01 · ConceptAlmost everything is dose-dependent.
The core idea of the Low FODMAP diet is more subtle than the lists of "forbidden foods" doing the rounds online would suggest. FODMAPs are fermentable carbohydrates, and their effect on the gut depends on the total amount that reaches the colon, not on whether a particular food "has them" or "doesn't". Almost no plant food is completely free of FODMAPs; what exists is a threshold below which the amount is so small that most sensitive people tolerate it without symptoms.
That's why Monash University, the institution that developed the diet, doesn't publish a simple "yes/no" for each food, but a portion: the serving size that stays below the threshold. The common tomato is the canonical example. In a portion of around 75 g (half a medium tomato) it's low FODMAP; but if you eat two or three tomatoes, the fructans build up and you cross into high territory. The food didn't change: the dose changed.
This has a practical consequence many people overlook: stacking (or FODMAP stacking). Even if each food in a meal is within its safe portion, if you combine several foods from the same FODMAP group, their amounts add up and the total can exceed your threshold. A meal with half a cup of chickpeas, a little onion and wheat bread can push the oligosaccharides over the edge even though each ingredient, on its own, looked "acceptable". Planning balanced meals across the day helps you avoid stacking without realising; our Low FODMAP weekly menu can serve as a guide.
Before we go on, if you're still not clear on exactly what FODMAPs are and why they cause symptoms, it's worth first reading our guide on what the Low FODMAP diet is. And to keep the detail to hand at the supermarket, the reference tool is the official Monash University FODMAP Diet app: it's the only source that publishes up-to-date portions based on laboratory analysis of each food.
02 · TableSafe portions per food.
The following table gathers everyday foods with their indicative low FODMAP portion and the FODMAP group that usually limits the amount. If you'd like a printable version for the supermarket, you can also download our free Low FODMAP list in PDF grouped by category.
Note: indicative amounts based on Monash University; tolerance is individual — check the exact portions in the Monash app.
| Food | Low FODMAP portion (approx.) | FODMAP group / note |
|---|---|---|
| Common tomato | ~75 g (half a medium tomato) | Fructans above that portion |
| Cherry tomato | A small handful | Fructans in larger amounts |
| Strawberries | ~10 medium strawberries | Low — tolerates generous servings |
| Firm banana | 1 medium | Low if under-ripe |
| Ripe banana | ~1/3 of a piece | Fructans increase as it ripens |
| Blueberries | ~1 handful | Low in a moderate portion |
| Orange | ~1 unit | Low |
| Kiwi | ~2 units | Low |
| Grapes | ~1 handful | Low in a moderate portion |
| Avocado | ~30 g | Polyol (sorbitol) in larger amounts |
| Carrot | No practical limit | Low FODMAP |
| Courgette | ~1/3 cup | Moderate portion — check in the Monash app |
| Cucumber | Generous portion | Low FODMAP |
| Spinach | ~1 cup | Low in a moderate portion |
| Sweet potato | ~75 g | Polyol (mannitol) above that portion |
| Potato | No practical limit | Low FODMAP |
| Broccoli (stalk) | ~75 g | Moderate portion — the stalk tolerates more than the head |
| Common mushroom | High — use oyster mushroom | Polyol (mannitol) |
| Cauliflower | High — avoid | Polyol (mannitol) |
| Rice | No practical limit | Low FODMAP |
| Cooked quinoa | ~1 cup (155 g) | Low — gluten-free |
| Gluten-free oats | ~1/2 cup | Low in a moderate portion |
| Almonds | ~10 units | GOS above that portion |
| Walnuts | ~10 halves | Low in a moderate portion |
| Canned chickpeas (rinsed) | ~1/4 cup (42 g) | GOS — rinsing reduces the load |
| Canned lentils (rinsed) | ~1/4 cup | GOS — rinsing reduces the load |
| Lactose-free milk | Generous portion | Low FODMAP |
| Cow's milk | High — avoid | Lactose (disaccharide) |
| Lactose-free yoghurt | Moderate portion | Low FODMAP |
Notice how the same type of food changes column depending on variety or state: the common tomato versus the cherry, the firm banana versus the ripe one, cow's milk versus lactose-free milk. There's no universal list; there are portions. Three of these foods deserve their own detailed analysis: the tomato, strawberries and quinoa.
03 · Traffic lightHow to read the Monash app traffic-light system.
The Monash app organises foods with a three-colour traffic-light system. Understanding exactly how it works is what avoids the most common mistake of all: remembering the colour and forgetting the amount it corresponds to.
- Green: the food is low FODMAP in the stated portion. You can eat it with confidence in that amount during the elimination phase. Green is never unconditional: it's always tied to a specific serving size.
- Amber: it contains a moderate amount of FODMAPs in that portion. It's best to limit the amount and not combine it with other foods from the same group in the same meal, to avoid stacking.
- Red: high in FODMAPs at the portion assessed. It's preferable to avoid it during the elimination phase, although in many cases a much smaller serving falls back into green.
The key point, and what hardly anyone internalises at first, is that the same food can be green, amber and red depending on the amount. The app explicitly shows you at what weight it changes colour. That's why "it's green" means nothing on its own: it means "it's green at this portion". Reading the colour alongside its serving is the difference between following the diet properly and just believing you're following it.
04 · FAQFrequently asked questions about portions.
Are tomatoes low FODMAP?
Yes, the common tomato is low FODMAP in a portion of around 75 g (roughly half a medium tomato). In larger amounts it starts to build up fructans and can shift to amber or red on the Monash traffic-light system. Cherry tomatoes are well tolerated in a small handful. As with almost everything on the diet, what matters is not the food but the amount. You can read the full tomato analysis for more detail.
Are strawberries low FODMAP?
Yes, strawberries are one of the most reliable low FODMAP foods: around 10 medium strawberries are considered a safe portion during the elimination phase. It's a convenient fruit because it tolerates generous servings without building up excess fructose or polyols. Even so, it's worth checking the exact portion in the Monash app and respecting your individual tolerance. More detail in the strawberries analysis.
Is quinoa low FODMAP?
Yes, cooked quinoa is low FODMAP in a portion of about 1 cup (155 g), which makes it a very useful gluten-free grain base (technically a pseudocereal) for the elimination phase. It works as an alternative to wheat and rye, which are high in fructans. Always check the portion in the Monash app, as individual tolerances vary. We go deeper on this in the quinoa analysis.
Is coffee low FODMAP?
Black coffee (plain or espresso) is considered low FODMAP in normal amounts. The problem usually comes from the milk: a coffee with cow's milk adds lactose and can trigger symptoms. The fix is to use lactose-free milk or a compatible plant-based alternative. Bear in mind too that caffeine can stimulate the gut on its own, independently of FODMAPs.
Is a ripe banana high FODMAP?
A firm (under-ripe) banana is low FODMAP in a medium piece. As it ripens, its starch turns into sugars and fructans increase, so a very ripe banana is limited to roughly a third of the piece to stay within a safe portion. It's a clear example of the same food changing FODMAP group depending on its state and its amount.
This content is informational and does not constitute medical advice. The Low FODMAP diet should be carried out under the supervision of a registered dietitian, especially in the elimination and reintroduction phases. The portions given here are indicative and tolerance is individual: always check the exact amounts in the official Monash University FODMAP Diet app.