Irritable bowel syndrome (IBS) affects about 20 percent of adults in the United States, and recent research shows that enjoying a low-FODMAP diet can help drastically reduce your IBS symptoms. But what are FODMAPs, and what do they mean for your digestive system? It’s a fairly complicated subject, but I will break it down for you so that will have an understanding of the following:
• What FODMAPs are
• What common foods contain FODMAPs
• Why FODMAPs cause digestive issues in some people
• How the diet works, including the elimination and rechallenge phases
• The difference between a food intolerance and a food allergy
• How to improve your digestion
• What foods to enjoy on the low-FODMAP diet
“FODMAP” stands for “Fermentable, Oligosaccharides, Disaccharides, Monosaccharides, And Polyols.” These are carbohydrates (or sugars) that are poorly absorbed in the small intestine. They end up traveling to the large intestine, where they become the perfect food for the bacteria that live in the large intestine. The bacteria eat away at these sugars and cause fermentation, which results in nasty symptoms like gas, pain, cramping, diarrhea, constipation, and nausea—typical symptoms for people who suffer from IBS. Being small molecules, they also attract water into the small intestine, causing symptoms. The term FODMAPs has been coined relatively recently, and it’s getting a lot of press in the diet and nutrition world these days since some people who thought they were sensitive to dietary gluten have realized that they’re actually suffering from a sensitivity to the fructans, or sugars, in wheat.
Research from Monash University in Melbourne, Australia, shows that avoiding FODMAPs can greatly improve symptoms in up to 76 percent of IBS patients.
Before we launch into the details of the low-FODMAP diet, let’s start with a brief refresher course in nutrition. The food we eat consists of three components: carbohydrates, proteins, and fats. Some foods consist mostly of protein (like the extra-lean ground turkey in tacos) and some foods consist of fat (like the olive oil you drizzle on salads). Other foods are completely carbohydrate-based, like the sugar you sprinkle on your morning oatmeal. And in terms of a low-FODMAP diet, the component we’re most concerned about is carbohydrates.
Carbohydrates, which consist of sugars, starches, and fiber, are an important component of our diets since they provide our bodies with energy. Here’s how: Our digestive systems break down the carbs we eat until they can be absorbed through the intestinal wall into the bloodstream, where they’re converted into energy. And they’re in a lot of the foods we eat, including fruits, vegetables, breads, and pasta. But certain carbs—the FODMAPs—can cause issues in people with IBS and other digestive disorders.
Carbohydrates include monosaccharides (such as glucose, fructose, and galactose); disaccharides (for example sucrose—composed of glucose and fructose and lactose—composed of glucose and galactose); polyols (such as sorbitol and mannitol); oligosaccharides (such as fructooligosaccharides and galactooligsaccharides), and polysaccharides (resistant starch and non-starch polysaccharides, also known as fiber).
Starches come from plant-based foods, like grains, vegetables, and fruit. When you eat starchy foods, natural enzymes in your digestive system break the starch down into the simplest sugars—glucose, fructose, and galactose—which are then absorbed into the bloodstream. But some carbohydrates (known as FODMAPs) are poorly absorbed in the small intestine. While malabsorption of these carbohydrates is a normal event (for example, the human intestine lacks enzymes to digest oligosaccharides and approximately 40% of the population regardless of an IBS diagnosis malabsorbs fructose); it is the response to this malabsorption that is abnormal in people with IBS. In people with IBS, the bowel wall is hypersensitive to stimulation (visceral hypersensitivity) and is more likely to cause pain when stimulated. Therefore, when FODMAP containing foods are consumed, there is an influx of water and gas into the intestines, causing stretching and distension. In the presence of visceral hypersensitivity, this stretching and distension may induce symptoms of pain, bloating, abdominal distension, diarrhea, and/or constipation.
Now that you’ve gotten a quick rundown on what carbs are and how they’re digested, here’s a brief overview of each FODMAP carbohydrate and the foods in which they occur. We already know that the F in FODMAP stands for “fermentable.” Fermentation happens when intestinal bacteria consume the undigested carbohydrates in the large intestine, creating gas.
