Name: Low FODMAP “Onion” Soup
Prep time: 10 min
Cook time: 70 min
Total time: 80 min
Ingredients: 4 tablespoons (57 g) unsalted butter, (cut into pieces); 2 tablespoons extra-virgin olive oil or Garlic-Infused Oil,; 3 to 4 leeks, (to yield 125 g of bulb, 100 g of greens, all finely chopped); 3 large bunches of scallions, (to yield 80 g of bulb, 40 g greens, all finely chopped); 2 quarts (2 L) beef stock, homemade or purchased low FODMAP beef stock; 4 sprigs fresh flat leaf parsley; 2 small springs fresh thyme; 1 bay leaf; Kosher salt; Freshly ground black pepper; 8 slices low FODMAP gluten-free baguette; 12 ounces (340 g) Swiss or Gruyere cheese, (shredded)

Can “Onion” Soup Be Low FODMAP? YES!

Robin and I were hankering for French Onion Soup, and seeing that I am following the low FODMAP diet, that didn’t seem possible—at first. But then I got thinking… what if I used low FODMAP amounts of leek and scallion greens and bulbs and applied an otherwise classic approach to this soup? What would happen? Would it work? Only a test would tell!

French onion soup in a brown bowl with melted cheese and red and orange flowers in the background

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Onion Flavor Without Onions

If you are a FODMAP Everyday® fan then you already know that we use a lot of leek greens and scallion greens in our cooking to bring onion-y flavor to our cooking, as well as the low FODMAP amounts of bulbs. Off to the market I went and there is a caveat here.

You have to have access to leeks that are sold with a good amount of their green tops intact. Not every store sells them like this. In fact, many supermarkets sell them trimmed of most if not all of their greens.

Many shoppers like this because they don’t have to pay for the weight of the part of the leek that is normally discarded. For those following the low FODMAP diet, we have to become savvy shoppers. For me, this means getting my leeks at our local Whole Foods store, or from our garden when the season is here!

PS: There are low FODMAP amounts of bulbs, and this recipe has been updated to include those, now that they have been lab tested by both Monash University and FODMAP Friendly.

Beef Stock

The classic French onion soup relies on good beef stock (and we have a homemade version), tons of onions, butter, French bread, and lots of melted cheese. So the two main issues are replacing the onions with suitable low FODMAP substitutes and using a great stock.

We recommend making your own stock, but you can use a purchased beef stock; read labels and make sure you are using a low FODMAP version. Gourmend has an excellent beef stock.

The French bread is easy to replace with a low FODMAP gluten-free version, and thankfully, the cheese is low FODMAP!

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French onion soup with melted cheese on top, with a spoon pulling at the cheese

Patience is Key

The other ingredient necessary for this Onion Soup recipe is patience. The large amount of leek and scallion greens and bulbs needs to be cooked for about an hour over low heat, with occasional stirring. They must not overly brown, especially at the beginning of cooking, and you must encourage them to soften and caramelize. It will seem like it is never going to happen; it will.

Be patient and you will be rewarded with the rich flavor that these onion substitutes provide.

Colorful Expectations

Classic French Onion Soup is a deep brown color that comes from the beef stock. Although our version is based upon beef stock as well, the green pigments in the leek and scallion greens do come through.

Onions, whether white or yellow, have very little color and permit the brown stock to be predominant. Expect this low FODMAP version to be a bit green, a bit brown. And speaking of visual expectations, this soup was incredibly hard to photograph! I hope it entices you, as it actually tastes superb

Melted Cheese Makes it Good

The image of the classic French Onion Soup in a bowl with a mass of melted Gruyere cheese on top is hard to resist. Swiss cheese is Green Lighted by Monash and Gruyere is a type of Swiss cheese, so we have taken the liberty to use it. If you want to use Swiss, be our guest.

We have done fine with the digestibility of Gruyere. Monash recommends 40 g of Swiss cheese per serving. It is, however, low FODMAP up to 500 g, the largest amount tested. (This does not mean it becomes high FODMAP at 501 g).

The best way to get the most bang for your FODMAP buck is to shred the cheese so that it melts easily and you can cover the top of your bread and soup. The slice of low FODMAP baguette, by the way, is nestled in the soup, under the cheese.

FODMAP Information

All recipes are based upon Monash University & FODMAP Friendly science at time of initial publication.

Butter: Both Monash University and FODMAP Friendly have lab tested butter. Monash states that a low FODMAP Green Light portion is 1 tablespoon or 19 g and also states that “butter is high in fat and does not contain carbohydrates (FODMAPs)”. FODMAP Friendly used to give it a “Pass” at 1 tablespoon or 19 g. Both recommended serving sizes are/were presented as part of healthy eating guidelines, not as maximum FODMAP serving size. Fat can affect guy motility and trigger IBS symptoms in some people. Currently FODMAP Friendly lists butter as containing no FODMAPs, which is more accurate to FODMAP content, and does not overlay government guidelines. Eat to your tolerance.
Cheese: Many cheeses have low FODMAP serving sizes. The low FODMAP diet is not a dairy-free diet. Hard cheeses such as Parmigiano Reggiano or Pecorino Romano have been lab tested by Monash University and are low FODMAP in 40 g amounts – and the servings remain low FODMAP up to 500 g.
Dairy: The low FODMAP diet is not a dairy-free diet. It is however, low in lactose. Many dairy ingredients are low in lactose, such as heavy cream and many cheeses.
Leeks: Both Monash University and FODMAP Friendly have lab tested leeks – greens (leaves) and bulbs. Monash University recommends a low FODMAP serving size of 100 g for the greens (updated to 75 g), and 14 g for the bulb. FODMAP Friendly suggests a serving size of leek greens of 37 g, with a low FODMAP max serve of 83 g (updated to 82 g). Their recommended max low FODMAP leek bulb amount is 46 g (updated to 47 g).
Scallions: Monash University lab testing initially found no FODMAPs detected in scallion greens; in subsequent tests, scallion greens showed fructose content. The suggested serving size is 75 g. Monash states the scallion bulb low FODMAP serving is 32 g (about ⅓ cup). FODMAP Friendly has also lab tested scallions: their recommended serving size for the green parts is 16 g, with a max low FODMAP serving between 160 g and 176 g (from different tests). FODMAP Friendly says the bulb is low FODMAP in 19 g to 20 g portions, which is about 2 tablespoons finely chopped.

Please always refer to the Monash University & FODMAP Friendly smartphone apps for the most up-to-date lab tested information. Foods will be retested from time to time; in the case of raw ingredients, such as fruits and vegetables, results may vary. All lab tested results are valid and represent a snapshot in time. As always, your tolerance is what counts; please eat accordingly. The ultimate goal of the low FODMAP diet is to eat as broadly as possible, without triggering symptoms, for the healthiest microbiome.

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