Glycemic index of different varieties of yam as influenced by boiling, frying and roasting

Tuber crops could be a potential food component for lowering starch digestibility and estimated glycemic index in rice

BACKGROUND

Rice is considered a high estimated glycemic index (eGI) food because of its higher starch digestibility, which leads to type II diabetes and obesity as a result of a sedentary life style. Furthermore, the incresaing diabetes cases in rice-consuming populations worldwide need alternative methods to reduce the glycemic impact of rice, with dietary prescriptions based on the eGI value of food being an attractive and practical concept. Rice is often paired with vegetables, pulses, tubers and roots, a staple food group in Africa, Latin America and Asia, which are rich in fibre and health-promoting compounds.

RESULTS

Rice from four categories (high protein, scented, general and pigmented) was analyzed for eGI and resistant starch (RS) content. Among the genotypes, Improved Lalat had the lowest eGI (53.12) with a relatively higher RS content (2.17%), whereas Hue showed the lowest RS (0.19%) with the highest eGI (76.3) value. The addition of tuber crops to rice caused a significant lowering of eGI where the maximum beneficial effect was shown by elephant foot yam (49.37) followed by yam bean (53.07) and taro (54.43).

CONCLUSION

The present study suggests that combining rice with suitable tuber crops can significantly reduce its eGI value, potentially reducing the burden of diet-associated lifestyle diseases particularly diabetics. © 2024 Society of Chemical Industry.

Suppression of the postprandial hyperglycemia in patients with type 2 diabetes by a raw medicinal herb powder is weakened when consumed in ordinary hard gelatin capsules: A randomized crossover clinical trial

INTRODUCTION

Contradictory claims about the efficacy of several medicinal plants to promote glycemic control in patients with type 2 diabetes mellitus (T2DM) have been explained by divergences in the administration form and by extrapolation of data obtained from healthy individuals. It is not known whether the antidiabetic effects of traditional herbal medicines are influenced by gelatin capsules. This randomized crossover trial aimed to evaluate the acute effect of a single dose of raw cinnamon consumed orally either dissolved in water as a beverage or as ordinary hard gelatin capsules on postprandial hyperglycemia (>140 mg/dL; >7.8 mmol/L) in T2DM patients elicited by a nutritionally-balanced meal providing 50 g of complex carbohydrates.

METHODS

Fasting T2DM patients (n = 19) randomly ingested a standardized meal in five experimental sessions, one alone (Control) and the other after prior intake of 3 or 6 g of crude cinnamon in the form of hard gelatin capsules or powder dissolved in water. Blood glucose was measured at fasting and at 0.25, 0.5, 0.75, 1, 1.5 and 2 hours postprandially. After each breakfast, its palatability scores for visual appeal, smell and pleasantness of taste were assessed, as well as the taste intensity sweetness, saltiness, bitterness, sourness and creaminess.

RESULTS

The intake of raw cinnamon dissolved in water, independently of the dose, decreased the meal-induced large glucose spike (peak-rise of +87 mg/dL and Δ1-hour glycemia of +79 mg/dL) and the hyperglycemic blood glucose peak. When cinnamon was taken as capsules, these anti-hyperglycemic effects were lost or significantly diminished. Raw cinnamon intake did not change time-to-peak or the 2-h post-meal glycaemia, but flattened the glycemic curve (lower iAUC) without changing the shape that is typical of T2DM patients.

CONCLUSIONS

This cinnamon's antihyperglycemic action confirms its acarbose-like property to inhibit the activities of the carbohydrate-digesting enzymes α-amylases/α-glucosidases, which is in accordance with its exceptionally high content of raw insoluble fiber. The efficacy of using raw cinnamon as a diabetes treatment strategy seems to require its intake at a specific time before/concomitantly the main hyperglycemic daily meals. Trial registration: Registro Brasileiro de Ensaios Clínicos (ReBEC), number RBR-98tx28b.

The structure-glycemic index relationship of Chinese yam (Dioscorea opposita Thunb.) starch

Yam (Dioscorea opposita Thunb.) is an important functional food in Asia. Yam starch usually has a low glycemic index. What is the structure requirement of starch to obtain a low glycemic index remains unknown. In order to understand the structure-glycemic index relationship, six yam starches from various regions with apparent structure difference were analyzed. Chinese yam starch (CYS) showed the lowest glycemic index. It presented as oval or round granules. Meanwhile, CYS showed a distinct A-type crystal structure while the others presented C-type crystal structure. The largest crystallinity, R_w, M_w/M_n, RS level, RS + SDS level, and the lowest peak viscosity, trough viscosity and C_∞ values were found for CYS. These data explained the lowest glycemic index of CYS. The above results suggested that CYS was a good neutraceutical candidate and could be used in the diet of diabetes population.

Evaluation of in vitro and in vivo Glycemic Index of common staples made from varieties of White Yam (Dioscorea rotundata)

Consumption of high Glycemic Index (GI) foods is a risk factor for increasing prevalence of diabetes mellitus (DM). The extent of variation in starch digestibility and GI of Yam varieties and products is not yet fully understood. This study was therefore designed to evaluate in vitro and in vivo Glycemic Index properties of commonly consumed products prepared from varieties of White Yam. Four products (boiled, fried, pounded yam, and Amala) were prepared from 5 common varieties of Yam and evaluated for Digestible Starch (DS) and Resistant Starch (RS). Based on results, two products-pounded yam and Amala-were processed from three of the most popular varieties. Analysis of Rapidly Digestible Starch (RDS), Slowly Digestible Starch (SDS), and estimated in vitro GI (eGI) were then carried out in this stage. Glycemic Index (GI) of these products consumed by apparently healthy young adults were also determined. Variety Amula had highest DS in Amala (19.1/100 g) and pounded Yam (20.4/100 g) while variety Alumaco had highest RS in all the products (2.9–3.3/100 g). When compared with RS in its raw tuber, RS of Alumaco generally increased after processing. Variety Alumaco had lowest RDS in Amala (0.6/100 g) and pounded yam (0.3/100 g) while eGI was lowest in Alumaco made into Amala (53) and pounded yam (48). Assessment of GI resulted in high GI for all products across each variety. Irrespective of variety, processing Yam into Amala released RDS fraction faster when compared with pounded yam. Generally, even though the products are considered as having high GI, Amala raised eGI and GI faster than Pounded yam. Variety-Alumaco particularly showed favorable properties applicable to dietary management of diabetes. Exploring more processing methods and genetic diversity is recommended.