FODMAP Stacking Explained

The concept of FODMAP stacking causes considerable confusion in the FODMAP community, with a lot of misinformation out there contributing to this. We’ve addressed this concept in previous blog posts (here and here), so in this blog post, we will answer some of your burning questions about the topic of FODMAP stacking.

What is FODMAP stacking?

FODMAP stacking refers to the notion that when multiple ‘green serves’ of food are eaten in one sitting, there is an accumulation of FODMAPs in the gut, triggering symptoms. While the term ‘FODMAP stacking’ does not appear in the scientific literature, the concept is based on observations from research which showed that:

• symptoms are induced to a greater extent when people consume multiple FODMAPs in one sitting (e.g. fructose + fructans) compared to one FODMAP alone (e.g. fructose)[1], and that
• the collective reduction of all FODMAPs (fructans, GOS, lactose, fructose and sugar polyols) improves IBS symptoms to a greater extent than the restriction of any one FODMAP in isolation[2].

Are FODMAP amounts cumulative?

The short answer is, yes. In one sitting, the total amount of FODMAPs consumed (be it from fructose, fructans, lactose, GOS or sugar polyols) influences whether the meal is tolerated or whether symptoms are induced.

The Monash University FODMAP diet app uses a traffic light system to indicate the rating of each FODMAP in individual foods (fructose, sorbitol, mannitol, lactose, fructans and GOS), and the overall FODMAP rating (low (green), medium (amber), high (red)) of food at different serving sizes[4]. But we know that people don’t just eat individual foods, they eat mixed meals including multiple different foods. For this reason, Monash’s cut-off criteria for the rating of FODMAP content of food were set conservatively, allowing people to include more than one ‘green serve’ of food per sitting.

The point here is that everyone’s threshold level of FODMAP tolerance is different. While FODMAP stacking will be relevant to some people who may find they experience IBS symptoms when multiple ‘green serves’ are eaten in one sitting, for many, the conservative FODMAP cut-offs set by Monash mean they will achieve good symptom control when consuming a varied diet that includes numerous ‘green serves’ at each sitting.

Does stacking relate to the foods eaten over a whole day or just in one meal?

As a general rule, the concept of stacking relates to a single sitting or meal. This of course assumes that meals are spaced out over the day, with at least 2-3 hours between each meal or snack. This allows food to be digested between meals and slows the rate at which the gut is exposed to the FODMAPs. If you find you are constantly snacking and experiencing IBS symptoms, spacing out your meals may help. Tips to achieve this include:

• Including low FODMAP, protein and fibre-rich foods with each meal/snack to assist with satiety (see tips at the bottom for some great snack ideas!)
• Paying attention to your appetite and why you’re eating. If you find yourself constantly snacking, or eating very shortly after a meal, you may be doing so for reasons other than physical hunger. Keeping a simple food diary that notes how hungry you are on a scale of 1-10 at each eating occasion can assist you to pay more attention to your appetite. Working with an experienced dietitian can also help.

Do I need to track what FODMAPs I eat to avoid stacking?

First of all, if your symptoms are well controlled and you haven’t been thinking about FODMAP stacking, then don’t start worrying! We understand that the low FODMAP diet can be confusing and burdensome already, so our conservative FODMAP “cut-offs” used in the app take away the need to “track” specific FODMAP quantities (e.g. similar to tracking calorie/kilojoule intake).

FODMAP stacking is only something you might consider if you notice that a low FODMAP diet has improved most of your symptoms, but you still experience some symptoms even though you are only eating low FODMAP foods.

For some people, it will be that factors other than FODMAPs are affecting their IBS symptoms (e.g. stress or anxiety). For others, it might be that they are quite sensitive to FODMAPs and thus need to consider ‘stacking‘. Keeping a food and symptom diary and working with a GI dietitian specialised in using a FODMAP diet is the best way to work out what your individual IBS triggers are, and whether FODMAP stacking is an issue for you.

Safe meal example

It is important to note that even if foods have amber or red lights for larger serve quantities, you can safely consume the green serving sizes combined in one meal without the worry of triggering symptoms.

It is still low FODMAP to have 

• 1 slice of wholemeal bread (green light) and 40g of raspberry jam (green light) even though they both contain fructans at higher serves 
• 2 rice cakes (green light), 30g of tahini (green light) and 45g/3 sliced cherry tomatoes even though they contain fructans, GOS and fructose (respectively) in higher serves

Key take-home messages:

• FODMAP stacking refers to IBS symptoms possibly occurring due to consuming multiple “green” FODMAP servings of foods (particularly when they contain amber and red amounts of FODMAPs in higher quantities), therefore “stacking” up the total amount of FODMAPs eaten in one sitting/meal
• Stacking refers to the consumption of foods with any type of FODMAP, not just the consumption of only the same type of FODMAP
• There is no need to worry about stacking if your symptoms are well controlled
• The Monash FODMAP Diet App green light cut-offs are conservative to allow for safe combinations of multiple foods together in a meal

Tips:

• Space out your meals - try to leave 2-3 hours between meals and snacks to avoid potential additive effects. If you are peckish, look for foods that a naturally low in FODMAPS (e.g. protein foods like eggs/meat/fish, grains like rice or vegetables like carrots). Snack ideas include:
  
  - Small handful of nuts (e.g. almonds or walnuts)
  - Eggplant dip with vegetable sticks
  - Fruit (e.g. orange, banana) and low lactose yoghurt
  - Cheese and seeded crackers
  - Small tin salmon/tuna
  - Boiled egg
  - Plain popcorn
• Keep a food and symptom diary - if you’re struggling to resolve all your symptoms, or feel like you are highly sensitive to some FODMAPs, try keeping a food and symptom diary, and where possible work with a Monash FODMAP-trained dietitian to help assist you.

Monash FODMAP developed recipes are all checked to ensure they are still classified as low FODMAP in each serving, and we have a new tool to help combine our recipes to ensure stacking does not occur in a sitting. We have explained this tool in our next blog! LEARN MORE HERE

References:

1. Shepherd, S.J., et al., Dietary triggers of abdominal symptoms in patients with irritable bowel syndrome: randomized placebo-controlled evidence. Clin Gastroenterol Hepatol, 2008. 6(7): p. 765-71.
2. Gibson, P.R. and S.J. Shepherd, Personal view: food for thought--western lifestyle and susceptibility to Crohn's disease. The FODMAP hypothesis. Aliment Pharmacol Ther, 2005. 21(12): p. 1399-409.
3. Halmos, E.P., et al., A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology, 2014. 146(1): p. 67-75 e5.
4. Varney, J., et al., FODMAPs: food composition, defining cutoff values and international application. J Gastroenterol Hepatol, 2017. 32 Suppl 1: p. 53-61.