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Humble miso soup may have saved lives when the atomic bomb was dropped on Nagasaki. Science now confirms miso prevents radiation injury. It may also prevent cancer and hypertension. Here's why you need at least one cup a day.
When the second atomic bomb was dropped on Nagasaki on August 9th, 1945, 21 healthcare workers were attending 70 tuberculosis patients in a hospital 1.4 km from ground zero. None of them suffered from acute radiation poisoning.
Dr. Tatuichiro Akizuki, a physician at the hospital, credited this miracle to the fact that everyone was consuming daily cups of miso soup garnished with wakame seaweed.
In a new comprehensive review of both epidemiological and experimental studies, Japanese researcher Hiromitsu Watanabe from the Research Institute for Radiation Biology and Medicine at Hiroshima University confirms the power of miso to prevent radiation injury.
His review also documents the ability of miso to prevent many forms of cancer (colon, liver, breast, lung and stomach), as well as hypertension.
Miso, or fermented soy bean paste, is a traditional staple of the Japanese diet. Soy beans are fermented with sea salt, koji (a mold starter), and sometimes rice, wheat, oats or other grain. The mixture is fermented for three months to three years.
The resulting enzyme-rich paste contains vitamins, microorganisms, salts, minerals, plant proteins, carbohydrates, and fat. But fermented foods are more than the sum of their ingredients. Fermentation gives rise to compounds that have amazing healing properties. Fermented foods like kimchi, natto, apple cider vinegar, and even wine and beer have been called "medical foods."
Watanabe's review of the science emphasizes the importance of traditional fermented foods like miso to prevent disease and maintain health. Here is just a brief sampling of his findings.
Miso Protects Against Radiation Injury
In a series of experimental studies, mice were fed a regular diet, or a regular diet with 10% dried red rice miso. After a week, the mice were subjected to radiation. The group fed miso had significantly greater numbers of surviving intestinal crypts – glands found in the epithelial lining of the small intestine and colon. Damage to crypts is believed to lead to colorectal cancer.
But when miso was fed to mice after radiation treatments, it didn't have the same effect. The researchers concluded that in order to reap the benefits, the blood must contain a certain concentration of the active compounds in miso before exposure to radiation.
The researchers believe miso's beneficial effect is closely related to substances produced during fermentation stages. They tested miso fermented for three to four days, 120 days and 180 days. Miso fermented for longer periods resulted in increased survival rates. Miso fermented for 180 days was considered most beneficial.
In other studies, miso fermented for 180 days significantly reduced tumor size and the number of tumors in the lungs of experimental rats.
Miso Prevents Breast Cancer
According to one epidemiological study, consuming a cup of miso three times a day reduced the occurrence of breast cancer. Tofu, natto, soybean and fried bean curd did not have the same effect.
In laboratory studies, rats fed miso developed fewer tumors when they were subjected to a cancer causing agent. And the rats fed miso were slower to develop tumors.
Researchers also investigated the incidence of tumors with miso and tamoxifen, a drug used for breast cancer treatment. The number of tumors per rat in the control group was 4.5. But in the group given miso, that number dropped to 2.4 and in the tamoxifen group it dropped to 1.4. When miso was given with tamoxifen, the number further decreased significantly to just 0.2 tumors per rat.
According to Watanabe, this investigation clearly indicates that miso can reduce the occurrence of breast tumors as effectively as tamoxifen at the beginning of cancer treatment, and can also suppress the number of tumors.
Miso Prevents Liver Tumors
When certain male mice were bred under normal conditions, 89% of them naturally developed liver cancer. But the mice fed diets containing 10% miso had their cancer rate drop to 32%.