Natto: Another fermented food I probably should be eating

Prior to Seth Roberts mentioning it on his blog (here), I had never heard of the Japanese dish called “Natto,” which is a fermented soybean product. Apparently, it contains a great deal of Vitamin K2, is anti-bad-bacterial, and effectively lyses human thrombus. If you’re like me, that last bit probably made no sense to you, so below are some definitions until I paste liberally from an interview on Natto held with a Japanese expert on the food, Professor Hiroyuki Sumi, who has been nicknamed “Dr. Natto.”

• Natto — “A high protein food consisting of sticky, fermented whole soybeans cooked in Bacillus natto.”
• lyse — “To dissolve or destroy.”
• thrombus — “A clot within the cardiovascular system. It may occlude (block) the vessel or may be attached to the wall of the vessel without blocking the blood flow.”
• fibrinolytic — “Fibrinolysis is the process wherein a fibrin clot, the product of coagulation, is broken down.”

The K2 angle on Natto is particularly fascinating, particularly in light of how expensive it is to supplement K2 via products like butter oil. I’ve been wondering in reading more into fermentation from sources like Seth Roberts when I would see a tie-in to Vitamin K2, which is produced by our own gut bacteria as noted below.

In an experiment conducted out of sheer curiosity, I found that natto contained a strong enzyme that lyses thrombus.

I am Japanese and regularly eat natto, so one day I took some natto to my laboratory. That was in 1980. I usually prepared thrombus in a laboratory dish and measured its strength by adding urokinase to it, but that day, I added natto instead. I found that natto contained a strong fibrinolytic enzyme, judging from the large area lysed. After coming back to Japan, I repeated various experiments, and first presented the results of my research in 1986. NHK and various newspapers reported my discovery of the enzyme named ’nattokinase ’,and before I knew it, I had become Dr. Natto. Originally, I was interested in fermentation. After I graduated from the Department of Fermentation Technology at Yamanashi University, I entered the Department of Medicine because I wanted to continue my study of enzymes further. In the field of fermentation, Japanese technology is the most advanced in the world. I think this is the field in which we achieve our most original results.

I studied more than 200 foods from all over the world, but none surpassed natto in terms of fibrinolytic activity.

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――What are the functions of nattokinase and Vitamin K2, which are contained in natto?

Dr. Sumi: It is said that natto became a popular food in the Edo period, and that the voice of natto sellers was constantly heard in the city of Edo.Regarding the effects of natto,there are many anecdotes concerning its efficacy for stomachache, and flu, and for helping women give a birth. This is because natto has a high nutritive value and is easy for the body to absorb. In addition, natto has an antibacterial effect. In the old days, food poisoning was very common, and people used natto in order to prevent cholera, typhoid and dysentery.

Natto is highly antibacterial, and also contains di-picolinic acid, which suppresses O-157.

In a food dictionary of the Edo period, it is written that natto neutralizes poisons and stimulates the appetite.Neutralize poisons refers to an antibacterial effect. Recently, it has been found that natto contains di-picolinic acid, which suppresses O-157, and that natto has an antibiotic effect. Natto suppresses the growth of harmful bacteria while encouraging the growth of beneficial bacteria such as lactobacillus. The best-known component of natto is nattokinase, an enzyme that lyses thrombus. Recently, the Japanese diet has come to resemble the American one, and consequently, the incidence of thrombosis in Japan has increased. The incidence of thrombosis in the heart and brain is higher than that of cancer, if myocardial infarction and cerebral infarction are included in the total. Natto has attracted attention as a food that helps to prevent senile dementia, which is one type of thrombosis, because nattokinase lyses thrombus for a very long time when eaten directly instead of taken by injection.

Vitamin K2 in natto is essential for preventing osteoporosis.

Natto contains another useful component, named Vitamin K2. It is said that 60% of women over the age of 60 suffer from osteoporosis, which Vitamin K2 helps to prevent. In order to maintain healthy bones, a number of studies suggest that it is important to obtain Calcium and Vitamin D from milk. Recently, however, it was found that a protein named osteocalcin acts as a kind of glue that helps to incorporate Calcium into the bones, and that Vitamin K2 is necessary in order to produce this protein. Furthermore, according to the results of recent epidemiological research, the amount of Vitamin K2 in the body of people who suffer from osteoporosis is decreasing compared with that of healthy people.

Obtaining sufficient Vitamin K2 is not a problem for healthy people, because they have a colon bacillus that is constantly producing Vitamin K2 in the alimentary canal. However, when people become older, or take medicine containing antibiotics, this bacillus weakens and produces less Vitamin K2. It is becoming clear that Vitamin K2 produced by this bacterium is closely connected with the prevention of osteoporosis, and the Ministry of Health and Welfare has approved Vitamin K2 as a medicine for osteoporosis. Unlike natto, yeast, a lactobacillus, and Koji do not contain Vitamin K2 that comes from a bacterium. Bacillus natto is a unique bacterium throughout the world, and moreover people can ingest it in the raw. Therefore, natto is receiving considerable attention as the only food that contains Vitamin K2 from a bacterium.

Vitamin K2 has the chemical name menaquinone 7. At present, Vitamin K1, or menaquinone 4, is synthesized for use in the medicines approved by the Ministry of Health and Welfare. When the components of blood are analyzed, one vitamin that is found more often in healthy people than in osteoporotic people is menaquinone 7. A lack of menaquinone 7 causes osteoporosis. Because Bacillus natto produces menaquinone 7, eating natto helps to prevent osteoporosis. It is important to obtain the fundamental components of bones by consuming milk and Shiitake mushrooms, but Vitamin K2 is also necessary. Menaquinone 7 has only recently appeared in the analysis data of the Science and Technology agency, and samples are not on sale yet.

It is possible to obtain enough vitamin K2 from one packet (100 g) of natto.

One hundred grams of natto contains approximately 1,000μg of menaquinone 7. A normal person is supposed to consume 1μg per 1 kg of body weight each day, which means that a person of 60 kg should consume 60μg of menaquinone 7. Therefore, 10 g of natto supplies enough menaquinone for one day. If the colon bacillus is weakened, a packet of natto supplies a sufficient amount of menaquinone 7.

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As a result of attempts to make natto more palatable, the amount of its effective components decreased.

Extremely undeveloped natto has been increasing as a result of attempts to make natto more palatable, especially for people in the Kansai area in Japan. Such natto has a weaker odor and is less sticky. When the US authorities occupied Japan in 1945, they prohibited the sale of natto because they thought that cholera and typhoid were often caused by such a rotten food. Since then, about three types of purely cultured bacillus have been used to make natto. As a result, natto became tastier and safer, but on the other hand, the amount of the anti-bacterial material, Vitamin K2, and nattokinase decreased. Comparing a 1936 report on the components of natto and its activity with current data, it is found that the anti-bacterial component has dramatically decreased.