Natto

Why it matters

Natto is one of the most polarising foods on this list — sticky, pungent and an acquired taste — but its nutritional case is hard to argue with. It is the single richest known food source of vitamin K2, and one of the best sources of soy isoflavones, the plant compounds that gently mimic estrogen in the body. That combination makes it quietly powerful for women, particularly around menopause, when falling estrogen drives both symptoms and accelerating bone loss. A large 2020 Japanese cohort even linked regular fermented-soy intake (natto and miso) to lower mortality, and natto has long been considered one of the foods behind Japanese longevity.

What's inside

Vitamin K2 (MK-7) is the headline — natto carries roughly 1,000 µg per 100 g, far more than any other food — and K2's job is to direct calcium into bones and away from arteries, making it a key partner to vitamin D for skeletal health. Soy isoflavones (around 58–82 mg per 100 g) are phytoestrogens that can ease menopausal symptoms and support bone density. Fermentation also makes natto easier to digest than other soy and adds probiotics and the enzyme nattokinase, studied for circulation. Add solid plant protein, iron and magnesium, and the profile is genuinely impressive.

For men

Men are often warned off soy on the assumption it "raises estrogen" — but the evidence doesn't support that fear. Multiple meta-analyses show that soy and isoflavones, at normal dietary intakes, do not meaningfully lower testosterone or raise estrogen in men. So natto can be eaten without worry, and its K2, magnesium and protein support bone strength, circulation and recovery. It's a case where the reputation is scarier than the science.

For women

This is natto's home turf. The isoflavones act as gentle phytoestrogens that several studies link to fewer hot flushes and better menopausal comfort, while the unmatched vitamin K2 — working alongside calcium and vitamin D — directly supports the bones that estrogen loss puts at risk. For a woman building a long-term, food-first strategy for the menopausal transition, few single foods offer this much in one serving.

How to eat it

Tradition is the easiest route: a small pack of natto stirred until stringy, served over warm rice with a dash of soy sauce, mustard and chopped spring onion, often topped with a raw or soft egg. The strong flavour and sticky texture take some getting used to — start small, and pair it with familiar flavours. Natto is usually sold frozen or chilled in Asian supermarkets; it keeps well and a little goes a long way.

Worth knowing

The taste and texture are the real barrier — many people need a few tries to acclimate. More importantly, if you take blood-thinning medication such as warfarin, natto's very high vitamin K2 can interfere with it, so check with your doctor first. Otherwise, fermented soy like natto is well tolerated, easy to digest, and one of the most evidence-supported foods here for women's midlife health.

Bottom line

An acquired taste with an extraordinary payoff: natto is the richest food source of bone-protecting vitamin K2 and a gentle phytoestrogen, making it one of the most useful foods a woman can adopt for the menopausal years — and perfectly safe for men.