As discussed in Chapter 10, significant controversy exists regarding the role of diet in the treatment of irritable bowel syndrome. This controversy continues because of the diversity of IBS symptoms, the variety of ways individuals respond to certain foods, the difficulty of determining which food is causing the symptoms, and the overlap between IBS, food intolerances, food sensitivities, and food allergies.
For the majority of people who have IBS, symptoms wax and wane over time. Symptoms can fluctuate daily, making it difficult to tell whether a particular food has affected a person’s symptoms. Many people who have IBS say that a specific food seems to cause problems one day (more bloating, more gas, more diarrhea) but be well tolerated on other days. This lack of consistency makes it hard to determine the relationship between eating certain foods and the occurrence of symptoms. Keeping an IBS diary, as described in Chapter 13, is helpful when making such a determination.
People respond differently to particular foods and to specific dietary changes. One person who has IBS may react with severe cramping and diarrhea to a food that presents no problem to another person who also has IBS with diarrhea. One patient may obtain great success with a certain diet, whereas another person experiences no improvement at all. Irritable bowel syndrome is a complex disorder. Even if patients have similar symptoms, the triggers for those symptoms may be quite different, so they can’t all be treated in an identical manner.
In some individuals who have IBS, there is a direct relationship between consuming a certain food and experiencing symptoms shortly thereafter. Such people may be tempted to think that avoiding that food will cure their IBS. Although certain foods may trigger or worsen IBS symptoms, they are not the cause of the syndrome. The underlying mechanisms of IBS include abnormal gut motility, visceral hypersensitivity, prior infections, changes in colonic flora, and heightened brain-gut interactions (see Chapter 3). IBS symptoms are expressed differently among patients, and some people have food triggers that others do not. Avoidance of a problem food may lead to an improvement in some symptoms but will not produce complete resolution of all IBS symptoms.
Clinicians, researchers, and patients now have more information about specific foods, or food groups, that seem to worsen IBS symptoms for some people. Lactose intolerance, fructose intolerance, and sensitivity to fermentable foods, gluten, and carbohydrates appear to be the most bothersome conditions for people who have IBS. Diet modifications for each of these conditions are described below.
For people who have symptoms of IBS, a period of abstinence from dairy products is usually helpful to determine which symptoms, and the proportion of those symptoms, are due to lactose intolerance as opposed to IBS. I usually recommend 7 to 10 days of absolutely no dairy products as a reasonable trial. During this time, the patient is asked to maintain a diary of GI symptoms. If symptoms improve during this time period, then the patient probably has some degree of lactose intolerance. Milk products are then slowly reintroduced into the diet, typically by adding 2 to 3 ounces every day in any form the patient desires. This gradual rein-troduction allows the individual to determine where her or his threshold is and make appropriate dietary adjustments.
If people find it difficult to withhold milk products from their diet or to follow symptoms closely while reintroducing them, a milk challenge test can be easily performed at home. This test is simpler and speedier but less detailed and more uncomfortable than the milk cessation trial. In this method of determining whether lactose intolerance is present, the person is asked to drink two pints (32 oz) of low-fat milk in one sitting. Anyone who can drink this quantity of milk and not develop any symptoms of gas, bloating, abdominal distention, or diarrhea is not lactose intolerant.
Lactose intolerance can also be assessed in the laboratory. After fasting overnight, the patient drinks a predetermined quantity of lactose, usually 25 to 50 gm, dissolved in water. The patient is then asked to blow into a tube every 15 minutes for approximately 3 hours. The level of hydrogen gas in each exhalation is measured (this is similar to the breath hydrogen test to look for evidence of small intestine bacterial overgrowth, described in Chapter 11). Patients who are not lactose intolerant will have consistent levels of breath hydrogen during the three-hour study period, because the lactose is broken down slowly in the small intestine and absorbed by the body. Patients who are lactose intolerant, however, will have an increase in the amount of breath hydrogen in 1½ to 2½ hours, approximately the time it takes for the lactose to travel through the small intestine and reach the beginning of the colon, where it encounters the colonic bacteria, producing a sharp rise in breath hydrogen. I do not recommend the breath hydrogen test for the vast majority of patients who may be lactose intolerant, because it is somewhat expensive to perform and may not offer any more information than a simple milk challenge test (which costs the price of a quart of milk) or the milk abstinence trial. It can be helpful, however, for those individuals with confusing symptoms, those who seem to be intolerant to even small portions of milk products, and those who continue to have symptoms despite avoiding milk or using a lactase supplement.
