postprandial glycemic and insulinemic effects of three cooked vegetables: Corchorus olitorius, Spinacia oleracea, and Daucus carota on steamed white rice

ABSTRACT

Eating cooked vegetables with rice is quite common in Jordan and worldwide. Dietary fibers of vegetables are expected to play a role in the glycemic control of meals. To study the postprandial glycemic and insulinemic effect of three cooked vegetables mulukhiyah leaves [Corchorus olitorius], spinach [Spinacia oleracea] and carrots [Daucus carota]. The postprandial glycemic and insulinemic effect of the threecooked vegetables on steamed rice were studied by running the oral glucose tolerance tests on apparently healthy young adults, each of who served as his own control, using white bread as the reference. Insulin sensitivity was measured by calculating the composite insulin sensitivity index. The glycemic index [GI] of rice [84.2 +/- 10.5%] ingested with chicken broth was significantly lowered only by eating 120 g of mulukhiyah leaves [ML] and not by either carrots or spinach. The insulinemic index [II] of steamed white rice eaten with broth was significantly lowered by 120 g of ML [61.7 +/- 9.2%] and 150 g of spinach [42.9 +/- 9.0%]. Insulin sensitivity was only improved by spinach. All results are expressed as means +/- SEM and are considered statistically significant at P<0.05. The results also suggested that there was no significant difference between the calculated relative GI and relative II responses of the three cooked vegetables at the two assigned levels, each eaten with rice and broth compared to the corresponding GI or the II values of the individual foods from which they were composed of. Eating a relatively high portion of mulukhiyah leaves improves the glycemic response to white rice whereas only higher levels of carrots tended to improve the glycemic response of white rice, and spinach at either level had no apparent effect. While insulin level was lowered by the three tested vegetables, its sensitivity was improved by eating spinach only