Effect of Ginkgo biloba Extract Ingestion on Plasma Total Cortisol Levels during an Oral Glucose Tolerance Test in Normal Glucose Tolerant Individuals: Recent Study

Protracted periods of increased cortisol production, as may be seen in acute illness, may lead to
transient hyperglycemia. Increasing evidence suggests that cortisol may then mediate insulin
resistance and potentially lead to the development of diabetes. Evidence in animal studies also
suggests that under conditions of stress Ginkgo biloba extract could reduce plasma cortisol
production and so the primary aim of this study was to determine the effect of Ginkgo biloba extract
ingestion on plasma cortisol production during an acute period of glucose challenge. Healthy normal
glucose tolerant subjects (n=30, (10/20, M/F); age, 45.79.9 years old) completed a randomized,
double-blind, placebo-controlled crossover study when they ingested Ginkgo biloba extract (120
mg/day as a single dose) or placebo during each 3-month arm. A standard 75 g oral glucose
tolerance test was performed at the end of each cycle and blood was collected and used to measure
plasma glucose, insulin, c-peptide and cortisol. Fasting plasma cortisol was significantly lower after
the Ginkgo biloba cycle than the placebo cycle (9.74.4 vs. 11.85.4 g/dl, respectively; p<0.05). The
plasma cortisol area under the curve during the 2-hour test (AUC0-2) was also significantly lower after
ingestion of the Ginkgo biloba cycle compared to the placebo (19.27.7 vs. 24.14.9 μg/dl/h,
respectively; p<0.001). It is concluded that the ingestion of Ginkgo biloba extract has effect on the
hypothalamic-pituitary-adrenal axis leading to reduced basal cortisol levels and reduced cortisol
production in response to acute hyperglycemic challenge.