Are Walnuts Low FODMAP? What You Can and Cannot Control

Yes. Walnuts are low FODMAP at a 30 g serving, which Monash University lists as 10 walnut halves. The current Monash University FODMAP Diet App entry changes to moderate GOS at 31 g and high GOS at 36 g; fructans are not the limiting FODMAP at those portions. During the elimination phase, keep one serving to 30 g or less and weigh it rather than trusting a handful.

I have spent my working life answering food questions from behind a fish counter. A customer asks whether pollock is like cod; I ask how they plan to cook it, because texture and handling decide whether the substitution works. Walnuts deserve the same precision. The name of the nut gives you a starting point. Portion, added ingredients and your own test record decide what happens on the plate.

How many walnuts are low FODMAP?

Use 30 g of plain walnut kernels as the practical low FODMAP serving. Monash University's Getting Enough Fibre table gives the same amount as 10 walnut halves and counts it as a low FODMAP serve. That is the clearest answer to “how many walnuts low FODMAP?” during Step 1 of the diet.

The two measures do an uneven job. Halves vary in size and break in the bag; grams do not care whether the pieces are neat. Monash pairs 10 halves with 30 g in its published table, yet an individual packet may give you more or fewer pieces for that weight. I would use the kitchen scale and treat the count as a quick visual check.

Thirty grams is a tested low serving, not a promise that every gut will be comfortable with it. The Monash traffic light describes laboratory FODMAP content. It cannot account for your current IBS symptoms, how much you personally tolerate, or whether another ingredient in the meal causes trouble.

Which FODMAPs do walnuts contain?

The relevant FODMAPs in nuts are galacto-oligosaccharides (GOS) and fructans. Monash University's food list names those as the main FODMAP groups in nuts. In the current walnut entry, GOS is the fraction that changes the rating as the serving grows: 30 g is low overall, 31 g is moderate for GOS, and 36 g is high for GOS.

Fructans do not trigger the amber or red walnut rating at those tested amounts. That distinction matters. Cashews can be high in both GOS and fructans, while the current walnut thresholds are driven by GOS. “Nuts contain oligosaccharides” is too blunt to guide a meal.

The app reports traffic-light levels rather than absolute grams of GOS or fructans in the food. Monash's public material explains which FODMAP is present and whether a tested serving is low, moderate or high; it does not provide a food-label-style chemical weight for each fraction. So the defensible numbers are the tested serving thresholds: 30 g, 31 g and 36 g. A claim such as “30 g contains exactly X grams of GOS” would outrun the published data.

There is another limit to the figures. Monash reported in its 2025 reintroduction update that retesting can produce different FODMAP results because agricultural foods vary, and that the app can display only one dataset at a time. A one-gram boundary is useful for following the tested sample. Nature has not signed a contract to make every walnut identical.

Are walnuts lower FODMAP than pecans and cashews?

At an ordinary 30 g portion, walnuts and pecans test low FODMAP, while raw cashews test high. The useful comparison is the serving and the FODMAP fraction that sets its limit. The current app figures below were cross-checked against the August 2026 update of George Eats' transcription of Monash data.

| Nut | App-tested serving information | FODMAP fraction that changes the rating | What to use in the kitchen | |---|---|---|---| | Walnuts | Low at 30 g; moderate at 31 g; high at 36 g | GOS | Keep to 30 g during elimination | | Pecans | Low through 268 g; moderate at 269 g | Fructans | A 30 g recipe portion remains in the tested low range | | Raw cashews | Low at 3 g, about 2 nuts; high at 30 g | GOS and fructans | A walnut-sized handful is a poor swap during elimination |

The pecan result looks extraordinary because 268 g is far beyond a routine snack. Read it as a laboratory FODMAP ceiling, not a suggested portion. Monash's own low FODMAP pecan pie uses 240 g of pecans across 8 servings, which works out to 30 g per serving before any variation in slicing. That practical portion sits comfortably below the current fructan threshold.

Cashews are the awkward substitute. The current app entry allows 3 g, about 2 raw cashews, as low FODMAP; 30 g is high in GOS and fructans. Activated cashews have a separate entry and separate result, so the processing description on the packet matters.

Pecans are closer to walnuts in use. They are crisper and sweeter; walnuts are softer, slightly bitter and become pasty sooner when ground. For a salad topping or coarse crumb, the swap is easy by weight. For a filling built around pecan texture, keep the species the recipe calls for and portion the finished dish.

What can you control in a walnut serving?

You control the weight. Put the bowl on a scale, tare it, and stop at 30 g during elimination. That single act is more reliable than counting fragments or estimating what fits in your palm.

You also control the ingredient list. Plain raw or dry-roasted walnuts are the simplest test food. A flavoured packet may include honey, garlic powder or onion powder; Monash lists honey, garlic and onion among high FODMAP choices. Maple syrup, table sugar and garlic-infused oil have different ratings, but the whole recipe still needs checking at the serving you will eat.

The rest of the meal remains your decision. Monash identifies plain fish, meat, poultry and eggs as naturally free of FODMAPs, while marinades and sauces may add garlic or onion. This is familiar territory at my counter: a clean fillet and a heavily seasoned ready meal are different propositions even when the fish species is identical. A 30 g walnut crust on plain fish is easier to audit than a restaurant glaze with an undisclosed recipe.

