Vitamin K and Your Bones — Foods That Make a Difference

• The difference between vitamin K1 and vitamin K2
• How vitamin K2 helps strengthen bones
• The best food sources of K1 and K2
• Important safety information for people on blood thinners
• Whether vitamin K supplements are worth considering

Vitamin K comes in two main forms, and they have different roles:

Most people get plenty of K1 from eating vegetables. K2 is harder to get from a typical Western diet, and K2 appears to have the strongest link to bone health.

Vitamin K2 activates a protein called osteocalcin. Osteocalcin acts like a hook. Once activated, it grabs calcium from your blood and helps bind it into the bone matrix, making bones stronger and more resilient.

Without enough vitamin K2, osteocalcin remains inactive (called "undercarboxylated osteocalcin"), and calcium may float around in the bloodstream instead of being deposited in bone. Some research suggests this unguided calcium may end up in artery walls, contributing to cardiovascular calcification.

Vitamin D opens the door for calcium to enter your body, and vitamin K2 makes sure calcium goes to the right room: your bones, not your arteries.

Vitamin K2 is found primarily in fermented foods and certain animal products. The two most studied forms are MK-4 (from animal sources) and MK-7 (from bacterial fermentation).

Fermented foods rich in K2

Natto is by far the richest source of K2 in the world, but it's a Japanese fermented soybean dish with a strong flavor and sticky texture that many people outside of Japan find unfamiliar. If you enjoy it, it is very nutritious. If natto isn't for you, aged and fermented cheeses are a good and much more familiar way to get K2.

Aged cheeses like Gouda, Brie, and Jarlsberg are among the best Western sources of vitamin K2.

Animal sources of K2 (MK-4)

How much vitamin K do you need?

There's no established RDA specifically for K2 yet. The general adequate intake (AI) for all forms of vitamin K is:

• Women: 90 mcg/day
• Men: 120 mcg/day

However, researchers studying bone health suggest that higher K2 intakes, in the range of 100-200 mcg/day of MK-7, may be more beneficial for bone protection. This is an active area of research.

While K1 is primarily known for its role in blood clotting, it also contributes to overall vitamin K status. These green vegetables are the best sources:

Eating a generous serving of leafy greens each day easily covers your K1 needs.

If you take a blood thinner that works against vitamin K, do NOT suddenly increase or decrease your vitamin K intake without talking to your doctor. This type of medicine works by blocking vitamin K's role in blood clotting. Sudden changes in vitamin K intake can make the medicine less effective (increasing clot risk) or too effective (increasing bleeding risk). Your doctor adjusts your dose based on your current diet, so keep your intake steady.

This warning applies mainly to blood thinners that work against vitamin K. Many newer blood thinners work differently and are generally not affected by vitamin K intake. Still, always check with your doctor.

For most people, getting K2 from food is the best approach. However, if you don't regularly eat fermented foods or aged cheese, a supplement may be worth discussing with your doctor.

If you do supplement:

• MK-7 is the most studied form for bone health and has a longer half-life than MK-4
• Typical doses in studies: 100-200 mcg/day of MK-7
• Take with a meal containing fat (vitamin K is fat-soluble)
• Combination supplements with vitamin D3 and K2 are available and convenient

Simple ways to get more vitamin K2:

• Breakfast: Scrambled eggs (K2 from yolks) with a slice of aged Gouda
• Lunch: Salad with kale (K1), topped with crumbled Brie and walnuts
• Dinner: Chicken thighs (K2 from dark meat) with sauerkraut on the side
• Snack: Cheese board with aged cheeses and whole grain crackers

• Add aged cheese to your regular shopping list. Gouda, Brie, and Jarlsberg are good choices
• Eat leafy greens daily. A cup of kale or spinach covers your K1 needs
• Choose eggs with dark yolks from free-range hens when possible
• Try fermented foods. Sauerkraut, kefir, and fermented cheeses all contribute K2
• If you take a blood thinner affected by vitamin K, keep your vitamin K intake consistent day to day and inform your doctor before making dietary changes
• Ask your doctor whether a K2 supplement makes sense for you, especially if you have osteoporosis

Q. I've never heard of vitamin K2 before — is it really important for bones? Yes. Research over the past two decades has increasingly shown that vitamin K2 plays a real role in bone health by activating osteocalcin, the protein that helps deposit calcium into bone. While more large-scale studies are needed, the evidence is strong enough that the IOF includes vitamin K among the key nutrients for bone health.

Q. Can I get enough K2 from a regular Western diet? It's possible, but you have to choose foods with that in mind. The typical Western diet is relatively low in K2 compared to diets that include fermented foods regularly. Adding aged cheeses, eggs, and fermented foods like sauerkraut to your routine can make a significant difference.

Q. Is there a risk of getting too much vitamin K? No upper limit has been established for vitamin K, and toxicity from food sources is not a known concern. However, if you take a blood thinner affected by vitamin K, even moderate changes in intake matter, so keep your intake steady and keep your doctor informed.

Q. I take a calcium supplement and vitamin D. Should I add K2? Many bone health experts now recommend calcium, vitamin D, and K2 together. The idea is that calcium provides the raw material, vitamin D helps absorb it, and K2 directs it to the right place. Discuss with your doctor, especially if you have any cardiovascular concerns.

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• Knapen MH, et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013;24(9):2499-2507.
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• International Osteoporosis Foundation (IOF). Vitamin K — Nutrition Information.
• NIH Office of Dietary Supplements. Vitamin K Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
• Schwalfenberg GK. Vitamins K1 and K2: The emerging group of vitamins required for human health. J Nutr Metab. 2017;2017:6254836.