Edited by Haruhiko Nakayama
Power of Miso

There is one story took place in Nagasaki after the drop of atomic bomb on August 9th, 1945, that’s been told as a myth in the macrobiotic communities worldwide over and over again. The protagonist of this story is Dr. Tatsuichiro Akizuki who saved many lives of atomic-bomb sufferers including himself by feeding people the diet consisting of brown rice, miso soup, sea vegetables, and sea salt. Dr. Akizuki was the medical director at the Urakami Dai-Ichi Hosital (now known as the St. Francis Hospital).

After reading one of Dr. Akizuki books "Taishitsu (Constitution) and Shokumotsu (Foods)," a professor emeritus, Dr. Hiromitsu Watanabe at Research Institute for Radiation, Biology & Medicine in Hiroshima University was prompted to conduct radiation defense experiments with rats. The results of these experiments provided clear evidence to support the notion that “miso soup possibly prevented development of atomic-bomb disease” described by Dr. Akizuki’s memoir.


This issue of Muso News will feature two experiments and their findings by Dr. Watanabe and other experimental data that were originally on the article in September 2011 edition of the Macrobiotic Magazine called "Musubi," published by our sister company: Macrobiotic Association.

Dr. Watanabe in his office
1st Experiment

The first experiment involved feeding rats different types of feed (regular feed, feed containing 10% of salty rice miso, feed containing 10% of Shoyu, and feed containing 10% of table salt) and then measuring how much tissue regeneration took place in their small intestine after exposing them to a large amount of radiation one week later of feeding. The small intestine is an organ most sensitive to radiation among our internal organs. Acute disorder called “digestive tract termination” whose symptom includes diarrhea and bloody stool is said to occur within a few days to a week following the exposure to medium degree of radiation.

Following the exposure to radiation, the life cycle of intestine cells (from birth to death) is said to be three and a half days in general. Therefore, Dr. Watanabe observed the growth condition of cells called small intestinal crypt  located underneath of villus to see which rats are doing well.

What he found was that the cells of rats fed with feed containing 10% of salty rice miso regenerate more than any other rats. Now let us take a closer look at the chart on the right side.  
Small intestinal crypt regeneration
after exposure to radiation
Click to enlarge

The obvious gap is evident when comparing the result of experimenting a group with feed containing 10% of table salt with the result of group experimenting with feed containing 10% of shoyu. Each group retained a regeration rate of almost 100%with the radiation dose of 6 grey. The regeneration rate for the groups fed with regular feed and feed with 10% table salt went down to 0.1 (10%) when the radiation dose reaches 10 grey. The regeneration rate of the same groups went down to 0.01 (1%), the point where the regeneration is impossible, when the radiation dose reaching 12 grey. On the other hands, under the environment with the radiation dose of 12 grey, the group with feed containing 10% of miso retained its regeneration rate more than 0.1 (10%). However, there was no improvement on the small intestinal crypt regeneration rate seen with the rats that had been fed with regular feed before the irradiation even though they were fed with the feed containing 10% of miso after the irradiation


  Dr. Watanabe said in the research paper published in May of 2008, "In order to have the protective effect, especially maximizing the survival ability on digestive tract termination, it is prerequisite to have sufficient amount of miso and constant amount of blood level containing active elements that is bolstered by administering miso over a long period of time." In other words, miso consumption on a routine basis is necessary to provide protection against radiation in an emergency. In the interview with Musubi Magazine, Dr. Watanabe pointed out, "Miso consumption does not promise sheer protection against radiation in terms of human body; however, my stance is that we are  better off consuming miso if it is not poisonous.” Please note, in the article, he carefully chose his words, "I am calling for the need to consume two cups of miso soup a day."
The photo provided by
Marukawa miso

The longer miso’s maturity is, the longer life expectancy stretches

Three different types of salty rice miso (2-3 days old miso, 120 days old miso, and 180 days old miso) were compared in order to study the relationship between miso’s protective effect against radiation and the length of miso’s maturity. The finding was that miso’s protective effect against radiation became more effective as miso’s maturity advanced longer. Let us now take a closer look.

