This Powerful Food from Japan Can Prevent and Even Reverse Osteoporosis

Dr. Janet Zand
August 19, 2018


When most people think about treating osteoporosis naturally, they usually think of calcium, magnesium, boron, and strontium. All of these are great minerals for bone health. But there’s more to fighting osteoporosis than just taking minerals.

The Japanese found a food that’s such an effective bone builder that it will harden bones and completely reverse osteoporosis.

The evidence comes from a new study that shows just how effective this food is for your bones. The food used in the study is natto. We’ve talked about natto before. You may know it as fermented soy. This is the food that produces the enzyme nattokinase, which is known for its ability to prevent blood clots.

So just how well does natto work to strengthen your bones? In the study, researchers followed 394 premenopausal and 550 postmenopausal women from Japan. They evaluated the women’s bone mineral density at the start of the study and again after three years. They also measured their natto intake at the same time.

In the postmenopausal group, women who consumed more than four servings of natto weekly had a stunning 80% reduction in bone density loss at the top of their thigh bone compared to women who consumed no natto. And they also had a 60% reduction in loss in the bone in the wrist area.

What is really impressive about this study is what they found as the women got older. The benefit seemed to increase as the women aged. The researchers were careful to control for calcium intake and soy products (including tofu). That means the benefit was clearly from natto.

Why Is Natto So Effective?

One of the reasons natto is so effective at protecting your bones is simply that it’s fermented. Many fermented foods contain bacteria that are great for your gut health. Strong bones start in your gut. The better you’re able to digest and absorb the nutrients you eat, the more nutrients you have available for your bones to absorb. So if you don’t like fermented foods, then it makes taking a good probiotic to improve your gut health even more important.

But that’s not all natto has going for it. Fermentation in general creates incredible compounds not available otherwise.

In natto’s case, the fermenting bacteria in soy create a compound called menaquinone-7. It is also called vitamin K2. Each pack of natto contains about 350 micrograms of menaquinone-7. So in a week, the intake from four packs was about 1.4 mg. Since that’s a very small amount, you can see the power of this biochemical.

Isn’t Vitamin K2 for Blood Clotting?

You’ve probably heard of vitamin K in blood clotting. Coumadin, or rat poison, blocks vitamin K from working and making clotting proteins in your liver. Vitamin K is also a critical factor in inserting calcium into your bones. Without K, your bones will turn to mush. (That’s why people on Coumadin are at greater risk of osteoporosis. That’s another reason it’s important you do all you can to stay off Coumadin.)

People don’t often think of vitamin K2 in relation to bone health (if they think of it at all). But vitamin K2 has emerged as a star player in osteoporosis. In fact, vitamin K will likely be the new vitamin D as more and more research comes out. The reason is that the whole body needs vitamin K. We know that it’s vital for your blood, which travels throughout your body.

In one study, those who took the most K2 had a 50% reduced risk of arterial calcification. They also exhibited a 50% reduced risk for cardiovascular events during this 10 year period. So it’s vital for your heart and your entire cardiovascular system. In fact, every 10 mcg of vitamin K2 that you take will reduce your risk of coronary heart disease by 9%.

Your brain is just as dependent on vitamin K2. One study found that increased dietary vitamin K intake results in less severe subjective memory complaints from older adults. Other studies have shown that vitamin K2 is good for boosting your immune system and fighting some cancers, including gastric cancer, colon cancer, leukemia, and bladder cancer.

Why Your Bones Need Vitamin K2

Then there’s your bones, which need K2 to help them make osteocalcin in a process called carboxylation. Osteocalcin is a protein hormone. It helps build bones.

Previous studies have found an association between low intake of vitamin K1 and risk of hip fractures. If you have good digestion, you’re able to convert vitamin K1 from food into vitamin K2. But it’s common to skip the conversion step with supplements and go right to K2. That’s what researchers decided to do as they investigated this association.

