Spring Onion (white part)
Serving sizes
Spring Onion (white part) changes rating with portion size. These are the amounts tested in the literature behind our ratings.
- About ⅓ cup (30g)
- Larger portions
- Much larger portions
Spring onion (white part) is High FODMAP at a usual serving, though about ⅓ cup (30g) is low.
- At about ⅓ cup (30g) the white part is low.
- Fructans and Excess Fructose in the bulb build, so larger portions are moderate and much larger portions are high.
Reach for the green tops of the spring onion when you want more of that fresh oniony lift.
Why spring onion (white part) is rated high
The white bulb of a spring onion is rated high because of fructans, the same group that makes onion difficult, concentrated in the bulb end of the plant, with excess fructose building alongside. The low serve is about ⅓ cup (30g) of sliced white part; a larger portion is moderate and a much larger portion is high. The useful part of the story is that the plant is split: the fructans sit in the white bulb, while the green leaves are the part people on the diet actually cook with.
What changes your risk
- Which end of the plant you use This is the one lever that really matters. The white bulb climbs quickly past about ⅓ cup (30g), while the green tops are the part that fills the same role on a low FODMAP plate.
- A small low serve About ⅓ cup (30g) of the white part is low, larger portions are moderate and much larger portions are high. A handful of bulbs charred whole on the grill is well past the low serve.
- Cooking does not break fructans down Charring the bulbs on a grill, roasting them or stirring them through a hot wok leaves the fructans exactly as they were. Heat is not a fix.
- Infused oil carries the flavour without the fructan Fructans are water-soluble and do not dissolve into oil, so garlic-infused or onion-infused oil gives the savoury base, as long as no solid pieces are left sitting in it.
- Soups and broths spread it around Fructans are water-soluble, so simmering bulbs in stock moves some of them into the liquid. Straining the pieces out at the end does not make the broth low, it just hides where the fructans went.
- Stacking with other alliums and wheat Spring onion bulbs in the stir-fry, garlic in the sauce and wheat noodles under it all share fructans, and they add up across one meal.
Swaps
The swap here is unusually neat, because it is the other half of the same plant: use the green tops of the spring onion and leave the white bulb out. The green leaves of leek do the same job in soups and braises, chives work where you want a fine raw sprinkle, garlic-infused oil covers the savoury base, and a pinch of asafoetida adds the cooked-allium depth. What will not work is reaching for another bulb. Onion of any colour, shallot and the leek bulb all carry the same fructans, and onion powder, onion salt, stock cubes and most spice blends are that same problem printed on a label.
How to lower the load
Cut where the colour changes: keep the green leaves and set the pale bulb aside rather than slicing the whole thing into the pan. Store the greens rolled in a damp paper towel in the fridge, or slice them and freeze them flat in a bag so there is always a handful of greens ready. Add the greens late, in the last moment of a stir-fry or scattered raw over a finished bowl, since their flavour is brighter than the cooked bulb and fades with long heat. In restaurants, sliced spring onion is usually the green part on top, but the bulbs often go into the base of the sauce or the broth, so ask about the sauce rather than the garnish.
Common questions
is the white part of spring onion low fodmap
Only in a small amount. About ⅓ cup (30g) of the white part is low, larger portions are moderate and much larger portions are high, driven by fructans and excess fructose.
can i eat the green part of spring onions
Yes. The green tops are the part used on a low FODMAP diet, and they are the standard swap for onion flavour. It is the white bulb that climbs past about ⅓ cup (30g).
is spring onion high in fructans
The white bulb is. Fructans are the main group driving its rating, with excess fructose alongside, and they build past about ⅓ cup (30g).
does cooking spring onion bulbs make them low fodmap
No. Heat does not destroy fructans. Simmering moves some into the cooking liquid because fructans are water-soluble, which makes the broth carry them instead.
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Where this rating comes from
Spring Onion (white part) is rated from published lab measurements of its FODMAP content, using the low, moderate and high cutoffs of Varney et al. (2017).
Feedback sent through the FODMAP Foods app has led to changes in this list.
Sources
- Fructan and free fructose content of common Australian vegetables and fruit. Muir et al. (2007), J. Agricultural and Food Chemistry 55(16):6619-6627.
- Measurement of short-chain carbohydrates in common Australian vegetables and fruits by high-performance liquid chromatography (HPLC). Muir et al. (2009), J. Agricultural and Food Chemistry 57(2):554-565.
- Quantification of fructans, galacto-oligosaccharides and other short-chain carbohydrates in processed grains and cereals. Biesiekierski et al. (2011), J. Human Nutrition and Dietetics 24(2):154-176.
- Dietary sorbitol and mannitol: food content and distinct absorption patterns between healthy individuals and patients with irritable bowel syndrome. Yao et al. (2014), J. Human Nutrition and Dietetics 27(Suppl 2):263-275.
- FODMAPs: food composition, defining cutoff values and international application. Varney et al. (2017), J. Gastroenterology and Hepatology 32(Suppl 1):53-61. Supplies the low, moderate and high cutoffs used on this page.
Informational only, not medical advice. Individual tolerance varies. Talk to a healthcare professional or a dietitian for personal guidance.