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Monday, Oct. 16, 2000
Tasty seeds have hidden health benefits
By YUKO NAITO
Sprinkled on hamburger buns, bagels and cooked vegetables, sesame seeds add extra zest with their nutty flavor. Recent research has found, however, that there is much more to the humble sesame seed than just its good taste.
People have long believed sesame is good for one's health, but its beneficial effects were not scientifically proven until researchers finally began studying the seed in the 1980s. Since then, its hidden powers have gradually been revealed.
"Sesame is a great preventive medicine, because it contains substances called sesame lignans that work in the body as powerful antioxidants," says Toshihiko Osawa, a professor of agriculture at Nagoya University and a leading authority on sesame.
"Many diseases such as cancer, complications from diabetes and Alzheimer's disease are related to oxidation. There's nothing wrong with oxygen itself, but 2-3 percent of inhaled oxygen turns into toxic free radicals in the body. Usually the body detoxifies them, but our detoxifying ability declines as we get older. Sesame lignans can help remove those free radicals."
Lignans are substances that exist in roots, stems, leaves, flowers and seeds, and each lignan works differently in the body. About 10 kinds of lignans have been discovered in sesame seeds; the two most abundant are sesamin and sesaminol.
Sesamin is found mainly in sesame seeds, and comprises as much as 0.3-0.5 percent of its total weight. Research has shown that once its antioxidant effects are activated in the liver, it works to improve liver function and accelerate the decomposition of alcohol (preventing the unpleasant aftereffects of drinking and hangovers), lower high blood pressure, reduce the blood cholesterol level and prevent breast cancer. Whether it works on other types of cancers is still under study.
Sesaminol, the other main lignan found in sesame, is a water-soluble antioxidant formed in the process of making sesame oil, and is found in only tiny amounts in unprocessed seeds. While most cooking oils (except olive oil) start oxidizing as soon as they are exposed to air, sesame oil can retain its purity for a long time due to sesaminol's strong antioxidant power. Research on rats shows that sesaminol slows aging and prevents a variety of ailments, including heart disease, strokes and diabetes.
About a year ago, Osawa and his research team isolated a new substance from the crushed seeds left after pressing oil. Its molecular structure is similar to sesaminol, and the team found that it is changed into an oil-soluble form of sesaminol in the body by intestinal bacteria.
Usually, sesame grounds are discarded, but Osawa says this is a waste as the grounds contain other nutrients such as protein, vitamins and minerals.
"We perhaps could save many malnourished people in the world if we could make use of the sesame grounds and equally nutritious soybean grounds left from pressing soybean oil," he says.
Growing awareness of the health benefits of sesame has led to an increase in its domestic consumption (18,000 tons in 1997, 4,000 tons more than 1993), and products using sesame have appeared one after another: cookies, puddings, ice creams, instant ramen, soy milk with black sesame paste, candies, salad dressing and bread spread. There is even a theme park in Gifu Prefecture called Goma no Sato (Sesame Village) which opened this April, where visitors can learn all about sesame, from its history to health benefits.
Osawa warns, however, against eating too much sesame or treating it as a form of medicine. (Suntory has already developed a sesame-based nutritional supplement, Sesamin E.) The recommended daily intake is a tablespoonful of sesame -- about 10 grams. He points out that the possible side effects from an excessive intake of sesame are still unknown, and notes the danger of weight gain due to sesame's rather high caloric content -- 60 calories per tablespoonful of sesame seeds and 120 calories for the same amount of sesame oil.
Osawa suggests that sesame lignans can be ingested most effectively by grinding the seeds, because the hulls are hard and indigestible.
"It's best to grind it right before you eat, if possible, since the ground sesame starts oxidizing very quickly," he says. "Ground sesame should be kept in an airtight container and stored in the refrigerator."