Get the brief

The Evidence

Page 26

Vitamin K and K2 on a vegan diet

Vitamin K1 is one of the easiest nutrients to get on a plant diet: it is what makes leafy greens green. K2 is the one people worry about, and the honest answer involves natto, gut bacteria, and your own biology.

Vegan Brief Evidence last reviewed July 15, 2026

This is a summary of the cited evidence, not medical advice.

  • K1 source Green leafy vegetables
  • Vegan K2 Natto and other ferments
  • Also made By the body from K1

K1 is the easy part

Vitamin K comes in two families, and the first is a vegan strong suit. The NIH fact sheet, a public-domain US government document, is plain about where the main dietary form lives.

Primary source 01 / 04

Phylloquinone is present primarily in green leafy vegetables and is the main dietary form of vitamin K

NIH Office of Dietary Supplements US National Institutes of Health Vitamin K: Fact Sheet for Health Professionals, 2021

One caveat worth knowing: the K1 in leaves is bound up tightly, so you absorb only a fraction of the amount on the label unless you add a little fat.

Primary source 02 / 04

the body absorbs only 4% to 17% as much phylloquinone from spinach as from a tablet

NIH Office of Dietary Supplements US National Institutes of Health Vitamin K: Fact Sheet for Health Professionals, 2021

That is an argument for dressing your greens, not for worrying: the amounts in a normal plate of vegetables are large enough that even a modest absorbed fraction meets the requirement.

K2, the part people ask about

The second family, the menaquinones or K2, is the one that fuels supplement marketing aimed at vegans. Here the picture is more nuanced than either side usually admits.

Primary source 03 / 04

Menaquinones, which are predominantly of bacterial origin, are present in modest amounts in various animal-based and fermented foods

NIH Office of Dietary Supplements US National Institutes of Health Vitamin K: Fact Sheet for Health Professionals, 2021

So some K2 does sit in animal foods, but the richest source on the planet is a vegan one: fermented soybeans.

Primary source 04 / 04

Natto (a traditional Japanese food made from fermented soybeans) has high amounts of menaquinones

NIH Office of Dietary Supplements US National Institutes of Health Vitamin K: Fact Sheet for Health Professionals, 2021

On top of natto and other ferments, gut bacteria produce menaquinones, and the body converts some K1 into the K2 form on its own. A vegan who eats greens is not short of vitamin K. Someone who wants a direct K2 source can eat natto or take a vegan menaquinone supplement, most of which are made by fermentation anyway.

  • Calcium and bone health on a vegan diet This is the page where being on veganism's side means telling you the uncomfortable finding: vegans break more bones in the data, and calcium is the lever that moves it.
  • Vitamin D on a vegan diet Vitamin D is the one almost everyone runs low on in winter, vegan or not. The plant-friendly fix is D2 or lichen D3, plus fortified foods and sensible sun.
  • Plant-based diets, bone health and fracture risk Publishing the unflattering finding is the point: in the best cohort, vegans broke more bones. The risk is real, it mostly tracks calcium, protein and body weight, and it is fixable.

Frequently asked

Can vegans get enough vitamin K?

Easily for K1, the main dietary form, which the NIH describes as abundant in green leafy vegetables. Adding a little fat improves absorption. For K2, natto and other fermented foods supply it, gut bacteria make more, and the body converts some K1 to K2, so a vegan eating vegetables is well covered.

Where do vegans get vitamin K2?

The richest source is natto, fermented soybeans, which the NIH lists as having high amounts of menaquinones. Other ferments contribute smaller amounts, gut bacteria produce K2, and the body makes some from K1. Vegan K2 supplements exist and are usually produced by bacterial fermentation.

The primary sources

The documents this page quotes. Read them yourself.

Evidence first, every morning.

The standard behind these pages, applied to each day’s news: the study quoted and graded before the headline reaches you. One short brief, free.

Free, every morning. No guilt. No preaching.