A low-FODMAPs diet, the abbreviation for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, has been shown to reduce symptoms of irritable bowel syndrome, IBS, in studies conducted at Monash University in Australia. It is a diet crafted to remove fructans, fructooligosaccharides (inulin), galactooligosaccharides, lactose, fructose, sorbitol, and mannitol that human bowel flora metabolize and many need to survive. A low-FODMAPS diet is therefore designed to starve bowel flora that metabolize such sugars. You can find a listing of FODMAPS eliminated and permissible foods here.
Does it work to reduce symptoms of IBS? Yes, it does. a FODMAPs-reduced diet reduces the bloating, abdominal discomfort, and unpredictable bowel urgency and diarrhea characteristic of IBS. The relief provided can be considerable.
Recall that most IBS is really SIBO. In other words, efforts to reduce diarrhea, cramping, and urgency typically ignore the cause: unhealthy changes in bowel flora that have ascended up from the colon and into the ileum, jejunum, duodenum, and stomach.
But the FODMAPs diet has triggered considerable confusion on what it accomplishes and what it does not accomplish, some even advocating it as a panacea. And is it good for you? Does it improve health? And what is the effect on the microbiome? Is it really an answer for health issues? Does reducing the symptoms of IBS lead to better bowel and overall health long-term?
I believe it helps to view a FODMAPs-reduced diet as nothing more than a symptom-reducing maneuver. By depriving bowel flora—both unhealthy undesirable species such as E. coli, Campylobacter, and Shigella, as well as desirable species such as Lactobacillus, Bifidobacteria, Akkermansia, and selected Clostridia—of necessary nutrients, bacterial counts in the gastrointestinal tract drop. With their reduced numbers, toxic components such as lipopolysaccharide, LPS, released with the death of undesirable microorganisms, is reduced, leading to less intestinal inflammation, less body-wide inflammation. FODMAPs reduction can therefore lead to reduced bloating, abdominal discomfort, and diarrhea that may or may not return upon resumption of FODMAPS consumption after several weeks to months of engaging in the diet.
But it is important to recognize that a low-FODMAPs diet also introduces undesirable changes in the microbiome:
- Reduces bacterial species diversity—Species diversity is a consistent marker of better health.
- Reduces Bifidobacteria substantially–Bifidobacteria confer a number of important health benefits.
- Reduces Clostridia species that produce butyrate—Butyrate is a mediator of a number of important health benefits.
Most important of all, a low-FODMAPs diet does nothing to restore a healthy microbiome, certainly not if you begin with severe dysbiosis, SIBO, or intestinal fungal overgrowth. Yes, it reduces the numbers of pathogenic bacteria but does not restore healthy balance of microorganisms. A diet temporarily deprived in FODMAPs cannot yield the increased butyrate required for intestinal healing. It does not restore the healthy balance of Akkermansia that increases the production of protective mucous. It does not replenish or seed the intestines with healthy species such as (our favorite species) Lactobacillus reuteri.
A FODMAP-elimination effort is therefore useful to reduce symptoms in IBS, SIBO, and dysbiosis, much like taking an opiate can relieve a headache from having a brain tumor—but symptom relief is not the same as disease reversal. So should you choose to follow a low-FODMAP lifestyle, recognize that it is only a symptom-reducing effort but does little to nothing to restore a healthy microbiome. It takes additional efforts to accomplish that, efforts such as supplementing curcumin to rebuild the integrity of the intestinal barrier, efforts to increase Akkermansia populations, and efforts to reduce fungal populations.