Identifying lactose intolerance is important for people who have IBS because it may lead to a significant reduction in some symptoms. (Obviously, if all symptoms disappear, then the true diagnosis for the patient was only lactose intolerance, not IBS and lactose intolerance.) Many individuals who have lactose intolerance are unaware that they are intolerant to milk, which complicates treatment, because medications designed to treat IBS won’t help the symptoms caused by lactose intolerance. Sorting this issue out allows the patient and the physician to better understand which symptoms occur because of dietary problems and which symptoms occur due to IBS and to appropriately treat both.
For treating lactose intolerance, pills containing lactase are available over the counter at most grocery stores and pharmacies. People who have lactose intolerance should take one or more pills before they consume a milk product (the dose depends on the level of lactose intolerance and the size of the serving of dairy food). Lactase-supplemented milk products are sold under the brand name Lactaid. Patients who are strongly lactose intolerant are advised to use soy milk, rice milk, almond milk, or lactaid-100 milk (in which 100 percent of the lactose is already broken down). Lactose-free cheeses and other products (for instance, ice cream made from rice or soy) are also available.
Some people note that they can tolerate a serving of dairy if ingested with a meal (such as drinking a glass of milk with dinner). Taking the dairy product with a meal causes the dairy product to move more slowly through the GI tract, allowing for increased absorption of calcium and Vitamin D and decreased symptoms of gas and bloating. Other patients are able to tolerate dairy products more easily if they slowly add a small amount of dairy to their daily routine over the course of several months. Because nearly all of the milk sugar has been broken down during its production, yogurt can be a good way to take in protein, calcium, and Vitamin D. Very hard cheeses (extra sharp cheddar, parmesan) have little lactose remaining and can also be well tolerated in small servings.
Finally, note that there are some clinical consequences to avoiding dairy products. Vitamin D and calcium are found in dairy products, and avoiding all dairy products may lead to Vitamin D deficiency and low levels of calcium, which can contribute to osteoporosis and possibly even hypertension. If necessary, both Vitamin D and calcium can be replaced with over-the-counter or prescription medications.
A simple way to determine whether some of your symptoms are the result of fructose intolerance rather than IBS is simply to avoid all fructose-containing liquids and foods—all carbonated drinks, all fruit juices, all types of sports drinks, and those fruits and vegetables that contain fructose (such as pears, apples, mangos, peaches, Mandarin oranges, watermelon, and pineapple). Continue this test for 7 to 10 days. If, during this trial, your symptoms of gassiness, bloating, and diarrhea improve, you are probably fructose intolerant to some degree. You can then gradually reintroduce small amounts of fructose-containing foods and liquids in an attempt to determine your threshold of tolerance (a reasonable goal is less than 25 gm of fructose per day). Alternatively, your doctor can schedule you for a fructose tolerance test. This test is similar to the breath hydrogen test used to diagnose lactose intolerance.
The acronym FODMAP stands for Fermentable Oligo-, Di-, and Mono-saccharides and Polyols. This term is meant to group a variety of food products that are more likely to cause gas, bloating, and distention. These symptoms may develop because some of these food substances (such as fructose) are poorly absorbed in the small intestine and thus pass undigested into the colon, where they are broken down by colonic bacteria. Symptoms may also develop because many of these food substances are very small in size and, as such, draw water into the intestinal tract (making stool loose and watery). Finally, many of these food products are rapidly fermented by bacteria. The rate of fermentation of food products in the colon is determined by the length of the carbohydrate chain. The short-chain carbohydrates that should be avoided on the low-FODMAP diet are more rapidly fermented in the colon, and therefore they quickly cause distention and discomfort.