Oligosaccharides are chains of sugars, such as:
▪ Fructans (or fructooligosaccharides)—Fructans are chains of fructose molecules. They are found in onions, garlic, wheat, chicory root (inulin), asparagus, and artichokes.
▪ GOS (also known as galacto-oligosaccharides)—GOS are polymers of galactose, glucose, and fructose. They are found in beans, legumes, peas, and soybeans.
Disaccharides are two monosaccharides linked together, such as:
▪ Lactose—Lactose is composed of one glucose and one galactose molecule and is found in dairy products such as milk and soft cheeses. Lactose only causes trouble for the small minority of folks who lack the enzyme that’s necessary for breaking it down.
Monosaccharides contain only a single sugar molecule, such as:
▪ Fructose—Fructose is found in fruits and sweeteners. From a low-FODMAP perspective, we’re only concerned with the fruits that contain an excess of fructose—that is, more fructose than glucose. That doesn’t apply to all fruits and sweeteners. For example, sucrose (granulated sugar) is composed of one fructose molecule and one glucose molecule. Because the glucose helps the body to absorb the fructose, granulated sugar is well tolerated by folks with IBS. Foods that contain more fructose than glucose (excess of fructose), like apples, pears, mangoes, honey, high-fructose corn syrup (HFCS), and agave nectar should be avoided.
Polyols are sugar alcohols, such as:
▪ Xylitol, mannitol, sorbitol, and maltitol—These are naturally found in mushrooms, apples, and stone fruits (such as peaches, nectarines, apricots, plums, and cherries). They’re also found in processed foods such as sugar-free sweeteners, which turn up in sugar-free chewing gum and candy.
The low-FODMAP diet shows you how to figure out which foods are your personal “triggers,” and then it helps you avoid those foods in order to manage your IBS symptoms. The diet is generally divided into two phases. First is the elimination phase, in which you eliminate high-FODMAP foods from your diet for two to six weeks. The second phase is the reintroduction phase, or “rechallenge” phase. In this stage, you’ll intentionally eat higher-FODMAP foods in order to test your reactions to them. After that, it’s up to you to avoid the foods that cause your symptoms.
Before we go any further, let’s talk about what the low-FODMAP diet is not. Although it has the word “diet” in its name, the low-FODMAP diet is not intended for weight loss. Also, it isn’t black and white. Notice that it’s called a low-FODMAP diet and not a FODMAP-free diet? That’s because it’s nearly impossible to eat absolutely zero FODMAPs and still maintain a healthy diet. Unless all you eat is meat—and that’s hardly a balanced eating plan!—you’re going to end up eating some FODMAPs. The trick is to minimize them to the point at which your symptoms improve. And it’s important to not be too restrictive in the process, or you could end up suffering from malnutrition.
The low-FODMAP diet is not necessarily a gluten-free diet. Gluten is a protein found in wheat, barley, and rye, which celiacs must eliminate from their diets. But wheat, barley, and rye also contain FODMAPs, which are carbohydrates. It is possible for people with celiac disease to have IBS-like symptoms as well: These folks should continue to eat gluten-free, but they might want to consider reducing their consumption of FODMAPs, too. While research is currently being conducted on the existence of non-celiac gluten sensitivity, it may actually be the fructans, not the gluten, in wheat that cause reactions in some people. Keep in mind that gluten-free foods are not necessarily low-FODMAP foods. Wheat-free foods may contain high-FODMAP ingredients, such as onions, garlic, or pear juice, to name a few.
The low-FODMAP protocol is not one size fits all. Not everyone reacts to the same foods in the same way. You may find that you can tolerate some FODMAPs—but you may also find that you can’t tolerate them at all. Either way, it’s good to know, and that’s the whole point: The low-FODMAP diet is all about you and how you react to certain foods.
Ultimately, the low-FODMAP diet is a tool to help you feel your best. So don’t panic—this protocol doesn’t mean that you’ll have to say goodbye to your favorite foods forever! The elimination phase of the diet (usually 2 to 6 weeks in duration) is the most restrictive, but afterward, you’ll reintroduce new foods, and ideally you’ll find out that you can tolerate more than just the “safe” foods. Plus, food intolerances can change over time, so you might want to wait a few months before testing certain foods again. You may find that you’re able to tolerate them the next time around.
