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

By Elizabeth Crawford contact

- Last updated on GMT

Research review questions if low FODMAP diets can solve digestive woes
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?”

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FODMAP is Gluten-Casein Free, Fructose Free

Posted by Amy Brown, PhD, RD,

The FODMAP Diet is automatically gluten-casein free. Try that less restrictive diet first. Some people are sensitive to fructose, so eliminating fructose containing foods might also help. In fact, two of the four clinical studies testing the FODMAP diet selected for IBS patients with fructose malabsorption. The easy way to test for fructose malabsorption is to see if you get symptoms after eating honey. Also, fructose sugar can be purchased online or in some health food stores to put it in your tea or coffee to see if any symptoms occur. A study by Bohn in the August 6 issue of Gastroenterology just published that FODMAP did make a difference in a multi-center, parallel, single-blind study of 75 IBS patients. The review in the above article criticizing the FODMAP diet for limited studies is incorrect because there have been at least 5 clinical studies. How many more studies do you need? Also, it only takes 4 weeks or less to see a difference in symptoms, so using 6 weeks as an arbitrary point pulled out of the air for disqualifying these studies and the diet itself is less than honest. It is unethical to publish incorrect information in the scientific community and worse to propagandize it to the public via a press release.

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Posted by Gail T. Kessler,

I am a registered dietitian and I thought I had IBS most of my life but 2 years ago I was diagnosed with microscopic colitis. I have always had food intolerances but after a recent flare-up I reviewed the foods in the FODMAP diet and realized that cherries were the culprit. I stopped eating them and now I can have a few occasionally. The diet is a good guide and expands on advice I've provided to clients throughout my career.

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Posted by Barb Stuedemann, MS, RD, LD,

I, too, am a registered dietitian who suffered for many years with IBS which was getting worse and debilitating. I received my FODMAP guidance from another RD and have followed it for 2 1/2 yrs now. It has been an incredibly beneficial diet for me. It is restrictive, but in some ways, I am eating healthier than before because I was restricting a lot of foods in search of the foods that were causing my horrible symptoms. I was eliminating some foods that I thought were problematic, but in fact, I can eat and tolerate well on the FODMAP diet. I don't believe this is a trend, as the gluten free diet has become for many. I believe that, if you have severe IBS as I did, you will benefit greatly and you can learn to eat in a healthy manner on the FODMAPS diet.

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