Acute effects of a beverage containing bitter melon extract (CARELA) on postprandial glycemia among prediabetic adults

BACKGROUND: Acute ingestion of bitter melon (BM) has been shown to suppress the postprandial glycemic response in diabetics, but its impact on glucose regulation among individuals with impaired glucose tolerance is unclear. Moreover, one's glucose tolerance level may influence the effectiveness of BM. This study aimed to examine the acute effects of a beverage containing BM extract on blood glucose regulation during an oral glucose tolerance test (OGTT) among prediabetics. METHODS: Ten prediabetic adults completed two OGTTs-glucose only (D2) and glucose+BM (D3). Responders were identified as subjects whose area under the glucose curve (AUC(glu)) during D3 was lower than D2. To compare the acute effects of the beverage among individuals with varying glucose tolerance levels, subjects were grouped by their glucose response pattern-Fast(peak) (peak glucose (Glu(peak)) at 30 min postglucose (30P)) and Slow(peak) (Glu(peak) after 30P). RESULTS: During D3, responders (n = 5) experienced a 13.2% reduction in AUCglu (95% confidence interval (CI): -18.1% to -8.3%), 12.2% reduction in mean glucose (95% CI: -17.3% to -7.0%) and 10.6% reduction in Glu(peak) (95% CI: -17.5% to -3.7%); plasma glucose was reduced by 9.1% at 30P (95% CI: -15.6% to -2.6%), -24.0% at 60P (95% CI: -36.8% to -11.2%) and -20.0% at 90P (95% CI: -35.8% to -4.2%) during D3. No between-trial differences were noted for Fast(peak) or Slow(peak). CONCLUSIONS: Acute ingestion of BM prior to the second OGTT (D3) led to a reduced postprandial glucose response in 50% of the subjects but did not affect the insulin response. Furthermore, the effectiveness of the beverage was seemingly uninfluenced by the subjects' glucose tolerance level. Although BM has shown to aid blood glucose management in diabetics, it remains uncertain why only a portion of subjects responded positively to the BM extract in the current study.