The Awesome Power of Natto & K2: Demonstrated to Benefit Your Bones
Natto: Good to the Bone
Health is a long term project. The influence of lifestyle and nutritional choices on disease risk and health outcomes are undeniable. Small everyday choices can have a huge cumulative impacts on disease prevention. A great example of this is getting ahead of age-related bone loss by incorporating more Vitamin K2 into your diet to help build & strengthen bones earlier in life and to protect yourself from the natural decline in bone mineral density and osteoporosis later.
The 2020 Integrative Health Symposium was held recently here in NYC, where many medical leaders (including Drs. Mark Hyman, Mimi Guarneri, David Perlmutter) delivered inspiring messages supporting a shift in primary medicine toward more holistic and preventative methods. More and more, progressive healthcare providers are recognizing the central role of food & diet in disease prevention. Empowering people to take more control of their own health by choosing nutritious and functional foods simply makes medical, economic, and common sense!
Check out this natto-centric highlight of the IHS conference:
Pioneering advocate of Japanese functional ingredients, award-winning chef & restauranteur David Bouley, talks about natto (full of probiotics & MK-7) with conference keynote speaker Dr. Mark Hyman, teaching him how to deal with that slime factor! Chef Bouley also brings up the clinical connection to bone health, the subject of this deep dive.
Many of you have shared that you found natto through your search for healing functional foods that have been rigorously examined in clinical outcome-based human studies relevant for bone issues like osteoporosis, osteopenia, Paget’s disease or recovery from bone injury or dental damage.
There is no better food source of Vitamin K2 you can eat to support bone health than natto!
Why Natto?
Published, peer-reviewed, credible scientific studies in Japan have shown:
Post-menopausal women who eat at least four servings of natto weekly show significantly reduced rates of bone density decline—in some cases similar back to premenopausal levels. (Ikeda et al. 2006. J Nutrition)
A direct association between dietary intake of natto and bone mineral density (BMD). (Fujita et al. 2012.Osteoporosis International)
Post-menopausal women who eat natto daily had up to 49% lower risk of osteoporosis-related bone fractures! (Kojima et al. 2019. J Nutrition)
Certainly, more work is necessary to fully understand the mechanism of these effects, and new studies are also needed in Western populations. Yet these data may the strongest case for any single food’s direct clinical impact on bone health.
Did we get your attention yet?
In this article, I share some of the recent clinical research evidence that suggest that eating natto regularly could play an important role in preventative care for bone health. It’s very compelling data, including a brand new study just published in December 2019. We want to break it down and share it with you.
So please read and let the evidence speak for itself . . .
Why is Natto so Good for Bone Health?
Vitamin K2 appears to be at the heart of natto’s impact on bone biology. Natto is the most concentrated food source of Vitamin K2 (MK-7) which functions to help build and maintain bone mass.
No other food even comes close to natto in levels of this bacterially derived micronutrient! Vitamin K2 found naturally in natto is almost exclusively the MK-7 long-chain isoform, which may be most beneficial for bone health. For more background info, see our previous post on K2, with information on Vitamin K2 benefits and foods with Vitamin K2.
K2: the Missing Micronutrient for Bone & Cardiovascular Health
Still underappreciated even in the medical community, recent science has shown that Vitamin K2 helps us to move calcium within the body—getting it out of our bloodstream, where we don’t want it to accumulate, and into our bones, where we really do want calcium to go.
Please also note that high doses of K2 may be contraindicated for some patients receiving warfarin blood thinners because K vitamins interfere with the action of these drugs. Do consult your healthcare provider before combining regular natto consumption with coumadin-type drugs to decide whether INR monitoring and dosage adjustment may be an option for you.
Obviously, one must consume enough calcium to build and support healthy bone mass. And Vitamin D3 plays a critical role in getting that calcium from your gut into your bloodstream. However, no matter how much calcium you eat, it won’t do you much good unless you can absorb and transport it to the sites of bone formation.
A growing body of evidence suggests that this is what K2 helps you do. Getting calcium out of your bloodstream, where its accumulation can lead to arterial calcification, atherosclerosis and cardiovascular disease is just as important as getting calcium to your bones! This may partially explain a recent study showing that Japanese people who ate natto regularly showed 20% lower rates of cardiovascular disease and death. See our previous blog post for more about this.
