Ginseng and ginsenoside Re do not improve β-cell function or insulin sensitivity in overweight and obese subjects with impaired glucose tolerance or diabetes.

The short version

This randomized, double-blind, placebo-controlled pilot trial with 15 adults explored whether oral ginseng or a purified ginseng compound, ginsenoside Re, improves how the body handles blood sugar. Ginseng is a popular herbal product promoted for diabetes, and earlier work in cells and rodents, mostly using injected ginseng, suggested that ginsenoside Re raises insulin sensitivity, meaning how well tissues take up glucose in response to insulin. Participants were overweight or obese adults with impaired glucose tolerance or newly diagnosed type 2 diabetes, chosen because their metabolism was thought most likely to improve. The volunteers, 14 women and 1 man averaging 46 years old, took placebo capsules, Korean red ginseng extract (3 g a day for two weeks, then 8 g a day) or ginsenoside Re (250 mg a day, then 500 mg a day) for four weeks, with five people per group. Before and after, researchers used a frequent-sampling glucose tolerance test and the hyperinsulinemic-euglycemic clamp, a research method that holds blood sugar steady while insulin is infused, together with tracer sugars, to measure insulin sensitivity and beta-cell function (how well insulin-making cells respond). Nothing improved. The disposition index, a beta-cell function score, was unchanged in the placebo group (5.8 to 5.8 x 10^-3, P = 0.99), the ginseng group (7.7 to 6.0, P = 0.29) and the ginsenoside Re group (7.4 to 5.9, P = 0.50). Insulin sensitivity on the clamp also did not shift significantly: placebo 165% to 185% (P = 0.34), ginseng 171% to 137% (P = 0.88), ginsenoside Re 117% to 134% (P = 0.44). Body weight, fasting glucose, HbA1c and cholesterol stayed the same, and no adverse events were reported. Blood tests could not detect ginsenosides Re, Rb1 or Rb2 after dosing, so the compounds did not appear to reach the bloodstream in measurable amounts. Liver glucose output and fat breakdown, tracked with labeled glucose and glycerol, also responded the same way before and after treatment in every group. The authors interpret the results as evidence that these oral ginseng products do not improve glucose control, likely because absorption is poor, and they note that injected ginseng helped in animal studies. Limits include only 15 participants, a four-week duration, a single ginseng product, and the possibility that other ginseng components or other commercial products behave differently from those tested here.

Key findings

• In a four-week trial of 15 overweight adults with impaired glucose tolerance or new type 2 diabetes, oral ginseng extract (up to 8 g a day) and ginsenoside Re (up to 500 mg a day) did not improve insulin sensitivity or beta-cell function compared with placebo.
• Insulin sensitivity was measured with the hyperinsulinemic-euglycemic clamp (a research test that holds blood sugar steady while insulin is infused); results were, for example, 171% to 137% with ginseng and 165% to 185% with placebo (all P above 0.29).
• Ginsenosides Re, Rb1 and Rb2 (the main ginseng active compounds) were not detectable in blood after dosing, which the authors take to mean poor oral absorption.
• The trial was very small (five people per group), short and tested one ginseng product, so it cannot rule out effects of other products or other ginseng components.

Common questions