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Tuesday, Sep. 20, 2011
Hold the cesium: Ways to reduce radiation in your diet
By TOMOKO OTAKE
Is our food really safe?
Six months into the nuclear crisis at the Fukushima No.1 power plant, this is a question many consumers have been asking — particularly those in eastern Japan who get most of their daily foods from Tohoku, the nation's agricultural heartland.
While readings of radiation in the air have returned to pre-3/11 levels in most areas of Japan — not including areas close to the plant and the so-called hot spots — the contamination of soil, which affects the food chain, could pose a long-term health risk, experts say. Iodine-131, cesium-134 and cesium-137 were released in large quantities by the nuclear plant, and if they are accumulated in the body, they could cause cancer.
Since the disaster struck, the government has been monitoring radiation levels of food from Fukushima and neighboring prefectures and barring the distribution of any items containing radioactive materials exceeding the national safety limits. Still, public fears over food safety are hard to quell, even in Tokyo, more than 200 km away from the Fukushima plant. A recent letter to The Japan Times attests to the wide-spread sentiment:
"Each time I go to a supermarket, I pause in front of the shelves, at a loss as to what to buy," a Tokyo woman, who called herself Yasuko Okayama, wrote in a letter to the JT published Sept. 8. "I choose food that comes from as far away from the Fukushima No. 1 nuclear plant as possible. I wonder if I am overreacting."
She may be overreacting, but somewhat understandably. There are a lot of unknowns regarding the effects of long-term, low-dose exposure to radiation, and children are believed to be far more vulnerable than adults.
Kunikazu Noguchi, lecturer at Nihon University and an often-quoted expert on radiological protection, assures that consumers need not worry too much about any produce on the market, because at present, radiation levels in most vegetables, meat, dairy and other foods, even those from Fukushima Prefecture, are far below the government's safety limits and often undetectable. But for consumers concerned about the few incidents of tainted food slipping through the government checks (such as the beef from cattle that had been fed with tainted straw in Fukushima, which was shipped nationwide in July), or families with small children, Noguchi suggests a simple way to minimize their radiation exposure through food: rinse it.
Noguchi says that radiation, though invisible and odorless, can be treated and cleaned up like a stain, noting that by rinsing the food well before cooking, preferably with hot water, and/or boiling or stewing it, a large portion of radioactive elements can be removed. In his book, published in Japanese in mid-July, "Hoshano Osen kara Kazoku wo Mamoru Tabekata no Anzen Manyuaru" ("The Safety Manual for Protecting Your Family From Radiation Contamination"), Noguchi offers tips on how to prepare food, item by item, so consumers can reduce their radiation intake at home.
In the book, he refers to data released in 1994 by Japan's semi-public Radioactive Waste Management Center (now the Radioactive Waste Management Funding and Research Center). The center's report, titled "Removal of Radionuclides during Food Processing and Culinary Preparation," compiled results of detailed tests conducted in Europe and Japan following the 1986 Chernobyl nuclear disaster.
"This is not something we must absolutely do," he said about radiation-removal steps. "But since we don't know how much — within the safety limits — food is irradiated, taking these steps can safeguard us further."
Here are some of Noguchi's tips on preparing major food groups:
A series of hydrogen explosions at the plant in March resulted in the release of large amounts of radioactive particles into the atmosphere, tainting vegetables and fruits grown outdoors. They also contaminated soil with iodine-131, cesium-134 and cesium-137. Iodine-131 is no longer detectable due to its short half-life of eight days. The cesium isotopes, meanwhile, need long-term monitoring because cesium-134 takes two years to decrease by half and cesium 137's half-life is 30 years.
The good news is, cesium can be easily dissolved in water. So the best way to prepare vegetables and fruits is to rinse them well before cooking. If possible, cut vegetables into small pieces and soak them in water for a while.
More radiation in spinach and other leafy vegetables can be removed if they are boiled. As for lettuces, throw away the outer leaf and rinse the rest well. Data from Chernobyl shows that rinsing lettuce can remove up to half of the cesium-134 and two thirds of the cesium-137. Cucumbers can be pickled with vinegar, which cuts radiation by up to 94 percent. Peeling carrots and boiling them with salted hot water would also help reduce cesium levels.
Meat and fish
Livestock can be tainted through the grass and water they consume. Well-grilled, salt-sprinkled beef poses less risk than anything cooked to a medium-rare or medium state, by cutting 28 percent of cesium, according to a Chernobyl-tied study. Boiling leg meat has been proved to reduce cesium by about 50 percent. Make sure to drain off the hot water. Don't worry about the pork bone broth; cesium accumulates mostly in meat, not bones, and the levels of strontium-90, which does accumulate in bones, are negligible.
For fish and other seafood, however, watch out for strontium-90, which has a half-life of 29 years. According to Noguchi, far greater quantities of strontium-90 were released into the ocean than into the air and ground. Contrary to popular thinking, large fish are not necessarily riskier to consume. Though large fish do eat smaller fish, which leads some to believe they accumulate more radioactive materials, Noguchi says it is the small fish and flat fish that have stayed close to the Fukushima plant that pose more risk. Unlike large fish that swim longer distances, small fish cannot move far from contaminated areas.
With tuna fish, rinse with water before eating or cooking. Boiling or marinating salmon helps remove cesium-137, and avoid eating fish bones, as they could contain strontium-90.
Rice and wheat
Much has been said about the nutritiousness of brown rice, but when it comes to radiation, it is the bran layer beneath the husk that absorbs and accumulates cesium from soil. That means white, polished rice, which has no bran layer, is a safer option — though it does contain fewer vitamins, minerals and fiber than brown rice. If you rinse white rice well before cooking, you can also remove radiation-emitting residue on the grain.
Wheat products such as bread, spaghetti and noodles pose very little risk, since 90 percent of wheat in Japan has been imported from overseas. For those concerned with radiation in pasta or noodles made from wheat in Japan, the thinner the noodle, the more cesium released when cooked.
Fresh milk from Fukushima Prefecture was suspended from the market from mid-March until the end of April after it was found to contain radioactive iodine. The air and grass consumed by dairy cows had been contaminated. Authorities have since been keeping an eye on levels of radiation in milk, so you need not worry too much about the products currently on sale.
Cheese and butter are fine, too, because, during their production, the milk whey — the liquid that gets separated from curd — is removed. While rich in nutrition, cesium and strontium tend to remain in whey. Yogurt, which usually has whey floating on top, also undergoes radiation checks before going on the market, but if you are still worried, pour off the whey before you eat the yogurt.
Wakame (soft seaweed) and kombu (kelp) are integral parts of the Japanese diet. They flew off store shelves in the wake of the nuclear disaster, when consumers heard that the natural iodine in them might help them fight radiation contamination.
Seaweed from the sea close to the nuclear plant, however, will likely absorb high levels of radiation in the coming years. You can rinse it before cooking, or choose seaweed harvested elsewhere.
Kunikazu Noguchi's book, "Hosha no Osen kara Kazoku wo Mamoru Tabekata no Anzen Manyuaru" ("The Safety Manual for Protecting Your Family from Radiation Contamination"), was published by Seishun Shuppansha in July, in Japanese only, priced at ¥1,000.