Age-Related Bone Loss
Loss of bone density and strength is an inevitable part of the human life cycle. We build bone mass early in life, peaking during late adolescence and continuing until about age 30. During our 30’s and 40’s, a healthy diet and regular physical exercise help us to maintain bone mass by balancing normal bone loss and replacement.
Cells called osteoblasts are responsible for incorporating calcium to form new bone and replacing bone mass lost from damage or resorption by osteoclast cells. This continuous remodeling, the building and breaking down of bone tissue by osteoblasts and osteoclasts, is a normal feature of maintaining healthy and strong bones.
(Image credit: Medscape.org)
As we age, bone-building activity by osteoblasts slows down more than bone-resorption function of osteoclasts, leading to a net loss of bone mass. Estrogen hormone exerts bone-protective effects and has been shown both to promote the activity of bone-building osteoblasts as well as down-regulation/turnover of osteoclasts.
Accelerated loss of bone mass generally occurs earlier in women than in men because of hormonal changes, primarily a dramatic drop in estrogen levels. Women experience a sudden increase in bone loss around menopause (usually ~50y) while men tend not to experience significantly accelerated bone loss until their 70’s. For all of us, bone loss is a serious health concern, and preventative measures are best started early before bone loss becomes debilitating and irreversible.
Early Evidence for Natto Consumption & Osteoporosis Prevention
In the 1990s, epidemiologists and clinical scientists studying osteoporosis in the aging population of Japan noticed something remarkable—a very strong positive correlation between bone health and natto consumption. Regions of Japan where people consumed more natto had the lowest rates of osteoporosis-related bone fractures. Conversely, regions with lower rates of natto consumption showed higher rates of bone fractures.
When it comes to nutritional epidemiology, this may offer some of the best conditions for a “natural experiment” imaginable. In Japan, natto is consumed regularly by a significant chunk of the population. Dietary intake of natto is also relatively easy to track since natto is sold in individual serving size packaging and eaten fresh. And the relatively consistent homogeneous population and diet across regions mean that it’s easier to rule out many sources of demographic and dietary variation that would complicate observations in other countries.
By contrast, osteoporosis is more difficult to track as it often goes undiagnosed. The best clinical markers to represent it are bone fractures, acute injuries, which often stem from reduced bone strength for which medical intervention and therefore records exist.
It is immediately apparent how very closely matched these geographic patterns are! The colorized maps above show: (left) natto consumption: high (green)/medium (yellow)/low (red) & (right) frequency of bone fractures: high (red)/ medium (yellow)/ low (green).
These data suggest that there is an inverse relationship between natto consumption & bone fracture frequency. Of course, correlation does not prove causation, but this relationship in such a comprehensive analysis of nation-wide data was striking, making a great starting point for more rigorous investigation.
Many subsequent clinical investigations ensued, homing in on the effects of natto on clinical outcomes on both a population and individual level. Many later studies consistently strengthened the case that regular natto consumption is correlated with lower rates of osteoporosis.
Natto, Vitamin K2 & Bone biology
Meanwhile, scientists around the world were in the process of drawing the connection between dietary Vitamin K2 and bone biology. To briefly summarize a great deal of work in this area, scientists found that Vitamin K2 is an essential cofactor required to activate an important bone-building protein called osteocalcin. In the presence of Vitamin K2, the osteocalcin is modified (by post-translational carboxylation) and allows it to bind and recruit calcium to build new bone.
(Image: https://www.unik2.com)
Osteocalcin activity in promoting bone mineralization and growth was now understood to be dependent on Vitamin K2. Among the many isoforms of Vitamin K, menaquinone MK-7 emerged as having the most significant effects on bone. This is because MK-& accumulates more efficiently than shorter chain menaquinones in bone tissue. Thus levels of MK-7 were measured as a read-out of osteocalcin bone-strengthening activity.
There exists some debate about what is the best serum marker to monitor Vitamin K2 and osteocalcin-mediated bone-building activity. Vitamin K isoforms are absorbed from the bloodstream at different rates and may continue to act in tissues long after they have been cleared from the bloodstream. This means that measuring serum concentrations of Vitamin K2 may not necessarily reflect the amounts acting in tissues like bone. These days, carboxylated osteocalcin is more commonly used, but since osteocalcin protein levels can vary in individuals, some scientist believe that the ratio of carboxylated: uncarboxylated osteocalcin is a better readout of osteocalcin’s bone activity.
