A recent publication from the GI Health Foundation carries the ominous title, “Westernized Diet is the Most Ubiquitous Environmental Factor in Inflammatory Bowel Disease.” It echoes several other studies that point to a “Western” diet as a key driver of IBD.

But what, exactly, is a “Western” diet? If scaremongering headlines are to be believed, it’s a diet that’s heavy in red meat, saturated fat, and sodium—and the chronic, non-communicable diseases we suffer are punishment for enjoying juicy steaks, salty bacon, fatty salami and creamy cheese. But if indulging in these rich foods were truly the cause of IBD, then the populations of France, Spain, Italy and other countries where these foods have been celebrated for centuries would have been debilitated by IBD ages ago.

It takes only a quick stroll through the aisles of a typical American supermarket to see that the vast majority of “foods” (or, as author Michael Pollan calls them, “edible food-like substances”) on offer are not meat- and saturated fat-centric but rather, are loaded with refined sugars, grains, and industrial seed oils, which are high in polyunsaturated fat. 

According to the 2015 dietary guidelines from the US Department of Health and Human Services (HHS; based on NHANES data from 2007-2010), the American population as a whole exceeds recommended intakes for added sugars, saturated fats, and sodium. But increasing evidence suggests the guidelines themselves may be problematic. For example, numerous studies now show sodium intakes that are too low are more dangerous than consuming higher amounts of sodium, and since a meta-analysis of prospective cohort study determined there is “no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD,” it’s hard to imagine why the public is still cautioned to limit saturated fat intake. In fact, replacement of saturated fats with refined carbs and/or omega-6-heavy seed oils appears to be highly damaging for health, and responsibility for at least some of the cardiometabolic disease epidemic the nation now faces may be attributed to this transition.

If a “Western” diet is a primary player in IBD, it’s difficult to separate and isolate the effects of any one individual food or compound. Is it the refined grains? The sugars? The omega-6 fats? The animal protein? Inadequate fruit and/or vegetable intake? (Despite there being no absolute “requirement” for carbohydrate in the human diet.) The GI Health Foundation abstract acknowledges: “Despite many review articles on environmental factors in IBD, no consensus exists regarding which factor contributes most to trigger the onset of IBD.” A review looking at the role of diet in the pathogenesis and management of IBS found that “the intake of calories, carbohydrates, proteins and fat by IBS patients does not differ from that of the background population.” No wonder it’s almost impossible to identify the true offenders. (Not to mention that sensitivity to different foods or food components may differ among individuals, so it’s possible one person’s IBS could be triggered by something that’s benign to someone else.)

The HHS guidelines report noted that about three-fourths of the US population consumes below the recommended intake for vegetables, fruits, dairy and oils. But increasing whole grains, vegetables and fruit might not be the best strategy for many with IBD. (One study showed a possible association between long-term vegetarianism and IBD in a French cohort.) Certain plant foods—specifically, wheat or gluten-containing foods and items high in FODMAPs—may trigger or exacerbate IBD. (Click here for a guide to FODMAPs.)

Low FODMAP diets are highly effective for irritable bowel conditions, producing symptom improvement in nearly 75% of patients. A systematic review and meta-analysis found that low FODMAP diets led to significant improvement in quality of life scores, abdominal pain, bloating and overall symptoms in both randomized and non-randomized trials. So maybe a “Western” diet that’s simply low in FODMAPs would be effective for some.

One study noted that gluten, wheat, related proteins and FODMAPs “are the most relevant IBS symptom triggers,” although they acknowledged that the most significant offenders among that list have not yet been elucidated. Modern processing technology has made it possible to isolate gluten protein from the carbohydrate it typically comes along with in wheat and select other grains, but grain-based products are likely the biggest source of gluten in the American diet. It’s interesting to note, then, that a very low-carbohydrate diet was shown to improve symptoms and quality of life in overweight patients with diarrhea-predominant IBS (IBS-D). This protocol called for just 4% of total calories from carbohydrate (and all meals were provided to participants). Such a dramatically low carb intake allowed for very little total plant food—grains, vegetables and fruits—yet the subjects had “a profound clinical response in their IBS-D symptoms.” Physicians using low-carb and ketogenic diets in their practices have reported dramatic improvements in their patients with IBS. There’s certainly room for fiber on ketogenic diets, but it’s possible that individuals with IBS who adopt a keto diet may do better with less fiber, rather than more.

Clinical trials, reports from physicians, and patient self-reports show that Paleo, Primal, low-carb and low FODMAP diets can all be effective for improving IBS symptoms. These dietary approaches are customizable and can be constructed with a large or small proportion of vegetables, a high or low amount of saturated fat or other types of fat, plant-based or animal-dominant, and include grains and legumes or prohibit them. So perhaps there’s not a one-size-fits-all solution to IBS, but rather, different approaches may be needed for different individuals.