Chronic administration of apple polyphenols ameliorates hyperglycaemia in high-normal and borderline subjects: A randomised, placebo-controlled trial.

Aims: We previously reported that apple polyphenols (AP) and their major active components, procyanidins, had beneficial effects on glucose homeostasis and diabetes in diabetic ob/ob mice. The present study was performed to evaluate the effects of chronic AP administration on glucose tolerance in high-normal and borderline human subjects.

Methods: Subjects (n=65) with a fasting plasma glucose (FPG) level of 100-125mg/dL determined during a recent health check-up were randomised to receive tablets containing AP (600mg/day) or placebo tablets for 12weeks in a double-blinded, placebo-controlled clinical trial. The primary outcome was insulin resistance, assessed using a 75g oral glucose tolerance test (OGTT).

Results: The 12-week chronic administration of AP significantly reduced the increase in glucose at 30-min post-75g OGTT (OGTT) value, compared to the placebo regimen. Furthermore, in a subgroup of the high-normal (FPG value, 100-109mg/dL; 2-h post-75g OGTT glucose (OGTT) value, <140mg/dL) and borderline (FPG value, 110-125mg/dL; OGTT value, <140mg/dL and FPG value, <126mg/dL; OGTT value, 140-199mg/dL) subjects, OGTT value in the AP group (164.0±7.4mg/dL) was significantly lower than that of the placebo group (194.7±10.4mg/dL, p<0.05). No significant changes in the other lipid parameters and cytokine levels were observed.

Conclusions: Chronic AP administration significantly improved impaired glucose tolerance in high-normal and borderline subjects. Larger and/or longer-term scale human studies are required to confirm the potential glucose homeostasis of AP.