Onions: Not Just Flavour. It's Other Jobs.

Sulfur, signals, and why the most basic foods often do the most.

Onions aren't pretty. They’re not precious. But they show up in more meals than almost anything else.

And there’s a reason for that.

Onions are foundational. Not just to flavour, but to function. They support the gut. Speak to inflammation. Feed your microbes. And even when they bring tears, they bring something else too: information.

This is food the body recognises. Not for novelty. For memory.

Why the Body Knows Onion

Cut into one and it reacts. Sharpness, sting, scent. The onion defends itself right to the end.

What’s actually happening?

The moment the onion is sliced, enzymes convert sulfur containing amino acids into volatile compounds. These are what make your eyes water. But they’re also what make onions therapeutic.

That sulfur is part of a family of compounds that support your body’s internal clean-up systems:

• They feed the glutathione cycle, boosting your capacity to neutralise oxidative stress

• They activate detox enzymes, especially Phase II pathways

• They support methylation, working alongside B-vitamins and amino acids to regulate gene expression

And it doesn’t stop at sulfur. Onions are also rich in quercetin, a polyphenol known to:

• Calm inflammatory cascades (especially NF-κB)

• Stabilise mast cells and histamine response

• Protect mitochondrial membranes during oxidative load

On a cellular level, this is regulation. Balance. Repair. From a food we usually treat as background.

What They Do in the Gut

Onions are prebiotic powerhouses. They contain fructooligosaccharides (FOS), a form of fermentable fiber that feeds beneficial gut microbes.

When digested properly, these compounds:

• Support short-chain fatty acid production (especially butyrate)

• Help maintain gut lining integrity

• Reduce pro-inflammatory signals from the microbiome

• Improve insulin sensitivity and blood sugar handling

This is real metabolic support. Not from a supplement, but from the thing you cook before you even start cooking.

When They Don’t Sit Well

Of course, for some people, onions don’t land softly.

They’re one of the most common triggers for bloating, cramping, or digestive discomfort, and there are a few good reasons why:

Sulfur Overload

Onions are rich in sulfur compounds, which is part of what makes them therapeutic.

But if your sulfur pathways are sluggish, whether due to genetic variations (like CBS or SUOX), low molybdenum, or depleted cofactors, your body might struggle to metabolise them efficiently.

The result?

• Headaches

• Fatigue

• Brain fog

• That "ugh" feeling you can’t quite trace

Your body wants to use the sulfur. But it needs support to process the byproducts.

FODMAP Sensitivity

Onions contain fructans, a type of fermentable carbohydrate classified under the FODMAP umbrella. In sensitive guts, especially those with SIBO (Small Intestinal Bacterial Overgrowth) or dysbiosis, these carbs get rapidly fermented in the wrong place.

Symptoms include:

• Bloating (think balloon, not bloat)

• Gas (the kind that makes you reconsider your life)

• Cramping, urgency, or constipation

It’s not that onions are bad. It’s that your microbes are responding out of proportion.

Histamine Intolerance

Onions aren’t high in histamine, but they can liberate histamine already stored, which matters if your body has trouble breaking it down. This is often due to low DAO enzyme activity or genetic variants in HNMT or MAOA.

If onions give you a runny nose, flush, anxiety, or weird heart flutters, it might be histamine trying to leave the building without permission.

What You Can Do

If you react to onions, you’re not alone. You’re not broken. And you don’t have to swear off sulfur forever.

Here are some gentle ways to work with the food:

• Cook them long and slow – Caramelising or stewing reduces sulfur volatility and breaks down fermentable fibers.

• Use onion-infused oil – You’ll get the flavour without the FODMAPs.

• Support your sulfur pathways – Add magnesium, B6, molybdenum, and glycine-rich foods.

• Heal the gut terrain – Address SIBO, dysbiosis, and lining repair so you can reintroduce slowly later.

Sometimes food reactions aren’t rejections. They’re reminders. The body saying: I want this, I just need a little more support right now.

How I Use Them

I cook onions almost every day. They soften a dish. They ground a moment. They tell the senses, “Something warm is happening".

I use them:

• In slow braises and broths where their sweetness comes through without effort

• Caramelised under greens or beans, where they create depth without needing meat

• Pickled with ACV and pink salt to brighten anything from salad to soup

• Baked whole with ghee and herbs, for a soft, savory companion that asks nothing of you

They don’t need to be the main event. They’re the base that lets everything else unfold.

What They Represent

Onions are honesty food. They make you feel. They make you notice. They don’t hide behind sweetness or shine.

And yet, they do the kindest work.

They support detoxification, mitochondrial resilience, gut integrity, immune balance, even histamine regulation. All while sitting quietly in the pan, turning golden.

This is food that teaches something. About what it takes to transform something raw into something ready.

It might sting first. Then it sweetens. Just like healing.

Bottom Line

We tend to chase novelty in nutrition. The rare berry. The expensive extract. The superfood of the season.

But your body doesn’t need trend. It needs relationship.

And sometimes the most powerful foods are the ones that have been there all along. In every culture. Every stew. Every kitchen with a light on.

Onions aren’t glamorous. They’re generational. And if they work for your body, they’re worth keeping close.

Because food doesn’t have to be fancy to be functional.