Is Sourdough Low FODMAP? 6 Checks Before You Buy

Is sourdough low FODMAP? Sometimes, yes, but not automatically. A traditional loaf that ferments slowly can contain far fewer FODMAPs than a quick yeast loaf, and Monash University has found some wheat and spelt sourdoughs to be low FODMAP in a set portion. Many shop loaves labelled "sourdough" are rushed, though, so the flour, the fermentation time and the portion all matter. Below you will find what the research says, a table of bread types, a label checklist and a simple way to test a loaf without guessing. The low FODMAP diet is a temporary plan that is best followed with a doctor or dietitian.

In brief:

• Slow, traditional fermentation can break down part of the fructans in flour.
• Spelt sourdough and some wheat sourdoughs have been tested as low FODMAP.
• A "sourdough" label alone proves nothing: check flour, yeast and fermentation time.
• Stick to the tested portion and confirm it in the Monash FODMAP app.
• Sourdough is not gluten free, so it does not suit coeliac disease.

In this article · 11 min read

1. Is sourdough low FODMAP? What the research says
2. Which sourdough breads are more likely to suit you?
3. Is gluten the problem?
4. A label checklist for sourdough on a low FODMAP diet
5. How to test a sourdough loaf, step by step
6. What to eat with it
7. Where a cookbook can help
8. When to talk to a doctor or dietitian
9. Who it is for
10. Key terms
11. Frequently asked questions
12. Sources

FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) are short-chain carbohydrates that some people digest poorly. In wheat, rye and barley the main one is fructan, which is why ordinary bread sits on most "avoid" lists during the elimination phase. Sourdough is different because of how it is made: instead of relying on baker's yeast for a couple of hours, the dough is left for many hours with a starter of wild yeasts and lactic acid bacteria. Those microbes feed on carbohydrates in the flour, including some of the fructans. How much disappears depends on the process, and that is the whole story of whether sourdough is low FODMAP.

Is sourdough low FODMAP? What the research says

Monash University, where the diet was developed, explains that sourdough is left to prove for a long time, typically more than 12 hours, during which yeast and bacteria use up carbohydrates, FODMAPs included. Monash adds that spelt has a notably lower fructan content than modern wheat, and that sourdough spelt breads made this way meet the low FODMAP criteria in its app (Monash University FODMAP, November 2017).

A dietitian who writes about the diet reports that Monash later tested wheat sourdoughs too: a wholemeal and a white sourdough met the low FODMAP criteria at two slices (Kate Scarlata, RDN, 2015). Two slices is a tested serving of those particular loaves, not a rule for every sourdough.

The science of baking explains why results differ so much. A review of low FODMAP baking by Jussi Loponen and Michael Gänzle (Foods, 2018) gives these figures:

• Wheat grain contains roughly 1 to 2 % fructans and rye grain about 4.3 to 5 %.
• Ordinary yeast bread leaves about 1 to 1.5 % fructans in wheat bread and about 3 % in rye bread, because baker's yeast breaks fructans down only partly.
• A dough fermented with sourdough alone typically ferments about 10 % of the flour for more than 12 hours. Industrial "sourdough" use often ferments only 5 to 20 % of the flour for that long, and the rest of the dough for about 2 hours (Foods, 2018).

That last point is the catch. A loaf can contain some sourdough and still be mostly a fast yeast bread.

A German study of 21 wheat varieties found that the FODMAP content of the flour varied by a factor of four between varieties, and warned against concluding from the fermentation time alone how much has been broken down (Universität Hohenheim, 2020). So time helps, but it is not a guarantee.

Which sourdough breads are more likely to suit you?

Treat this table as a map for your questions to the baker and your dietitian, not as a list of safe foods. Amounts always come from the Monash app.

Is gluten the problem?

Not exactly. The University Hospitals of Geneva state plainly that FODMAPs have nothing to do with gluten, and note that many foods containing gluten happen to be rich in FODMAPs (HUG). Wheat, rye and barley contain both fructans and gluten, but they are separate issues. Sourdough bread made from wheat or spelt still contains gluten, so if you have coeliac disease or a wheat allergy, a low FODMAP sourdough is not the answer. Ask your doctor.