CONSULT A PROFESSIONAL
I like to think of the low-FODMAP approach as a kind of an experiment that you conduct on your digestive system. As with any scientific experiment, you need a test subject (you!), a control (the low-FODMAP diet), and a variable (high-FODMAP foods). Finally, repeated trials (the challenge phase) are needed to establish a conclusion.
In the first phase, the elimination phase, FODMAPs are avoided as much as possible for four to six weeks. If you don’t feel any better after four to six weeks, the low-FODMAP approach may not be for you, and you may want to talk to your doctor about trying a different approach. Remember, most studies show the low FODMAP diet is effective in only around three quarters of people. For everyone else, other factors may trigger symptoms.
Keep these important tips in mind during the elimination phase:
▪ Eat a well-balanced diet. Include foods from each of the food groups—protein, grains, fruits and vegetables, and dairy, if desired—in every meal. When it comes to fruits and vegetables, keep it colorful. The more color in the produce, the more vitamins and nutrients it contains.
▪ Stick to the serving sizes recommended by your dietitian or doctor.
▪ Keep the overall FODMAP load low throughout the day. In other words, if you’re going to eat foods that have some FODMAPs (for instance, a little milk in your coffee or a little celery on your salad), don’t eat them all at once. Instead, spread them throughout the day. Sue Shepherd, author of The Complete Low-FODMAP Diet, recommends eating no more than one serving of fruit at a sitting in order to spread out the fructose load.
▪ Keep a food diary. This will help you keep track of what foods you’re eating and of any resulting symptoms.
▪ Avoid foods that you already know you’re sensitive to.
▪ If you are unsure if a food is low-FODMAP or not, don’t eat it until you’re in the rechallenge phase.
During the rechallenge phase, or reintroduction phase, FODMAPs are systematically reintroduced into your diet to see whether they produce symptoms. This phase will take about six weeks to complete, but it’s worth it. You’ll have identified your trigger foods, and you’ll be better able to manage your symptoms. The challenge phase follows these basic steps:
▪ Reintroduce one FODMAP at a time. Try to choose a food that contains only one FODMAP; for example, the fructans in wheat or the lactose in milk.
▪ Eat a typical serving of the FODMAP food (such as one slice of bread or half a cup [120 ml] of milk) and record your symptoms over the next 24 hours. If symptoms occur, then it’s likely that that food, eaten in that quantity, is a trigger. If no symptoms are present, then you’ll know that it’s safe to eat the FODMAP food in that amount.
▪ If symptoms do occur, wait for them to abate before you test again.
▪ Next, you can either try a new FODMAP food or retest the same food you tried in step 2, only in a larger or smaller serving. If you couldn’t tolerate the food you tested in its standard serving size, you might try it in a smaller amount (for example, half a slice of bread or a quarter cup [60 ml] of milk). If you were able to tolerate the food you tested, you can try eating more of it (for example, two slices of bread or one cup [235 ml] of milk). In this way, you’ll be able to determine your individual threshold for particular foods.
▪ Repeat this process until you’ve tested all the FODMAP foods you want. Always remember to wait until any symptoms subside before testing again. And try to reintroduce foods that contain only one type of FODMAP at a time; that way, it’ll be easier to isolate the FODMAPs that you can—or can’t—tolerate.
While the low-FODMAP diet has made a world of a difference for me and many of the readers of my blog, this approach will not work for everyone. Like I said earlier, the low-FODMAP diet isn’t one size fits all. If you don’t notice any improvement after you complete the elimination and challenge phases, you might want to explore other food intolerances or allergies. For example, after a while I realized that I was reacting badly to eggs even though they aren’t high in FODMAPs.
The FDA recognizes these eight foods as the most common allergens: milk, eggs, fish, shellfish, tree nuts, peanuts, wheat, and soybeans. According to Food Allergies and Food Intolerance by Jonathan Brostoff and Linda Gamlin, commonly reported food intolerances include corn, potatoes, rice, and sesame. These foods rarely provoke a true allergic response, but they can be common culprits when it comes to food intolerance.
