One of the most frequent questions I get through this website is about the low-FODMAP diet. This popular approach to easing symptoms of irritable bowel syndrome (IBS) eliminates (at least initially) many plant foods. It’s definitely a bit of a challenge for vegans, but may be worth it if you suffer from IBS.
The FODMAP Diet
IBS affects as much as 15% of the population in North America, so it is no small problem. And while it’s not life-threatening, it can have a significant effect on quality of life.
The idea behind the low-FODMAP diet is that certain fermentable short-chain carbohydrates contribute to symptoms in people with IBS. Some of these carbs are poorly digested and some are not digested at all. Others, like lactose in milk or the sugar fructose, are digested by some but not all people.
Since they aren’t digested, these carbs aren’t absorbed. Instead, they travel to the colon where they are fermented by bacteria, resulting in gas production. They can also pull water into the lower intestines, creating an uncomfortable feeling of distension. For most people, these effects are not a problem or at least, they are felt to only a minor degree. But people with IBS may be hypersensitive to the effects of water and gas in their lower intestines.
The FODMAP approach limits these fermentable carbs for several weeks to see if IBS symptoms improve. If you feel better after avoiding these foods, the next step is to determine which type of fermentable carbs are responsible for your symptoms. This is achieved by gradually adding foods back one at a time.
Some research suggests that about 75 percent of people with IBS may be helped with the FODMAP approach.
The FODMAP Family of Foods
The term FODMAP is an acronym for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are all short-chain carbs that are not bad for you in general. In fact, they have prebiotic effects that may lower risk for colon cancer. You don’t need to eliminate them completely (and you couldn’t unless you ate an all-meat diet) but, if you suffer from IBS, a low-FODMAP diet can help you determine which of these carbs you can comfortably eat.
Here are the groups of foods that are avoided during the elimination phases:
Galactans: These are oligosaccharides (short chains of sugars) that are abundant in beans. No one can digest these carbs, since humans lack the appropriate enzymes. That’s why beans can cause gas even in people who don’t suffer from IBS.
Fructans: Another type of oligosaccharide, these are chains of fructose that occur naturally in artichokes, garlic, onions, leeks, wheat, rye, and barley. Certain types of fructans called inulin and FOS are also added to foods for their prebiotic effects.
Lactose: A disaccharide—two simple sugars linked together—found in milk and other dairy foods. It’s an issue for vegans only in that it shows up as an additive in some foods and supplements that vegans might sometimes unwittingly eat.
Fructose: A simple sugar (also called a monosaccharide) found in sugars and fruits. The ratio of fructose to the sugar glucose is more important than the total amount of fructose in the diet since this ratio affects absorption. As a result, some fruits that are high in fructose, like apples, pears, watermelon, and mango, can be worse for IBS symptoms than plain old table sugar which has both fructose and glucose. Agave nectar, on the other hand, should be avoided due to its high fructose content. During a low-FODMAP diet, fruit should be limited to one serving of a low-FODMAP fruit per meal. Choose well-ripened fruit since it’s lower in fructose.
Polyols: Also called sugar alcohols, these include sorbitol, xylitol and mannitol. They’re used in sugarless gums and candies because they are poorly absorbed. They also occur naturally in some fruits like apples, apricots, avocado, cherries, nectarines, pears, plums, prunes, and mushrooms.
Eating a Low-FODMAP Diet
I’ve created a pdf of vegan foods you can eat as part of a low-FODMAP diet (and also lists of foods to avoid). Keep in mind, that you are limited to these foods for just 6 to 8 weeks. After that, you’ll start to add back other carb-rich foods to see which you can tolerate. It’s important to add foods back in small amounts and to test one type of fermentable carb at a time. For example, apples provide both polyols and fructose. If eating them causes you discomfort, you won’t know which of those types of carbs you are sensitive to. Instead, choose a food like apricots to test your sensitivity to polyols and then try some mango to test your tolerance for fructose.
Make sure you start with small quantities. You may be able to tolerate ¼ cup of high-FODMAP beans but not ½ cup. If you start with ½ cup, you’ll never know whether you can eat those beans at all. You’ll need to keep a food diary, and it can be very helpful (highly advised, in fact) to work with a professional who has expertise in the low-FODMAP diet.
Sample Low-FODMAP Menu
Even if you could never eat any high-FODMAP foods—if you ended up being sensitive to all of them—you could eat a vegan diet. Low-FODMAP foods include tofu, tempeh, peanut butter, many nuts and seeds, many fruits and vegetables, added fats, plenty of condiments, and gluten-free grains. You can also have small amounts of certain beans.
Here is one example of a low-FODMAP menu.
Oatmeal with almond milk, blueberries, and chopped walnuts
Coffee or tea
Gluten-free toast with peanut butter
Vegetable soup with potatoes, tomatoes, green beans, ¼ cup well-cooked lentils
Salad with oil and vinegar dressing
Tofu or tempeh sautéed with zucchini, bok choy, and spinach seasoned with ginger, miso and sesame oil
Quinoa or brown rice
Rice cakes with sunflower seed butter