Natto and Viscous Vegetables in a Japanese Style Meal Suppress Postprandial Glucose and Insulin Responses

Naturally viscous vegetables and natto, made by fermenting soybeans, are very palatable and considered to be healthy foods in Japan. The objective was to assess whether the consumption of natto and viscous vegetables as part of a traditional Japanese breakfast based on high-glycemic index white rice affects glycemic, insulinemic, lipidemic and satiety responses in healthy subjects. Eleven healthy subjects consumed the reference, control and test meals in a randomized cross-over design. The test meal, comprising 200 g of boiled white rice with viscous meal (50 g natto, 60 g Japanese yams and 40 g okras), and the control meal, comprising 200 g of white rice with non-viscous boiled soybeans, potatoes and broccoli, contained comparable amounts of carbohydrate, fat, protein and fiber. In addition, whiter rice was used as a reference meal. Blood samples over 180 min were analyzed for glucose, insulin, non-esterified free fatty acid and triacylglyceride. Peak glucose and insulin concentrations after the test meal (6.0 mmol/L and 262 pmol/L) were significantly lower than after the control meal (6.8 mmol/L and 360 pmol/L). The incremental areas under the curve for glucose and insulin over 0-120 min after the test meal were also significantly reduced as compared with the control meal (28 and 27%). The consumption of naturally viscous vegetables with white rice reduced acute glycemia and insulinemia. This practical dietary combination would ensure compliance and favorably alter the risk for diabetes and cardiovascular diseases.