Is a Low-FODMAP Diet Best for Digestive Disorders?

Do patients come to you with stubborn digestive disorders? When basic dietary changes aren’t enough, removing certain types of carbohydrates called FODMAPs from the diet may be helpful. Read on to learn the evidence for a low-FODMAP diet, how to implement it, and why it should only be used as a short-term therapeutic strategy.

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Digestive disorders are perhaps the number one complaint I see clinically. They range from irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) to gastroesophageal reflux disease (GERD) and everything in between. In many cases, adopting an anti-inflammatory, nutrient-dense Paleo diet that supports gut health leads to complete resolution of digestive disorders. In other cases, a more drastic intervention may be necessary. For example, I recently wrote about the Paleo autoimmune protocol (AIP) and its success for patients with IBD.

Another potential intervention is a low-FODMAP diet. FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. In a patient with healthy gut function, many of these carbohydrates are beneficial, acting as prebiotics that stimulate the proliferation of healthy gut microbes. In patients with digestive disorders, however, they can exacerbate symptoms like gas, bloating, diarrhea, gut pain, and even GERD.

In this article, I’ll discuss the evidence for a low-FODMAP diet, how to implement it, and the long-term consequences of a low-FODMAP approach.

Should you stay on a low-FODMAP diet forever?

Efficacy of Low-FODMAP for Symptom Reduction

Low-FODMAP diets have been studied extensively for “functional gut disorders” like IBS. Consuming FODMAPs does not actually cause the gut disorder; rather, it exacerbates symptoms because it feeds the microbes in the small intestine. Thus, reducing FODMAPs may provide significant relief by reducing small intestinal bacterial overgrowth (SIBO) (1). About 84 percent of patients with IBS have a positive lactulose breath test for SIBO (2).

Unfortunately, no studies to date have looked at the effect of a low-FODMAP diet on long-term SIBO outcomes. Still, the low-FODMAP diet can provide effective short-term relief. One study found that low-FODMAP diets reduced symptom severity in 76 percent of patients with IBS compared to a 54 percent reduction in a group receiving standard diet advice. Bloating, flatulence, and abdominal pain were all reduced on the low-FODMAP diet (3). Clinically, I’ve also found low-FODMAP diets to be useful in patients with Crohn’s disease, ulcerative colitis, and diverticulosis.

What Foods Have FODMAPs?

Now that we’ve established why low-FODMAP is an appropriate choice for symptom relief, let’s look at what foods contain FODMAPs:

Excess fructose: Honey, apple, mango, pear, watermelon, high-fructose corn syrup, agave syrup, dried fruit, fruit juice

Fructans: Artichokes (globe), artichokes (Jerusalem), asparagus, beetroot, broccoli, Brussels sprouts, cabbage, eggplant, fennel, okra, chicory, dandelion leaves, garlic (in large amounts), leek, onion (brown, white, Spanish, onion powder), radicchio, lettuce, spring onion (white part), wheat, rye, pistachio, inulin, fructo-oligosaccharides.

Lactose: Milk, ice cream, custard, dairy desserts, condensed and evaporated milk, milk powder, yogurt, soft unripened cheeses (such as ricotta, cottage, cream, and mascarpone cheese).

Galactans: Legumes (such as baked beans, kidney beans, soybeans, lentils, chickpeas).

Polyols: Apple, apricot, avocado, blackberry, cherry, longan, lychee, nectarine, pear, plum, prune, mushroom, sorbitol, mannitol, xylitol, maltitol, and isomalt.

I usually recommend removing all FODMAPs from the patient’s diet for a period of 30 days.

Individualizing Low-FODMAP

This may seem like a lot, but in my clinical experience, most patients do not have the same reaction to each class of FODMAPs listed above. For example, some people seem to have no trouble with lactose but do very poorly with excess fructose. Others may tolerate polyols but not fructans. After the initial 30-day period, I recommend reintroducing FODMAPs one category at a time to see which are well tolerated. For instance, once the patient knows how fructans affect her, then you could recommend reintroducing the foods with excess fructose, and so forth.

It’s also rarely necessary to completely eradicate FODMAPs from the diet. FODMAP intolerance is not like gluten or casein intolerance. In those cases, the immune system reacts—regardless of how much of that food you eat. With FODMAP intolerance, it’s more of a threshold response. If a person is eating a lot of FODMAPs daily, the threshold for tolerating FODMAPs will be quite low. However, if the overall intake of FODMAPs is low, the patient may be able to tolerate small amounts without much problem. This can make things a little easier when people are eating out, traveling, or are in an environment where they don’t have as much control over their food choices.

The Dangers of Long-Term Low-FODMAP

Another reason to reintroduce at least some FODMAPs back into the diet is their function as prebiotics. At least two studies have shown that long-term low-FODMAP diets alter the colonic environment and reduce the levels of beneficial bacteria in the colon (4, 5).

Some of my patients have found that a few months on a low-FODMAP diet was sufficient to reduce their sensitivity to FODMAPs upon reintroduction. If you reintroduce FODMAPs and the patient still has symptoms, consider testing the patient for SIBO. After SIBO treatment, patients may be able to tolerate some or all FODMAPs again.

Conclusion

Digestive disorders are complex, multifactorial conditions. However, I’ve seen many patients achieve complete resolution with the proper diet, lifestyle, and supplemental support. Here’s a quick summary of my recommendations:

• Start patients with a 30-day Paleo reset. Many patients have digestive disorders that resolve simply from removing inflammatory foods from their diet.
• Try a low-FODMAP diet for 30 days. This can provide significant symptom relief and may reduce proliferation of bacteria in the small intestine.
• After 30 to 60 days, reintroduce FODMAPs by category. Staying on a low-FODMAP diet long term can negatively impact beneficial microbes that rely on fermentable carbohydrates.
• Test and treat SIBO. Most patients find that their symptoms are only managed by a low-FODMAP diet; they do not disappear completely. Addressing SIBO using antimicrobials should improve FODMAP intolerance over time in those with digestive abnormalities. Be sure that the patient is not on a low-FODMAP diet during SIBO treatment though!

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