Researchers conducted a randomized, placebo-controlled, double-blind study. They wanted to see if vitamin K2 supplements would affect bone mineral density. One group got 375 ug of vitamin K2. The other received a placebo. The study lasted for 12 months. The participants also received calcium and vitamin D supplements.

At the end of the study, the researchers measured levels of undercarboxylated osteocalcin. The vitamin K2 group experienced a change of -70.3. For the placebo group, the change was only -7.2. This represented a big difference in the body’s ability to synthesize osteocalcin. 

I don’t agree with the researchers’ decision to give the participants calcium. You get all the calcium you need from food. Calcium supplements can cause hardened arteries and many other health problems. But I do think the vitamin D was a good idea. I’ve written before about how vitamin D can help your bones. Combining it with vitamin K2 can offer your bones some essential tools. 

Vitamin K2 is more active by far than the more common vitamin K1. So for osteoporosis, make sure that the supplements you use contain vitamin K as K2. The main source of vitamin K2 in supplements is natto. An 80% reduction in bone loss with a whole food is nothing to sneeze at. It’s huge!

How Much Vitamin K2 Should You Take?

Eating a diet rich in green veggies will probably give you enough vitamin K to provide for normal blood clotting. But you most likely do not consume enough vitamin K to provide for optimal bone health. For example, to get an optimum amount of the bone protein osteocalcin, adults need a daily K1 intake of 1,000 mcg.

Currently, the average vitamin K1 intake in this country is only 75 to 125 mcg. Unless you are a “greens” lover, you might find it difficult to consume 1,000 mcg of vitamin K in foods.

Where to Find Natto

Natto is readily available at Asian markets. Be aware that it does have a strong odor. Most people in the U.S. don’t care for natto. But it’s worth giving it a try, especially if you suffer from osteoporosis.

If you don’t care for the odor, don’t like the taste, or need more vitamin K2 in your system, then at the very least you can look for a supplement containing vitamin D3 and K2. The authors of this study did note that the benefit was probably due to vitamin K2 and the increased isoflavones, both created by the fermentation process. Here’s another opportunity for you to get remarkable help from food or food supplements.

How to Eat Natto

Natto is gooey, smelly and slimy – sounds like something you would want to eat – NOT. But it is extraordinarily healthy and actually loved by many Japanese. The Japanese commonly eat if for breakfast over rice. Most Japanese I know mix natto with a soy sauce (I prefer the gluten free tamari), also known as mentsuyu, and stir the mix well. Then they take the natto and just place it on the rice.

You can also add all sorts of toppings, such as a sprinkle of chopped green onions, dried seaweed, dried bonito flakes, or anything that suits your taste buds. Some Americans, trying to avoid too much carbohydrate in the morning, will take it over lightly steamed spinach. If you are looking to have the natto at dinner – you can serve it over hot rice noodles for a tasty and healthy dish. Season to taste.


Ikeda, Y., M. Iki, et al. “Intake of fermented soybeans, natto, is associated with reduced bone loss in postmenopausal women: Japanese Population-Based Osteoporosis (JPOS) Study,” J Nutr., 2006; 136(5): 1323-8.

Ronn SH, Harslof T, Pedersen SB, Langdahl BL. Vitamin K2 (menaquinone-7) prevents age-related deterioration of trabecular bone microarchitecture at the tibia in postmenopausal women. European Journal of Endocrinology. (2016) 175(6):541–549.

Szulc P, Chapuy MC, Meunier PJ & Delmas PD. Serum undercarboxylated osteocalcin is a marker of the risk of hip fracture in elderly women. J Clinical Investigation. 1993 91 1769–1774. (doi:10.1172/JCI116387)

Booth SL, Tucker KL, Chen H, Hannan MT, Gagnon DR, Cupples LA, Wilson PW, Ordovas J, Schaefer EJ, Dawson-Hughes B et al. Dietary vitamin K intakes are associated with hip fracture but not with bone mineral density in elderly men and women. Am J Clin Nutr. 2000 71 1201–1208.

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