[If you want to know more, I’ve written a detailed post here.]
Mistake #1: Commencing a low FODMAP diet without being medically diagnosed with IBS
Being medically diagnosed with IBS means that your doctor has ordered all the necessary tests to rule out any serious medical explanation for the symptoms you are experiencing. Before starting a low FODMAP diet you will need to be tested for coeliac disease and also ideally have an endoscopy/colonoscopy performed to rule out IBD (inflammatory bowel disease) and any other serious condition such as bowel cancer.
Therefore commencing a low FODMAP diet before these tests are performed means that you risk a false negative result in the case of coeliac disease (you need to be consuming gluten for at least 4 weeks prior to blood test for coeliac disease antibodies) as well as going through a potentially unnecessary (and strict!) elimination diet when there may be another medical reason for your symptoms.
Mistake #2: Continuing with the strict elimination phase of the low FODMAP diet long term
The low FODMAP diet has two phases. Phase one is the elimination phase whereby all high FODMAP foods are eliminated from your diet for a few weeks. Once symptoms have resolved (no more bloating, diarrhoea, excess flatulence etc) you need to progress through phase two, the challenge phase, in order to determine what types of high FODMAP foods are causing discomfort for you as an individual (everyone is different and I am yet to come across someone who is intolerant to ALL high FODMAP foods).
Continuing the strict elimination phase beyond 6-8 weeks will put you at risk of disrupting the balance of healthy gut bacteria (as high FODMAP foods are the major food source for these bacteria). The long term aim of a low FODMAP diet is to be able to identify your unique trigger foods and after completing the challenge phase, being able to enjoy as many high FODMAP foods that you can tolerate without uncomfortable symptoms.
Mistake #3: Eliminating whole food groups
Yes, there is a huge list of foods that will need to be eliminated from across all core food groups on a low FODMAP diet. However, there are still foods that are low in FODMAPs from each core food group, and you will need to include some from each group every day to ensure you are not missing out on any key nutrients.
This is one of the reasons why I would strongly recommend that you find an Accredited Practising Dietitian in your area who specialises in IBS and low FODMAP diets to ensure you are not over-restricting and putting yourself at risk of nutritional deficiencies. They will be able to make sure you are getting the correct number of servings from each core food group whilst following the elimination diet. A low FODMAP diet can be tricky but it can definitely be balanced when done correctly.
Constipation can be a side-effect of a low FODMAP diet as eliminating high FODMAP foods also eliminates many good sources of fibre (e.g. wholegrains, legumes and certain fruits and vegetables). Adult men and women need 25-30g fibre every day, which can still be achievable when following a low FODMAP diet.
Good sources of fibre whilst following a low FODMAP diet include:
- 2 servings of low FODMAP fruit each day (e.g. banana, strawberries, orange, kiwi fruit)
- 5 servings of low FODMAP veggies each day (e.g. spinach, carrot, silverbeet, kale, green beans, jacket potato)
- Rolled oats, quinoa and brown rice
- Chia seeds, LSA mix, rice bran
Although bananas, strawberries, oranges, kiwi fruits, mandarins and grapes are all suitable for a low FODMAP diet, eating more than 1 serving of fruit at a time can still overload your system with excess fructose.
If you have been following the strict low FODMAP elimination diet for more than a few weeks and are still feeling uncomfortable, make sure you wait at least 2-3 hours between each serving of fruit. For reference 1 serve of fruit = 1 medium orange/banana/mandarin OR 2 small kiwi fruits OR 1 cup grapes/berries/chopped fruit. If you have a serve of fruit with breakfast at 7am, wait until 9 or 10am before enjoying another serving.