OTHER SYMPTOM-CAUSING FOODS
True allergies can be diagnosed by a skin-prick test, in which a small amount of purified allergen is injected into the skin and then left alone in order to see whether an immune response occurs at the site. A food intolerance is much more difficult to detect and involves—you guessed it!—an elimination diet. However, there is no firm guidance on how to implement an elimination diet, in terms of the foods consumed in the elimination period or the type and quantity of food introduced in the reintroduction period. Elimination diets are also labor intensive and time-consuming to complete and being highly restrictive, they may compromise nutritional status.
Food additives may also prevent the low-FODMAP diet from working for you. For example, my husband and I both recently suspected that we were having bad reactions to xanthan gum, an emulsifier that’s commonly added to gluten-free products. This is why none of the recipes in this book call for it. A recent study by the Georgia State University Institute for Biomedical Sciences suggested that there could be a link between emulsifying additives in foods and IBS: Such emulsifiers may disturb gut microbiota, which promotes inflammation and can lead to colitis. However, this was an early study in mice, so data from human studies are needed to confirm these results. So, if you’ve completed the elimination and rechallenge phases and you’re still experiencing symptoms, there might be other dietary factors to consider. Seeing a dietitian about identifying these other dietary triggers may be a good idea, especially if you’re considering trialing a strict elimination-rechallenge diet. (That said, following a low-FODMAP diet can still be helpful even if you do find that additives are triggering your symptoms.)
NINE WAYS TO IMPROVE YOUR DIGESTION
So, what can you eat on the low-FODMAP diet? Plenty. As you’ll see from the recipes in this book, there’s so much you can do with low-FODMAP foods. Many dietitians and researchers agree that the foods listed below are generally well-tolerated. Either consult with your physician or dietitian or the Monash FODMAP app for a complete list with serving sizes.
Strawberries, blueberries, raspberries, bananas, oranges, and grapes are considered low-FODMAP in the appropriate serving sizes. Note that drying fruit increases the concentration of FODMAPs as the water content is reduced: for example, low-FODMAP grapes become high-FODMAP raisins.
Avoid these fruit ingredients on food labels: some fruit juices, such as pear juice and apple juice.
Examples of low-FODMAP vegetables are carrots, certain lettuces and greens, tomatoes, zucchini, potatoes, bell peppers, and the green parts of scallions. Be aware of the serving sizes for vegetables. The cruciferous vegetables (cabbage, broccoli, and Brussels sprouts) are known for causing gas, but they’re considered tolerable in small amounts. Don’t eat more than the recommended serving during the elimination phase of the diet.
Avoid these vegetable ingredients on food labels: onion powder, dehydrated onion, garlic powder, and dehydrated garlic.
Rice, quinoa, and cornmeal are excellent low-FODMAP grain choices. Researchers at Monash have tested the FODMAP content of starches such as tapioca, corn, and potato—all of which are generally considered well tolerated. Oats and amaranth are an exception: They have moderate levels of FODMAPs, so be mindful of the serving sizes for these grains.
If the following are major ingredients in grain-based products, you may need to limit your intake or avoid consumption during the strict elimination phase of the diet: wheat, Kamut, spelt, and sprouted wheat. This said, food processing affects FODMAP content and Monash has found some spelt sourdough breads to be low FODMAP, if they’re made using a long fermentation period. Also look out for chicory root/inulin, high-fructose corn syrup, honey, agave, and molasses.
Since animal proteins such as beef, chicken, and fish consist mainly of protein and contain very few carbohydrates, they’re very low in FODMAPs. But be wary of processed meats such as sausage and deli meat. Always check the list of ingredients before you buy.
Avoid these ingredients on food labels of meat-based products: garlic and onion.
Most legumes are not low-FODMAP because of GOS, but canned lentils are more tolerable because the FODMAPs leach out into the liquid, which is then drained off before use.
