Irritable Bowel Syndrome (IBS)
Dietary considerations such as reducing daily intake of caffeine and fatty foods may benefit individuals with IBS (Lee 2012). Individuals with IBS are often aware of some foods that exacerbate symptoms; thus, they may be able to improve symptoms by avoiding those foods (Torpy 2011). The following specific diets may help manage IBS symptoms. Each involves the selective exclusion of one or more types of food.
FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols)
A low FODMAP diet is based on the hypothesis that impaired carbohydrate absorption allows excess undigested carbohydrates to reach the lower GI tract (large intestine). There, undigested carbohydrates stimulate the growth of pathogenic microbes, leading to excess gas, diarrhea, and constipation (Ostgaard 2012). Theoretically, the restriction of fermentable foodstuffs deprives the dysbiotic gut flora of their energy source and results in decreased symptoms.
Foods typically avoided on a low FODMAP diet include: fructo-oligosaccharides (eg, wheat, rye, onions, garlic, artichokes), galacto-oligosaccharides (eg, legumes), lactose (eg, milk), fructose (eg, honey, apples, pears, watermelon, mango), sorbitol (eg, apples, pears, stone fruits, sugar-free mints/gums), and mannitol (eg, mushrooms, cauliflower, sugar-free mints/gums). In one study, IBS sufferers assigned to a low FODMAP diet experienced significant improvement in their symptom response (ie, bloating, abdominal pain, and flatulence) relative to a standard diet group (Barrett 2012; Staudacher 2011). These results are supported by a later study showing that IBS patients who were guided to eat a low FODMAP diet experienced a significant decrease in abdominal pain (Ostgaard 2012).
While a gluten-free diet is required for patients with celiac disease, there is a wide spectrum of non-celiac gluten sensitivities that present like IBS (Volta 2012). Gluten is found in grains (eg, wheat, barley, rye), breads, pasta, etc. Similar to the gluten-free diet, the low FODMAP diet also restricts gluten. Both diets are used to manage food sensitivities, suggesting that gluten sensitivity might be a more common contributor to IBS symptoms than previously thought (Carroccio 2012). In one double-blind, randomized, placebo-controlled study of IBS sufferers who specifically did not have celiac disease, addition of gluten worsened abdominal pain, bloating, fatigue, stool consistency, and overall symptoms of IBS (Biesiekierski 2011).
Food Sensitivities and IBS
Many features of IBS are similar to food sensitivities. A food allergy or food sensitivity is an inappropriate immune response to one or more components of the diet. Following ingestion, the immune system “attacks” particles of the problematic food(s). This “attack” is mediated by antibodies, which are components of the immune system that normally identify pathogens and trigger an immune response. In the case of food sensitivities or food allergies, antibodies mark certain food particles as pathogens and initiate a wider immune response that can lead to tissue inflammation and/or dysfunction.
Conventionally recognized “food allergies” are primarily mediated by two specific types of antibodies: immunoglobulin E (IgE) and immunoglobulin A (IgA). However, evidence suggests that “food sensitivities,” which are triggered primarily by the immunoglobulin G (IgG) antibody, may contribute to intestinal disorders as well, although mainstream medicine typically refutes this hypothesis. The reduction in IBS symptoms seen following the elimination of IgG-positive foods attests to the viability of this theory (Drisko 2006).
In one study, IBS patients were tested for IgG antibodies against a variety of foods, including chicken, wheat, soybeans, and rice (Atkinson 2004). They were then assigned to diets that excluded the foods to which they were IgG positive. In almost every case, this resulted in a significant improvement, which was reversed when the troublesome foods were re-introduced (Atkinson 2004). Similar findings were discovered in a 2012 study that demonstrated the existence of an IgG-mediated food sensitivity (Carroccio 2012). In this study, IgE testing was important to exclude food allergy, whereas IgG testing was important to diagnose food sensitivity. Taken together, these findings suggest that specific elimination diets may be successful and that IgG food sensitivity testing may help identify foods that contribute to IBS (Shanahan 2005).