7 Reasons Why the Low FODMAP Diet Might Not Be Working
If you are still suffering from abdominal pain and other IBS symptoms despite being low FODMAP, then it’s time to double check your diet and look at your stress levels. The low FODMAP diet is a learning diet and it can take a few weeks to change your food habits to make sure you aren’t eating high FODMAP foods. Additionally, even though many people experience symptom relief in the first couple of weeks, it can take longer for your body to adjust. Before you give up and decide the diet doesn’t work for you, there are a few things you need to check:
1. Ignoring recommended portion sizes for low FODMAP foods
I know it is easy to devour a large portion of a low FODMAP food when you discover something safe that you enjoy eating! However, you need to keep in mind that some low FODMAP foods become high FODMAP when you exceed a certain portion size (1 2).
A common example of this is rice cakes. Rice cakes make a delicious low FODMAP snack, especially when you top them with peanut butter or safe cheese. The recommended serving size is two rice cakes; if you increase your serving size to four they become high FODMAP as you will consume higher levels of fructans (oligosaccharides) (3).
This means it is important that you stick to the recommended serving sizes for low FODMAP foods. The Monash Low FODMAP app contains the most up-to-date lists of low and high FODMAP foods, as well as information on recommended serving sizes. If you want to increase your low FODMAP serving size, check the food for a warning note first. Please read my article on portion control and the low FODMAP diet for more information.
2. Consuming sneaky FODMAPs in processed foods, supplements & medications
Manufacturers often add high FODMAP ingredients to processed foods to enhance their texture and taste. Some common examples are inulin, chicory root, agave syrup, HFCS, sorbitol (E420), mannitol (E421), maltitol (E956), xylitol (E967), and isomalt.
The FODMAP content of most pharmaceutical tablets should not be high enough to cause any issues. However if you are having cough syrup, throat lozenges, or liquid suspensions that contain sugar alcohols then these could be making your symptoms worse. Also check your supplements and probiotics, as these can contain inulin, which is high FODMAP even in small amounts. Chewable supplements can also contain lactose, fructose, or sugar alcohols so read the ingredients carefully.
3. Having too much low FODMAP fruit in one meal
There are plenty of safe fruit options to choose from on the low FODMAP diet and it is easy to have too much fruit in one sitting. Low FODMAP dietitians recommend that you only have one serve of fruit at a time (2 4). You also need to stick to the recommended serving size for the fruit (unless you know you can tolerate more) (2 4). This means if you want to have two serves of fruit per day you can, but you need to leave at least two to three hours in between (2 4). To begin with I would recommend having one serve in the morning and another serve in the evening. Over time you can test your tolerance levels and see if you can reduce the time between your servings, or have more than two serves of low FODMAP fruit in a day.
4. Not consuming enough fibre to keep you regular
Fibre keeps us regular and plays an important part in our diet. The low FODMAP diet removes some high fibre foods, which means it is important that you make sure you are getting enough fibre. Insoluble fibre can be problematic for some people with IBS (5 6 7), so you might need to focus on increasing your soluble fibre (you can find out more about the low FODMAP diet and fibre here). If your constipation has increased, then you should talk to your dietitian about your fibre intake, what fibre is appropriate, and if you need a fibre supplement. Also remember that you need to drink plenty of water (at least 4 to 6 cups per day) to help fibre work properly in your gut (3).
5. Ignoring other IBS trigger foods
Some low FODMAP foods may contain other common IBS trigger foods that need to be considered, to gain good symptom control. Other common IBS triggers foods include fatty or fried food, caffeine, alcohol, carbonated drinks, insoluble fibre, resistant starches, and spicy foods (8 9). You can find more information on these trigger foods here. If you think some of these trigger foods are causing your problems, you can remove them from your diet, along with the high FODMAP foods. Make sure you then test the foods you remove to make sure they are additional triggers.
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6. Undiagnosed additional food intolerances
Even though a food may be low FODMAP, you might not be able to tolerate it. For example, I cannot tolerate lactose free milk or cheeses even though they are low FODMAP. This is because we have identified that I have an additional intolerance to dairy protein. To help you identify additional food intolerances you can keep a food diary. You and your dietitian can then review the diary and identify symptom patterns and potential trigger foods.
7. Stress as an IBS trigger
Stress can be a strong IBS trigger. This means if you are feeling stressed, it might not be just the food causing your symptoms. You may need a combination of the low FODMAP diet and stress management to manage your IBS symptoms.
If you are still having symptoms, despite being low FODMAP and dealing with the issues mentioned above, then further investigation might be needed. It is possible that you could have additional sensitivities to gluten, have food chemical intolerances (histamine, salicylate, amines, glutamates, sulphites), small intestine bacterial overgrowth (SIBO), or another condition that needs treatment (10 11). Also note that the low FODMAP diet does not work for everyone. This means, if possible, you should work with a dietitian who has specialized in FODMAPs and gastroenterology, to find a treatment path that works for you.
Do the recommended serving sizes take into account that one is probably consuming multiple fodmap foods in one sitting? Should I reduce the serving if I’m combining foods together? Can I have more if I’m only having one thing?
Alana Scott says
If you are struggling to get good symptom control then it is a good idea to check that you are consuming low FODMAP foods. If two low FODMAP foods contain the same FODMAP group then try a full serve of one and a 1/2 serve of the other food. That will help reduce the FODMAPs stacking.
Can I eat for example one portion of strawberries and one portion of raspberries in one sitting?
Alana Scott says
Thanks for commenting. The general guidelines is to only eat 1 portion for fruit per meal. If you want to combine two fruits then try a half serving of each. For example, 5 strawberries and 15 raspberries. We hope that helps.
Martin silcock says
Im struggling with which butter/spread to eat. And how much per day is ok of all
Alana Scott says
Butter is high in fat and does not contain carbohydrates (FODMAPs) so from a FODMAP perspective the amount doesn’t need to be limited. Sometimes fat can affect gut motility and can trigger symptoms for some people. If you think this might be an issue for you then we’d suggest talking to a dietitian who can provide you with personalised advice.