Current research evidence suggests that Vitamin K2 stimulates osteocalcin’s bone-building functions and that the MK-7 form of Vitamin K2 may be targeted best to bone tissue.
Natto Consumption Increases Serum Vitamin K2
In 2001, Japanese and British scientists reported that geographic differences in average population circulating serum Vitamin K2 (MK-7) levels correlated directly with consumption of natto. The study compared blood concentrations of MK-7 in populations of post-menopausal women in Tokyo (where natto consumption is reasonably high), Hiroshima (where natto consumption is lower) and London, England (where natto consumption is very low indeed!)
Though the study size was small (25-49 women in each geographic group), the differences in detectable serum MK-7 were significant; 5.26 ± 6.13 ng/ml in Tokyo, 1.22 ± 1.85 ng/ml in Hiroshima, and 0.37 ± 0.20 ng/ml in London. Further, elevation of serum MK-7 levels appeared to be correlated with how frequently individuals consumed natto each week, though these data were not statistically significant due to outliers in the small study samples. There was no correlation found between MK-7 levels and consumption of other soy (edamame. tofu, soymilk) or even fermented (soy sauce, miso) soy food products.
Can Eating Natto Prevent Osteoporosis?
What we really want to know is, does natto consumption impact bone density? In 2006, a clinical research study was published supporting that very result.
In this cohort study (Japanese Population-based Osteoporosis Study, JPOS) nearly a thousand healthy women (ages 20-79) participated in a long-term examination of bone mineral density (BMD) and its association with individual natto consumption. Bone density scans were performed on each person at four sites (spine, neck, hip and forearm) over a three-year time span.
Post-menopausal women were grouped into three categories according to how much natto they regularly ate: those who ate four or more (45g) servings per week, those who consumed 1-3 servings/week, and those who never ate natto. Average bone density loss for each consumption level group was compared to the overall averaged data for all pre-menopausal women included in the study.
As summarized in the chart above, post-menopausal women who consumed higher amounts of natto (dark blue: intake of four or more servings per week) appeared to have lower average rates of bone density loss, close to nearly pre-menopausal rates (shown by dotted yellow lines).
Presented in another way, the JPOS study showed that prior to menopause, the average rate of bone density loss (in neck scan) was -0.3% per year. During and after menopause, this rate of bone loss was increased over 5-fold to -1.6% in women who did not consume natto.
In contrast, women who ate at least 4 servings (45g) of natto weekly had a reduced average BDM loss rate of -0.5%, nearly the same as pre-menopausal women! Another way of stating this result: Post-menopausal women who regularly consumed (≥180g or 4 servings) of fresh natto weekly had >3-fold reduced rate of Bone Mineral Density (BMD) loss!
Take-Home Message: Eating Natto Can Reduce Bone Mass Density Loss and Risk of Osteoporosis
Bone Density Loss & Gender
Natural bone loss can begin after age 30 in both men and women, but women are especially vulnerable to age-related bone loss because of the hormonal changes that accompany menopause. For most women, this starts around age 50 although, for some, higher rates of bone loss begin much earlier.
During menopause, natural serum estrogen levels fluctuate and then drop dramatically. One function of this hormone in the body is to promote the activity and biogenesis of osteoblasts, the cells responsible for building bone. With a drop in estrogen levels, osteoblast-mediated bone regeneration becomes outpaced by natural bone disassembly (resorption) by osteoclasts.
Men are certainly at risk for osteoporosis too, though bone mass reduction tends to be more gradual mirroring testosterone hormone decline. Though diagnosis of osteoporosis is significantly less prevalent in men than women over 50, 30% of hip fractures in older adults occur in men, and the fracture‐related mortality rate is also higher in men.
Natto & Bone Density in Men
A clinical analysis in men called the Fujiwara Osteoporosis Risk in Men study (FORMEN) showed a positive relationship between bone mineral density (BMD) and natto consumption. In 1,662 men (≥65y), BMD was evaluated at three sites (lumbar spine, hip & femoral neck) and interviewed to determine habitual natto intake along with other dietary, lifestyle and health status information. A small but statistically significant direct association between BMD and natto intake was found at all sites tested.
