――Why did you begin your research on the function of natto?
At present, the fibrinolytic enzymes utilized in medicine are urokinase, which is obtained from human urine, and TPA, which is obtained from cancer cells called melanoma. However, when I was studying thrombosis in Chicago, USA, only urokinase was available. In Europe, streptokinase and staferokinase were discovered, which are protein components obtained from bacteria. I found that injections of those enzymes could be used to cure myocardial infarction and cerebral infarction if used at an early stage.
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.
I continued my research on natto because I wanted to study something that was particularly interesting to me, and because I had already discovered enzymes that lyse thrombus in food. I have examined more than 200 foods from all over the world so far. As a result, I have found that natto is the most effective food for the lysis of thrombus. I don't know why natto contains such a strong enzyme that can lyse human thrombus. There is no enzyme that has a stronger fibrinolytic activity than nattokinase. Moreover, natto is a food that is completely safe to eat.
――Is it possible to make nattokinase from natto based on anything other than soybeans?
Yes, black beans can be used instead of soybeans, and natto can also be made from azuki beans and kidney beans. Even sunflower seeds can be used efficiently. However, Bacillus natto thrives best on soybeans. It appears that soybean's protein helps to produce nattokinase more efficiently. Although natto originated in Asia, it seems that natto is naturally produced by Bacillus natto inhabiting straw, but only if soybeans are present. In the USA, it took about 150 years to become to plant soybeans. I think that Bacillus natto has only recently become established in the USA.
――What are the functions of nattokinase and Vitamin K2, which are contained in natto?
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.
The level of menaquinone 7 in the blood was measured for people in Tokyo, Osaka and London. People in the Kansai area (Osaka) have only half the amount of menaquinone 7 compared to people in the Kanto area (Tokyo). This is because people in the Kansai area eat natto less frequently. Of course, people in London have even less menaquinone 7. Recent epidemiological research has shown that people who regularly eat natto have a large amount of menaquinone 7 in their blood. This fact was also approved systematically. Therefore, there is scientific evidence that eating natto helps to prevent osteoporosis.
In addition, an isophrabon compound is one of the antioxidants in natto. A packet of natto provides 50 mg of isophrabon, which is the minimum amount recommended in the US for the prevention of cancer. In the US, the incidence of prostate cancer is 15 times that in Japan, and natto is also being examined with regard to the prevention of prostate cancer and breast cancer. Moreover, isophrabon has the same effect as a type of female hormone, and it is said that the female hormone of soybeans influences that of human beings.
As regards antioxidative activity, fermented soybeans have about four times the activity of unfermented soybeans. This is because Bacillus natto produces a specific antioxidant. The nature of this antioxidant has not yet been clarified.
――Even though some people dislike the taste of natto and its stickiness, do you think it is important for everyone to eat plenty of natto?
The components of natto are effective in preventing diseases such as thrombosis, so I think it is necessary to consume natto for health reasons. In the Japanese law, medicine for disease treatment is admitted, but medicine for disease prevention is not allowed at present. Therefore, I think that more and more foods for disease prevention will be developed in the near future.
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.
――Natto seems to set to become popular as an ideal food throughout the world, doesn't it?
Natto is compatible with the bacteria in the Japanese body, and conversely, Japanese people seem to need the bacterium from Bacillus natto in order to keep their digestive system in good condition. Natto contains between one million and one billion active bacteria per 1 g. Bacillus natto is a medicine approved by the Ministry of Health and Welfare, and a stomach medicine containing Bacillus natto is available. Natto has been utilized as a natural medicine for many years.
Natto has attracted great interest throughout the world as a food that increases longevity.
Soybeans are known as vegetable cheese abroad, and dried natto, which was developed about ten years ago, is used by JAL for in-flight meals and as a snack with beer. An international conference on the prevention of disease using soybeans has been held in the US, where there is currently a big natto boom. Because Japan has the highest average longevity in the world, people in the USA are interested in this mysterious food natto, which is not eaten outside Japan. The first time natto was mentioned in an English academic journal was in 1896. Since then, more than a century has passed, and natto has attracted interest all over the world as a food for promoting longevity.