Vitamin K and Natto – What’s the Connection?
Natto is one of the richest sources of vitamin K2, which is important for bone and heart health. Here’s what you need to know about this little-known nutrient and even lesser-known food source.
Nutrition Diva listener Janet writes:
“I was doing some internet research on foods that promote bone growth and came across a food called natto, which is supposed to be a good source of vitamin K2. My doctor had never heard of natto or vitamin K2. Is natto really a superfood for bone health and, if so, what’s the best way to serve it?”
Sponsor: Squarespace, the all-in-one platform that makes it fast and easy to create your own professional website, e-commerce site, or online portfolio. For a free trial and 10% off, go to squarespace.com/diva and use offer code Diva2.
What Is Vitamin K?
Although vitamin K was identified in the 1920s, right around the same time as vitamins C and E were discovered, it doesn’t have anywhere near the name recognition as other nutrients. It was first identified by German researchers who discovered that it was essential for proper blood-clotting. The “K” stands for “koagulation.”
Without this nutrient in your system, you might bleed to death. Later, it was discovered that vitamin K also plays an important role in bone formation (something I talked about in episode #853, Diet for Healthy Bones) as well as heart health.
The Different Forms of Vitamin K
In terms of helping to build healthy bones and other health benefits, vitamin K2 is thought to be the more potent form.
Vitamin K is actually a family of closely related compounds. Vitamin K1, also known as phylloquinone, is the form that’s found in vegetables, in particular, leafy greens like kale, collards, and spinach. Vitamin K2, also known as menoquinone, is a form produced in animal tissues. In terms of helping to build healthy bones and other health benefits, vitamin K2 is thought to be the more potent form.
Where Do You Get Vitamin K2?
The good news is that there are lots of potential sources for vitamin K2:
- Your body will convert some of the vitamin K1 that you get from vegetables into K2.
- You can get pre-formed vitamin K2 from meat, eggs, and dairy products.
- The friendly bacteria that live in your intestines synthesize some vitamin K2 for you.
- Fermented foods, such as yogurt, kefir, and sauerkraut also contain vitamin K2.
See also: Fermented and Cultured Foods
One of the richest food sources of vitamin K2 is a traditional Japanese food called natto. Studies have found that Japanese women who eat two or more servings of natto a week have higher levels of menaquinone in their blood, and significantly fewer hip fractures than European women who do not eat natto. That’s not the same as a controlled trial, of course, but it’s certainly an interesting observation.
What Is Natto?
Natto is made from fermented soybeans. Although it’s a daily staple for many Japanese, most Westerners have never heard of it, much less tried it. Like many fermented foods, natto has a somewhat strong flavor and aroma. Some might even describe it as “funky.” Let’s just call it an acquired taste.
If you want to try it, I suggest first preparing it in the traditional Japanese way. Here’s how a friend who grew up with a Japanese mom once made it for me:
Whisk together 1 raw egg, 4 tablespoons low sodium soy sauce, 1 teaspoon sesame oil, 1 teaspoon prepared mustard or wasabi, and 1 finely chopped green onion. Combine natto with the sauce mixture and spoon over hot white rice. The result is a flavorful, savory dish that you can enjoy as a light lunch, snack, or appetizer.
In addition to being a potent source of vitamin K2, natto is also a good source of protein, fiber, and isoflavones.
See also: All About Soy
In addition to being a potent source of vitamin K2, natto is also a good source of protein, fiber, and isoflavones.
You can vary the proportions of soy sauce, sesame, and mustard to suit your taste. Although the raw egg is traditional (and does a lot to mellow the flavor of the raw natto), you can omit this if you have any concerns about eating raw eggs — or use eggs that have been pasteurized in the shell.
See also: Foods to Avoid During Pregnancy
Where to Find Natto?
You’ll find natto at Asian grocers or health food stores. It’s usually sold frozen or in vacuum-sealed pouches. If you can’t find it locally, there are several online Japanese and Asian grocers who can ship it to you. Natto is very inexpensive, about $1 per serving. Serious do-it-yourself-ers can even make natto at home, using dried soybeans and natto spores. Natto spores and instructions are available from www.culturesforhealth.com
Keep in Touch
Post your comments, questions, and or topic suggestions below, or join the conversation on the Nutrition Diva Facebook page. I always love to hear from you!And don’t forget to subscribe to my free weekly newsletter for more nutrition tips, recipes, and answers to your questions.
Have a great week and eat something good for me!
You May Also Like…
About the Author
Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes’ most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation’s leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.
