What Type of Onion is Low FODMAP? A Complete Guide to Gut-Friendly Options

November 14, 2025 •

4 min read

An estimated 10-15% of the global population suffers from Irritable Bowel Syndrome (IBS), with fructans found in high-FODMAP foods like standard onions often being a significant trigger. To add that beloved onion flavor without discomfort, it's essential to understand what type of onion is low FODMAP, as the answer lies not in the whole vegetable but in specific parts and effective substitutes.

Quick Summary

Specific parts of certain onions are low FODMAP, particularly the green tops of spring onions (scallions) and leeks, along with chives and infused oils.

Key Points

Green Tops Only: Only the green, leafy parts of scallions (spring onions) and leeks are low FODMAP; the white bulbs are high in fructans.
Chives are Safe: Chives are a low FODMAP herb that adds a delicate, onion-like flavor and can be used generously.
Use Infused Oil: You can safely use onion-infused oil, as fructans are not oil-soluble and will not leach into the oil.
Try Asafoetida: For a cooked onion flavor, a small amount of asafoetida (hing) powder is a low FODMAP alternative.
Avoid Bulbs: During the elimination phase, avoid the white bulbs of all standard onions (yellow, white, red) and shallots.
Regrow Scallions: Save the white bulbs of scallions in water to regrow a continuous supply of low FODMAP green tops.

The Low FODMAP Onion Rule: Think Green

For those following a low FODMAP diet, the general rule is to avoid the bulb of most onions, as this is where the fructans are concentrated. Fructans are a type of oligosaccharide that is poorly absorbed and can cause digestive issues. Fortunately, not all parts of the onion family are off-limits, and focusing on the green, leafy parts is the key to adding a mild, savory flavor safely.

Green Onion Tops (Scallions)

The green tops of spring onions, also known as scallions, are one of the most reliable low FODMAP options. These can be chopped and used raw as a garnish or added to cooked dishes for a mild onion flavor. The high-FODMAP white bulb must be discarded, but the vibrant green stalks are safe for consumption in generous amounts, with Monash University testing showing low FODMAP servings of up to 75g. They are versatile enough for stir-fries, soups, salads, and more.

Leek Leaves

Similar to scallions, the dark green, leafy part of the leek is low in FODMAPs, while the white bulb is high. Leek greens can be finely chopped and sautéed to form an aromatic base for soups and stews, providing a sweeter, milder onion-like flavor than their bulb counterpart. They are slightly tougher than scallion greens and benefit from a longer cooking time to soften.

Chives

Chives are another excellent low FODMAP choice for adding a delicate oniony flavor to dishes. These slender, hollow green stems are low in FODMAPs and can be used liberally, both fresh and dried. They are perfect for sprinkling over eggs, baked potatoes, and dips for a fresh, mild taste without the digestive distress.

Comparison: Low FODMAP vs. High FODMAP Onion Options


Feature	Low FODMAP Options	High FODMAP Options
Parts	Green tops of scallions, green leaves of leeks, whole chives	White bulb of scallions, white bulb of leeks, yellow/red onions, shallots
Flavor Profile	Mild, subtle, fresh onion taste	Strong, pungent, concentrated onion flavor
FODMAP Content	Low in fructans, safe for restricted diet	High in fructans, can trigger IBS symptoms
Best Usage	Garnish, added towards end of cooking, saute base (leek greens)	Avoid during elimination phase; use infused oil instead
Example Dishes	Topped on salads, soups, omelets, stir-fries	Traditional onion base for sauces, stews, and casseroles

How to Safely Infuse Onion Flavor into Your Cooking

Beyond using the green parts, there are other clever ways to get that classic onion flavor without the FODMAPs. This is possible because fructans are water-soluble but not oil-soluble, meaning their flavor can transfer to oil without the carbohydrates.

Onion-Infused Oil: This is a fantastic way to add deep onion flavor to dishes. You can purchase commercially certified low FODMAP onion-infused oils or make your own by gently heating large pieces of onion in oil for several minutes. The crucial step is to discard all solid onion pieces before using the infused oil in your cooking.
Asafoetida Powder (Hing): This potent spice, commonly used in Indian cooking, develops a savory, onion-like aroma when heated in oil. A very small pinch goes a long way, and it's a great option for mimicking onion flavor in curries, stews, and other cooked dishes. Check for brands that use rice flour as a carrier instead of wheat if you are also gluten-sensitive.
Regrowing Scallion Greens: For a continuous supply of green onion tops, you can regrow them from the white bulb. Simply place the white bulb with the roots in a small glass of water on a sunny windowsill. Change the water every few days, and fresh green shoots will grow back, which you can snip as needed.

Handling High FODMAP Onions

While most onions and their bulbs are high in fructans, a few exceptions and caveats exist based on testing by organizations like Monash University. For example, a very small, specific serving of pickled onion or certain onion bulbs might be deemed low FODMAP, but these amounts are tiny and can be confusing. During the elimination phase of the diet, it is safest to avoid all traditional onion bulbs (red, yellow, white, shallots) entirely.

Conclusion

Navigating the low FODMAP diet doesn't mean sacrificing the rich, foundational flavor that onions provide. By understanding that the fructans reside primarily in the bulb, you can effectively use the low FODMAP green parts of scallions and leeks to add a fresh, mild onion taste. Coupled with flavor-enhancing options like infused oils, chives, and asafoetida powder, you can create delicious, gut-friendly meals without compromise. This allows individuals to manage their IBS symptoms while still enjoying a diverse and flavorful culinary experience. Remember, the goal is to expand your dietary freedom over time, and these swaps are a fantastic starting point.

For more in-depth information on food testing and FODMAP thresholds, consult the Monash University FODMAP Diet App, which serves as a comprehensive resource for the diet.

Frequently Asked Questions

Yes, onion-infused oil is safe for the low FODMAP diet because fructans, the carbohydrates in onions that cause symptoms, are water-soluble but not fat-soluble. This means the onion flavor transfers to the oil, but the problematic fructans do not.

While both are low FODMAP options, they are different. Chives are an herb with a milder, more delicate onion flavor. The green tops of scallions (green onions) provide a slightly stronger onion taste. Both are excellent choices, and you can use them interchangeably or together.

No, this method does not work for a low FODMAP diet. Because fructans are water-soluble, they will leach out of the onion and into the liquid, making the soup high FODMAP.

Asafoetida, also known as hing, is a resinous spice used in Indian cooking that mimics the flavor of onions and garlic. It has a very pungent smell when raw but mellows significantly when cooked in oil. Use a very small amount, typically a pinch, and add it to heated oil at the beginning of cooking.

While the pickling process can reduce FODMAPs, the levels vary significantly depending on the onion and process. Monash University data shows that large onions pickled in vinegar can have a low FODMAP serving of about 60g, but it's best to check a reliable source like the Monash app for specific products.

Yes, you can eat the dark green, leafy tops of leeks. The white bulb is high in FODMAPs and should be avoided during the elimination phase.

Even very small amounts of standard red or yellow onion can be high in fructans. While some testing may show a tiny low FODMAP serving (e.g., 10g for red onion), it is generally recommended to avoid the bulbs of all standard onions during the initial elimination phase to minimize symptoms.