The low-FODMAP diet has received a lot of attention from the media and the medical community for a number of reasons. One, it is a diet and not a medication and thus, theoretically, it will usually not cause any adverse side effects. Two, since it is not a medication, it will normally not be expensive (however, there are always costs associated with changing your diet; some of these costs may be monetary, and other costs may include an investment of time). Three, since it is a diet, many patients and health care providers believe that it will be easy to institute and follow (not necessarily true—see the guidelines below). Finally, the low-FODMAP diet puts the patient in control and allows the patient to monitor his or her own symptoms.
If the goal of the low-FODMAP diet is to avoid foods that either can rapidly pass through the GI tract into the colon undigested or are more likely to ferment in the colon (and thereby to improve symptoms of gas, bloating, and diarrhea), then how should a person who has IBS modify his or her diet accordingly?
• Foods with excess fructose. This means fruits such as apples, cherries, mango, pears, peaches, canned fruits in their natural fruit juice, watermelon, and large quantities of fruit juice or dried fruit. Vegetables to be avoided include asparagus, artichokes, and sugar snap peas. Honey and products with high-fructose corn syrup (juices, regular soft drinks, sports/energy drinks) should also be avoided.
• Fructans (fructo-oligosaccharides). These are made up of short chains of fructose with a glucose molecule on the end. These include grains (rye, wheat bread, crackers, biscuits, wheat pasta, couscous); fruits such as peaches, persimmons, plums, and watermelon; and vegetables such as onions, peppers, artichokes, brussels sprouts, broccoli, cabbages, fennel, garlic, okra, leeks, and legumes (beans, peas, lentils).
• Galactans (galacto-oligosaccharides). These are short chains of sucrose with galactose (similar to the fructans list above).
• Polyols (also called sugar alcohols). These include low-calorie sweeteners such as sucralose as well as sorbitol, mannitol, xylitol, and malitol (which are often used in sugar-free candies, gums, and mints). Fruits that contain sorbitol include apples, apricots, pears, blackberries, nectarines, and plums. Vegetables that contain mannitol include cauliflower, mushrooms, and snow peas.
Note that avoiding lactose is not considered a part of the low-FODMAP diet. However, if a person is lactase deficient, then lactose cannot be broken down, and it acts similarly to fructans and galactans in producing gastrointestinal distress.
• Gluten-free or spelt toast
• Corn or rice cereals
• Eggs
• Lean proteins (chicken, turkey, fish, lean pork, lean lamb, lean red meat)
• Cheeses with no/low lactose (typically the hard cheeses)
• Rice cakes
• Quinoa
• Select fruits (smaller volumes of bananas, grapefruit, grapes, kiwi, honeydew melons, tangelos, oranges, strawberries, lemons, limes, and blueberries)
• Select vegetables (bamboo shoots, bok choy, carrots, eggplant, green beans, lettuce, tomato)
As described in a recently published study, 82 patients who had IBS and attended a dietetic outpatient clinic found that, compared to a standard diet, the low-FODMAP diet significantly improved their symptoms of bloating, abdominal pain, and flatulence. Overall compliance with the diet was high in this study (the participants were counseled by dieticians). The average time to improvement of symptoms of gas and bloating was 3½ weeks—a sign that people who have IBS should not expect all of their symptoms to improve quickly with this diet. Note that, if followed very carefully, the low-FODMAP diet may create some problems with constipation in individuals who have IBS with mixed or alternating diarrhea and constipation and will probably worsen constipation symptoms in people who have IBS with constipation. I generally recommend at least four weeks on the low-FODMAP diet to see if there is any improvement or change in symptoms.
Until recently, other than anecdotal reports, there were no good data to show that a gluten-free diet might improve symptoms of IBS. In 2011, researchers evaluated the benefits of a gluten-free diet in a study of 34 patients (30 women and 4 men) who met specific criteria for the diagnosis of IBS. All 34 patients were carefully tested to make sure that they did not have celiac disease. Patients were then randomized to either a diet containing gluten or a gluten-free diet for six weeks (food was prepared for them so that it appeared identical, regardless of whether it contained gluten or not). Symptoms were monitored throughout the six weeks and serum, urine, and blood samples were checked at the beginning and the end of the study period. The authors reported that patients who had IBS and ingested gluten were more likely to report typical symptoms of IBS, compared to those patients who had IBS and ingested foods without gluten. Specifically, symptoms of abdominal pain, bloating, and tiredness were all worse in the gluten group compared to the gluten-free group.
