Cornstarch is low FODMAP and safe to use in servings up to two-thirds of a cup (about 100 grams). For most people following a low FODMAP diet, this is far more than you’d ever use in a single sitting, since recipes typically call for just a tablespoon or two as a thickener. It’s one of the most IBS-friendly pantry staples available.
Why Cornstarch Is Low FODMAP
Cornstarch is pure starch extracted from the endosperm of the corn kernel, with the fiber, protein, and sugars largely removed during processing. FODMAPs are specific types of fermentable carbohydrates (certain sugars and fibers), and the refining process that produces cornstarch strips those components away. What remains is almost entirely glucose chains, which your small intestine absorbs efficiently without sending undigested material to the large intestine where fermentation and symptoms occur.
How Much You Can Use
The tested safe serving is two-thirds of a cup, or about 100 grams. In practice, you’ll rarely come close to that threshold. A typical recipe uses 1 to 2.5 tablespoons of cornstarch as a thickener, which works out to roughly 8 to 16 grams per batch, split across multiple servings. Even if you’re making a thick gravy or sauce, you’re well within safe territory.
As a reference point, Monash University’s own low FODMAP teriyaki sauce recipe calls for about 2.5 tablespoons (16 grams) of cornstarch for the entire batch. That’s a fraction of the tested limit.
Cornstarch vs. Corn Flour: A Naming Trap
This is where things get confusing, especially if you’re reading recipes from different countries. In the United States, cornstarch and corn flour are two distinct products. Cornstarch is the fine white powder used for thickening. Corn flour (sometimes labeled corn meal when coarsely ground, or polenta when very coarse) is the whole corn kernel milled into flour.
In Australia, New Zealand, and the UK, the product labeled “corn flour” on supermarket shelves is actually cornstarch. If a recipe from one of these countries calls for corn flour as a thickener, it means cornstarch.
The good news: both products are low FODMAP at the same serving size of two-thirds of a cup. So regardless of which one you grab, you’re safe. But knowing the difference matters when you’re following recipes, because whole corn flour behaves differently in cooking than pure cornstarch does.
Other Corn Products and FODMAP Status
Corn in general is well tolerated on a low FODMAP diet. Maize flour (the whole kernel milled into flour) is low FODMAP at the same 100-gram serving. Plain popcorn, corn tortillas, and polenta are also considered safe options. Where you need to be careful is with processed corn products that have added ingredients, like corn-based sauces, seasoned tortilla chips, or corn bread mixes that may include high FODMAP additions such as honey, garlic powder, or onion powder. Always check ingredient lists on packaged products.
Using Cornstarch in Low FODMAP Cooking
Cornstarch is one of the easiest ways to thicken sauces, soups, and gravies without introducing FODMAPs. The basic technique: whisk cornstarch into a small amount of cold water until it dissolves completely, then slowly pour the mixture into your simmering liquid while stirring. This prevents clumps and gives you a smooth, glossy finish. You can adjust thickness by adding more or less of the slurry.
It also works well as a coating for pan-fried or stir-fried proteins, giving a light crispy texture without needing wheat flour. For baking, cornstarch can replace a portion of wheat flour to create a softer, more tender crumb in cakes and cookies. Some gluten-free low FODMAP flour blends use cornstarch as a base ingredient for this reason.
One limitation: cornstarch doesn’t hold up well to prolonged cooking or reheating. Sauces thickened with cornstarch can thin out if cooked too long or frozen and reheated. For dishes you plan to make ahead, tapioca starch (also low FODMAP) tends to hold its texture better through storage and reheating.