Starting in the 1960s, the word "hijiki" started to be used widely in the United States, and the product (imported in dried form from Japan) became widely avaialable at natural food stores and Asian-American grocery stores, due to the influence of the macrobiotic movement, and in the 1970s with the growing number of Japanese restaurants.
Hijiki is green to brown in colour when found in the wild. After collection, it is boiled and dried to be sold in the form of dried hijiki. Dried processed hijiki turns black. To prepare dried hijiki for cooking, it is first soaked in water then cooked with ingredients like soy sauce and sugar to make a dish.
Hijiki is black when found packaged in stores. It is a slightly bitter tasting seaweed that comes in short strips about the size of a match. It is similar in texture and appearance to black spaghetti.
Okinawans usally eat it simmered with vegetables and soybeans, as hijiki is best used in dishes that require simmering. To prepare; soak hijiki and dried soybeans for about two hours until tender (Okinawans prepare them the night before). Then, simmer them in water with carrots and konnyaku. Fianlly, season with soy sauce, sugar, and sake. A half cup of dried hijiki will do for four people.
Several government food safety agencies advise consumers to avoid consumption of hijiki seaweed. Test results have indicated that levels of inorganic arsenic were significantly higher than in other types of seaweed. These results have been independently verified
Government food safety agencies that have issued warnings include:
The Ministry of Health, Labour and Welfare of Japan has responded with a report pointing out that, while the consumption of more than 4.7g hijiki seaweed per day could result in an intake of inorganic arsenic that exceeds the tolerable daily intake for this substance, the average daily consumption for Japanese people is estimated at 0.9g. Several of the reports from other food safety agencies acknowledged that occasional Hijiki consumption was unlikely to cause significant health risks, but advised against all consumption regardless.
Although no known illnesses have been associated with consuming hijiki seaweed to date, inorganic arsenic has been identified as carcinogenic to humans, and exposure to high levels of inorganic arsenic has been linked with gastrointestinal effects, anemia and liver damage. People who follow a macrobiotic diet that often includes large amounts of seaweed may be at greater risk.