To evaluate the effect of natto and soybeans on postprandial blood glucose level, a crossover study was conducted in 12 healthy male volunteers.
Subjects were given a control meal (white rice), a natto meal (white rice with natto), or a soybean meal (white rice with steamed soybeans), and blood glucose level in each group was measured before and 15, 30, 45, 60, 90, and 120 minutes after intake.
After both the soybean and natto meals, the blood glucose level at 60 minutes after intake was significantly lower than after the control meal. However, only the natto meal, and not the soybean meal, significantly suppressed the rise in blood glucose level at 60 minutes compared to the control meal. Furthermore, the area under the glucose curve from 0 to 120 min after the natto meal was significantly smaller than for the control meal.
These results suggest that natto is useful for the control of postprandial blood glucose level.