This study was not designed to understand the mechanism of how gluten might cause symptoms of IBS, but its results are intriguing in that they appear to show gluten as a trigger for a variety of GI symptoms in people who have IBS. Although a gluten-free diet can be difficult to follow, for those who have persistent symptoms of IBS and who wish to use only dietary treatment measures, a gluten-free diet is safe and certainly worth trying.
Another diet modification that can improve symptoms of gas and bloating is decreasing or eliminating carbohydrates. The theory is that carbohydrates contain starches and sugars, and these are the substances that are likely to ferment while being broken down in the colon (large intestine). If carbohydrates are removed from the diet, then (again, theoretically) there is less material to ferment in the colon, with less production of gas, which leads to an improvement in symptoms of bloating, distention, and diarrhea. A small clinical trial tested this theory with people who had IBS with diarrhea (IBS-D) by placing some patients on a very low-carbohydrate diet (only 4 percent of daily calories were from carbohydrates) and comparing their symptoms to that of patients who had IBS-D and were maintained on a normal carbohydrate diet (55 percent of daily calories). All meals were prepared by a commercial kitchen, and the calorie content was balanced so that patients did not lose or gain weight. During this four-week study, patients who had IBS-D and were placed on a very low-carbohydrate diet felt better, had reduced stool frequency, and had an improvement in stool consistency (loose stools became more formed) and abdominal pain. Overall, patients tolerated the diet well. However, the study was only four weeks long and the meals were prepared for the patients, which made the diet easy to follow (and less costly). The downsides to the low-carbohydrate diet followed by the patients who had IBS-D included the following: (1) 51 percent of the calories consumed were from fat, which is detrimental to long-term health; (2) 45 percent of the calories consumed were from protein, which can be expensive, potentially detrimental to health over the long run, and not necessarily sustainable; (3) essentially no fruits or vegetables were allowed in the diet, which may be detrimental to a patient’s long-term nutritional status. Additional studies are needed to confirm these results. However, if a person who has IBS is going through a particularly difficult time with gas, bloating, and diarrhea, a diet that focuses on lean proteins and much smaller servings of carbohydrates (with an emphasis on simple carbohydrates such as white rice and white potatoes) may help.
Despite the fact that IBS is so common and causes so many debilitating symptoms, little research has been performed on the effect of diet on people with functional bowel disorders. However, most experienced clinicians offer the following advice. One, avoid fad diets and diets that emphasize extremes (for example, the all-grapefruit diet). These are rarely helpful and in the long run rarely healthful. Two, don’t become food phobic. Use the food diary described in Chapter 13 to track your symptoms, and enjoy the foods you tolerate well. Three, for many people who have IBS, it is not what they eat but rather the act of eating that often causes symptoms. If you have a hypersensitive gut, a smaller-portioned meal will usually be less challenging to your GI tract and better tolerated than a large meal. This is especially important for patients who have IBS and diarrhea and who frequently have very urgent diarrhea during or shortly after a meal. A large meal will trigger a stronger gastrocolic reflex, resulting in more urgent diarrhea, whereas a smaller meal won’t elicit such a powerful response. Finally, having a set routine, especially for the timing of meals, can be helpful to all people who have IBS, whether they have diarrhea or constipation or alternate between the two. It may take a little time and recording of symptoms and events to discover what works best for your gut, but most people’s GI tracts respond well to the rhythm of predictable routine.
• For people who have symptoms of IBS, a period of abstinence from dairy products is usually helpful to determine which symptoms, and the proportion of those symptoms, are due to lactose intolerance as opposed to IBS.
• To determine whether symptoms are the result of fructose intolerance rather than IBS, avoid all fructose-containing liquids and foods—all carbonated drinks, all fruit juices, all types of sports drinks, and those fruits and vegetables that contain fructose (such as pears, apples, mangos, peaches, Mandarin oranges, watermelon, and pineapple).
• The low-FODMAP diet has been shown to improve symptoms of gas and bloating in some people who have IBS.
• Avoiding gluten may improve symptoms in some individuals who have IBS, even if they don’t have a wheat allergy.
• An eating regimen that features smaller, more-frequent meals and emphasizes regular routine will be less likely to trigger IBS symptoms.