Under the radiation dose of 8 grey, the rats fed with regular feed started to die on the 10th day from the initial radiation exposure, the rats fed with 2-3 days old miso and 120 days old miso started to die on the 11th day, and the rats fed with 180 days old miso started to die on 13th day. As these finds show, there was a tendency of “the longer miso’s maturity is, the longer life expectancy stretches." Looking at the result of the intestinal crypt regeneration rate under the radiation dose of 10 and 12 grey, the same pattern was observed: "the longer miso’s maturity, the higher regeneration rate became."


The photo provided by
Maruya Hacho miso


According to the experiment results, it is speculated that fermentation and maturation are closely related with miso’s protective effect against radiation. And Dr. Watanabe took particular note of melanoidin, a pigment responsible for transforming miso’s color to distinctive dark brown color as the fermentation advances. Melanoidin is a substance formed when saccharide and amino acids are combined. It is present in coffee, beer, natto, bread crust, and so forth. The effectiveness of melanoidin was confirmed by another experiment by Dr. Watanabe’s team which the small intestinal crypt regeneration rate improved after administering 0.1% of artificially composed melanoidin to rats. However, Dr. Watanabe insisted matter-of-factly, "Melanoidin is a possibility but not conclusive. It is not all of the reasons but [is perhaps] one of the reasons."

According to Dr. Watanabe, after the nuclear accident in Fukushima, the Self-Defense Forces took steps to protect their dispatched personnel from the radiation through the administration of vitamin C, which has a strong antioxidant effect, the same as melanoidin is.

Power of Sea Salt

Besides miso’s protective effect against radiation, Dr. Watanabe offered us some interesting experimental data obtained by his team. Let us take a look at the chart of "Pathological Change of a Precancerous Colon"on the right side.



Pathological Change of a Precancerous Colon
Click to enlarge

This experiment involved feeding rats different types of feeds (see the chart for details) after administering carcinogen to rats and then comparing the conditions of pathological change of precancerous colon by dissection. Looking at the result with miso, no effect was observed with 5%. However, as salt content increases to 10% or to 20%, pathological change of precancerous colon was suppressed. Moreover, the experiment with various types of miso with different maturation length showed that 180 days old miso suppressed oncogenesis more effectively than a few days old miso or 120 days old miso.

In addition to miso, it is worth paying attention to the differences between various types of salt. There was not much difference between regular feed (with 0.3% of table salt) and other types of feed with table salt whose component consisting of high level of sodium chloride (more than 99%). However, a pathological change of precancerous colon receded with the groups fed with other types of salt: sea salt, rock salt, and coarse salt, etc. According to Dr. Watanabe, micronutrients such as calcium and magnesium are supposed to suppress the occurrence of pathological change to a precancerous state. He pointed out consuming natural salt is more effective in preventing colon cancer.

Consuming salt through miso


Miso has been demonized by low sodium movement insisting that Japanese diet consisting of high salt content facilitate the high incidence of stomach cancer. However, the animal experiment conducted by Dr. Watanabe’s team confirmed that consuming salt through miso lessened the incidence of stomach cancer rather than direct intake of salt itself. Again this experiment showed that the longer Miso ages and matures, the stronger inhibitory effect becomes. Perhaps the secret of miso lies in the fermentation process.

Like the case with stomach cancer, it has been said that high intake of salt leads to high blood pressure. Nonetheless, the result of another experiment conducted by Dr. Watanabe’s team tells a different story. His team conducted a comparative experiment involved feeding salt-sensitive rats with the same amounts of salt; 1st group with salt itself and another with miso containing the same amount of salt that group 1 took. And the result showed that blood pressure of rats that consumed only salt had increased whereas there was no change of blood pressure among the rats consuming salt through miso. Furthermore, according to the research paper published in the U.S. last year, the surveys conducted in four countries (China, England, Japan, and U.S.A) showed that the Japanese tend not to have high blood pressure despite of the fact that the Japanese take higher amount of salt than other three countries. Dr. Watanabe sumed up this result with saying "perhaps because we take a lot  of salt by consuming miso, there is less incidence of high blood pressure among us."


The world of fermentation is like the cosmos in the sense that modern science has not yet figure out what is really going on within it even though the technique of fermentation has been with us throughout the human history. But the bottom line is that longer aged and mature miso is good for you despite of its high sodium content; it offers us not only protective effect against radiation but also other health benefits. Most miso Muso offers are naturally fermented and aged at least for one year.

Based on what we’ve learned about aged, fermented miso, we hope you appreciate the true value of our artisanal miso that’s imparted generation after generation.