Public health recommendations almost always include an increase in consumption of vegetables. This is based on the fact that vegetables provide many essential vitamins and minerals within a low-calorie food. Vegetables also provide many antioxidant compounds along with a variety of health-promoting phytochemicals.
But the recommendation often overlooks a category of vegetable foods that is common in Japan, China, Korea and Hawaii: limu.
QUESTION: What exactly is limu?
ANSWER: “Limu” is the Hawaiian word for water plants but most commonly refers to edible seaweeds. Sometimes called sea vegetables, they are categorized into three general types of algae: green, red and brown. Although seaweeds have been part of Asian and Hawaiian diets for a long time, they often are overlooked as a source of essential nutrients. Due to the potential health benefits of sea vegetables, it makes sense to include them as part of one’s vegetable fare.
Q: What are common limu sources in local foods?
A: Perhaps the most common seaweed ingredient used by Hawaii cooks is nori, the paperlike sheets of dried laver seaweed of Japanese origin, used as a wrap for sushi and the ubiquitous Spam musubi.
Another product of Japanese origin is the condiment mixture called furikake, which is sprinkled on hot rice. It is typically a mixture of small seaweed flakes, sesame seeds and powdered or flaked dried fish along with a variety of other possible ingredients. Furikake is increasingly common in Asian fusion cuisine, in menu items such as furikake-crusted fish.
The traditional Hawaiian diet generally uses fresh, rather than dried, limu. Limu is common in poke.
Q: How well does limu substitute for other common vegetables?
A: Limu provides many of the same nutrients as land vegetables. A sheet of nori, for example, provides vitamins A and C as well as dietary fiber in amounts comparable to a typical serving of vegetables.
But the nutrient that makes seaweeds unusual is iodine. For a variety of reasons, iodine intake in the United States has declined during the past decade or two. Since most iodine comes from the ocean or soils located near the ocean, land plants often contain little. Seaweeds and other seafood are generally more reliable sources, but types of limu vary greatly in iodine content. According to the Office of Dietary Supplements, the iodine in a serving of seaweed can range from 11 to 1,990 percent of daily recommended intake.
Q: Are there concerns about eating too much limu?
A: As with any nutrient or individual food, too much of a good thing can be harmful. In the case of limu, the risk comes from potential arsenic accumulation. Not all types of limu are high in arsenic, but the Food Standards Agency in the United Kingdom advises citizens to not consume hijiki seaweed products because of excessively high levels of arsenic.
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Joannie Dobbs, Ph.D., C.N.S., and Alan Titchenal, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dobbs also works with University Health Services.
