Research review questions whether low FODMAP diets are solution to digestive woes

06-Aug-2015 - Last updated on 07-Aug-2015 at 12:22 GMT

Limiting consumption of certain carbs may not be the panacea once thought for bloating and abdominal pain caused by irritable bowel syndrome, and actually could cause more harm if not overseen by a healthcare provider, a new data review suggests.

In recent years, poorly absorbed short-chain carbohydrates, collectively known as FODMAPs, have been blamed for triggering digestive discomfort in some people – prompting some dietitians to advocate limiting them.

But a review of the available data published Aug. 6 in the journal Drug and Therapeutics Bulletin suggest “there is very limited evidence” to support a diet low in FODMAPs, which are found in wheat, onions, legumes, some dairy and some natural and artificial sweeteners.

“Evidence for the efficacy of the low FODMAP diet to improve symptoms of irritable bowel syndrome is based on a few relatively small, short-term unblinded or single-blinded controlled trials,” none of which exceeded six weeks, according to the review in DTB. Likewise, the ideal duration of diet adherence is unknown, the review adds.

The review also points out the restrictive diet could cause harm if not properly followed. For example, some adherents might not consume sufficient nutrients or fiber while on the diet. In addition, some FODMAPs are prebiotics that promote the growth of probiotic bacteria in the gut, such as bifidobacteria, which could improve digestive health, the review notes.

The review’s fears about harm, however, are not grounded in the research. The authors acknowledge they are not aware of any published data that has assessed the nutritional adequacy of patients’ intake while on a low FODMAP diet. They also note that there were few reports of adverse events in the studies.

However, they suggest that people who self-diagnose their digestive problems as related to FODMAPs and do not seek a healthcare provider’s guidance could go astray on what is a very difficult diet to which to safely adhere.

Low FODMAP diet could reset the gut

While the research may be limited, a statistically significant portion of participants in all the studies reported some level of relief from IBS symptoms on the low FODMAP diet.

Even a little relief may be enough for some patients to try the diet, given that many people who suffer from IBS have done so for years and tried many potential solutions without luck, said Cynthia Harriman, director of Food and Nutrition Strategies at Oldways Whole Grains Council. She added that the goal of the low FODMAP or any restrictive diet is to only temporarily restrict foods until the gut is “back in order” and then reintroduce foods slowly so patients can eat healthy foods without drastic long-term restrictions.

She suggested a main advantage to restrictive diets, such as the low FODMAP diet, might be their initial restrictive stage, which “serves to starve out the bacteria species that have been hanging around in your gut, shaking things up a bit and making a change possible – if you eat the right foods to recolonize yourself with ‘better’ bacteria.”

Indeed, the review noted in one study participants who took a probiotic supplement saw similar beneficial results to those who were on the low FODMAP diet compared to those who were in the control group.

“Let’s not blame the canary”

With this in mind, Harriman suggested blaming FODMAPs, or before that gluten, for digestive problems may be misplaced.

“Gluten, FODMAPs, and whatever will be the NEXT candidate (and there will be one!) are really canaries in the coal mine. Let’s not blame the canary: Let’s clean up the mine!”

To do this, she suggested tackling the question: “What has our overall Western Diet done to our digestive tracts that we have trouble digesting wonderfully healthy foods that people have eaten as far back as we can remember?”