FODMAP is an acronym. It stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols – referring to a group of carbohydrates  that ferment easily when they come in contact with bacteria. 

Foods high in these fermentable carbohydrates are difficult to digest, even for the healthiest among us, but for some people they can cause a lot of digestive upset.  When they enter the colon, which is teaming with microbes, the fermentation process can produce a lot of gas.

Most of us have experienced the gas that comes from beans, right?  Beans are high FODMAP foods.  So is garlic and so is cabbage – other notoriously gassy foods.

Healthy, but highly fermentable.

If you (or your child) experience excessive and mysterious gas, bloating, cramps, diarrhea, constipation, nausea, indigestion or belching after eating some healthy meals, it is worth looking for patterns to see if you are reacting to high FODMAP foods.  

FODMAP intolerance can be caused by a lack of digestive enzymes (You know Beno? Or Lactaid? Those are carbohydrate-digesting enzymes you could take as a supplement that focus on FODMAPs).  

It can also be caused by a lack of GLUT-5 which is needed to transport fructose across the gut membrane.  

Regardless of the cause, the result is that these carbohydrates are not absorbed through the digestive membrane and are left in the colon where they quickly ferment and cause the uncomfortable gassy symptoms.  

A low FODMAP diet is a temporary diet designed to help relieve discomfort caused by the poor digestion of these carbohydrates.

FODMAP intolerance is sometimes called “fructose malabsorption”, though the two are not exactly the same.  Fructose is one kind of FODMAP – it is the “M”, the  monosaccharide.  

A fructose malabsorption issue can be diagnosed by a hydrogen breath test. But the only good test for a full blown FODMAP sensitivity is an elimination diet. 

The FODMAP-brain connection

Fructose malabsorption, a type of FODMAP intolerance, is associated with low tryptophan levels because high blood  fructose levels seem to interfere with tryptophan metabolism.  Tryptophan is a building block for serotonin and melatonin, low levels of which have been associated with depression and anxiety. 

A low FODMAP diet can also be helpful for persistent constipation, which can be a contributor to sluggish brain function.  

Interestingly, some people might find that as they reduce fructose, melatonin and serotonin levels stabilize. Constipation is also often relieved because melatonin and serotonin play a role in regulating peristalsis.  Sometimes it’s the constipation that is causing behaviour and mood issues either due to pain and discomfort or the reabsorption of metabolites. 

It can be a bit of a “chicken-or-egg” thing but there is a definite relationship between gut function and brain function.

When to give low FODMAPs a “go”

A low FODMAP diet is quite restrictive of otherwise healthy foods.  It’s not generally my first go-to for families but I do think of it, particularly if we reach a plateau with other interventions we have tried. 

I think of limiting FODMAPs if a family is dealing with severe intestinal distress, or behaviour issues that we think might be resulting from gastrointestinal distress (like pain from persistent constipation, for example, that we can’t get a handle on in other ways).

I think of reducing FODMAPs if we can see clear patterns indicating that these carbohydrates are causing digestive symptoms.

I think of reducing FODMAPs if we are dealing with persistent diarrhea that won’t abate – high FODMAP foods attract water into the intestine and can lead to diarrhea (which is why prunes, a high FODMAP fruit, is a go-to for constipation)

I think of taking out  FODMAPs if there are persistent yeast or SIBO (small intestine bacterial overgrowth) problems that we can’t resolve. 

If we do try a low FODMAP diet, we do so only temporarily while we try to replenish enzymes, rebalance the microbial landscape and soothe the gut’s mucosal lining.  We then re-introduce these foods after about 6 weeks.  

Sometimes, after reintroducing foods, you might find a sensitivity to some, but not all, of the high FODMAP foods.  You might also find your “tolerance level” – meaning that a low amount is ok, but too much brings back the symptoms.

If you are using a probiotic, it’s important to check it for the presence of FOS or inulin. These are common prebiotics added to feed the probiotics, but in a person sensitive to FODMAPs they can cause digestive upset.

The low FODMAPs diet is a rather new kid on the block.  It has only really been around since 1999 and has been undergoing trials since then.  It has been shown to be quite effective for reducing symptoms of digestive upset such as gas, pain, bloating, diarrhea, constipation, nausea and belching.

A short list of high FODMAP foods (this list is NOT complete)

Oligosaccharides: artichokes, beans, lentils, chic peas, wheat, garlic, onions, inulin, coconut, soy, barley, rye

Disaccharides: Lactose (all forms of dairy)

Monosaccharides: Fructose (high-fructose fruits like apples, pears, watermelon, mango; honey; agave syrup; high fructose corn syrup)

Polyols: sugar alcohols like maltitol, sorbitol, xylitol; some fruits like prunes, apricots, plums, avocado