One of the biggest points to emphasise with the low FODMAP diet is yes, portions absolutely matter, even if you’re eating all low FODMAP foods. So, let’s take a look at why!
Why do portions matter?
Even when sticking to low FODMAP foods, if your portions aren’t correct, then your diet can become high in FODMAPs. Incorrect portions is one of the key reasons individuals find they still get symptoms when on a low FODMAP diet.
What may seem like a minor difference in portion sizes can make a big difference in terms of FODMAP levels. To demonstrate, we’ve put together a table of some examples below where small changes in portion size result in a big change in FODMAP content.
| Food | Low FODMAP | Moderate FODMAP | High FODMAP |
| Blueberries | 40g (1/4 cup) | 50g (1/3 cup) | 125g (1 cup) |
| Avocado | 30g (1/8 avocado) | 45g (1/4 avocado) | 80g (1/2 avocado) |
| Green beans | 75g (15 beans) | 125g (25 beans) | 175g (35 beans) |
| Zucchini | 65g (1/3 cup) | 75g (1/2 cup) | >85g |
| Sweet potato | 75g (1/2 cup) | 100g (2/3 cup) | 112g (3/4 cup) |
| White bread | 24g (1 slice ) | 36g (1.5 slice) | 49g (2 slice) |
For more information on portion and high vs low FODMAP foods, check out the Monash University FODMAP App.
Other reasons why portions matter
We know that portions are super important for those with IBS, but not just due to FODMAPs. Other nutrients/factors which are important to be mindful of with portions are:
- Dietary fats: excess dietary fats are a common trigger of IBS symptoms. This is due to the role of fat in increasing gut motility (moves things along faster). Individuals vary greatly with their fat tolerance levels. Check out our article on dietary fats and IBS for more info.
- Fibre: excess and lack of fibre can both cause trouble with IBS symptoms. The type of fibre also plays a big role. See our article on balancing FODMAPs and fibre here
- Alcohol: alcohol is a common trigger for triggering IBS symptoms, even in small amounts if sensitive. Check out our article here for more information on alcohol and IBS.
- Caffeine: caffeine occurs both naturally and is added to various foods and beverages. It is also a key trigger for IBS symptoms for many individuals, and like with dietary fat and fibre…tolerance levels vary. For more info on caffeine and IBS, see our article here.
- Volume: large volumes of food can also cause discomfort and symptom flare-ups for individuals with IBS. You may tolerate smaller frequent meals/snacks across the day more than three large meals a day.
- Chilli/spices: hot and spicy foods can aggravate IBS symptoms as well, so you may find milder foods more tolerable.
Spreading your intake of FODMAPs across the day
It is important to manage your intake of FODMAPs across the day to avoid ‘FODMAP stacking’. FODMAP stacking is where you eat too much of a single FODMAP (e.g eating various ‘safe’ portions of the same FODMAP), resulting in an overall high intake of that FODMAP. So in addition to correct portions, evenly distributing a variety of FODMAPs is also important. For more information, see our article on managing your intake of FODMAPs across the day.
Stay tuned for our up coming article which delves into FODMAP stacking even further!
IG: @amanda_gaukroger_dietitian
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Start feeling better now! By signing up to The FODMAP Challenge you will receive meal plans, recipe ideas, and regular support with other resources, such as a private Facebook group, to make this as easy for you as possible.