A label checklist for sourdough on a low FODMAP diet

You can often tell a lot from the bag. Here is a checklist built from the dietitian's tips and Monash's explanation:

1. Short ingredient list. Flour, water, salt and starter is the ideal. Look out for honey, high-fructose corn syrup, inulin or chicory root.
2. Look for added yeast. Yeast in the ingredient list suggests a faster rise and less time for FODMAPs to break down.
3. Check the sugar line. Scarlata notes that the microbes use up most added sugars, so a long-fermented loaf should show close to zero sugar on the nutrition label.
4. Ask the baker. A good bakery can tell you how many hours the dough ferments. One to two days of natural leavening is the kind of answer to look for.
5. Look for certification. Monash runs a Low FODMAP Certified programme, and some sourdough breads have been certified. A certified loaf has been tested at a stated serving.
6. Check the flour. Wheat, spelt and rye behave differently. If a mix contains rye or added fibres, treat it as a separate test.

For a short explanation from the people who test these breads, A Little Bit Yummy talks with Chloe Valentine, a research dietitian on the Monash University FODMAP team, about the science behind sourdough and how to choose a loaf.

How to test a sourdough loaf, step by step

If your dietitian agrees that bread can be part of your plan, a calm routine takes the guesswork out. This is a general outline, not a medical protocol.

1. Choose one loaf, ideally a traditional spelt or long-fermented wheat sourdough that fits the checklist above.
2. Start with one slice, not two, and eat it as part of a meal without other new foods.
3. Write it down. Note the loaf, the portion and how you feel over the next day or two, in the same food and symptom diary you already use.
4. Increase only if all is well. If you feel fine, try the tested portion on another day. If symptoms appear, stop and wait until you have settled before the next test.
5. Change one thing at a time. Do not test a new bread on the same day as a new fruit, dairy product or sauce.
6. Share the results with your dietitian, who can tell you whether to keep the bread in your plan.

Why this approach? Because FODMAPs add up, and tolerance varies from person to person. Monash describes the diet as a short period of restriction followed by a step-by-step return of foods to find out which ones you tolerate (Monash University FODMAP).

What to eat with it

A tolerated slice of sourdough works well with simple toppings: a little olive oil, a boiled egg, smoked salmon and cucumber, or peanut butter with a few strawberries. Avoid garlic butter, honey and onion-based spreads. If you are looking for more ideas, see low FODMAP breakfast ideas and low FODMAP snacks.

Where a cookbook can help

If you like having your meals planned, our book The Delicious Low-FODMAP Diet Cookbook by Zoe Patton is a beginner-friendly option. It has 70 easy recipes, food lists, a four-step method and a printable day-by-day plan that covers 60 days. One honest note first: the book does not discuss sourdough. It uses gluten-free bread, for example for the smoked salmon and cucumber toast in recipe 7, and its "foods to avoid" list names wheat, barley and rye products. So it will not tell you whether a given loaf is right for you; for that you need the Monash app and a dietitian. What it adds is a way to organise your pantry, read labels for hidden garlic, onion, honey and inulin, and plan your meals so you are not deciding what to cook while symptoms are on your mind. The book gives yes/no food lists without serving sizes, and a few of its recipes include foods from its own avoid list, so choose with care. Books Go Publications builds its guides on reliable sources, which is why the Monash research and a peer-reviewed baking review come first in this one.

Zoe Patton's view

In The Delicious Low-FODMAP Diet Cookbook, Zoe Patton asks readers to begin before day one with a pantry audit: empty the cupboards, fridge and freezer and read every label, because FODMAPs hide in sauces, condiments and packaged foods. Her usual suspects are garlic and onion powder, honey, high-fructose corn syrup, inulin and chicory root extract, even in products sold as "healthy" or "natural". The same habit works at the bread shelf, where a loaf sold as gut-friendly may contain added inulin. The book does not cover sourdough itself, so check any loaf and its serving size in the Monash app, and make these changes after a doctor has diagnosed irritable bowel syndrome (IBS), ideally with a registered dietitian, keeping in mind that the strict phase is temporary.

