The best (and worst) ways to prepare 20 trigger foods
By Mira Sefton · 13 June 2026 · 4 min read
Ever had the same vegetable treat you kindly one day and badly the next? A lot of that comes down to one thing you can actually control: how it's prepared.
We went through every food in the database and compared its score across different cooking methods. The pattern is clear, and it's good news. For most foods you don't need to fuss. For a handful, a small change makes a big difference. And for two in particular — onion and garlic — preparation is the whole ballgame.
Here's what helps, what doesn't, and the few things worth knowing.
The biggest trick: infuse the oil
If you take one thing from this, make it this. Onion and garlic are the only foods where preparation completely changes the picture — and the move that wins is infusing the oil.
Here's why it works. The carb that causes the trouble in onion and garlic is a type called fructans. Fructans dissolve in water, but not in oil. So if you gently warm garlic or onion in oil and then lift the pieces out, the flavour comes across into the oil and most of the fructans stay behind in the bits you throw away. You keep the taste and leave most of the wind behind.
In our scores, that one change moves onion and garlic from the middle of the pack right down into the green band — the biggest drop of any food we have.
The flip side is just as striking. The single harshest food-state in the whole database is onion powder (garlic powder isn't far behind). Drying concentrates the fructans, so a small sprinkle packs the punch of a much bigger serving. It's the one to keep an eye out for on labels — it hides in stock cubes, packet seasonings and a lot of sauces.
What helps everything else
Beyond the aromatics, the wins are smaller but they're real, and they follow simple rules.
- Boil and drain your firmer veg. Broccoli, cauliflower, cabbage, Brussels sprouts, kale, kohlrabi, leek, celery, green beans — cooking them in water and tipping the water away leaches out some of the fermentable carbs. For most of these, it's enough to nudge them from amber into green.
- Purée or peel the softer ones. Spinach, tomato and kale get gentler once they're broken down or skinned — less coarse residue to push through.
- Can and drain your beans. Tinned, rinsed legumes (navy, pinto, borlotti, black-eyed and friends) tend to score a little better than home-boiled, because more of the gassy carbs have leached into the liquid you pour off.
- Roast nuts rather than eating them raw. Almonds, hazelnuts, cashews and pine nuts all come down a touch once roasted.
- Reach for tinned stone fruit. Canned, drained peaches and lychees are gentler than the fresh, raw versions.
If you want a single rule of thumb: raw is the harshest form for almost everything, and cooking in water is the quiet hero.
A few things that backfire
Not every kind of "processing" helps. Three to know:
- Powdering aromatics (onion and garlic powder) — the big one, as above.
- Eating firm veg raw — raw broccoli or cabbage scores worse than the cooked version, not better.
- Puréeing beans — mashing a legume actually scores a little worse than tinning it. Mashing concentrates the gassy carb; it doesn't rinse any away. So hummus is lovely, just don't expect it to be gentler than the same beans drained from a tin.
And one for the curious: roasting a Jerusalem artichoke is its harshest form, because there's no cooking water to carry the fructans away. They're a famously windy vegetable for a reason.
The "don't sweat it" list
Here's the freeing part. For plenty of foods, how you cook them barely moves the needle. Carrot stays gentle and green whether it's raw, boiled, roasted or mashed. Green cabbage, green peas and beetroot are much the same. If a food is already easy on you, you don't need to overthink the method — cook it however you enjoy it.
The cheat sheet
| Food | Gentlest way | Harshest way |
|---|---|---|
| Onion | Infused oil 🟢 | Powdered 🔴 |
| Garlic | Infused oil 🟢 | Powdered 🟠 |
| Broccoli, cauliflower, cabbage | Boiled & drained 🟢 | Raw 🟠 |
| Brussels sprouts, kale, kohlrabi, leek | Boiled & drained / puréed 🟢 | Raw 🟠 |
| Celery, green beans | Boiled & drained 🟢 | Raw 🟠 |
| Spinach, tomato | Puréed / peeled 🟢 | Raw 🟠 |
| Beans (navy, pinto, borlotti…) | Canned & drained | Puréed |
| Almonds, hazelnuts, cashews | Roasted | Raw |
| Peach, lychee | Canned & drained 🟢 | Raw 🟠 |
| Carrot, green peas, beetroot | Doesn't matter much — all gentle | — |
One honest note
These scores are modelled estimates, not lab measurements — our best read of how foods tend to behave, and we'd rather tell you when something is an educated guess than pretend it's settled. Your own gut is the final word. So treat these as a starting point, change one thing at a time, and see how you go.