Whether or not soy products are low-FODMAP is a complicated topic. Soy milk is considered low-FODMAP if it is made from soy protein rather than the whole soybean. Unfortunately, most soy milk in the United States is made from whole soybeans, so it is not low-FODMAP. As for tofu, if it comes in a block, it’s probably low-FODMAP. Tofu is made by curdling soy milk with a coagulant; then, it’s cut into blocks and drained. Most of the FODMAPs are contained in the liquid that’s drained off, making block tofu generally tolerable. However, tofu also comes in a silken variety, from which the liquid is not drained. While silken tofu hasn’t yet been tested, it’s probably best to avoid it during the elimination phase of the diet. But the good news is that tempeh (made from fermented soybeans) and soy sauce are low-FODMAP.
Avoid these ingredients on food labels of soy-based products: soybeans, soy milk, peas, and beans that aren’t tolerated.
If you are lactose-intolerant, lactose-free milk is an excellent low-FODMAP choice, and it’s widely available in supermarkets. While there are a growing number of nondairy milks on the market today, you should talk to your dietitian about choosing one that’s right for you.
As for cheese, remember that not all cheese is laden with lactose. The fact is, most hard cheeses, such as Cheddar and Swiss, contain very little lactose. Check the nutrition label: If the amount of total carbohydrates listed is zero, then the cheese contains little to no lactose. Softer cheeses, like ricotta and cottage cheese, do have more lactose, so limit your consumption of these during the elimination phase.
Nondairy yogurts are easier to find these days, but pay attention to their ingredients: they often contain chicory root or inulin. Also, watch out for yogurts that are sweetened with honey, agave, and fruit juices such as pear and apple.
Avoid these ingredients on dairy food labels: chicory root, inulin, honey, agave, high fructose corn syrup, and fruit juices.
Although butter is a dairy product, it is considered low-FODMAP because it contains very little lactose. All other oils are considered low-FODMAP because they are carbohydrate-free. Nonetheless, remember that some people with IBS cannot tolerate fats in larger amounts, so keep your intake moderate.
Avoid eating excess fat: It can trigger IBS symptoms.
Beware of an excess of fructose when it comes to sweeteners, for example high fructose corn syrup. Granulated sugar, also known as sucrose, consists of equal amounts of glucose (also known as dextrose or corn sugar) and fructose, so it’s generally well tolerated. Molasses hasn’t been tested yet, so it’s best to avoid it during the elimination portion of the diet. Stevia is considered tolerable, too, but you should avoid the packets containing powdered stevia with inulin, since inulin is a FODMAP.
Chocolate lovers can rejoice: Dark chocolate is low in FODMAPs in the appropriate serving size. While there are some recipes in this book that call for chocolate chips, it is best to stick with chopped dark chocolate in the strict phase of the diet since chocolate chips have not been tested yet.
Avoid these ingredients on food labels: honey, agave nectar, high-fructose corn syrup, inulin, and sugar alcohols such as sorbitol, xylitol, and others ending in “–ol.”
Mayonnaise, Dijon mustard, and soy sauce are commonly recommended condiments on a low-FODMAP diet. Ketchup is low FODMAP in small servings (1 packet), however, larger servings may trigger IBS symptoms. (You can make your own instead: Check out my recipe for Cheeseburger and Fries Casserole with ketchup!) Only a couple types of vinegars have been tested for FODMAPs, but dietitians tend to allow most vinegars, such as red wine vinegar, on the elimination diet. In a few recipes, I do not specify a type of vinegar; in those cases, use what works best for you.
Avoid these ingredients on condiment food labels: high-fructose corn syrup, onion powder, garlic powder, inulin, and FOS.
Since fruit consumption is fairly limited during the elimination phase, you should also avoid most fruit juices. The same goes for alcohol and caffeine. Even though some alcoholic and caffeinated beverages are low-FODMAP, such as dry wines, coffee, and green tea, alcohol and caffeine can irritate your digestive system, so try to keep consumption to a minimum.
Avoid these beverages: sweet wines, sweet alcoholic drinks such as margaritas and other drinks containing fruit juices, chicory root/inulin (found in some coffees and teas), milk products, and high-FODMAP sweeteners.
TIPS FOR VEGETARIANS AND VEGANS