By Marie Spano, M.S., R.D., Contributing Editor
The longevity enjoyed by the Japanese may involve a genetic component; however, many ascribe their long lifespan to diet, as well. While the Japanese diet is typically low in fat and high in vegetables, several traditional foods are standouts for health, including fermented soy, seafood and green tea.
Fermented soy. Fermented soy products include miso, natto and soy sauce. Miso, a paste of rice and soybeans fermented with the vitamin B12-producing fungus Aspergillus oryzae, contains protein, manganese, vitamins K1 and K2, zinc, and copper. Natto is fermented with Bacillus subtilis and contains protein, probiotics, and vitamins K1 and K2.
Vitamin K2 might help calcify bone tissue while preventing artery calcification. Studies show that vitamin K2 improves bone quality and successfully treats osteoporosis. The research on vitamin K2 and arterial calcification, though in the early stages, is exciting. One cross-sectional study of 564 postmenopausal women found that dietary intake of vitamin K2 was associated with a trend toward decreased coronary calcification.
For traditionally brewed soy sauce, soybeans and wheat are crushed and blended into a mash, and mold, typically Aspergillus, is added to make koji. Koji is mixed with water and salt to make moromi, which is fermented with lactic-acid bacteria and yeast for three to six months. Just three tablespoons of soy sauce make this food a good source of manganese, niacin and protein. One tablespoon of soy sauce contains 0.03 grams tryptophan (9.4% of the daily recommended value), an essential amino acid that the body uses to produce serotonin, a compound that is believed to promote sleep and stabilize moods.
Though high in sodium, fermented soy sauce can be used to decrease foods’ total sodium content. A small amount adds a lot of flavor due to soy sauce’s complex mix of flavor-enhancing compounds such as amino acids, organic acids and other fermentation products.
Seafood. A lower intake of meat and higher intake of fish in the Japanese diet, compared to U.S. and European diets, may contribute to a lower risk of coronary artery disease. Fatty fish is rich in the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which decrease triglycerides in a dose-dependent manner, slightly decrease blood pressure (AHRQ Publication Number 04-E010-1) and are inversely related to risk of fatal coronary heart disease.
In addition, omega-3 fatty acids may lower risk of age-related macular degeneration. And DHA may be an effective treatment for dry eye, and may help regenerate damaged corneal nerves.
Green tea. Tea produced from Camellia sinensis is calorie-free, rich in flavonoids and a natural source of caffeine and L-theanine. Green tea consumption is associated with a decreased risk of CAD and some types of cancer.
In a meta-analysis examining the association between green tea and CAD, the highest intake of green tea was related to a reduced risk of CAD. An increase in green tea of one cup per day was associated with a 10% decrease in the risk of developing CAD. Additionally, a meta-analysis examining green tea and stroke found that individuals consuming three or more cups of tea (green or black) per day had a 21% lower risk of stroke than those consuming less than one cup per day.
Studies also suggest that green tea consumption is inversely associated with breast cancer recurrence and may play a role in preventing prostate cancer. A meta-analysis examining green and black tea consumption and lung cancer risk found a significant association between the highest intake of green tea and reduced lung cancer risk. Also, an increase in green tea consumption of two cups per day was associated with an 18% decreased risk of developing lung cancer.
Marie Spano, M.S., R.D., CSCS, is a nutrition communications expert whose work has appeared in popular press magazines, e-zines and nutrition-industry trade publications. She has been an expert guest on NBC, ABC and CBS affiliates on the East Coast. For more information, visit mariespano.com. Research citations are available at foodproductdesign.com.
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