Natto served on rice as a source of vitamin K

Nattokinase and Vitamin K: The Hidden Link

By: Jason Knapfel, Health & Wellness Writer

Scientifically Reviewed By: Michael A. Smith, MD

While it's virtually unheard of here in the U.S., natto has been enjoyed in Japan for ages. With its distinctive pungent smell and gooey consistency, odds are pretty good it will remain a niche delicacy in Western culture.

But you don't have to be an adventurous eater to reap the health benefits of natto–specifically, it's a great source of vitamin K. While it may be an acquired taste, the gooey goodness of natto can also be found in the form of nutritional supplements.

What is nattokinase?

Nattokinase served on rice is a good source of vitamin K

Nattokinase is an enzyme found in natto, a popular Japanese fermented soy food. Nattokinase is created by bacteria during the fermentation of the soybeans.

Does nattokinase with vitamin K help with blood flow?

Nattokinase is known for its ability to help your body's natural blood-clotting process, promote healthy circulation and help maintain already-healthy blood pressure. In one study, nattokinase was shown to effectively and safely maintain healthy blood flow. Nattokinase not only helps maintain healthy blood coagulation, it also supports a healthy inflammatory response and protects against oxidative stress.

Natto happens to also be a significant food source of vitamin K2 (MK-7), which is a member of the fat-soluble vitamin K family. Vitamin K2 is necessary for depositing calcium into your bones and teeth, while also inhibiting its accumulation in the vascular wall; keeping calcium "where it belongs" is key to healthy blood flow.

Vitamin K is an essential nutrient, meaning it cannot be made by the body, so we need to get it from food or supplements. While bacteria that reside in our digestive tracts make a small amount of vitamin K2, if you seek optimal levels, you will likely need to supplement.

In nattokinase supplements, the enzyme nattokinase has been isolated from natto. Therefore, the product may not contain vitamin K. Check the label to be sure.

Who should not take nattokinase with vitamin K?

Doctor discussing fermented foods like natto

The National Academies of Sciences Food and Nutrition Board has not established an upper limit for vitamin K since it has a minimal potential for toxicity, and has stated that: "No adverse effects associated with vitamin K consumption from food or supplements have been reported in humans or animals."

Seeing a cardiologist or other specialist to keep tabs on your heart health? Because of nattokinase's effect on blood clotting, you should get an OK from your doctor before consuming natto or vitamin K supplements.

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Recipe: How to make your own natto

Sticky nattokinase lifted from bowl with chopsticks

Feeling adventurous? If you have a yogurt maker, you can make your own natto: you just need soybeans, water, natto bacteria…and a lot of patience! (Like Rome, natto isn't built in a day…or two!)

Rinse the soybeans (remove any broken ones) and soak them overnight, for a minimum of 12 hours. Cook them with water until soft (a pressure cooker is the fastest way to do this). Keeping the beans sterile, transfer to your yogurt maker with the natto bacteria. Let them stay in there for a full day, then cover them with foil and refrigerate. You'll need to let them stay in there chilled for at least two days before they are ready to eat.

Season this gooey goodness with salt, miso, and any other flavors you're craving.

Food sources of vitamin K

Natto is a great source of vitamin K, but it's not the only one. Here is a complete list of foods rich in this nutrient.

  • Vitamin K1

    • Collard greens
    • Turnip greens
    • Spinach
    • Kale
    • Broccoli
    • Soybeans
    • Carrot juice
    • Soy oil
  • Vitamin K2 (MK-4)

    • Chicken
    • Beef
    • Liver
    • Ham
    • Cheese
    • Eggs
  • Vitamin K2 (MK-7)

    • Natto
    • Sauerkraut
    • Kimchi
    • Cheeses such as Muenster

Other ways to promote healthy blood circulation

Busy woman on hands-free phone increasing her body's circulation

Living in a technology-driven world has made it more challenging to avoid a sedentary lifestyle. Even if you exercise, it's not healthy to be immobile for long periods of time. We need to be more mindful than ever about getting up and moving throughout the day to maintain a healthy circulatory system and overall health.

One way to use technology to your benefit is with an app that reminds you to stand every hour. Even just getting up to stretch your legs and refill your water bottle can go a long way towards promoting healthy circulation. A standing desk is a great way to keep that blood flowing all day long.

If you have a little more time on your hands, make short walks every few hours your go-to way to keep moving. Circle the block, walk the dog, or, if you're in a time crunch, start taking some of those conference calls while you're on the move. Every little bit helps!

About the Author:

Jason Knapfel graduated from Florida Atlantic University with a BA in English. Since 2000, Jason has held various content marketing roles, much of it in the health and wellness field. He is currently a Copywriter at Life Extension.


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