directionally through the vagus nerve.
But as you can tell from the above, it’s much more complicated than that.
How a low FODMAP diet works for IBS
Recent evidence points to some very interesting findings in regards to people with IBS. Several lines of evidence indicates that people with IBS have a lower distribution of enteroendocrine cells(EECs).
EECs are critically important to the microbiome-gut-brain-axis. They sense the presence of contents in the GI tract and release hormones that regulate motility, secretion, and appetite.
For example, one type of EEC called an I cell secretes a hormone called cholecystokinin(CCK) in the presence of fat and protein. CCK tells our gallbladder to release bile and our pancreas to release digestive enzymes and bicarbonate.
As you can tell, a lower density of EECs can completely wreck digestion. The interesting part about this is that a low FODMAP diet restores the density of EECs in the duodenum of people with IBS. In particular, I cell density was essentially restored to normal.
It did not restore all EECs, so further work is needed. A recent review covers the recent research on the topic.
Conclusion
While there is still more work to be done, it’s clear that a low FODMAP diet is a starting point for managing IBS. But the important point is that it’s a starting point, not the finish line.
Further tweaking and development of a personalized diet may help steer the microbiome in a direction that improves tolerance to FODMAPs. And addressing other components of the microbiome-gut-brain axis may help people with IBS improve digestion and increase the variety in their diet.
One interesting takeaway is that this approach may help other people with digestive problems improve their gut health. The gut is extraordinarily plastic due to the high turnover of cells.
Perhaps a gut reset centered around the microbiome-gut-brain axis can help many people with subclinical digestive problems improve their digestion and optimize their gut health.