Keep the test portion separate when you need a clear answer. A mixed nut bowl hides both species and weight. Granola may combine walnuts with cashews, dried fruit, inulin or honey. “Contains walnuts” tells you almost nothing about the FODMAP load of the serving.

What can you not control about walnuts and IBS?

You cannot control the walnut batch that Monash's laboratory tested. Its retesting guidance names growing conditions, cultivars and post-harvest storage among the reasons agricultural products can return different results. The current app entry represents the latest dataset, not every harvest in every country.

You cannot make a green traffic light predict symptoms. FODMAP testing measures fermentable carbohydrates in food. IBS symptoms can still vary with an individual's tolerance and the wider meal. A portion that is green in the app may be too much for you; a portion above green may later prove tolerable during a structured challenge.

You also cannot learn much from a bad day with several variables. Walnuts eaten with a new cereal, a sweetener and a restaurant sauce produce a muddled result. The symptom is real. Its cause remains unknown.

How do you reintroduce walnuts after elimination?

Reintroduce a larger walnut portion only after symptoms have settled on the low FODMAP phase. Monash University specifies 2–6 weeks for Step 1 under a dietitian's supervision. Its reintroduction guidance then uses one challenge food across 3 days while the background diet stays low FODMAP.

1. Establish your baseline. Record symptoms before the challenge. Start when they are well controlled, after the 2–6-week Step 1 period, rather than testing during a flare.
2. Weigh the walnut doses. A walnut-specific trial can use the current app bands: 31 g for the moderate GOS serve on Day 1 and 36 g for the high GOS serve on Day 2. Monash advises a higher red or usual serving on Day 3; agree that final amount with your dietitian and stop sooner if symptoms become unpleasant.
3. Keep the test clean. Eat the challenge at roughly the same time each day, use plain walnuts, and change no other challenge food. This tells you about that walnut portion, not every source of GOS or fructans.
4. Score, stop and reset. The Monash app user guide uses a 1–10 symptom scale, where 1 means “excellent/none at all” and 10 means “the worst it has been/really awful.” Record the same symptoms daily. Monash advises a 2–3-day break between challenges, or until symptoms settle.

Walnuts are an imperfect stand-in for a broad fructan challenge because their current higher-serving ratings are driven by GOS. Monash's 2025 reintroduction list uses cashews among the foods for a combined fructan-plus-GOS challenge. Your walnut trial answers a narrower and more useful kitchen question: how much walnut can you eat?

How can walnuts fit into low FODMAP meals?

Treat 30 g as a portion to allocate, not a garnish that disappears from the count. Use it whole beside fruit already rated low at your chosen serving, chop it over oats, or crush it into a coating for plain fish. If a recipe serves 4, 120 g of walnuts divides to 30 g each only when the portions are genuinely equal.

For low FODMAP nuts and nut butters, read the ingredient list before doing serving arithmetic. A homemade walnut butter made from a weighed 30 g portion still contains 30 g of walnut if you eat all of it. A commercial jar can include cashews, honey, chicory root fibre or flavourings, so its spoonful needs its own check.

Frequently asked questions

How many walnuts can I eat on a low FODMAP diet?

Monash University lists 30 g of walnuts, or 10 walnut halves, as a low FODMAP serving. Use the gram weight because halves vary in size and broken pieces are hard to count. The current app rating becomes moderate for GOS at 31 g, so 30 g is the practical elimination-phase limit per sitting.

Are walnuts low FODMAP according to Monash?

Yes. Monash University includes walnuts among low FODMAP nuts and gives 30 g, listed as 10 halves, as a low serving. Its current app data identifies GOS as the limiting fraction when portions increase: 31 g is moderate and 36 g is high. Personal IBS tolerance can still be lower or higher.

Are pecans low FODMAP?

Yes. Current Monash app data rates pecans low FODMAP through 268 g and moderate for fructans at 269 g. That upper tested amount is far larger than a usual snack. For a practical comparison, Monash's low FODMAP pecan pie supplies 30 g of pecans per serving, assuming 8 equal slices.

Are cashews low FODMAP?

Raw cashews have a very small low FODMAP serving: 3 g, or about 2 nuts, in the current Monash app data. A 30 g portion is high in both GOS and fructans. Activated cashews have a separate tested entry, so check the product description rather than applying the raw-cashew result to every form.

Can I eat nuts on a low FODMAP diet?

Yes, provided you choose the nut and serving separately. Walnuts are low at 30 g, pecans remain low at a practical 30 g portion, and raw cashews are low only at 3 g in current Monash data. Weigh mixed nuts by species because one total handful can hide a high FODMAP cashew portion.

Does roasting make walnuts high FODMAP?

Monash's public food list does not publish a separate threshold for roasted walnuts. During elimination, use 30 g as a conservative limit for plain dry-roasted walnuts and check the current app entry. A flavoured product needs a fresh ingredient check because honey, garlic and onion are high FODMAP choices in Monash's food list.