This article is general food information, not medical or dietary advice. If you follow a low FODMAP diet for IBS or another condition, work with a doctor or dietitian, and check the current Monash University FODMAP Diet app for up-to-date serving sizes.
Are pickled onions low FODMAP?
Onions are normally high in fructans, one of the FODMAPs that bothers many people with IBS. Pickled onions are a surprising exception, at least in small servings. Monash University FODMAP testing has listed large pickled onions as low FODMAP at about 60 grams per serving, with moderate fructans in servings above about 85 grams. Small cocktail onions are a different story, with no low FODMAP serving size listed.
The leading explanation is that fructans are water-soluble, so some of them move out of the onion and into the brine over time, as happens with canned legumes. Because Monash updates its testing, treat these numbers as a starting point and check the app before relying on them.
Why serving size and onion type matter
- Large onions vs cocktail onions: use full-size onions and cut them yourself. Small pearl or cocktail onions are listed as high in FODMAPs.
- Portion: 60 grams is not a tiny amount. It is a few slices of onion, enough to top a taco or burger. Staying within that range is the safe guideline.
- Variety: Monash testing did not separate onion varieties for pickled onion. Red, white, brown and sweet onions are all used in recipes, but tolerance varies by person.
- Drain well: the brine holds water-soluble FODMAPs, so lift the slices out and let them drip rather than spooning in liquid.
It is not known precisely how long onions must soak before the fructan level drops, and Monash has not specified a pickling time. Some people introduce pickled onion slowly over several days to see how they respond.
Ingredients
Makes about one pint.
- 2 medium onions, red or white (about 12 ounces), peeled and sliced
- 3/4 cup distilled white vinegar or apple cider vinegar, labeled 5% acidity
- 3/4 cup water
- 1 1/2 teaspoons fine pickling salt (about 9 grams)
- 1 tablespoon white sugar, optional (not honey or high fructose syrups)
- Optional low FODMAP flavorings: black peppercorns, mustard seeds, a bay leaf, fresh dill, a pinch of chile flakes
Leave out garlic, shallots and honey. You can pickle garlic in the same brine but do not add it to this jar.
Method
- Wash a pint jar and lid in hot, soapy water and rinse well.
- Slice the onions however you like: thin half-moons for sandwiches and tacos, or thicker wedges for a snack.
- Heat the vinegar, water, salt and sugar in a saucepan until it boils and dissolves.
- Pack the onions into the jar with spices. For softer onions that are easier to arrange, simmer them in the brine for a minute or two before packing.
- Pour the hot brine over the onions so they are completely covered. Cool, cover and refrigerate.
- Eat after a few hours for crunchy pickled onion, or wait a day or more for a more mellow flavor.
Lime juice is sometimes suggested as a substitute for vinegar, but its acidity varies, so it is not a safe substitute for the vinegar in a jar you plan to keep. You can add a little extra lime juice for flavor on top of the vinegar.
Storage and safety
- Keep the jar refrigerated, with the onions under the brine.
- Use clean utensils.
- For best quality, eat within two to three weeks.
- Throw out any jar that smells off, looks moldy or fizzes.
- This is not a shelf-stable recipe.
Frequently asked questions
Are pickles low FODMAP or high FODMAP? It depends on what is pickled and what is in the brine. Plain cucumber pickles in modest servings are usually considered low FODMAP, while pickles flavored with garlic, onion, honey or high fructose corn syrup may not be. Check ingredient labels and the Monash app.
Are pickled onions gut friendly? Vinegar pickles do not contain live cultures, so they are not probiotic. Only fermented pickles that have not been pasteurized, such as salt-brined sauerkraut, contain live bacteria. Whether any pickle suits your gut depends on your own tolerance.
What are some IBS-friendly pickles? Pickled cucumbers, carrots and some other vegetables made without garlic or onion are often tolerated in small servings. Our pickled cauliflower, carrots and celery recipe can be made without garlic, but cauliflower and celery have their own FODMAP limits, so check the app for serving sizes.
Why is garlic not low FODMAP? Garlic is high in fructans, and there is no low FODMAP serving size for the fresh clove. Because fructans dissolve in water but not in fat, garlic-infused oil is often used as a flavoring on the diet, with the cloves removed. Do not make garlic-in-oil at home without proper guidance, because it carries a botulism risk when stored incorrectly.