When to talk to a doctor or dietitian

A low FODMAP diet is not something to start alone. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains that a doctor may suggest it for irritable bowel syndrome for a few weeks and, if symptoms improve, slowly add foods back, because you may be able to eat some foods with FODMAPs without symptoms (NIDDK). See a doctor if you have ongoing bloating or pain, blood in your stool, unexplained weight loss or night-time symptoms, so that other causes can be ruled out before you cut out foods such as bread. This article is for general information, not medical advice. The elimination phase is temporary: reintroduction and a personalized diet come next.

You will find more food guides on the Books Go Publications blog, for example a low FODMAP meal plan for one week, and our other books on the Books Go Publications home page.

Who it is for

This guide is for anyone on a low FODMAP plan who misses good bread and wants to know which loaf is worth testing.

• People in the elimination phase with a dietitian: a clear list of questions to ask before adding a loaf to the plan.
• Bread lovers with IBS: a way to test sourdough calmly instead of giving up bread for good.
• Home bakers: an explanation of why a long, slow fermentation matters if you bake your own sourdough.
• Family and friends who cook for someone with IBS: what to look for on the bag before you buy bread for them.

Key terms

• FODMAPs: fermentable oligosaccharides, disaccharides, monosaccharides and polyols, short-chain carbohydrates that some people absorb poorly.
• Fructans: chains of fructose found in wheat, rye, barley, onion and garlic, the main FODMAP in bread.
• Sourdough starter: a mix of flour and water full of wild yeasts and lactic acid bacteria that raises the dough slowly.
• Elimination phase: the short first stage of the diet, when high FODMAP foods are swapped for low ones for a few weeks.
• Reintroduction: testing FODMAP groups one at a time to learn which ones you tolerate.
• Coeliac disease: an immune reaction to gluten that needs a strictly gluten-free diet, whatever the FODMAP content.

Frequently asked questions

Is sourdough bread low FODMAP?

Some is, in a set portion. Monash has found spelt sourdough and some wheat sourdoughs to meet the low FODMAP criteria, but a loaf labelled "sourdough" is not automatically suitable. Check the flour, the fermentation time and the portion in the Monash app.

Is spelt sourdough low FODMAP?

Monash says sourdough spelt breads made with a traditional long process meet its low FODMAP criteria, because spelt has a notably lower fructan content than modern wheat. Spelt still contains gluten and some fructans, so keep to the tested portion.

How many slices of sourdough can I eat?

It depends on the loaf. Two slices is the portion at which the wholemeal and white wheat sourdoughs mentioned above met the low FODMAP criteria. Another loaf can have a different serving, so look it up in the app and start smaller if you are unsure.

Is rye sourdough low FODMAP?

Rye flour contains more fructans than wheat flour, so it is a less obvious choice. Some people tolerate small amounts, but it is best discussed with a dietitian before you try it.

Is sourdough gluten free?

No. Sourdough made from wheat, spelt or rye contains gluten. The low FODMAP diet and a gluten-free diet are different, and people with coeliac disease need a gluten-free bread.

Why does fermentation time matter?

During a long ferment, the microbes in the starter use up part of the carbohydrates in the flour, including fructans. A quick dough with a little starter leaves much less time for that to happen.

Can I eat sourdough in the elimination phase?

That is a question for your dietitian. Some plans allow a tested sourdough in a small portion, others leave bread out until reintroduction.

Sources

• Sourdough processing and FODMAPs, Monash University FODMAP, November 2017
• Use of Sourdough in Low FODMAP Baking, Loponen and Gänzle, Foods, 2018
• Let's talk about sourdough bread and FODMAPs, Kate Scarlata, RDN, 2015
• Durch Teigführung und Rohstoffauswahl sind die Gehalte von FODMAPs im Brot gering, Universität Hohenheim, 2020
• Approche alimentaire FODMAP, Hôpitaux universitaires de Genève
• Eating, Diet & Nutrition for Irritable Bowel Syndrome, NIDDK
• Starting the low FODMAP diet, Monash University FODMAP