Osteoporotic bone fractures are a direct consequence of bone density loss and can have devastating consequences for many older patients. One fracture event often leaves individuals with diminished quality of life, productivity and independence, and greatly increases the risk of subsequent fracture injuries.
Natto & Bone Density in Women
Finally, this brings us to a brand new study result just published in the Journal of Nutrition in December 2019, further supporting an association between natto consumption and improved bone density.
This latest cohort study followed 1,417 healthy postmenopausal women, recording their natto intake and the incidence of bone fractures. Over a 15-year period, 172 women in this group experienced bone fracture events. In the analysis, these participants were divided into three groups based on their habitual weekly levels of natto intake: 0 servings (none), 1- 6 servings (sometimes), or ≥7 servings (daily). The statistical analyses were adjusted to account for confounding factors such as age, BMD, BMI, and many other medical and lifestyle factors.
Results showed that women who consumed at least one serving of natto (40g) per day had a 49% lower risk of osteoporotic fracture relative to women who ate no natto (44% risk reduction when adjusted for lifestyle factors). The effect was dose-dependent. Those who ate natto less frequently (1 - 6 servings per week) also displayed lower risk of bone fractures, 21% less risk than the control (no natto) group.
The effect was specific to natto. No association between frequency of intake other soy foods (tofu, soy sauce, miso, soymilk, edamame) was seen with bone breakage risk.
Impact of Osteoporosis & Bone Injury
In 2020, an estimated 14 million people aged 50+ (80% female) in the US suffer from osteoporosis and 34 million more may have low bone density (osteopenia) putting them at high risk for osteoporosis and related bone weakness-related fractures. According to the International Osteoporosis Foundation, worldwide, 1 in 3 women over the age of 50 years and 1 in 5 men will experience osteoporotic fractures in their lifetime.
Osteoporosis is notoriously underdiagnosed. Sobering data on the national impacts of osteoporosis from the National Osteoporosis Foundation: “In 2015, ~2 million Americans sustained 2.3 million osteoporotic fracture. Within 12 months of experiencing an osteoporotic fracture, approximately 15% of patients suffered one or more subsequent fractures and nearly 20% died. Mortality was highest in those with hip fracture, with 30% dying within 12 months.”
Current medical treatments for osteoporosis, namely bisphosphonate drugs, can slow the progression of disease and bone loss. Oral formulations of these medications are associated with many negative side effects and are not well tolerated by many patients. Thus, bisphosphonate therapy is generally used only for limited periods of time. Another form of bisphosphonate therapy can require inconvenient medically-assisted infusion, reducing side effects, but resulting in low patient compliance.
Especially when persistent rates of underdiagnosis are factored in, there remains significant unmet medical need among osteoporosis sufferers. This explains why there has historically been such a high “appetite” for dietary approaches that can complement medical intervention. Based on the evidence reviewed above, we believe that natto as a food could play an important role here.
Key Clinical Outcome Lessons: Natto's Impact on Bone Health
I’ve shown you current scientific evidence suggesting that eating natto may:
Significantly slow down age-related bone loss
Is associated with higher BMD in both women and men
Reduces risk of osteoporotic fractures, the primary cause of disability and mortality associated with osteoporosis
Plus, eating fresh natto has been found to have a far greater positive impact on bone health than Vitamin K2 supplements alone (stay tuned for more on this point!)
Until recently, fresh natto has been very difficult to get in America; we aim to change that. With such compelling evidence that natto can truly help people towards better health, we have made it our passionate mission to make the best possible version of this incredible functional food available to you.
Disclaimer: Statements in this article are the summary of our evaluation of scientific literature and have not been evaluated by the FDA. This product is not intended to diagnose, treat or cure disease.
NYrture New York Natto is dedicated to providing America access to fresh, premium natto, the best natural source of Vitamin K2, nattokinase & spore probiotics. Our natto is produced by hand, fresh and never frozen, to deliver the best quality natto with maximum potential health benefits to you.
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Natto recipes : How can I eat my natto?
