Foods High in Vitamin K: Leafy Greens, Fermented Foods and K1 vs K2 Sources

If you take warfarin or a similar blood thinner

Vitamin K is the vitamin that warfarin works against. The NIH Office of Dietary Supplements (ODS, US) says people taking warfarin and similar anticoagulants need to maintain a consistent intake of vitamin K from food and supplements. [1] The NHS (UK) says you can still eat foods high in vitamin K, such as broccoli, spinach and other green leafy vegetables, but that you should talk to your warfarin clinic for advice. [2] The NHS also says not to take vitamin K supplements while on warfarin. [2] Do not change how you eat or stop any medicine on the strength of this page. Your anticoagulation clinic, doctor or pharmacist decides what is right for you. See Medication interactions.

Overview

Vitamin K is a group of fat-soluble vitamins. Two kinds matter in food. Phylloquinone (K1) comes mainly from plants. Menaquinones (K2, written MK-4, MK-7 and so on) come from fermented foods and animal foods. The ODS says the most common sources in the US diet are spinach, broccoli, iceberg lettuce, and soybean and canola oil. [1] The NHS lists green leafy vegetables and vegetable oils, with small amounts in meat and dairy foods. [3]

How the two kinds differ in the body, and what trials of K2 supplements show, is covered in Vitamin K1 vs K2 and Vitamin K2 (MK-4 and MK-7): bone and heart evidence. The full profile is Vitamin K.

Food amounts

Amounts are phylloquinone unless the row says MK-4 or MK-7. The ODS notes that data on menaquinones in food are limited. [1] Serving sizes are US household measures from the ODS table, which draws on USDA FoodData Central (ODS page updated 2021).

K1 and K2 in foods

• Leafy greens and oils supply mostly K1. [1]
• Natto has high amounts of menaquinones. [1] Other fermented foods, such as cheese, also contain menaquinones, but the forms and amounts likely vary with the bacterial strains and fermentation conditions. [1]
• Meat, dairy and eggs have low phylloquinone and modest menaquinones. [1] The ODS says poultry and pork products contain MK-4 if menadione (a synthetic form) is added to animal feed. [1] A US Department of Agriculture and Tufts analysis of meat, dairy, eggs and fast food found that no single food item in these categories is a rich source of any one form of vitamin K. [4]
• Fortified foods: few foods are fortified with vitamin K. [1]

Absorption and cooking

The ODS says phylloquinone in plant foods is tightly bound to chloroplasts, and that the body absorbs only 4% to 17% as much from spinach as from a tablet. [1] Eating vegetables with some fat improves absorption from the vegetables. [1] In a laboratory study of cooked vegetables, microwaving caused the greatest vitamin K loss in crown daisy and mallow but the least in spinach and chard, so there is no single rule. [5] For more see Cooking, processing and storage: vitamin losses. Food amounts above are not a promise about any one portion at home.

Intake references

These are published reference levels for stated groups, not advice for you.

The US Food and Nutrition Board did not set an upper limit for vitamin K because of its low potential for toxicity. [1] The NHS says taking 1 mg or less of vitamin K supplements a day is unlikely to cause harm, and that there is not enough evidence to know the effects of high daily doses. [3] These figures do not apply to people on warfarin; see the top of the page.