The Low FODMAP Diet

by Akil Palanisamy, M.D.

You may have heard or read about a diet known as the Low FODMAP diet, commonly recommended as a treatment for irritable bowel syndrome. The diet works by shifting the bacterial composition of your microbiome.

FODMAP stands for Fermentable, Oligo-, Di-, Mono-saccharides and Polyols. Foods that contain FODMAPs have certain carbohydrates that are poorly absorbed and pass into the large intestine where they are fermented by bacteria. It is not intuitive which foods are FODMAPs and which ones are not–for example, apples are FODMAPs but not bananas; blackberries are FODMAPs but not blueberries, etc.

If you have irritable bowel syndrome, small intestinal bacterial overgrowth, or nonspecific GI symptoms, a low FODMAP diet would be a reasonable approach. I suggest trying it for a minimum of 2 months to see if it will work for you.

Remember that the issue as with all things relates to the dose. You don’t have to completely avoid FODMAPs but simply follow a diet that is relatively low in them. Also this is not a diet for life as this diet removes a lot of the components that feed your beneficial bacteria as well. If you are not feeling better after 2 months following this diet, consult with your functional medicine practitioner.

Here are some guidelines on what to eat and what not to eat:

Food Category What to eat What to avoid
Grains Gluten-Free Grains: quinoa, millet, white rice, brown rice, wild rice, oatmeal, amaranth, buckwheat, corn, sorghum, teff; processed foods such as bread or pasta if they are gluten-free Wheat, rye, barley, glutencontaining grains
Fruits bananas, blueberries, cantaloupe, cranberries, grapes, honeydew, kiwi, lemon, lime, mandarin, orange, passion fruit, pineapple, raspberries, rhubarb, strawberries, tangerine apples, applesauce, apricots, blackberries, boysenberries, canned fruit, dates, dried fruits, figs, guava, mango, nectarines, papaya, peaches, pears, plums, persimmon, prunes, watermelon
Meat Chicken, fish, beef, shellfish, lamb, eggs, natural bacon Any processed meats containing high fructose corn syrup
Dairy Butter, ghee, aged cheese in moderation Milk, yogurt, fresh cheese, icecream
Nuts/Legumes In moderation, macadamia nuts, pumpkin seeds, sunflower seeds, chia seeds, sesame seeds Almonds, hazelnuts, cashews, beans, black eyed peas, bulgur, lentils, miso, pistachios, soybeans, soy
Fats Coconut oil, olive oil, butter, ghee, lard, macadamia nut oil Avocados, avocado oil
Beverages Water, tea, coffee, sparkling water Wine, beer, fruit juices
Seasonings/Sweeteners Salt, pepper, and spices are acceptable except for garlic and onions Avoid any seasonings made with honey or high fructose corn syrup. Avoid any candies or chocolates containing sorbitol, mannitol, xylitol, or maltitol

The Low FODMAP Diet works essentially by slowly starving your intestinal bacteria. If you have small intestinal bacterial overgrowth or abnormal bacteria in your large intestine, this diet will reduce their numbers significantly by removing the foods that bacteria rely on for energy.

If you find that this diet leads to a big improvement in your symptoms, it is likely that you have some type of imbalance in your microbiome. Consult your local functional medicine practitioner for evaluation and treatment. Stool tests which assess your microbiome can help guide therapy to rebalance your bacteria and improve your digestive symptoms.