Low glycemic load after digestion of native starch from the indigenous tuber Belitung Taro ( Xanthosoma sagittifolium) in a dynamic in vitro model of the upper GI tract (TIM-1)

Background: Low glycemic foods are beneficial for people with type II diabetes. At the same time, sustained glucose release is also beneficial for people suffering from glycogen storage diseases. Taro (Xanthosoma sagittifolium) is a tuber indigenous to Indonesia, which has starch as the major storage carbohydrate.

Objective: The aim of the current study was to determine the speed of digestion of native and modified taro starch, compared to free glucose and wheat starch.

Design: This was investigated in a validated, dynamic computer-controlled in vitro model of the stomach and small intestine (TIM-1). Samples were taken from the dialysate, which reflected glucose absorbed in the blood stream.

Results: Native taro starch showed a ~1.5-fold reduced digestibility compared to glucose and a ~ 1.35-fold compared to wheat starch. In addition, digestion of native taro starch was moved towards the ileum, and later in time compared to glucose and wheat. With modified taro starch, these effects were not observed.

Conclusion: In conclusion, native taro starch showed a lower glycemic load than wheat starch and modified taro starch and could be used as a substitute for refined foods by diabetics and people suffering from other glucose metabolic diseases.

Keywords: diabetes; digestibility; glycemic load; starch; taro tuber.