What's the deal with FODMAP stacking?

If you’re following the low FODMAP diet, you may have already heard of FODMAP stacking. It’s an important concept to be aware of when following a low FODMAP diet, particularly during the elimination and challenge stages.

What is FODMAP stacking?

Basically, FODMAP stacking is when foods containing the same FODMAP are eaten in the same meal or in meals close together, adding up to a high level of FODMAPs. This can often occur when different foods which are low FODMAP or have a green FODMAP rating are consumed in a combination meal. This is a common and very easy mistake to make on the low FODMAP diet.  

To put this into context, here are some examples of FODMAP stacking:

• A meal containing 75g green beans, ½ cup green capsicum and 30g of avocado. Each serve is low FODMAP, but each contains the polyol sorbitol.  So, three serves of the polyol sorbitol, despite each being low FODMAP, is likely to ‘stack’ and become moderate-high FODMAP.
• A fruit salad containing 40g blueberries, 60g raspberries, ⅓ ripe banana, and 120g rockmelon. Each serve is low FODMAP, but all contain fructans. Therefore, four low FODMAP serves of fructans will likely ‘stack’ and become moderate-high FODMAP.
• A snack of 10 almonds and 10 hazelnuts. Both are low FODMAP serves, but both contain galacto-oligosaccharides (GOS) and will therefore likely ‘stack’ and become moderate-high FODMAP.

Why is it important to avoid FODMAP stacking?

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From the examples above, it is clear that FODMAP stacking should be avoided to reduce the risk of aggravating symptoms and accidentally converting a low FODMAP meal or snack to a moderate-high FODMAP meal or snack.  

FODMAP stacking is an easy way to trigger IBS symptoms through consuming a moderate-higher FODMAP meal without even realising it.  

During the elimination phase, the goal is to get symptoms as minimal as possible prior to commencing the challenge phase.  

Accidental FODMAP stacking can interfere with this by worsening symptoms. FODMAP stacking could also cause a reaction when trialling challenging individual FODMAPs. This could lead an individual to believe the FODMAP they challenged triggered the reaction, rather than a different FODMAP they accidentally stacked in a meal.

Tips to avoid FODMAP stacking

Some key tips to avoid FODMAP stacking include:

• Spread your FODMAPs across the day, particularly for fruit to avoid the ‘stacking’ of fructose.
• Plan your meals and snacks ahead of time to ensure even distribution of different FODMAPs across the day.
• Aim for a limit of 1-2 green serves of the same FODMAP per meal and avoid having meals containing multiple serves of the same FODMAP too close together.

Reviewed by the Healthylife Advisory Board March 2022