What is the Low-FODMAP Diet?

Integrative nutritionist Janet Lau breaks down the foods and explains how they affect the body.

Food is a common culprit behind many digestive issues. Eliminating certain foods for a period of time can help in understanding which ones are contributing to unpleasant symptoms. Dietitians and nutrition experts often rely on a low-FODMAP diet to get to the bottom of digestive issues.

Health Matters asked Janet Lau, an integrative dietitian at Integrative Health and Wellbeing at NewYork-Presbyterian, in collaboration with Weill Cornell Medicine, to explain the ins and outs of a low-FODMAP diet, what FODMAPs are, and who should avoid them.

What is a low-FODMAP diet?
A low-FODMAP diet is a temporary dietary protocol in which, for a period of time, you eliminate certain foods from your diet in order to uncover which ones might be causing digestive problems. This diet is often used for people who are experiencing symptoms such as bloating, gas, diarrhea, and constipation.

It is also for people who have tested positive for small intestinal bowel overgrowth (SIBO), a condition in which there is an excess of bacteria not normally found in the small intestine. In short, food travels through the digestive tract to be absorbed as nutrients and discarded as waste. The microorganisms that reside along the small bowel help to absorb nutrients. However, due to an abnormal overgrowth of bacteria not typically found in the small intestine, bloating occurs as foods are fermented by the gut’s excessive bacteria. The low-FODMAP diet serves to stop the fuel source of bacteria, allowing the adverse digestive symptoms to subside.

What are FODMAPs? Which foods contain them?
FODMAP is an acronym that stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These are mainly short-chain carbohydrates (sugars) that exist in certain foods including vegetables, fruits, dairy, beans, grains, alcohol, artificial sweeteners, soft drinks, and supplements such as prebiotics. Here are some examples:

Fermentable: Oligosaccharides
Food Group(s): Vegetables, Fruits, Grains, Legumes, Supplements
Examples: Broccoli, Brussels sprouts, beans, onion, garlic, apples, watermelon, wheat grains, chicory, inulin

Fermentable: Disaccharides
Food Group(s): Dairy
Examples: Milk, yogurt, soft cheeses, ice cream

Fermentable: Monosaccharides
Food Group(s): Vegetables, Fruit, Sweeteners
Examples: Mangos, apples, dried fruit, honey, asparagus, sugar snap peas, high-fructose corn syrup

Fermentable: Polyols
Food Group(s): Fruits, Vegetables, Sugar Alcohols
Examples: Pears, blackberries, nectarines, apples, cauliflower, sorbitol, mannitol

What happens when you eat them? How do they affect your gut’s microbiota?
There are trillions of a diverse array of bacteria that inhabit the intestines. If your diet mainly consists of highly processed carbohydrates in addition to high-FODMAP carbohydrates (see examples in the table above), this can cause an imbalance to gut health where bad bacteria thrive as they are fed by these carbs and start fermenting them. This is what causes digestive symptoms to occur. Additionally, worsening effects like leaky gut and inflammation may be a likely outcome if persistent adverse digestive symptoms are not addressed.

Janet Lau

Who should avoid FODMAPS?
People who experience bloating, gas, constipation, or diarrhea have found benefit in following a low-FODMAP diet. In addition, people who have tested positive for SIBO and those with sensitive digestive systems in cases such as irritable bowel syndrome (IBS), Crohn’s disease, and ulcerative colitis have found comfort in following a low-FODMAP diet during flare-ups or to relieve an upset stomach.

What are the benefits of a low-FODMAP diet?
Following this diet removes foods that mainly cause bloating, gas, constipation, or diarrhea, thus preventing or reducing the severity and/or frequency of digestive issues. The benefits include relief from these symptoms, and therefore fewer sick days and less stress and anxiety, and ultimately improving one’s quality of life.

Is there any research out there that shows it’s beneficial?
There are several studies that looked at the efficacy of the low-FODMAP diet, specifically for treating IBS. These studies have documented substantial evidence that following a low-FODMAP diet is an effective approach for people experiencing persistent and recurring adverse gut symptoms.

What are some low-FODMAP breakfast, lunch, and dinner options?

Breakfast

Option 1: Gluten-free oatmeal + nondairy milk and/or water + fresh fruit (blueberries, raspberries, </= ½ banana). Optional additions: nuts, spices (cinnamon, nutmeg), <2 Tbsp nut butter, <1 Tbsp chia seeds, <1 Tbsp ground flaxseeds

Option 2: 1-2 eggs + gluten-free bread (1-2 slices) + 1-2 cups veggies (arugula/spinach/ tomato). Optional additions: vinaigrette, fresh fruit bowl (melons, orange, blueberries, raspberries, pineapple)

Lunch

Hot meal: Grilled/baked chicken + quinoa/gluten-free pasta + sautéed zucchini/squash/bok choy

Cold meal: Corn flour wrap/baked (sweet) potato + tofu/chicken/fish + grilled eggplant + green beans

Dinner

Hot meal: Stir-fry with ground beef + brown rice + <⅓ cup peas, carrots, bean sprouts, spinach. Optional additions: shredded ginger, basil, thyme, chives, green parts of scallions

Light dinner: Nondairy yogurt + gluten-free granola + fresh fruit + <2 Tbsp nut butter. Optional additions: spices (cinnamon/nutmeg), <1 Tbsp chia seeds, <1 Tbsp ground flaxseeds

How long should someone stay on a low-FODMAP diet?
A low-FODMAP diet should be implemented for as little as two weeks and up to six weeks depending on their symptoms and, in some cases, how long they’ve experienced adverse side effects. It’s advisable to work with a registered dietitian to map out meals and ensure you’re getting enough vitamins and nutrients on a daily basis.

Are there any cons to a low-FODMAP diet? Is this kind of diet sustainable?
There are many high-FODMAP foods that are staples in an individual’s diet (for example, garlic, onions, broccoli, beans), so finding suitable alternatives may be difficult on a low-FODMAP diet. Also, following a low-FODMAP diet can be quite challenging for people who are already picky eaters. However, given all the healthy options available, this diet is sustainable for a temporary amount of time.

Once the low-FODMAP diet phase has ended, it’s important to reintroduce foods slowly in order to increase diet variety and promote gut health. For this reason, it is not advised to follow a low-FODMAP diet, in its entirety, for a long period of time. The reintroduction step also helps to determine which types and amounts of FODMAPs you can tolerate. Reintroduce foods one by one and observe how your gut reacts.

While restrictive, following a low-FODMAP diet can be a great tool in identifying trigger foods and clearing up unpleasant symptoms. It is highly advised to work with a registered dietitian who is knowledgeable on the low-FODMAP diet to ensure you are getting well-balanced meals despite the restrictions of this diet.

Read more on digestive health and learn more about nutritional counseling.

Janet Lau, RDN, CDN, CLT, is an integrative dietitian at Integrative Health and Wellbeing at NewYork-Presbyterian, in collaboration with Weill Cornell Medicine. She specializes in weight management, diabetes, digestive disorders, kidney health, and heart disease. She provides guidance to healthy individuals who want to improve their nutrition IQ.