Vitamin K: K1 vs. K2, and Where Each Comes From

Vitamin K1 and vitamin K2 are two forms of the same vitamin, but they act a bit differently in the body. K1, called phylloquinone, is the main form found in leafy green vegetables and plant oils.

K2, called menaquinone, comes mostly from fermented foods and animal products. Your gut bacteria also make a small amount of K2.

Both forms of vitamin K help your blood clot normally. Both also play a role in bone health by helping calcium bind to bone tissue.

The main difference is where they come from and how well your body absorbs them. Research shows the food matrix, meaning how the vitamin is packaged inside a food, changes how much reaches your blood.^[1]

Vitamin K is best known for helping blood clot. Without enough of it, cuts and injuries would bleed for much longer.

Vitamin K also activates proteins that help move calcium into bones and away from soft tissues like blood vessels. This is one reason researchers study vitamin K alongside vitamin D and calcium for bone health.

• Helps activate clotting factors in the liver
• Supports proteins that guide calcium into bone
• May play a role in keeping calcium out of artery walls
• Works alongside vitamin D in bone metabolism

K1 is the main form circulating in your blood after a meal with leafy greens. It clears from the blood fairly quickly and is used mostly by the liver for clotting.

K2 stays in the blood longer.

It travels to a wider range of tissues, including bone and blood vessel walls, which is why some researchers think it may matter more for bone and heart health.

Absorption also differs.

Studies show that vitamin K1 bound inside plant cells, like in spinach or kale, is harder for your body to pull out than vitamin K1 from oils or supplements.^[1]

Cooking with a bit of fat, like olive oil, can help release more vitamin K1 from vegetables. Fat helps because vitamin K is fat soluble, meaning it needs fat to be absorbed well.

Vitamin K1 is the main form of vitamin K in most diets. It comes mostly from green plants, since plants use it in photosynthesis.

• Kale
• Spinach
• Collard greens
• Broccoli
• Brussels sprouts
• Soybean oil and canola oil
• Parsley

Vitamin K2 shows up in much smaller amounts in most diets. It is found in fermented foods and some animal products.

• Natto, a fermented soybean food, which has the highest known amount
• Hard and soft cheeses
• Egg yolks
• Butter and other full fat dairy
• Chicken
• Liver and other organ meats

Your gut bacteria also produce some vitamin K2, but scientists are still not sure how much of this actually gets absorbed and used by the body.

True vitamin K deficiency is rare in healthy adults who eat a varied diet. It shows up more often in newborns, people with fat malabsorption conditions, or people on long term antibiotics.

• Easy bruising
• Bleeding gums
• Heavy menstrual bleeding
• Blood in urine or stool
• Slow healing after cuts

People with conditions like Crohn's disease, celiac disease, or cystic fibrosis can have trouble absorbing fat soluble vitamins, including vitamin K.

This can raise their risk of low levels.

Most healthy diets that include vegetables already supply enough vitamin K1. Vitamin K2 is harder to get in large amounts unless you eat fermented foods or certain animal products regularly.

Researchers are still studying whether getting more K2 specifically offers extra benefits for bones or blood vessels beyond what K1 already provides.

The evidence so far is promising but not conclusive.

If you eat a mix of leafy greens, dairy, eggs, and occasional fermented foods, you are likely covering both forms without needing to think about it too hard.