Natto

Introduction: Natto — the Treasures of Japanese Fermentation

Natto (in Hebrew “נאטו”) is an ancient traditional Japanese food made of whole soybeans that have gone through a unique fermentation by Bacillus subtilis bacteria. It has a reputation as a genuine “superfood” in Japanese culture, where it is eaten regularly, usually for breakfast over a bowl of rice.

Natto has unusual sensory qualities that often put off Western tasters at first: it has a strong smell (a bit reminiscent of blue cheese or mild ammonia, due to protein breakdown), a deep, nutty umami taste, and above all an especially slimy, sticky texture (mucilage), created by the polymer chains of polyglutamic acid that the bacteria produce. Beyond taste and texture, natto is an unrivaled nutritional powerhouse. It is considered the most natural and accessible source of vitamin K2 in nature, and it is the exclusive source of an enzyme with medicinal properties — nattokinase.

Advanced Nutritional Profile of Natto

An average serving of natto (about 100 grams) is exceptionally rich in macro- and micronutrients, which are significantly upgraded by fermentation, making them especially available for absorption (the process reduces phytic acid, which is common in unfermented soybeans and inhibits mineral absorption):

• Calories: about 210 calories.
• Protein: about 18 to 20 grams of complete plant protein. The protein itself has already been partially broken down by the bacteria, which makes its amino acids very easy to digest and quick to absorb.
• Carbohydrates: about 14 grams, of which more than 5 grams are soluble and insoluble dietary fiber.
• Fat: about 11 grams, the vast majority unsaturated fatty acids.
• Iron: about 48% of the reference daily intake (RDI). Fermentation significantly increases the availability of iron compared with regular soy.
• Calcium and magnesium: about 20% and 29% of the daily intake, respectively.
• Vitamin C and B vitamins: a respectable amount of riboflavin (B2), B6 and folate.

However, the real “stars” of natto, which make it a unique preventive remedy, are its unprecedented bioactive components:

Active Nutritional and Health Benefits of Natto

Nature’s richest source of vitamin K2 (Menaquinone-7)

While vitamin K1 (from plant sources such as spinach or kale) is mainly responsible for the body’s general blood-clotting mechanism, vitamin K2 occupies a completely different place in human metabolism. K2’s critical role is to activate proteins (such as osteocalcin) whose job is to move excess calcium out of the bloodstream and into the bones and teeth, instead of letting it settle — a deadly process — on the walls of blood vessels, the kidneys or soft tissues. Natto is, by a huge margin, the world’s number 1 source of this essential nutrient in its long-chain form (MK-7), containing on average about 1000 micrograms of vitamin K2 per 100 grams, an amount 100 times greater than aged hard cheeses or egg yolk. This pathway alone has been documented to reduce the risk of bone fractures in old age by very high rates.

Nattokinase and active protection of the blood vessels and heart

Another property unique in the world to natto is the enzyme called nattokinase. This proteolytic (protein-digesting) enzyme is produced during fermentation by this specific bacterium. Consistent medical studies have shown that nattokinase has a natural, powerful ability to dissolve fibrin — the main protein that makes up blood clots. This means that consuming nattokinase thins the blood naturally, directly reduces the risk of pathological blood clots (thrombosis, stroke), helps break down cholesterol and dramatically improves blood flow in the cardiovascular system, without the harsh side effects of chemical blood thinners.

An ocean of hardy probiotics

Natto contains billions of live bacteria of the fermenting microbe, B. subtilis. Unlike many delicate probiotic strains that do not survive the aggressive acidity of human gastric juices, B. subtilis is unique in forming a tough “spore” around itself. This hardiness allows a decisive share of the bacteria to reach the large intestine intact, where they establish resilient colonies, suppress contaminating pathogens and significantly improve constipation and digestive irregularity.

Lowering blood pressure and widening blood vessels

In addition to nattokinase, which lowers blood viscosity, natto contains a variety of small active peptides and antioxidants produced as the complex soybeans are broken down. Various (IN-VIVO) studies have found that natto has an inhibitory effect on the enzyme ACE (Angiotensin-Converting Enzyme) — exactly the mechanism most conventional prescription blood-pressure drugs work on.

Side Effects and Warnings You Should Know

• A strong interaction with blood-thinning drugs: this is probably the most critical warning. Because of the double, powerful effect of both the clot-dissolving enzyme nattokinase and the enormous load of vitamin K, people actively taking blood thinners (from preventive aspirin, through warfarin/Coumadin, to modern anticoagulants such as Xarelto or Eliquis) must consult closely with a cardiologist before eating natto, because it changes the blood’s clotting parameter (the INR) quickly and strongly. For healthy people this is an amazing preventive benefit; for complex patients it is a powerful clinical intervention that requires monitoring.
• Soy in the context of phytoestrogens and the thyroid: for most of the population, the doses of phytoestrogens (isoflavones) in soy, certainly in its safer fermented form, are not a problem, and their effect even protects against hormonal cancers. However, for people with an underactive thyroid (hypothyroidism) and low iodine levels, or with special clinical conditions, eating large amounts of soy products may call for caution.

Culinary Use and Fitting It Into Your Diet

Natto’s unique taste and stringy texture are undoubtedly a challenge for the average Israeli/Western palate. The right way to eat it is to balance it with strong spicy-salty flavors that cut through the slimy texture:

• The traditional Japanese way: in Japan, natto in its small containers is customarily stirred vigorously for a full minute (which boosts the release of nutrients and the formation of the sticky “threads”), and then a little soy sauce (shoyu) or very hot Japanese mustard (karashi) is mixed in. After seasoning, the whole mixture is poured over a deep bowl of hot steamed rice and garnished with an adventurous topping of finely chopped fresh green onion and a fresh egg (usually just a raw yolk).
• Adding it to flavorful salads: for those who struggle with the concentrated traditional way, you can add a spoonful of natto to a large, well-seasoned green salad with a lemony vinaigrette, where the texture gets lost and the nutrients remain.
• No intensive heating: as with other live fermented foods such as kefir and kombucha, cooking natto heavily and bringing it to a boil kills the bacteria. The important enzyme nattokinase is especially sensitive and breaks down at temperatures above 60 degrees (140°F). Eating it at room temperature or warmed passively by the rice is the ideal choice.

Summary

Natto is not just another “high-fiber vegetable,” and it is definitely an acquired taste. From a purely bio-engineering standpoint, it is one of the most impressive natural functional foods available to modern humans, and anyone wise enough to include it in their diet will gain a range of survival advantages. Its global monopoly on vitamin K2 enables a proper, healthy synergy of storing calcium and phosphorus in the bones without the danger of calcification of the heart’s blood vessels in women and men around menopausal age. The added protection provided by nattokinase effectively acts as a shock absorber for the arteries, lowering the chances of destructive blood clots and supporting healthy blood pressure. If you get past the deep smell and sometimes off-putting texture, you discover a whole health laboratory in a spoonful of fermented beans — an inspiration for a diet full of benefits and for the remarkable longevity that characterizes specific regions of Japan, which eat it devoutly.