Onions

Why it matters

Onions belong to the same allium family as garlic and share a similar hormone story. Animal studies — some using onion juice — have shown quite striking increases in testosterone, apparently by boosting antioxidant defences in the testes and supporting the hormonal signals that drive testosterone production. As with garlic, the human evidence hasn't caught up, so the claim is "promising, mostly animal-based." But onions also bring quercetin (a standout antioxidant) and prebiotic fibre that feeds the gut, making them a worthwhile everyday food regardless of how the testosterone research ultimately lands.

What's inside

Onions supply sulphur compounds similar to garlic's, linked to the testosterone findings in animal studies, plus quercetin — one of the most potent dietary antioxidants — which reduces inflammation and protects cells, including hormone-producing ones. They're a good source of vitamin C and especially of inulin, a prebiotic fibre that feeds the beneficial gut bacteria involved in regulating hormones, including estrogen.

For men

For men, the animal evidence on onions (particularly onion juice) and testosterone is genuinely eye-catching, working largely through antioxidant protection of the testes — though it remains unproven in humans. The quercetin and sulphur compounds support lower inflammation and better circulation. Treat it as a promising, flavour-rich support rather than a guaranteed booster, and eat onions freely.

For women

For women, onions' quercetin and antioxidants support cellular health and lower inflammation, while the prebiotic inulin feeds the gut bacteria that help regulate estrogen — a quietly valuable contribution to hormonal balance. The vitamin C and overall nutrient profile support skin and immunity. A foundational flavour base with real, if understated, hormonal relevance.

How to eat it

Raw onion (in salads, salsas) retains the most active sulphur compounds and quercetin; cooking mellows the flavour and reduces some — but not all — of the benefit, and gentle cooking still leaves plenty. Red onions are particularly high in quercetin. Use onions as a base for almost any savoury dish; even cooked, they contribute prebiotic fibre and antioxidants. Let chopped onion rest a few minutes before cooking, as with garlic.

Worth knowing

Onions can cause digestive discomfort and gas in sensitive people, partly because of the very inulin that benefits the gut — those with IBS or FODMAP sensitivity may need to moderate. Raw onion affects breath. For most people, onions are a safe, cheap, flavour-and-health staple with no meaningful downside.

Bottom line

Onions share garlic's promising (animal-based) testosterone story and add quercetin antioxidants plus gut-feeding prebiotic fibre — a flavourful, foundational food that supports hormones from several directions at once.